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Java And XSLT

1. Element personalDataElem doc creat pageElem appendChild personalDataElem DocumentBuilderFactory newInstance Element personalData use a private helper function to avoid some of DOM s tedious code addElem doc personalDataElem firstName personalData getFirstName true addElem doc personalDataElem lastName personalData getLastName true addElem doc personalDataElem daytimePhone personalData getDaytimePhone true addElem doc personalDataElem eveningPhone personalData getEveningPhone false addElem doc personalDataElem email personalData getEmail true return doc A helper method that simplifies this class iparam doc the D x creating param parent the DOM Element to add the child to param elemName the name of the XML element to create param elemValue the text content of the new XML element param required if true insert required true attribute Rf private void addElem Document doc Element parent String elemName String elemValue boolean required Element elem doc createElement elemName elem appendChild doc createTextNode elemValue if required elem setAttribute required true OM Document used as a factory for lements to p parent appendChild elem The following code begins w
2. Le Ck Ck Ck KK KK KKK KKK KKK kk kk kk kk Ck Ck Ck Ck Ck kk Sk Ck Sk kk Ck Sk Sk Ck ck Sk Ck ck Sk Mk ko Sk ko Mk Mk ko kx ko ko ko parseDepends template Tokenizes and prints a comma separated list of dependencies The first token is printed and the remaining tokens are recursively passed to this template KCKCkCkCkCkCk ck ck k ck ck kc kckckckck ck ck ck ck ck k ck ck kckckck ck ck ck ck kc kck ck ck ck kck ck kck ck ck ck kck ck k KKK KKK KK lt xsl template name parseDepends gt this parameter contains the list of dependencies gt lt xsl param name depends gt grab everything before the first comma or the entire string if there are no commas lt xsl variable name firstToken gt lt xsl choose gt xsl when test contains Sdepends xsl value of select normalize space substring before depends xsl when xsl otherwise lt xsl value of select normalize space depends gt xsl otherwise xsl choose xsl variable lt xsl variable name remainingTokens select normalize space substring after depends 1 output the first dependency lt xsl value of select SfirstToken gt 1 recursively invoke this template with the remainder of the comma separated list gt lt xsl if test SremainingTokens gt xsl text lt xsl text gt xsl call template name parseDepends xsl wit
3. until lt xsl value of select endTime hour gt xsl text xsl text lt xsl value of select endTime minute gt lt p gt lt xsl template gt lt xsl stylesheet gt The first part of this stylesheet should look familiar The first four lines are typical of just about any stylesheet you will write Next the output method is specified as xm1 because this stylesheet is producing XHTML instead of HTML xsl output method xml doctype public W3C DTD XHTML 1 0 Transitional EN doctype system http www w3 org TR xhtml1 DTD xhtml1l transitional dtd The xsi output element produces the following XHTML content lt xml version 1 0 encoding UTF 16 gt lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Transitional EN http www w3 org TR xhtmll DTD xhtmll transitional dtd Moving on the first template in the stylesheet matches and outputs the skeleton for the XHTML document Another requirement for XHTML is the namespace attribute on the lt html gt element html xmlns http www w3 org 1999 xhtml The remainder of schedule xslt consists of additional templates each of which matches a particular pattern in the XML input Because of its XML syntax XSLT stylesheets can be hard to read If you prefix each template with a distinctive comment block as shown in Example 2 6 it is fairly easy to see the overall structure of the stylesheet Without consistent
4. http javax xml transform sax SAXTransformerFactory feature xmlfilter 7 protected SAXTransformerFactory public abstract TemplatesHandler newTemplatesHandler throws TransformerConfigurationException public abstract TransformerHandler newTransformerHandler Templates templates hrows Trans c abstract TransformerH hrows TransformerConfig ormerConfigurationException ndler newTransformerHandler rationException publi publi ndler newTransformerHandler Source src t u i a u ic abstract TransformerHa throws TransformerConfigurationException i w t u i w t u public abstract XMLFilter newXMLFilter Templates templates hrows TransformerConfigurationException XMLFilter Source src c abstract XMLFilter ne rationException publi hrows TransformerConfig TemplatesHandler This acts as a SAX 2 ContentHandler which receives SAX events as a document is parsed Once parsing is complete it returns a Templates object Instances are constructed using SAXTransformerFactory public interface TemplatesHandler extends ContentHandler String getSystemId Templates getTemplates void setSystemId String systemId TransformerHandler Instances of this interface receive SAX events and produce Transformer objects once parsing is complete Instances are constructed using SAXTransformerFact
5. AND boardID boardID while rs next long msgID rs getLong 1 long inReplyTo rs getLong 2 int createDay rs getInt 3 String subject rs getString 4 String authorEmail rs getString 5 DayMonthYear createDMY new DayMonthYear createDay month getMonth month getYear allMsgs add new MessageSummaryImpl msglID createDMY boardSum subject authorEmail inReplyTo return allMsgs iterator catch SQLException sqe Sqe printStackTrace throw new DataException sqe finally DBUtil close stmt con return an iterator of all lt code gt BoardSummary lt code gt objects ur public Iterator getAllBoards throws DataException List allBoards new ArrayList Connection con null Statement stmt null Statement stmt2 null try con DBUtil getConnection dbURL stmt con createStatement stmt2 con createStatement ResultSet rs stmt executeQuery SELECT id name description FROM Board ORDER BY name while rs next long id rs getLong 1 String name rs getString 2 String description rs getString 3 get the months with messages Use a different Statement object because we are in the middle of traversing a ResultSet that was created with the first Statement List monthsWithMessages this getMonthsWithMessages id stmt2 allBoards add new
6. A utility class that parses a Comma Separated Values CSV file and outputs its contents using SAX2 events The format of CSV that this class reads is identical to the export format for Microsoft Excel For simple values the CSV file may look like this pre b c d e f pre parser And double quotes are used when the values contain quotes is smart enough to trim spaces around commas as well author Eric M Burke ud public class CSVXMLReader extends AbstractXMLReader an empty attribute for use with SAX private static final Attributes EMPTY ATTR new AttributesImpl Parse a CSV file param input the comma separated values file to parse public void parse InputSource input throws IOException InputSt SAXException if no handler is registered to receive events don t bother to parse the CSV file ContentHandler ch getContentHandler if ch null return convert the InputSource into a BufferedReader BufferedReader br null if input getCharacterStream null br new BufferedReader input getCharacterStream else if input getByteStream null br new BufferedReader new InputStreamReader input getByteStream else if input getSystemId null java net URL url new URL input getSystemId br new BufferedReader new reamRead
7. Perform a single XSLT transformation zy public static synchronized String transform String xmlFileName String xsltFileName throws TransformerException MapKey key new MapKey xmlFileName xsltFileName File xmlFile new File xmlFileName File xsltFile new File xsltFileName MapValue value MapValue cache get key if value null value isDirty xmlFile xsltFile this step performs the transformation value new MapValue xmlFile xsltFile cache put key value return value result prevent instantiation of this class private ResultCache MIMUML MB M MILII PP BgBgMPMMMMMMPMoyMME MMPMPMoEMVEI CCo AVIV IL LL P PL BP P G LL GN B gg aMlll l TT a helper class that represents a key in the cache map MIMEMIMMMMPMLPMMEMMPMPMlPMlMlMlMlM ellllllllllllldMllMldlHMlMMMMllMMlllMdMdMlddMlMMdMMdMHdMldi static class MapKey String xmlFileName String xsltFileName MapKey String xmlFileName String xsltFileName this xmlFileName xmlFileName this xsltFileName xsltFileName public boolean equals Object obj if obj instanceof MapKey MapKey rhs MapKey obj return this xmlFileName equals rhs xmlFileName amp amp this xsltFileName equals rhs xsltFileName return false public int hashCode return this xmlFileName hashCode this xsltFileName hashCode MIMML MB M MLIIIPMPMBLPMM PHIEPMPMPMIMIMIIIIIIIIII p TPLYYVIII TP PC
8. See XSLT specification section 7 1 1 Literal Result Elements http www w3 org TR xsltzliteral result element xsl number xsl number level single or multiple or any count pattern from pattern value number expression format string lang nmtoken letter value alphabetic or traditional j grouping separator char grouping size number gt See XSLT specification section 7 7 Numbering http www w3 org TR xsltZ number xsl otherwise lt xsl otherwise gt Content template gt xsl otherwise See XSLT specification section 9 2 Conditional Processing with lt xsl choose gt http www w3 org TR xslt section Conditional Processing with xsl choose xsl output xsl output method xml or html or text or gqname but not ncname version nmtoken encoding string omit xml declaration yes or no standalone yes or no doctype public string doctype system string cdata section elements qnames indent yes or no media type string See XSLT specification section 16 Output http www w3 org TR xslt output xsl param xsl param name qname select expression gt lt Content template gt lt xsl param gt See XSLT specification section 11 Variables and Parameters htt
9. XML output array is empty when this happens The following code is a workaround byte origXML responseWrapper getBuffer if origXML null origXML length 0 just let Tomcat deliver its cached data back to the client chain doFilter req res return try do the XSLT transformation Transformer trans StylesheetCache newTransformer this xsltFileName ByteArrayInputStream origXMLIn new ByteArrayInputStream origXML Source xmlSource new StreamSource origXMLIn ByteArrayOutputStream resultBuf new ByteArrayOutputStream trans transform xmlSource new StreamResult resultBuf res setContentLength resultBuf size res setContentType text html res getOutputStream write resultBuf toByteArray y res flushBuffer yy catch TransformerException te throw new ServletException te The counterpart to the init method public void destroy this filterConfig null This filter requires the deployment descriptor to provide the name of the XSLT stylesheet as an initialization parameter The following line of code retrieves the parameter String xsltPath filterConfig getInitParameter xsltPath By passing the stylesheet as a parameter the filter can be configured to work with any XSLT Since the filter can be applied to a servlet JSP or static file the XML data is also completely configurable The doFilter method illus
10. 8 ELE L amp http localhost S080 servie BrowserrD M Seach e N TL A Home N My Netscape NetiProne Y 5 User Agent Nozilla 5 0 Windows U Windowsa NT 5 0 en US m18 Cecko 20001108 Netacape 0 Supporta CS3 true i JavaScript true Browser Name Mozilla Platform Windows Version 5 0 EE Docurnert Done we Seren NITET Fins Irtersce This servlet utilizes the org apache turbine util BrowserDetector class which is part of Apache s Turbine web application framework This class actually has only one dependency on anything else in Turbine so you can either comment out its reference to Turbine s RunData class or simply include the Turbine JAR files in your CLASSPATH Turbine can be obtained from http jakarta apache org The code for the servlet is shown in Example 8 8 14 This example is based on Version 2 1 of Turbine 15 Be sure to read and follow the Apache licensing agreement if you extract this cl ass from Turbine Example 8 8 BrowserlD java import java io import javax servlet import javax servlet http import org apache turbine util BrowserDetector public class BrowserID extends HttpServlet protected void doGet HttpServletRequest req HttpServletRespons res throws IOException ServletException BrowserDetector bd new BrowserDetector req getHeader User Agent res setContentType text plain PrintWriter pw res getWriter pw printl
11. lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Strict EN http www w3 org TR xhtmll DTD xhtmll Ltriet dtd html xmlns http www w3 org 1999 xhtml lt head gt tait lt hea Yn le Hello World lt title gt gt ello World lt p gt lt body gt lt html gt Some of the most important XHTML rules include e XHTML documents must be well formed XML and must adhere to one of the XHTML DTDs As expected with XML all elements must be properly terminated attribute values must be quoted and elements must be properly nested e The lt DOCTYPE gt tag is required e Unlike HTML tags must be lowercase e The root element must be lt html gt and must designate the XHTML namespace as shown in the previous example e lt head gt and body are required The preceding document adheres to the strict DTD which eliminates deprecated HTML tags and many style related tags Two other DTDs transitional and frameset provide more compatibility with existing web browsers but should be avoided when possible For full information refer to the W3C s specifications and documentation at http www w3 org As we look at more advanced techniques for processing XML with XSLT we will see that XML is not always dealt with in terms of a text file containing tags From a certain perspective XML files and their tags are really just a serialized representation
12. xsl template r 2 KKAKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKK KKK presidents templat Ck Ck ck Ck Ck kk Ck ck Ck Ck C Ck Ck CK Sk Ck Ck Ck Kk Ck kk Ck Sk Ck Sk Ck Sk Ck Ck ko kk Sk kk ko ko Sk ko ck ck Sk Ck ko Sk Mk ko Sk ko ko ko ko k gt lt xsl template match presidents gt ele KKEAKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKK Sorting using xsl for each Ck CK ck ck Ck Ck Sk Ck CK Ck SK Ck Ck Ck CK CK CC SK kk Kk Ck Ck Ck kk Sk CK Ck Ck kk Ck kk Ck kk kk Sk Kk kv ko Kk ko ko ko kk RH lt h2 gt All presidents sorted by first name using xsl for each h2 lt xsl for each select president gt lt xsl sort select name first gt lt xsl apply templates select name gt xsl for each See CK Ck ck Ck Ck ok CK kk kk kk Kk KK kk kk Sk Kk Kk kk kk kk SK Kk Kk KK Kk KG Ko k ok ckockokok ok Sorting using xsl apply templates Ck CK ck Ck kk Ck Sk Ck CK Ck Ck Ck Ck Ck KC CC Sk Sk Kk C Ck Ck Kk Sk Kk Ck Ck Ck Ck kk kk Ck Sk ko Sk ke kx o A kx ko ko ck X gt lt h2 gt All presidents sorted by first name using xsl apply templates lt h2 gt lt xsl apply templates select president name gt lt xsl sort select first gt xsl apply templates lt h2 gt All presidents sorted by date using xsl apply templates lt h2 gt xsl apply templates select president name gt xsl sort select term Gfrom data type number orde
13. year Integer parseInt request getParameter year catch Exception ex return new ErrorRenderer Invalid request BoardSummary board adapter getBoardSummary boardID if board null return new ErrorRenderer Invalid request return new ViewMonthRenderer board new MonthYear month year catch DataException de return new ErrorRenderer de Throughout this application a seemingly harsh approach to error handling is followed If any impossible requests are detected the user is presented with a terse error message try boardID Long parseLong request getParameter boardID month Integer parseInt request getParameter month year Integer parseInt request getParameter year catch Exception ex return new ErrorRenderer Invalid request When considering error handling approaches the primary concern should be break in attempts by hackers It is far too easy for a user to determine which parameters are passed to a web application and then try to wreak havoc by manually keying in various permutations of those parameters By checking for illegal parameters and simply rejecting them as invalid a web application gains a big security advantage Web Application Security In the ViewMonthRegHandler class a NumberFormatException is thrown if any of these parameters are nonnumeric or nul 1 Basically there are only two possible causes for t
14. lt xsl template gt This template matches all elements and the root node i e the document itself It will not match processing instructions comments attributes or text The lt xsl apply templates gt causes all children that are not attribute nodes or processing instruction nodes to be processed The second built in rule is identical to the first except it applies to each mode used in the stylesheet lt xsl template match mode m gt xsl apply templates mode m gt lt sl template gt Template modes are discussed in the next chapter so we will not go into details here The third built in rule simply copies all text and attribute nodes to the result tree lt xsl template match text gt value of select gt lt xs XSLT emplate gt And finally the built in rule for processing instructions and comments does nothing This is why comments and processing instructions in the input XML data do not automatically show up in the result tree lt xsl template match processing instruction comment 2 2 4 A Skeleton Stylesheet As your XML documents get more complex you will most likely want to break up your stylesheets into several templates The starting point is a template that matches the pattern lt xsl template match gt content lt xsl template gt This template matches the document itself and is usually where you output the basic lt htm1 gt
15. Example 10 5 Movie theater XML datafile lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xslt wml showtimes xslt gt lt movies gt 1 all movies gt moviedef id star warsl lt shortName gt Star Wars Ep 1 lt shortName gt lt longName gt Star Wars Episode I The Phantom Menace lt longName gt lt moviedef gt lt moviedef id star_wars4 gt lt shortName gt Star Wars lt shortName gt lt longName gt Star Wars A New Hope lt longName gt lt moviedef gt moviedef id star_wars5 gt lt shortName gt Emp Strikes Back lt shortName gt lt longName gt The Empire Strikes Back lt longName gt lt moviedef gt additional moviedef elements city id stl gt lt name gt St Louis lt name gt lt theater id westolivel6 gt lt name gt West Olive 16 lt name gt movie ref star warsl times 10 15a 3 30 12 30 5 45 7 15 10 30 lt times gt movie movie ref star wars4 lt times gt 1 30 4 00 6 00 lt times gt movie gt movie ref star_wars5 gt lt times gt 2 30 4 10 6 20 lt times gt movie gt lt movie ref back2future3 gt lt times gt 4 00 6 00 8 00 10 00 lt times gt lt movie gt lt theater gt theater id stcharles18 gt lt name gt St Charles 18 lt name gt lt movie ref star_wars4 gt lt times gt 10 15a 3 30 12 30 5 45 7 15 10 30 lt times gt lt movie gt movie ref star_wa
16. Let s look at some of the other options for St reamSource and St reamResult Example 5 4 is a modification of the Simp1eJaxp program that was presented earlier It downloads the XML specification from the W3C web site and stores it in a temporary file on your local disk To download the file construct a St reamSource with a system identifier as a parameter The stylesheet is a simple one that merely performs an identity transformation copying the unmodified XML data to the result tree The result is then sent to a St reamResult using its File constructor Example 5 4 Streams java package chap5 import java io import javax xml transform import javax xml transform stream A simple demo of JAXP 1 1 StreamSource and StreamResult This program downloads the XML specification from the W3C and prints it to a temporary file mf public class Streams an identity copy stylesheet private static final String IDENTITY_XSLT xsl stylesheet xmlns xsl http www w3 org 1999 XSL Transform version 1 0 gt lt xsl template match gt lt xsl copy of select gt lt xsl template gt lt xsl stylesheet gt the XML spec in XML format using an HTTP URL rather than a file URL private static String xmlSystemId http www w3 org TR 2000 REC xm1 20001006 xm1 public static void main String args throws IOException TransformerException show how to read from a system ide
17. a ow println div pw printin lt body gt pw printin lt html gt Beginning with the import statements note that the servlet API is in the javax serviet and javax servlet http packages These packages are not part of the Java 2 Standard Edition they are considered a required API of the Java 2 Platform Enterprise Edition Although many servlet implementations are available Apache s Tomcat is the reference implementation officially sanctioned by Sun Every example in this book works with Version 4 0 of Tomcat and should also work on any compliant servlet implementation You can download Tomcat at http jakarta apache org As shown in Figure 6 1 SplashScreenServiet is a subclass of HttpServiet The first method we override is getServletInfo which simply returns a brief description of this servlet Although optional this text will show up in the administrative console of many servlet containers The doGet method is next which is designed to handle each client request It is important to remember that this method needs to be thread safe because many clients could potentially share this servlet instance and call doGet concurrently You may notice that doGet isa protected method The call sequence is as follows 1 The servlet container invokes the service method on HttpServiet 2 HttpServlet figures out the type of request GET POST 3 HttpServlet invokes the correspo
18. a new message a publ 7 lic PostMsgRenderer BoardSummary board this board null false This constructor is used when the user submitted a form but did not fill out all required fields af publ lic PostMsgRenderer BoardSummary board MessageSummary inResponseToMsg boolean showError String msgSubject String authorEmail String msgText this board board this inResponseToMsg inResponseToMsg this showError showError this msgSubject msgSubject this authorEmail authorEmail this msgText msgText public void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException convert the data into XML a JDOM Document Document doc new Document PostMessageJDOM produceElement nis board his inResponseToMsg his showError his msgSubject his authorEmail nis msgText ct ct ct ct ct ct apply the appropriate stylesheet XSLTRenderHelper render servlet doc postMsg xslt response As the code shows this class has several constructors that support different modes of operation The first constructor does the most work prefixing the original message with gt characters as many email clients do when creating replies to existing messages Other than having several constructors however the renderer works just like other renderers in the
19. new org apache xml serialize OutputFormat doc UTF 8 true org apache xml serialize XMLSerializer serial new org apache xml serialize XMLSerializer System out fmt serial serialize doc getDocumentElement yey As we will see in Chapter 5 JAXP 1 1 does provide a mechanism to perform this task using its transformation APIs so we do not technically have to use the Xerces code listed here The JAXP approach maximizes portability but introduces the overhead of an XSLT processor when all we really need is DOM 1 2 4 3 JDOM DOM is specified in the language independent Common Object Request Broker Architecture Interface Definition Language CORBA IDL allowing the same interfaces and concepts to be utilized by many different programming languages Though valuable from a specification perspective this approach does not take advantage of specific Java language features JDOM is a Java only API that can be used to create and modify XML documents in a more natural way By taking advantage of Java features JDOM aims to simplify some of the more tedious aspects of DOM programming JDOM is not a W3C specification but is open source software available at http www jdom org JDOM is great from a programming perspective because it results in much cleaner more maintainable code Since JDOM has the ability to convert its data into a standard DOM tree it integrates nicely with any other XML tool JDOM can also utilize whatever XML parser
20. null amp amp te getCause te getException t te getCause printStackTrace pw return sw toString Part of the TableModel interfac ae public Object getValueAt int row int column if this exceptionList null return No errors or warnings else TransformerException te TransformerException this exceptionList get row SourceLocator loc te getLocator switch column case LINE_COL return loc null String valueOf loc getLineNumber N A case COLUMN COL return loc null String valueOf loc getColumnNumber N A case PUBLIC ID COL return loc null loc getPublicId N A case SYSTEM ID COL return loc null loc getSystemId N A case MESSAGE AND LOC COL return te getMessageAndLocation case LOCATION COL return te getLocationAsString case EXCEPTION COL return te getException case CAUSE COL return te getCause default return error shouldn t happen Part of the TableModel interfac public int getRowCount return this exceptionList null 1 this exceptionList size Part of the TableModel interfac T public int getColumnCount return this exceptionList null 1 COLUMN NAMES length Part of the TableModel interfac x public String getCo
21. xmlOut output xmlDoc sw this xmlArea setText sw toString catch Exception ex this statusLabel setText Data could not be displayed show the stack trace in the text area StringWriter sw new StringWriter ex printStackTrace new PrintWriter sw this xmlArea setText sw toString XMLOutputPanel is responsible for parsing the result tree to determine if it is well formed and valid XML It starts by parsing the text using a validating parser simply ignoring errors If no errors occur the document is well formed valid XML and can be displayed in the text area Otherwise the document is parsed again only without any validation This allows the code to determine if the XML is at least well formed If the document is not well formed or valid the parser s stack trace is displayed in the GUI For many XSLT transformations the result tree may not be XML and this message can simply be ignored When errors do occur however this should make it much easier to locate the problems 9 3 Performance Techniques One common criticism of XSLT is its performance The overhead of transformation from XML to another format is the price paid for clean separation between data and programming logic as well as the ability to customize transformations for different clients In this section we look at strategies for improving performance without giving up the benefits that XSLT offers The actual XSLT transformation
22. Figure 9 9 Generating XML in the EJB tier ainer Client XML Text object serialization XML Text cust cust TL Me 73 id 3 id 00110101000111 lt id gt 3 lt i gt lt Cust gt cust Another variation on this theme is to use a helper class whose sole responsibility is to produce XML from a bean rather than embedding the XML production directly in the bean The EJB component is responsible for generating XML before sending a response to the client Although DOM is shown in the figure JDOM or any other XML generation API may be used The client whether a servlet container or a standalone Java client sees XML only from the server At one extreme each of these XML strings is a well formed XML document Another option perhaps more useful is returning fragments of XML The client can then assemble many of these XML fragments into more complex XML documents While this does put slightly more burden on the client to assemble the pieces properly it does offer significantly more flexibility This approach may seem like it offers the cleanest interface to the EJB tier As long as the structure of the XML remains the same both client and server can change their internal object models without affecting the other Many DOM implementations are not comprised of Serializable Java objects Furthermore the client may not use the same DOM implementation that the server uses For these reasons it is
23. The following list summarizes the basic rules for a well formed XML document e It must contain exactly one root element the remainder of the document forms a tree structure in which every element is contained within exactly one parent e All elements must be properly terminated For example lt name gt Eric lt name gt Is properly terminated because the lt name gt tag is terminated with lt name gt In XML you can also create empty elements like lt married gt e Elements must be properly nested This is legal lt b gt lt i gt bold and italic lt i gt lt b gt But this is illegal lt b gt lt i gt bold and italic lt b gt lt i gt e Attributes must be quoted using either quotes or apostrophes For example lt date month march day 01 year 1971 gt e Attributes must contain name value pairs Some HTML elements contain marker attributes such as lt td nowrap gt In XHTML you would write this as lt td nowrap nowrap gt This is compatible with XML and should work in existing web browsers This is not the complete list of rules but is sufficient to get you through the examples in this book Clearly most HTML documents are not well formed Many tags such as lt br gt or lt hr gt violate the rule that all elements must be properly terminated In addition browsers do not complain when attribute values are not quoted This will have interesting ramifications for us when we write XSLT stylesheets
24. convert the data into XML a JDOM Document Document doc new Document HomeJDOM produceElement boards apply the appropriate stylesheet XSLTRenderHelper render servlet doc home xslt response catch DataException de new ErrorRenderer de render servlet request response ViewMonthRegHandler shown in Example 7 33 is slightly more complex than the home page request handler Since this request handler requires the board id month number and year number as parameters it must perform validation before it can handle the request properly Example 7 33 ViewMonthReqHandler java package com oreilly forum servlet import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import java io import javax servlet import javax servlet http Handle a request to view a month for a message board public class ViewMonthReqHandler extends ReqHandler protected String getPathInfo return viewMonth protected Renderer doGet HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException try DataAdapter adapter DataAdapter getInstance these are all required parameters long boardID OL int month 0 int year 0 try boardID Long parseLong request getParameter boardID month Integer parseInt request getParameter month
25. gt xsl apply templates select schedule show lt table gt lt body gt lt html gt lt xsl template gt show as a row in the table td xsl value of select channel gt lt td gt td xsl value of select from gt lt td gt td gt lt xsl value of select to gt lt td gt lt td gt lt xsl value of select title gt lt td gt lt tr gt lt xsl template gt xsl stylesheet The remaining piece of the puzzle is to write a servlet that combines all of these pieces and delivers the result of the XSLT transformation to the client see Chapter 6 In a nutshell the servlet acts as a controller between the various components doing very little of the actual work The client request is intercepted by the servlet which tells ScheduleJDO M to produce the XML data This XML is then fed into an XSLT processor such as Xalan along with schedule xslt Finally the output is sent to the browser as HTML XHTML WML or some other format Another interesting option made possible by this architecture is allowing the client to request raw XML without any kind of XSLT transformation This allows your web site to support nonbrowser clients that wish to extract meaningful business data in a portable way We examined the weaknesses of other approaches so it is only fair to take a critical look at the XSLT approach First XSLT is a new language that developers or web content authors have t
26. lt Recursively show the message tree gt xsl apply templates select viewMonth message gt lt body gt lt html gt lt xsl template gt 5 KEKKKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK ck Sk Sk kx ko kx k ko kx Display a one line summary for each message KKKKKKKKKKKKKK ck ck ck ck ck ck ck ck ck k ck ck kc kckck ck k ck ck k ck ck k KKK ck ck kck ck k KKK ck k k KK lt xsl template match message gt lt xsl param name indent select 0 gt indent according to the indent parameter gt lt div style margin left indent em gt lt a href viewMsg msgID id gt lt xsl value of select subject gt lt a gt lt xsl text gt posted by lt xsl text gt lt xsl apply templates select authorEmail gt lt xsl text gt on lt xsl text gt lt xsl value of select day gt xsl text disable output escaping yes gt amp amp nbsp xsl call template name utils printShortMonthName gt xsl with param name monthNumber select global monthNum gt xsl call template xsl text disable output escaping yes gt amp amp nbsp lt xsl value of select Sglobal yearNum gt lt recursively select all messages that are responses to this one Increment the indentation with each call gt xsl apply templates select message xsl with param name indent select indent 1 xsl apply templates div xsl templa
27. lt p gt 4 00 6 00 8 00 10 00 lt p gt lt card gt lt wml gt This WML file illustrates how to define and use a lt t emplate gt which is a piece of reusable markup that can be shared by all cards in the deck This particular template defines a Back button displayed on each instance of the Showtimes card allowing the user to easily return to the list of movies Since the Back button should not appear on the movie list card it is shadowed as follows do name common prev type prev gt lt noop gt lt do gt The lt noop gt element stands for No Operation and effectively removes the lt do gt element defined by the common prev template When cards define elements with the same names as templates the card elements take precedence The card can choose to modify the behavior of the template or simply suppress it with the lt noop gt tag as shown here The screen shot shown in Figure 10 7 illustrates how these cards look in a cell phone As shown the Back button does not appear in the list of movies but does appear in the Showtimes card Figure 10 7 Showtimes WML output P Nokia 7110 Jan 7000 ESI Ix Ea ooo 0020 Vv ELA l WM ILA Movies Showtimes O Fallon Cine Indiana Jones and The Select a movie Temple of Doom Raiders Lost Ark 1 30 4 00 6 00 Temple of The final screen shot shown in Figure 10 8 shows how a web browser takes advantage of its large display area by displayin
28. lt pathelement path z lib jdom beta6 jar path amp l KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKK Create the output directory structure KKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKK KKK KKK KK KKK KKK KK lt target name prepare gt lt mkdir dir builddir gt lt target gt lt KKEKKKKKKKKKKKKKKKKKKKEKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Show a brief usage message This is the default target and shows up when the user types ant KCKCKCkCkCkck ck ck k ck ck kc kckckckck ck ck k ck ck kck ck kc kckck ck ck ck ck k ck ck k ck ck k KKK ck ck kc KKK kk M target name help description Show a brief help message gt echo message Chapter 9 Example Ant Build File echo message Type ant projecthelp for more assistance target KKKKKKKKKKKKKKKK KKK KKK KK KKK KKK KKK KKK KKK ck k ck ck k ck ck kk ck k kk kk KK Remove th ntire build directory KCKCKCKCK kk Kk SK Kk KICK SK CK SK KIKI SKK Kk Sk KG KC Kk CK KKK ck kk k kk kk target name clean description Remove all generated code gt delete dir builddir gt target Sl Ck Ck kk Ck C Ck S Ck SC Ck KC Ck Ck Ck Ck Kk Ck C Ck Ck Ck Ck kk Sk kk Sk Kk kk ko ke A x kx ko ko ko kokok Compile the com oreilly javaxslt swingtrans package KCKCk CK CK kk CK Ck CK Kk CK CK SK Ck CK Ck SKK SIC Kk KU KK Sk KK KC KC kk k ck k ck k k ko kk gt target name compile de
29. lt ul gt lt xsl apply templates select customer gt lt ul gt lt xsl template gt lt the inner template is repeated for each customer gt lt xsl template match customer gt li xsl value of select name gt lt 1i gt lt xsl template gt 2 3 Another XSLT Example Using XHTML Example 2 5 contains XML data from an imaginary scheduling program A schedule has an owner followed by a list of appointments Each appointment has a date start time end time subject location and optional notes Needless to say a true scheduling application probably has a lot more data such as repeating appointments alarms categories and many other bells and whistles Assuming that the scheduler stores its data in XML files we can easily add features later by writing a stylesheet to convert the existing XML files to some new format Example 2 5 schedule xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href schedule xslt schedule owner name lt first gt Eric lt first gt lt last gt Burke lt last gt lt name gt lt owner gt lt appointment gt lt when gt date month 03 day 15 year 2001 gt lt startTime hour 09 minute 30 gt lt endTime hour 10 minute 30 gt lt when gt lt subject gt Interview potential new hire lt subject gt lt location gt Rm 103 lt location gt lt note gt Ask Bob for an updated resume lt note gt lt appoint
30. public Document createDocument Library library throws javax xml parsers ParserConfigurationException Use Sun s Java API for XML Parsing to create the DOM Document javax xml parsers DocumentBuilderFactory dbf javax xml parsers DocumentBuilderFactory newInstance javax xml parsers DocumentBuilder docBuilder dbf newDocumentBuilder Document doc docBuilder newDocument NOTE DOM does not provide a factory method for creating lt DOCTYPE library SYSTEM library dtd gt Apache s Xerces provides the createDocumentType method on their DocumentImpl class for doing this Not used here create the library document root element Element root doc createElement library doc appendChild root add publisher children to the library element Iterator publisherIter library getPublishers iterator while publisherIter hasNext Publisher pub Publisher publisherIter next Element pubElem createPublisherElement doc pub root appendChild pubElem now add lt book gt children to the lt library gt element Iterator bookIter library getBooks iterator while bookIter hasNext Book book Book bookIter next Element bookElem createBookElement doc book root appendChild bookElem return doc private Element createPublisherElement Document doc Publisher pub Element pubElem doc crea
31. tasks lt target gt lt target name compile depends prepare gt tasks lt target gt lt target name distribute depends compile gt tasks lt target gt project For each target Ant is smart enough to know if files have been modified and if it needs to do any work For compilation the timestamps of c ass files are compared to timestamps of java files Through these dependencies Ant can avoid unnecessary compilation and perform quite well Although the targets shown here contain only single dependencies it is possible for a target to depend on several other targets wyw X target name depends A B C gt Although Ant build files are much simpler than corresponding Makefiles complex projects can introduce many dependencies that are difficult to visualize It can be helpful to view the complete list of targets with dependencies displayed visually such as in a hierarchical tree view XSLT can be used to generate this sort of report 3 6 2 Stylesheet Functionality Since the build file is XML XSLT makes it easy to generate HTML web pages that summarize the targets and dependencies Our stylesheet also shows a list of global properties and can easily be extended to display anything else contained in the build file Although this stylesheet creates several useful HTML tables in its report its most interesting feature is the ability to display a complete dependency graph of all Ant build tar
32. xsl apply templates select city Qid city id lt p gt lt em gt lt a href movieguide gt Change city lt a gt lt em gt lt p gt lt card gt wml xsl template KKK KK KKK Ck Ck KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KK KK Show details for a city KKKKKKKKKKKKKKKKKKKKAKKKK KK KKKKKKKKKKKKKAKKKKKKKKKAKKKAKKKKKKK k ck ck k k ko KKK lt xsl template match city gt lt p gt lt big gt lt xsl value of select name gt lt big gt lt p gt lt p gt Select a theater lt p gt lt p gt show a list of all theaters in this city gt xsl apply templates select theater gt lt p gt lt xsl template gt Sie kkxkkx xkxkx x xk x xk xkx xkxk xk xk xkx x xkxkxkxk kxk x xkxk kx x xk x xk kxkx xkxkx xk xk xkxkxkx xkxkx kxk xk kx xkxkxkxkxk xkxk xkxk xkxkxk kxk xk xk kxx xxk kxx k Create a link for an individual theater CK CKCKCkCk ck ck ck ckck ck ckckckckckck ck ck ck ck ck ckckck ck ck ckck ck ck ck kckckck kckck ck k ck ck k ck ck k ck ck k ck k ck KKK KKK KKK KKK gt xsl template match theater a href movieguide action showtimes amp city Scity_id amp theater id gt lt xsl value of select name gt lt la gt lt br gt lt xsl template gt lt xsl stylesheet gt Unlike the first stylesheet this one requires a parameter for the city xsl param name
33. 7 public abstract void parse InputSource input throws IOException SAXException public boolean getFeature String name throws SAXNotRecognizedException SAXNotSupportedException Boolean featureValue Boolean this featureMap get name return featureValue null false featureValue booleanValue public void setFeature String name boolean value throws SAXNotRecognizedException SAXNotSupportedException this featureMap put name new Boolean value public Object getProperty String name throws SAXNotRecognizedException SAXNotSupportedException return this propertyMap get name public void setProperty String name Object value throws SAXNotRecognizedException SAXNotSupportedException this propertyMap put name value public void setEntityResolver EntityResolver entityResolver this entityResolver entityResolver public EntityResolver getEntityResolver yo i return this entityResolver public void setDTDHandler DTDHandler dtdHandler this dtdHandler dtdHandler public DTDHandler getDTDHandler return this dtdHandler public void setContentHandler ContentHandler contentHandler this contentHandler contentHandler public ContentHandler getContentHandler return this contentHandler public void setErrorHandler ErrorHandler errorHandler this errorHandler errorHandler public ErrorHandl
34. BorderLayout CENTER add this statusLabel BorderLayout NORTH iparam xml the actual XML data to display param uri the location of the XML thus allowing the parser to locate the DTD E public void setXML String xml String uri return quickly if the XML has already been set if xml null xml equals this xml return this xml xml use JDOM to parse the XML Document xmlDoc null try attempt to validate the XML SAXBuilder saxBuilder xmlDoc new SAXBuilder true saxBuilder build new StringReader this xml uri this statusLabel setText XML is well formed and valid catch Exception ignored the data is not valid but we should parse it again to see if it is well formed if xmlDoc null try don t validate SAXBuilder saxBuilder new SAXBuilder false saxBuilder build new StringReader this xml xmlDoc this statusLabel setText XML is well formed but not valid catch Exception ex this statusLabel setText Data is not well formed XML show the stack trace in the text area StringWriter sw new StringWriter ex printStackTrace new PrintWriter sw this xmlArea setText sw toString iff the document was parsed show it if xmlDoc null bry 4 pretty print the XML by indenting two spaces XMLOutputter xmlOut new XMLOutputter true StringWriter sw new StringWriter
35. Looking beneath the hood will reveal a much different picture however in which HTML is used only during the last instant of presentation Web applications must support a multitude of browsers and the easiest way to do this is to simply transform data into HTML before sending it to the client On the server side XML is the preferred way to process and exchange data because it is portable standard and easy to work with This is where Java and XSLT enter the picture 1 1 Java XSLT and the Web Extensible Stylesheet Language Transformations XSLT is designed to transform XML data into some other form most commonly HTML XHTML or another XML format An XSLT processor such as Apache s Xalan performs transformations using one or more XSLT stylesheets which are also XML documents As Figure 1 1 illustrates XSLT can be utilized on the web tier while web browsers on the client tier deal only with HTML Figure 1 1 XSLT transformation Web Browser 1 Web Tier i licii id tabase uipu XSL Proceso i O REILLY s XSLT Stylesheet Typically in an XSLT and Java based web application XML data is generated dynamically based on database queries Although some newer databases can export data directly as XML you will often write custom Java code to extract data using JDBC and convert it to XML This XML data such as a customized list of benefit elections or perhaps an airline schedule for a
36. case XHTML CLIENT TYPE res setContentType text html break case WML CLIENT TYPE res setContentType text vnd wap wml break default res sendError HttpServletResponse SC INTERNAL SERVER ERROR pageToShow return File xsltFile locateStylesheet req clientType prepare for the transformation using JAXP TransformerFactory transFact TransformerFactory newlInstance Transformer trans transFact newTransformer new StreamSource xsltFile pass parameters to the XSLT stylesheet if city null trans setParameter city id city if theater null trans setParameter theater id all pages XML data file both WML and XHTML theater share the exact same InputStream xmliIn getServletContext getResourceAsStream WEB INF xml movies xml do the transformation trans transform new StreamSource xmlIn new Strea catch TransformerE throw new Servlet iparam clientType one of the cons either WML CLIENT TYPE or XHTML Cl mResult res getOutput Stream xception te Exception te ta iT nts defined in this class ENT_TYPE param pageToShow one of the class _PAGE constants defined by this return a file representing the appropriate XSLT stylesheet a private File locateStylesheet HttpServlet Request req
37. gt html xmlns http www w3 org 1999 xhtml lt copy the head from the source document gt xsl copy of select html head body lt this table defines the overall layout of the page gt table width 100 cellpadding 4 cellspacing 0 border 0 gt tr bgcolor f0f0f0 gt lt td colspan 2 gt xsl call template name createTopNavbar gt lt td gt lt tr gt lt tr valign top gt td bgcolor cccccc width 150px gt xsl call template name createLeftNavbar gt lt td gt td bgcolor white gt d XC Ck C CK Ck C Ck C CC Ck KC Ck KC Ck C Ck Kk Ck CK Ck kk Ck kk Sk kk kk Ke x Mk Kk kx ko ko ko ko ko Copy all contents of the body from the source XHTML document to the result tree XHTML document KCKCK CK CK Ck SK KK Kk CK CK CK Ck KICK KK CK KK Kk KK KC KO KKK k ck ck k ko k kk xsl copy of select html body html body text td tr table body html xsl template fee AC Ck KC Ck C Ck S Ck KC Ck Ck SK Ck Ck Kk Ck Ck Kk Ck Ck Ck CK kk Ck Ck Ck Sk kk kk kk kk SK x Sk Kk kx ko k ko ko ko This template produces the top navigation bar KKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKK KC k ko k ck k kc k kk xsl template name createTopNavbar xsl call template name navButton gt xsl with param name category select home gt xsl with param name displayName select Home
38. import javax servlet http Handles GET and POST requests for the page that allows users to post or reply to a message public class PostMsgReqHandler extends ReqHandler protected String getPathInfo return postMsg When an HTTP GET is issued show the web page for the first time protected Renderer doGet HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException try mode must be postNewMsg or replyToMsg String mode request getParameter mode DataAdapter adapter DataAdapter getInstance if replyToMsg equals mode long origMsgID Long parseLong request getParameter origMsgID Message inResponseToMsg adapter getMessage origMsgID if inResponseToMsg null return new PostMsgRenderer inResponseToMsg else if postNewMsg equals mode long boardID Long parseLong request getParameter boardID BoardSummary board adapter getBoardSummary boardID if board null return new PostMsgRenderer board return new ErrorRenderer Invalid request catch NumberFormatException nfe return new ErrorRenderer nfe catch DataException de return new ErrorRenderer de Handles HTTP POST requests indicating that the user has filled in the form and pressed the Submit button 7 protected Renderer
39. link href SrootDir forum css rel stylesheet type text css gt lt head gt The XSLT processor does not actually deal with the CSS file From the perspective of XSLT the lt link gt tag is just text that is copied to the result tree during the transformation process Later when the web browser displays the XHTML page the actual CSS file is loaded This technique is great because styles can be shared across all web pages without complicating the XSLT stylesheets The remainder of the stylesheet is pretty basic just matching patterns in the XML and producing XHTML content to the result tree One important thing to point out here is the way that hyperlinks are created lt a href forum main postMsg mode postNewMsg amp boardID id gt Post Message lt a gt Since the ampersand character is not allowed in an XML attribute value it must be written using the amp built in entity As it turns out browsers deal with this just fine and the hyperlink works anyway We will see this again when dealing with WML in Chapter 10 What Is the URL You may be wondering how you are supposed to know what each hyperlink is actually supposed to be At this stage of the game you probably will not know and your links will actually look something like this a href TODO link to post a new message gt Post Message lt a gt This is fine for now because you really won t know what to put there until the servlets are f
40. oneQuoteFound true else oneQuoteFound false twoQuotesFound false if twoQuotesFound twoQuotesFound false oneQuoteFound false curIndex continue buf append curChar curindextt return buf toString CSVXMLReader is a subclass of Abst ract XMLReader so it must provide an implementation of the abstract parse method public void parse InputSource input throws IOException SAXException if no handler is registered to receive events don t bother to parse the CSV file ContentHandler ch getContentHandler if ch null return j The first thing this method does is check for the existence of a SAX ContentHandler The base class Abst ract XMLReader provides access to this object which is responsible for listening to the SAX events In our example an instance of JAXP s TranstormerHandler is used as the SAX ContentHandler implementation If this handler is not registered our parse method simply returns because nobody is registered to listen to the events In a real SAX parser the XML would be parsed anyway which provides an opportunity to check for errors in the XML data Choosing to return immediately was merely a performance optimization selected for this class The SAX Input Source parameter allows our custom parser to locate the CSV file Since an InputSource has many options for reading its data parsers must check each potential source in the order shown he
41. package com oreilly javaxslt swingtrans import java awt import java awt event import java io import javax swing The entry point into this application This class displays the main window allowing the user to select an XML file and an XSLT file public class SwingTransformer extends JFrame private JTextField xmlFileFld new JTextField 30 private JTextField xsltFileFld new JTextField 30 file filters used with the JFileChooser class private XMLFileFilter xmlFilter new XMLFileFilter yy private XSLTFileFilter xsltFilter new XSLTFileFilter private JFileChooser fileChooser new JFileChooser actions are hooked up to the JButtons private Action loadXMLAction new javax swing AbstractAction Select XML public void actionPerformed ActionEvent evt selectXMLFile private Action loadXSLTAction new javax swing AbstractAction Select XSLT public void actionPerformed ActionEvent evt selectXSLTFile private Action transformAction new javax swing AbstractAction Transform public void actionPerformed ActionEvent evt File xmlFile new File xmlFileFld getText File xsltFile new File xsltFileFld getText if xmlFile exists xmlFile canRead showErrorDialog Unable to read XML file return if xsltFile exists xsltFile canRead showE
42. public DayMonthYear getCreateDate return this createDate public BoardSummary getBoard return this board public String getSubject return this subject public String getAuthorEmail return this authorEmail public boolean equals Object obj if obj instanceof MessageSummaryImpl MessageSummaryImpl rhs MessageSummaryImpl obj return this id rhs id return false public int hashCode return int this id Sorts by create date followed by message subject tf public int compareTo Object obj if this obj return 0 MessageSummaryImpl rhs MessageSummaryImpl obj int comparison this createDate compareTo rhs createDate if comparison 0 return comparison comparison this subject compareTo rhs subject if comparison 0 return comparison return 0 MonthYear java shown in Example A 9 groups a month and year together It also supports sorting Example A 9 MonthYear java package com oreilly forum domain import java io Serializable import java util Represents a month and a year f public class MonthYear implements Comparable Serializable private int month private int year Construct a new object representing the current instant in time Laird public MonthYear this new Date Construct a new object with the given date public MonthY
43. term from selects the from attribute of term children of the context node s parent 2 5 Looping and Sorting As shown throughout this chapter you can use lt xsl apply templates gt to search for patterns in an XML document This type of processing is sometimes referred to as a data driven approach because the data of the XML file drives the selection process Another style of XSLT programming is called template driven which means that the template s code tends to drive the selection process 2 5 1 Looping with lt xsl for each gt Sometimes it is convenient to explicitly drive the selection process with an xs1 for each element which is reminiscent of traditional programming techniques In this approach you explicitly loop over a collection of nodes without instantiating a separate template as lt xsl apply templates gt does The syntax for xs1 for eacnh is as follows lt xsl for each select president gt esi res content for each president element lt xsl for each gt The select attribute can contain any XPath location path and the loop will iterate over each element in the resulting node set In this example the context is lt president gt for all content within the loop Nested loops are possible and could be used to loop over the list of lt vicePresident gt elements 2 5 2 Sorting Sorting can be applied in either a data driven or template driven approach In either case xsl sort is added as
44. As HTML grows ever more complex the benefits of a clean separation become increasingly obvious As you probably well know browsers are not entirely compatible with one another As a web application developer this generally means that you have to test on a wide variety of platforms XSLT offers support in this area because you can write reusable stylesheets for the consistent parts of HTML and import or include browser specific stylesheet fragments to work around browser incompatibilities Of course the underlying XML data and programming logic is shared across all browsers even though you may have multiple stylesheets Finally we have the issue of concurrency In the servlet model a single servlet instance must handle multiple concurrent requests Although you can explicitly synchronize access to a servlet this often results in performance degradation as individual client requests queue up waiting for their turn Processing requests in parallel will be an important part of our XSLT based servlet designs in later chapters 1 3 2 Web Applications The difference between a web site and a web application is subjective Although some of the technologies are the same web applications tend to be far more interactive and more difficult to create than typical web sites For example a web site is mostly read only with occasional forms for submitting information For this simple technologies such as HTML combined with JavaServer Pages JSPs c
45. For the constructors that take InputStream and Reader as arguments the first argument provides either the XML data or the XSLT stylesheet The second argument if present is used to resolve relative URI references in the document As mentioned before your XSLT stylesheet may include the following code xsl import href commonFooter xslt By providing a system identifier as a parameter to the St reamSource you are telling the XSLT processor where to look for commonFooter xsit Without this parameter you may encounter an error when the processor cannot resolve this URI The simple fix is to call the setSystemId method as follows construct a Sou Source mySrc n specify a system ID a String so the Source can resolve relativ URLS that are encountered in XSLT stylesheets mySrc setSystemId aSystemId ource that reads from an InputStream ew StreamSource anInputStream D The documentation for St reamSource also advises that Input St ream is preferred to Reader because this allows the processor to properly handle the character encoding as specified in the XML declaration StreamResult is similar in functionality to St reamSource although it is not necessary to resolve relative URIs The available constructors are as follows public StreamResult public StreamResult File f public StreamResult String systemId public StreamResult O public StreamResult W utputStream byteStream riter characterStream
46. In the previous example the overall performance of an application was measured with Apache s JMeter This is a great way to prove that an application scales well under stress and it allows for comparisons between different software hardware and database configurations If you reach a point where an application is simply not scaling as required however additional techniques must be employed to isolate bottlenecks within Java code Tools such as JMeter show performance from an end user s perspective rather than on a per method basis within a Java application 9 3 2 1 Commercial options One approach is to purchase a commercial profiling tool such as Sitraka s JProbe available from http www sitraka com or VMGear s Optimizelt from http www vmgear com Among other things these tools can report how many times each method in an application is called how much time is spent in each method and how much memory is allocated The huge advantage of tools such as these is their unique ability to tell you exactly where the hotspots are within Java code In general a small fraction of methods consumes a vast majority of resources Optimizing these specific methods often yields the biggest performance gains with the least amount of effort Typically referred to as the 80 20 rule 9 3 2 2 JVMPI Sun s Java 2 SDK offers a set of command line options that enable the Java Virtual Machine Profiling Interface JVMPI which can write detailed pr
47. It is assumed that the specified table has a column named id of type long It is assumed that that all parts of the program will use this method to compute new IDs return the next available unique ID for a table public static synchronized long getNextID String tableName Connection con throws SQLException Statement stmt null try if a max has already been retrieved from this table compute the next id without hitting the database if tableToMaxIDMap containsKey tableName Long curMax Long tableToMaxIDMap get tableName Long newMax new Long curMax longValue 1L tableToMaxIDMap put tableName newMax return newMax longValue stmt con createStatement s ResultSet rs stmt executeQuery SELECT MAX id FROM tableName long max 0 if rs next max rs getLong 1 maxt tableToMaxIDMap put tableName new Long max return max finally just close the statement close stmt null DBUtil has a private class field called t abl eToMaxIDMap that keeps track of the largest unique id found in each table This works in conjunction with the get Next ID method which returns the next available unique id for a given table name By keeping the unique ids cached in the Map the application reduces the required database hits It should be noted that this approach is likely to fail if anyone manually adds a new id to the database wi
48. Sglobal email size 60 maxlength 70 gt lt td gt lt tr gt lt tr valign top gt lt td gt Message lt td gt lt td gt xsl text prevents the XSLT processor from collapsing to lt textarea gt which caused problems with many browsers gt textarea name msgText wrap hard rows 12 cols 60 gt lt xsl value of select Sglobal message gt lt xsl text gt lt xsl text gt lt textarea gt lt td gt lt tr gt The last table row contains a submit and cancel button tr td td td input type submit name submitBtn value Submit gt input type submit name cancelBtn value Cancel td tr lt body gt lt html gt lt xsl template gt gla KKK KKK RK KKK KR KK KR KK KK KKK KKK KKK KKK KK RK KK KK KKK KKK KKK KKK KEKE Show the text In Response to Msg Subject Kok KK Ck kk ck kk KR OK ck ckckckckckckckckckckckckckckckckckckck kk kk lt xsl template match inResponseTo gt lt div gt In Respons lt span style font weight bold gt lt xsl value of select subject gt lt span gt lt div gt lt xsl template gt lt xsl stylesheet gt e tos Since this stylesheet must work for posting new messages as well as for replying to messages it must determine the appropriate mode of operation This can be accomplished by checking for the existence of elements that occur only in one mode or the other For exam
49. The deployment descriptor is always called web xml and must be placed directly in the WEB INF directory of your web application The job of the deployment descriptor is to provide the servlet container with complete configuration information about a web application This may include security attributes aliases for servlets and other resources initialization parameters and even graphical icons for Integrated Development Environments IDEs to utilize For our needs a very small subset of this functionality will be sufficient For SolashScreenServlet we need to list the Java class of the servlet an alias for that servlet and a URL mapping The complete deployment descriptor for SolashScreenServlet is listed in Example 6 2 Example 6 2 web xml for SplashScreenServlet java lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 2 EN http java sun com j2ee dtds web app 2 2 dtd web app lt servlet gt define an alias for the Servlet gt gt splashScreen lt servlet name gt A ervlet ervlet cla s chap6 SplashScreenServlet servlet class servlet mapping pl associate the with a URL pattern servlet name spla cen servlet name url pattern splash url pattern servlet mapping web app The DOCTYPE is a required element of a deployment descriptor and must match what is shown
50. but perhaps the most promising prospect is XHTML Basic XHTML Basic is backed by the W3C and is primarily based on several XHTML modules Its designers had the luxury of coming after WML so they could incorporate many WML concepts and build on that experience Because of the uncertainties in the wireless arena an XML and XSLT approach is the safest available today Encoding your data in XML enables flexibility to support any markup language or protocol on the client hopefully without rewriting major pieces of Java code Instead new XSLT stylesheets are written to support new devices and protocols An added benefit of XSLT is its ability to support both traditional browser clients and newer wireless clients from the same underlying XML data and Java business logic 1 4 Getting Started The best way to get started with new technologies is to experiment For example if you do not know XSLT you should experiment with plenty of stylesheets as you work through the next two chapters Aside from trying out the examples that appear in this book you may want to invent a simple XML data file that represents something of interest to you such as your personal music collection or family tree Using XSLT stylesheets try to create web pages that show your data in many different formats Once the basics of XSLT are out of the way servlets will be your next big challenge Although the servlet API is not particularly difficult to learn configuration and dep
51. call this method from its destroy method Wy public static void closeAllConnections NOTE if connection pooling is ever implemented close the connections here Store a long text field in the database For example a message s text will be quite long and cannot be stored using JDBC s setString method sy public static void setLongString PreparedStatement stmt int columnIndex String data throws SQLException if data length gt 0 stmt setAsciiStream columnIndex new ByteArrayInputStream data getBytes data length else this else condition was introduced as a bug fix It was discovered that the setAsciiStream code shown above caused MS Access throws a function sequence error when the string was zero length This code now works stmt setString columnIndex return a long text field from the database ef public static String getLongString ResultSet rs int columnIndex throws SQLException try InputStream in rs getAsciiStream columnIndex if in null return byte arr new byte 250 StringBuffer buf new StringBuffer int numRead in read arr while numRead 1 buf append new String arr 0 numRead numRead in read arr return buf toString catch IOException ioe ioe printStackTrace ys throw new SQLException ioe getMessage 3 Compute a new unique ID
52. city_id select st1 gt For testing purposes the parameter defaults to st 1 but in the real application it should always be passed from the servlet This is necessary because one big XML file contains data for all cities This parameter allows the stylesheet to extract information from this file for a single city For example the first lt xsl apply templates gt uses a predicate to select the city whose id attribute matches the cit y_id stylesheet parameter xsl apply templates select city id city_id gt The remainder of this stylesheet is very basic simply outputting a list of theaters in the city The final stylesheet shown in Example 10 12 creates a list of showtimes for a movie theater This is the most complex stylesheet merely because it produces multiple cards Example 10 12 Showtimes XSLT lt xml version 1 0 encoding UTF 8 gt slas CC CK Ck CK Ck C Ck CK C CK C CC C KC C Ck Ck Ck CK C CK C CCS CC Ck CK CK CK CK C C SC Ck C Ck C Ck SK S S A x M AG KG KKK Produces a list of showtimes for WML enabled devices KKKKKKKKKKKKKKKKKKKKKKKAKK CK CK KICK Ck SK Ck SK KK SKK KK Ck kk Sk Ck CK kk C MK Ck C KKK KKK kc k k kk xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl param name city id select 2 stl xsl param name theater id select ofallon gt xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public WAP
53. dist List of Targets Name Dependencies Description all clean dist lean t mai P L zif li cet tomcat 2ee dist j2ee main tomcat webapps epart tomcat prepare webapps prepare Global Properties Name Value ant home alcarta ant buld compiler classic debue on z Done hed My Computer The comma separated list of dependencies presents a challenge that is best handled through recursion For each target in the build file it is necessary to print a list of targets that depend on that target It is possible to have many dependencies so an Ant build file may contain a target that looks like this target name docs depends clean repare docs compile gt In the first prototype of the Antdoc stylesheet the algorithm to print the dependency graph uses simple substring operations to determine if another target depends on the current target This turns out to be a problem because two unrelated targets might have similar names so some Ant build files cause infinite recursion in the stylesheet In the preceding example the original prototype of Antdoc says that docs depends on itself because its list of dependencies contains the text prepare docs In the finished version of Antdoc the list of target dependencies is cleaned up to remove spaces and commas For example clean prepare docs compile is converted into clean prepare docs compile By placing the pipe character before and after every dependency
54. gt lt h2 gt All presidents and vice presidents using xsl apply templates lt h2 gt lt ul gt xsl apply templates select president gt lt xsl sort select name first order descending gt xsl apply templates ul lt xsl template gt ckok KKK KK KKKKKKKK KKK KKK KKK KKK KKK KKK KK KK KK KKK KK KK KK KK KK KK KK KKK KK KKK president template outputs the president s name and vice AW president s name CKCK Ck CK Kk SK Kk C Ck Ck CK KK Kk CK CK CK CK Kk CK CK CK Ck SK Sk Sk KC SK KC KC KC KG k Ck kck ck ck ck k k kk D gt lt xsl template match president gt lt li gt lt xsl apply templates select name gt lt li gt lt ul gt lt xsl for each select vicePresident gt lt xsl sort select name first gt li xsl apply templates select name li xsl for each ul lt xsl template gt Cckckckckck kck KKK ck kck ck k ck kckck kckck k KKK KKK CC CC Ck ck ck ck Ck ko ck ko ko ko kk kk A kA kA Sk Sk Ck Ck Sk ko ko ko ko ko Ax A KEK name template outputs first middle and last name KCKCKCKCkCk ck ck ck ck ckck ck kckckck k ck kc kc kckck ck ck ck ck k ck ck ck ck ck ck ck ck ck ck ck ck ck k ck ck k ck ck ck KKK KK KKK KKK kk M lt xsl template match name gt lt xsl text disable output escaping yes gt amp amp nbsp lt xsl text gt lt xsl value of select first gt xsl text disable output escaping yes gt amp
55. hl An Error Has Occurred lt hl gt lt pre gt throwable printStackTrace pw pw printin lt pre gt lt body gt lt html1 gt A helper method that retrieves the PersonalData object from the HttpSession private PersonalData getPersonalData HttpServletRequest request HttpSession session request getSession true PersonalData pd PersonalData session getAttribute chap6 PersonalData if pd null pd new PersonalData session setAttribute chap6 PersonalData pd Our servlet begins with a long list of import statements indicating dependencies on the servlet API as well as the JAXP package The servlet itself is a subclass of HttpServiet as usual and has three private fields extends HttpServlet onalDataXML new PersonalDataXML yy public class Pers te PersonalD itTempl vate Templates thanksTemplates 1 orivate Templ DEL It is important to ensure that each of these fields is thread safe Because many clients share the same servlet instance it is highly probable that these fields will be accessed concurrently Instances of PersonalDataXML are thread safe because they are stateless meaning they contain no data that can be concurrently modified The Templates instances are compiled representations of the two stylesheets this servlet uses and are also designed to be thread safe As the comments indicate the init method performs a
56. indentation and comments the markup tends to run together making the stylesheet much harder to understand and maintain The xsi text element is used to insert additional text into the result tree Although plain text is allowed in XSLT stylesheets the x51 text gt element allows more explicit control over whitespace handling As shown here a nonbreaking space is inserted into the result tree xsl text disable output escaping yes amp amp nbsp xsl text Unfortunately the following syntax does not work does not work This is because nbsp is not one of the five built in entities supported by XML Since XSLT stylesheets are always well formed XML the parser complains when nbsp is found in the stylesheet Replacing the first ampersand character with amp allows the XML parser to read the stylesheet into memory The XML parser interprets this entity and sends the following markup to the XSLT processor this is what the XSLT processor sees after the XML parser interprets the amp amp i xsl text disable output escaping yes amp nbsp xsl text The second piece of this solution is the 5ab1e output escaping yes attribute Without this attribute the XSLT processor may attempt to escape the nonbreaking space by converting it into an actual character This causes many web browsers to display question marks because they cannot interpret the character Disabling output esca
57. it becomes much easier to locate dependencies by searching for strings 3 6 3 The Complete Example The complete XSLT stylesheet is listed in Example 3 14 Comments within the code explain what happens in each step To use this stylesheet simply invoke your favorite XSLT processor at the command line passing antdoc xsit and your Ant build file as parameters Example 3 14 antdoc xslt lt xml version 1 0 encoding UTF 8 gt l Ok ck ck ck 0k ck Ck ck 0k kk ok Ck ck Ck Ck Ck ck ck ck kk Ck Ck Ck Ck Ck ck kk kk Ck kk ck Ck kk ck kk kk Sk kk ko ko Sk Sk Sk Sk ko kx ke X ko ko ko Antdoc v1 0 ck Written by Eric Burke burke_e ociweb com k k Uses XSLT to generate HTML summary reports of Ant build files KKKKKKKKKAKKKKKKKKKKKAKAKKKKKKKKKKKKKKKKKKKKKA KC Mk KKK KKK KKK k k kk M xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl output method xml doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtmll DTD xhtmll strict dtd indent yes encoding UTF 8 gt global variable the project name gt lt xsl variable name projectName select project name gt lt xsl template match gt lt html xmlns http www w3 org 1999 xhtm1 gt lt head gt lt title gt Ant Project Summary lt xsl value of select SprojectName gt lt title gt lt head gt lt body gt hl Ant Project Summary lt h1 gt x
58. lic Node getNode s lic String getSystemId lic void setNode Node node lic void setSystemId String systemId K f O QUO O OQ O c O O E O DOMSource This class allows a DOM tree to be used as an input source In practice the node parameter is usually an instance of a DOM Document However XSLT processors may also support any other type of DOM Node The system id is still important for resolving relative URI references public class DOMSource implements Source public static final String FEATURE http javax xml transform dom DOMSource feature public DOMSource Node node public DOMSource Node node String systemId public Source Ve public Node getNode ye public String getSystemId Jg e public void setNode Node node public void setSystemId String systemId Package javax xml transform sax This package defines how to perform transformations using SAX Example usages can be found in Chapter 5 SAXResult This class makes it possible to emit SAX events as the result of a transformation The ContentHandler parameter receives these events public class SAXResult implements Result public static final String FEATURE http javax xml transform sax SAXResult feature public SAXResult ContentHandler handler public SAXResult public ContentHandler getHandler js public LexicalHandler getLexicalHandler 3 publ
59. lt name gt lt party gt Federalist lt party gt lt vicePresident gt lt name gt lt first gt Thomas lt first gt lt last gt Jefferson lt last gt lt name gt lt vicePresident gt lt president gt remaining presidents omitted The complete file is too long to list here but is included with the downloadable files for this book The lt vicePresident gt element can occur many times or not at all because some presidents did not have vice presidents Names can also contain optional lt middie gt elements Using this XML data the XSLT stylesheet in Example 2 8 shows several location paths Example 2 8 Location paths lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl output method html lt xsl template match gt lt html gt lt body gt lt hl gt XPath Examplesc hl The third president was lt ul gt xsl apply templates select presidents president position 3 name gt lt ul gt Presidents without vice presidents wer lt ul gt xsl apply templates select presidents president count vicePresident 0 name lt ul gt Presidents elected before 1800 were ul xsl apply templates select presidents president term from amp 1t 1800 name ul Presidents with more than one vice president wer ul xsl apply templates select descendant presid
60. lt xsl variable name lang manager select Gerente gt lt xsl variable name lang programmer select Programador lt xsl variable name lang other select Otro xsl stylesheet The Spanish stylesheet is much shorter because it merely overrides each of the locale specific variables The xs1 import is key xsl import href directory en xslt Because of XSLT conflict resolution rules the variables defined in directory es xslt take precedence over those defined in directory en xslt The same logic can be applied to templates as well This is useful in scenarios where the importing stylesheet needs to change behavior in addition to simply defining text translations The following line is optional xsl output method html encoding UTF 8 gt In this example the output method and encoding are identical to the English version of the stylesheet so this line has no effect However the importing stylesheet may specify a different output method and encoding if desired To perform the Spanish transformation using Xalan issue the following command S java org apache xalan xslt Process IN directory xml XSL directory es xslt Figure 8 7 shows the result of this transformation when displayed in a web browser Figure 8 7 Spanish output b Empleado guia telef nica Microsoft Internet Explorer CE x Ele Edt View Favodes Took Hep EJ am m Back F Stop Relesh Home Search Go Address
61. many concurrent threads The transformer instance is then used to perform the actual transformation s applies the XSLT stylesheet to the L data sending the result to 5 5 2 2 XSLT Plugability Layer ct trans transform xmlSource result Qui ct JAXP 1 1 defines a specific lookup procedure to locate an appropriate XSLT processor This must be accomplished without hardcoding vendor specific code into applications so Java system properties and JAR file service providers are used Within your code first locate an instance of the TransformerFactory class as follows javax xml transform TransformerFactory transFact javax xml transform TransformerFactory newInstance Js Since TransformerFactory is abstract its newInstance factory method is used to instantiate an instance of a specific subclass The algorithm for locating this subclass begins by looking at the javax xml transform TransformerFactory System property Let us suppose that com foobar AcmeTransformer is anew XSLT processor compliant with JAXP 1 1 To utilize this processor instead of JAXP s default processor you can specify the system property on the command line when you start your Java application 2 System properties can also be specified in Ant build files java Djavax xml transform TransformerFactory com foobar AcmeTransformer MyApp Provided that JAXP is able to instantiate an instance of AcmeTransformer this is the XSLT processor that will
62. require that you add StylesheetCache class to your WAR file in the appropriate directory Another option is to place the stylesheet cache into a JAR file and place that JAR file into the TOMCAT HOME Iib directory This approach is taken when you download the example code for this book The biggest code savings occur in the init method because the filenames for the stylesheets are stored instead of Templates instances This is because the stylesheet cache requires filenames as inputs and will create its own instances of Templates which accounts for a majority of the simple changes throughout the servlet Once you get this example up and running testing the stylesheet reloading capability is a snap As before chap6 war is copied to the TOMCAT HOME webapps directory After you run the servlet the first time you will notice that the WAR file is expanded into the TOMCAT HOME webapps chap6 directory Simply go into the TOMCAT HOME webapps chap6 WEB INF xsit directory and edit one of the stylesheets Then click on the Refresh button on your web browser and you should see the results of the edits that were just made If you don t see the changes there might be some leftover files from earlier examples in this chapter Be sure to shut down Tomcat and remove both chap6 war and the chap6 directory from Tomcat s webapps directory Then re deploy and try again 6 5 Servlet Threading Issues Like it or not a servlet must be capable of serving m
63. splitPane setBottomComponent new JScrollPane this errorDetailArea return splitPane As the emphasized code shows the error listener table model is registered on the TransformerFactory as well as the Transformer instance In addition to registering the error listener exceptions also have to be caught because XSLT processors may still throw exceptions and errors even though an error listener is registered Generally errors on the TransformerFactory indicate problems while parsing the XSLT stylesheet while Transformer error listeners are notified of problems with the actual transformation or in the XML data The final class xMLOutputPanel is shown in Example 9 12 Example 9 12 XMLOutputPanel java package com oreilly javaxslt swingtrans import java awt import java awt event import java io import javax swing XML related imports import org jdom Document import org jdom input SAXBuilder import org jdom output XMLOutputter Displays XML text in a scrolling text area A status label indicates whether or not the XML is well formed and valid public class XMLOutputPanel extends JPanel displays the XML private JTextArea xmlArea new JTextArea 20 70 private String xml private JLabel statusLabel new JLabel Ve Construct the panel and layout the GUI components public XMLOutputPanel super new BorderLayout add new JScrollPane this xmlArea
64. test boolean expression gt Content template gt lt xsl when gt See XSLT specification section 9 2 Conditional Processing with xsl choose http www w3 org TR xslt section Conditional Processing with xsl choose xsl with param xsl with param name gname select expression gt Content template gt xsl with param See XSLT specification section 11 6 Passing Parameters to Templates http www w3 org TR xsit section Passing Parameters to Templates Colophon Our look is the result of reader comments our own experimentation and feedback from distribution channels Distinctive covers complement our distinctive approach to technical topics breathing personality and life into potentially dry subjects The animals on the cover of Java and XSLT are ermines also known as stoats or short tailed weasels Mustela erminea are found around the world between the Arctic Circle and approximately 40 degrees north latitude Their body length not including tail ranges from 7 to 12 inches with proportionately sized tails from 3 to 6 inches long They weigh between 1 5 and 11 5 ounces Males are on average larger than females Ermines can both swim and climb trees and though they live in such diverse habitats as grasslands tundra and deep forests they tend to prefer rocky or brushy areas They are carnivores and eat mostly rodents but they also enjoy small rabbits and birds fis
65. throws SAXException IOException public abstract Document parse InputSource is throws SAXException IOException public Document parse InputStream is throws SAXException IOException public abstract void setEntityResolver EntityResolver er public abstract void setErrorHandler ErrorHandler eh Fl ct tt DocumentBuilderFactory This class allows instances of Document Builder to be constructed using a factory pattern insulating application code from specific DOM implementations Various methods in this class allow programs to specify which features the parser will support If these features are not available the newDocumentBuilder throws a ParserConfigurationException The various accessor methods such as i sNamespaceAware do not indicate whether the underlying parser actually supports a given feature Instead these methods indicate whether the application configured those features on this Document BuilderFactory instance Before using this class call the newiInstance method to create an instance of it This object is then used to construct an instance of Document Builder using the newDocumentBuilder method public abstract class DocumentBuilderFactory protected DocumentBuilderFactory public abstract Object getAttribute String name throws IllegalArgumentException public boolean isCoalescing public boolean isExpandEntityReferences public bool
66. xsl variable Variables in XSLT are defined with the lt xs1 variable gt element and can be global or local A global variable is defined at the top level of a stylesheet which means that it is defined outside of any templates as a direct child of the lt xsi stylesheet gt element Top level variables are visible throughout the entire stylesheet even in templates that occur before the variable declaration The other place to define a EM is inside of a template These variables are visible only to elements that follow the xs1 variable declaration within that template and to their descendants The code in Ends 3 2 showed this form of xs1 variable asa mechanism to define the font color 3 2 1 1 Defining variables Variables can be defined in one of three ways lt xsl variable name homePage gt index html lt xsl variable lt xsl variable name lastPresident select president position last name xsl variable name empty In the first example the content of lt xsi variable gt specifies the variable value In the simple example listed here the text index html is assigned to the homepage variable More complex content is certainly possible as shown earlier in Example 3 2 The second way to define a variable relies on the select attribute The value is an XPath expression so in this case we are selecting the name of the last president in the list Finally a variable without a select attribute or cont
67. 1 else if this day gt rhs day return 1 return comparison public String toString 4 return getMonth getDay getYear FakeDataAdapter java shown in Example A 6 allows the discussion forum to be executed without any database This class was written before the database was implemented and is useful for testing purposes only Example A 6 FakeDataAdapter java package com oreilly forum fakeimpl com oreilly forum com oreilly forum adapter com oreilly forum domain java util import import import import public a list of private List BoardSummary objects allBoards private static long nextMessageID 0 private Map messageMap new HashMap public FakeDataAdapter throws this allBoards new ArrayList BoardSummary bs0 Java Programming Datal class FakeDataAdapter extends DataAdapter Exception new BoardSummaryImpl 0L General programming questions about Java BoardSummary bsl new BoardSummaryImpl 1L XSLT Stylesheet Techniques Writing effective XSLT stylesheets this allBoards add bs0 this allBoards add bs1 this postNewMessage 0L First subject in Java Prog burke_e yahoo com Sample message text iparam msgID must be a valid message identifier return the message with the specified id throws DataException if msgID does not exist or a databas
68. 2 C evsdata javaxsll examples chapters chap8 i1 ndi Empleado gu a telef nica Nombre Categoria Tel fono Joe Smith Gerente 4 0192 SallyJones Programador 42331 Roger Clark Programador 43345 il Done My Computer In the i18n example stylesheets presented in this chapter common functionality is placed into one stylesheet Importing stylesheets then replace locale specific text This same technique can be applied to any stylesheet and is particularly important when writing custom XSLT for a specific browser Most of your code should be portable across a variety of browsers and should be placed into reusable stylesheets The parts that change should be placed into browser specific stylesheets that import the common stylesheets 8 6 2 Encodings A character encoding is a numeric representation of a particular character The US ASCII encoding for the character for example is 65 When computers read and write files using US ASCII encoding each character is stored as one byte of data Of this byte only seven bits are actually used to represent characters The first most significant bit must always be 0 Therefore US ASCII can represent only 128 different characters Of course this presents a problem for languages that require more than 128 characters For these languages another character encoding must be used VI Refer to Java Internationalization by Andy Deitsch and David Czarnecki O Reilly for more d
69. 3 a Transformer object can be obtained from the TransformerFactory as follows javax xml transform TransformerFactory transFact javax xml transform TransformerFactory newInstance javax xml transform Transformer trans transFact newTransformer xsltSource The Transformer instance is wrapped around an XSLT stylesheet and allows you to perform as many transformations as you wish The main caveat is thread safety because many threads cannot use a single Transformer instance concurrently For each transformation invoke the transform method abstract void transform Source xmlSource Result outputTarget throws TransformerException This method is abstract because the TransformerFactory returns a subclass of Transformer that does the actual work The Source interface defines where the XML data comes from and the Result interface specifies where the transformation result is sent The TransformerException Will be thrown if anything goes wrong during the transformation process and may contain the location of the error and a reference to the original exception The ability to properly report the location of the error is entirely dependent upon the quality of the underlying XSLT transformer implementation s error reporting We will talk about specific classes that implement the Source and Result interfaces later in this chapter Aside from actually performing the transformation the Transformer implementation allows you to set output p
70. 4 Post Message prototype T Post New Message Microsoft Internet Explorer Ble gdt Yew Favorites oos Help Heak gt Qo GQ Deoh ijfewrtes Hoy cy p address BT v hitp sfllcahost S SJfcrum manjpostHsgnode posthefAsg boardiD O NE E Qe Subject Your Email Message This page is also used to reply to an existing message Although not shown here the title changes to Reply to Message and the subject and message text are pre filled with text from the original message If the user submits this form without filling in all values the web page is redisplayed with an error message The final screen prototype is shown in Figure 7 5 This screen allows users to view existing messages Figure 7 5 View Message prototype ETEN Message Microsoft Internet Explorer erie nix file Edt yew Favorites eds tep LI lige v D J A ewh Fates Sristory E5 ob fel a Address hitp jllozaleicet 6080 Forumjman vievf sg msgt oe 2 Links Custovizelinks FreeHotmal Windows amp Windows Media View Message XSLT Basics Quick Actions e Return to March messages for XSLT Basics e Return to the ho pag e Reply to this message Message Re First message posted posted by burke e yahoo com on Mar 11 2001 First Pespones gt This is line one gt line two gt third and final line EJ Cone E Localintranet 7 2 2 XML Samples While page designers are hard at work on the XHTML prototype screens
71. BoardSummaryImpl id name description monthsWithMessages return allBoards iterator catch SQLException sqe Sqe printStackTrace throw new DataException sqe finally if stmt2 null try stmt2 close catch SQLException ignored DBUtil close stmt con return a board summary for the given id throws DataException if boardID is illegal or a database error occurs ey public BoardSummary getBoardSummary long boardID throws DataException Connection con null Statement stmt null try con DBUtil getConnection dbURL stmt con createStatement return getBoardSummary boardID stmt catch SQLException sqe Sqe printStackTrace throw new DataException sqe finally DBUtil close stmt con private BoardSummary getBoardSummary long boardID Statement stmt throws DataException SQLException ResultSet rs stmt executeQuery SELECT name description FROM Board WHER id En boardID if rs next String name rs getString 1 String description rs getString 2 List monthsWithMessages getMonthsWithMessages boardID stmt return new BoardSummaryImpl boardID name description monthsWithMessages else throw new DataException Unknown boardID return a list of MonthYear objects ay private List getMonthsWithMessages long boardI
72. Content Any number of lt xsl sort gt or xsl with param lt xsl apply templates gt See XSLT specification section 5 4 Applying Template Rules http www w3 org TR xslt section Applying Template Rules xsl attribute xsl attribute name qname namespace uri reference gt Content template gt lt xsl attribute gt See XSLT specification section 7 1 3 Creating Attributes with lt xsl attribute gt http www w3 org TR xslt creating attributes xsl attribute set xsl attribute set name gname use attribute sets qnames gt Content Any number of lt xsl attribute gt gt xsl attribute set See XSLT specification section 7 1 4 Named Attribute Sets http www w3 org TR xslt attribute sets xsl call template xsl call template name qname Content Any number of xsl with param lt xsl call template gt See XSLT specification section 6 Named Templates http www w3 org TR xslt named templates xsl choose lt xsl choose gt Content One or more lt xsl when gt followed by an optional lt xsl otherwise gt lt xsl choose gt See XSLT specification section 9 2 Conditional Processing with lt xsl choose gt http www w3 org TR xslt section Conditional Processing with xsl choose xsl comment lt xsl comment gt lt Content template
73. ET gt lt th gt Name lt th gt lt th gt Dependencies lt th gt lt th gt Description lt th gt tr xsl apply templates select target mode tableRow xsl sort select count description order descending xsl sort select name gt xsl apply templates table lt p gt xsl call template name globalProperties gt lt xsl template gt Ses Ck Ck ck koc ck koc Ck Ck kk kk ck Ck kk kk Ck Sk kk kk Ck Ck Ck kk kk Ck ko ck Sk Ck ck Sk Ck ck Ck Ck ck Ck Ck ko Sk Sk ko kA Mk kx ko ko ko Create a table of all global properties KCKCKCkCkCkCkck ck kc kck ck ckckckckck ck ck ck ck ck k ck ck kckckck ck ck ck ck kc kck k ck ck kck k kck ck ck ck kck ck k ck ck kc KKK KK D gt lt xsl template name globalProperties gt lt xsl if test property gt lt table border 1 cellpadding 4 cellspacing 0 gt lt tr gt lt th colspan 2 gt Global Properties lt th gt lt tr gt lt tr gt lt th gt Name lt th gt lt th gt Value lt th gt lt tr gt xsl apply templates select property mode tableRow gt xsl sort select name gt xsl apply templates table xsl if xsl template e oe AC Ck KC Ck C Ck Ck KC Ck KC Ck C CC Ck Kk Ck Ck Ck Ck Ck Ck kk Ck Ck kk Ck kk kk kk Sk kx kx x kx kx A KG kx ko ko koko Show an individual property in a table row KCKCKCK CK KK Kk SK Kk CK SKK CK SK CK Kk SK CK CIC KK CC C KK SKK KKK KKK KKK KKK kc
74. FilterConfig filterConfig throws ServletException this filterConfig filterConfig xsltPath should be something like WEB INF xslt a xslt String xsltPath filterConfig getInitParameter xsltPath if xsltPath null throw new UnavailableException xsltPath is a required parameter Please check the deployment descriptor convert the context relative path to a physical path name this xsltFileName filterConfig getServletContext getRealPath xsltPath verify that the file exists if this xsltFileName null new File this xsltFileName exists throw new UnavailableException Unable to locate stylesheet this xsltFileName 30 public void doFilter ServletRequest req ServletResponse res FilterChain chain throws IOException ServletException if res instanceof HttpServletResponse throw new ServletException This filter only supports HTTP BufferedHttpResponseWrapper responseWrapper new BufferedHttpResponseWrapper HttpServletResponse res chain doFilter req responseWrapper Tomcat 4 0 reuses instances of its HttpServletResponse implementation class in some scenarios For instance hitting reload repeatedly on a web browser will cause this to happen Unfortunately when this occurs output is never written to the BufferedHttpResponseWrapper s OutputStream This means that the
75. In this case the VM would look for jaxp jar in the same directory as the JAR file that contains the manifest entry The best way to ensure that the correct version of XML parser XSLT processor and JAXP are installed is to manually copy the required JAR files to the installed optional package directory Software developers should have the Java 2 SDK installed and should place JAR files in the JAVA HOME jre lib ext directory End users however will probably use the Java 2 Runtime Environment instead of the entire SDK For these users the JAR files can be installed to the lib ext directory where the JRE is installed To uninstall a Java optional package merely delete the JAR file from the appropriate directory 9 1 1 5 Java IDEs Many developers use tools such as Borland s JBuilder as Java development environments These tools can introduce problems because they typically include a copy of the Java 2 SDK When running and compiling within the IDE the VM uses the tool s own Java directory rather than the Sun Java 2 SDK that is probably already installed elsewhere on the system Figure 9 3 is a typical directory structure that illustrates this potential problem Figure 9 3 Typical directory structure e root im Le Le lib L e ext the normal Java 2 SDK installed optional package directory Tm sunl e e In this example JBuilder is properly configured with JAXP 1 1 the Crimson XML parser and the Xalan 2 0 JAR file This me
76. Invalid request remove extra whitespace then verify that the user filled in all required fields msgSubject msgSubject trim authorEmail authorEmail trim msgText msgText trim try DataAdapter adapter DataAdapter getiInstance if msgSubject length authorEmail length 0 msgText length 0 BoardSummary board boardIDStr null null adapter getBoardSummary boardID MessageSummary inResponseToMsg origMsgIDStr null null adapter getMessage origMsgID return new PostMsgRenderer board inResponseToMsg true msgSubject authorEmail msgText If this point is reached no errors were detected so the new message can be posted or a response can be created Message msg null if replyToMsg equals mode msg adapter replyToMessage origMsgID msgSubject authorEmail msgText else if postNewMsg equals mode msg adapter postNewMessage boardID msgSubject authorEmail msgText if msg null MessageSummary inResponseTo null if msg getInReplyTo gt 1 inResponseTo adapter getMessage msg getInReplyTo return new ViewMsgRenderer msg inResponseTo return new ErrorRenderer Invalid request catch DataException dex return new ErrorRenderer dex Unlike other request handlers in this application Post MsgReqHandler also has adoPost method The doGet metho
77. J l if xsl if test required true gt lt x J gt PE lt xsl template gt lt xsl styleshee The first seven lines of editPersonalData xsit contain boilerplate code that configures the XSLT processor to produce XHTML 1 0 using the transitional DTD In particular our result tree uses the lt i gt lt i gt tag so we cannot use the XHTML strict DTD The top level template matches the pattern as usual outputting the framework for the XHTML document The next template matches the lt personalData gt element producing a heading followed by an optional error message The error message is displayed if the XML data contains the lt requiredFieldsMissing gt element which is easily determined via the lt xsi1 if gt element lt xsl template match personalData gt lt h3 gt Personal Information lt h3 gt lt xsl if test requiredFieldsMissing gt lt div style color red font size larger gt Error one or more required fields are missing lt div gt lt xsl if gt This template then produces the lt form gt element which specifies that HTTP POST should be used to submit the information The act ion attribute indicates that this form will send its data to our servlet As you will see the form action matches the URL pattern that we will set up in the deployment descriptor later in this chapter 2 To avoid hardcoding the form action in the XSLT stylesheet pass it as a stylesheet parame
78. OS X Aqua look and feel using Java Swing Figure 9 5 SwingTransformer frame Swing XSLT Transformer XML File Users oci Burke javaxslt chapters chap9 aidan xml Select XML XSLT File ci Burke javaxslt chapters chap9 condensePerson xslt Select XSLT Transform When the Transform button is clicked the window shown in Figure 9 6 appears Subsequent transformations can be performed and each one will cause an additional window to appear Since the XML and XSLT files are parsed with each transformation this application does not have to be restarted to see changes to those files Figure 9 6 XML output panel Text Output Transformation Problems XML Output XML is well formed and valid lt xml version 1 0 encoding UTF 8 7 lt DOCTYPE person SYSTEM file Users oci Burke javaxslt chopters chap9 condensed dtd person lt name gt Aiden Garrett Burke lt name gt lt birthDate gt 6 25 1999 lt birthDete gt The first tab Text Output is actually the first one to be displayed It is not shown here because it merely shows the raw text contents of the XSLT result tree which includes any whitespace produced by the transformation When the user clicks on the XML Output tab the result tree is parsed and validated against its DTD The XML is then displayed in the GUI using JDOM s XMLOutputter class which removes ignorable whitespace and pretty prints the XML If errors occur during the transformation p
79. Openwave OWG1 UP 4 1 20a UP Browser 4 1 20a XXXX UP Link 4 1 HTTP DIRECT In general a model number follows the vendor name However the Ericsson R380s does not follow this convention As mentioned in Chapter 8 almost every web browser reports a User Agent that begins with the text Mozilla which can be used to identify a web browser rather than a wireless device From the servlet it is quite easy to get to these HTTP headers protected void doGet HttpServletRequest reg HttpServletResponse res throws IOException ServletException String userAgent req getHeader User Agent String accept req getHeader Accept if userAgent null A more complete example is presented in the section Movie Theater Example 10 3 2 2 Setting the content type Once the client type has been identified as either a web browser or a specific type of wireless device the response must be sent back Table 10 3 lists the three most common content types a servlet will encounter Table 10 3 MIME content types MIME type Extension Description text vnd wap wml WML source code text vnd wap wmlscript wmls WMLScript source code image vnd wap wbmp wmlc This simply means that before sending a WML response back to the client device the following code must be present in the servlet public void doGet HttpServletRequest req HttpServletResponse res res setContentType text vnd wap wml now obtain a Pri
80. OutputStreamWriter fos UTF 16 write to pw just like any other PrintWriter pw close 8 6 3 Putting It All Together Getting all of the pieces to work together is often the trickiest aspect of i18n To demonstrate the concepts we will now look at XML datafiles XSLT stylesheets and a servlet that work together to support any combination of English Chinese and Spanish A basic HTML form makes it possible for users to select which XML file and XSLT stylesheet will be used to perform a transformation The screen shot in Figure 8 9 shows what this web page looks like Figure 8 9 XML and XSLT language selection Links Customize Links Free Hotmall lt Windows rii O Ee aie nalish 9o99 qc I haracter Encoding 9 99 CE Local intranet As you can see there are three versions of the XML data one for each language Other than the language the three files are identical There are also three versions of the XSLT stylesheet and the user can select any combination of XML and XSLT language The character encoding for the resulting transformation is also configurable UTF 8 and UTF 16 are compatible with Unicode and can display the Spanish and Chinese characters directly SO 8859 1 however can display only extended character sets using entities such as 25991 In this example users explicitly specify their language preference It is also possible to write a servlet that uses the Acce
81. Processor As shown the Employee object is serialized and the serialized object is sent from the EJB container to the client rather than a big text string of XML On the client machine the DOM API is used to convert the Employee into an XML representation which is fed directly into an XSLT processor By using DOM on the client the XML never has to be completely converted to text which tends to be slightly faster for transformations While custom XML production using DOM is common today more automated XML data binding technologies are becoming increasingly popular Sun s Java Architecture for XML Data Binding JAXB provides a standard Java API for mapping to and from XML documents and Java objects Although the bandwidth requirements for serialized objects are comparable to compressed XML more finely grained requests are easier when returning objects instead of XML text Consider an online benefit processing application In this type of application an employee may have a spouse children beneficiaries iin benefit elections As the user moves from page to page in this application the Employee object can be cached in the HttpSessi additional data they dh call methods on this cached Employ somewhere in simply generate XML for the employee do not call the EJB tier As the code fragment shows when an employee does not have a spouse no additional call to the EJB tier is required If the EJB tier returns pure
82. SampleUnitTest String name super name Initialization befor ach test method is called x public void setUp locate a file named test properties in the chap9 package ResourceBundle rb ResourceBundle getBundle chap9 test this workingDir rb getString chap9 workingDir assertNotNull workingDir assert Unable to locate this workingDir new File this workingDir exists this aidanXMLFile new File workingDir File separator aidan xml this johnXMLFile new File workingDir File separator john xml this condenseXSLTFile new File workingDir File separator condensePerson xslt this aidanCondensedXMLFile new File this workingDir ile separator aidanCondensed xml this johnCondensedXMLFile new File this workingDir johnCondensed xml this transFact TransformerFactory newInstance Clean up after each test method ay public void tearDown the transformation results could be deleted here but the cleanup code is intentionally commented out so the developer can see the generated files this aidanCondensedXMLFile delete this johnCondensedXMLFile delete An individual unit test E public void testTransformWithTemplates throws Exception Templates templates this transFact newTemplates new StreamSource this condenseXSLTFile Trans
83. Simple Example 5 2 Introduction to JAXP 1 1 5 3 Input and Output 5 4 Stylesheet Compilation 6 Servlet Basics and XSLT 6 1 Servlet Syntax 6 2 WAR Files and Deployment 6 3 Another Servlet Example 6 4 Stylesheet Caching Revisited 6 5 Servlet Threading Issues 7 Discussion Forum 7 1 Overall Process 7 2 Prototyping the XML 7 3 Making the XML Dynamic 7 4 Servlet Implementation 7 5 Finishing Touches 8 Additional Techniques 8 1 XSLT Page Layout Templates 8 2 Session Tracking Without Cookies 8 3 Identifying the Browser 8 4 Servlet Filters 8 5 XSLT as a Code Generator 8 6 I nternationalization with XSLT 9 Development Environment Testing and Performance 9 1 Development Environment 9 2 Testing and Debugging 9 3 Performance Techniques 10 Wireless Applications 10 1 Wireless Technologies 10 2 The Wireless Architecture 10 3 J ava XSLT and WML 10 4 The Future of Wireless A Discussion Forum Code B JAXP API Reference C XSLT Quick Reference Colophon Preface Java and Extensible Stylesheet Language Transformations XSLT are very different technologies that complement one another rather than compete Java s strengths are portability its vast collection of standard libraries and widespread acceptance by most companies One weakness of Java however is in its ability to process text For instance Java may not be the best technology for merely converting XML files into another format such as XHTML or Wireless Markup
84. StylesheetCache This class represents a value in the cache Map u static class MapEntry long lastModified when the file was modified Templates templates MapEntry long lastModified Templates templates this lastModified lastModified this templates templates Because this class is a singleton it has a private constructor and uses only static methods Furthermore each method is declared as synchronized in an effort to avoid potential threading problems The heart of this class is the cache itself which is implemented using java util Map private static Map cache new HashMap Although HashMap is not thread safe the fact that all of our methods are synchronized basically eliminates any concurrency issues Each entry in the map contains a key value pair mapping from an XSLT stylesheet filename to an instance of the MapEnt ry class MapEnt ry is a nested class that keeps track of the compiled stylesheet along with when its file was last modified static class MapEntry long lastModified when the file was modified Templates templates MapEntry long lastModified Templates templates this lastModified lastModified this templates templates Removing entries from the cache is accomplished by one of two methods public static synchronized void flushAll cache clear Ve public static synchronized void flush String xsltFileName c
85. Theater listing WML lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE wml PUBLIC WAPFORUM DTD WML 1 1 EN http www wapforum org DTD wml 1 1 xml lt wml gt card title Theaters id theaters gt lt p gt lt big gt St Louis lt big gt lt p gt lt p gt Select a theater lt p gt lt p gt lt a href movieguide action showtimes amp amp city stl amp amp theater westolivel6 gt West Olive 16 lt a gt lt br gt lt a href movieguide action showtimes amp amp city stl amp amp theater stcharles18 St Charles 18 a br a href movieguide action showtimes amp amp city stl amp amp theater ofallon O Fallon Cine lt a gt lt br gt lt p gt lt p gt lt em gt lt a href movieguide gt Change city lt a gt lt em gt lt p gt lt card gt wml This WML file is shown on the left side of Figure 10 6 using a different cell phone simulator On the right side of this figure an XHTML representation of the same data is shown in a web browser These images were generated using the same servlet and XML datafile but different XSLT stylesheets Figure 10 6 Theater listing output MADE Simulator WML al Ix Ele fo Settings pep Go 1 8880 chap1 movieguide Please Select a Theater Microsoft Internet Explorer joj x a e poaae E Freerotnal z wndows 3 MOTOROLA Theaters Select a dM St Louis Please select a theater fram t
86. This is just another odd limitation of DOM that forces you to include implementation specific code in your Java applications Another area where JDOM shines is in its ability to create new elements Unlike DOM text is set directly on the Element objects which is more intuitive to Java programmers private Element createPublisherElement Publisher pub Element pubElem new Element publisher ubElem addAttribute id pub getId ys ubElem ado tent new Element name setText pub getName DDF ubElem ack nt setText pub getStreet O QC QQ O 5 Content new Element pubElem ad new Elemen pubElem ad tent t city setText pub getCity Content new Element State setText pub getState 335 Content E t postal setText pub getPostal Q OQ OQ pubElem ad emen return pubElem Since methods such as addContent and addAttribute return a reference to the Element instance the code shown here could have been written as one long line This is similar to StringBuffer append which can also be chained together buf append a append b append c In an effort to keep the JDOM code more readable however our example adds one element per line The final piece of this pie is the ability to print out the contents of JDOM as an XML file JDOM includes a class called xMLOut putter which allows us to generate the XML for a
87. XML then additional calls to the EJB tier are almost certainly required for each web page that is displayed This is because the web tier sees only big blocks of XML text from the EJB tier making it much more difficult to add any business logic to the web tier The biggest advantage of returning objects instead of XML is the ability to keep presentation logic out of the EJB tier Most web applications combine data from several EJBs onto each web page End user requirements for the user interface tend to change much more frequently than data requirements It makes sense to keep the EJB tier stable while changing the XML generation code in the web tier more frequently Chapter 10 Wireless Applications Cellular phones personal digital assistants PDAs and various other forms of wireless devices are taking the world by storm opening new avenues for development as well as a whole host of challenges for developers These devices are tiny compared to PCs both in terms of physical size and processing power This means that traditional HTML web pages are unacceptable opening the door for new markup languages based on XML to take center stage This chapter introduces key concepts behind wireless technologies with particular emphasis on Wireless Markup Language WML a concise alternative to HTML that is custom made for wireless devices The role of XSLT and servlets will also be explored though an example application that allows wireless users to br
88. XML format is tedious because it requires you to manually write code that encodes and decodes messages between the client and the web application Simple Object Access Protocol SOAP is a standardized protocol for exchanging data using XML messages SOAP was originally introduced by Microsoft but has been submitted to the W3C for standardization and is endorsed by many companies SOAP is fairly simple allowing vendors to quickly create tools that simplify data exchange between web applications and any type of client Since SOAP messages are implemented using XML they can be created and updated using XSLT stylesheets This means that data can be extracted from a relational database as XML transformed with XSLT into a standard SOAP message and then delivered to a client application written in any language For more information on SOAP standardization efforts visit http www w3 org TR SOAP 1 3 4 Wireless Cell phones personal digital assistants PDAs and other handheld devices seem to be the next big thing From a marketing perspective it is not entirely clear how the business model of the Web will translate to the world of wireless It is also unclear which technologies will be used for this new generation of devices One currently popular technology is Wireless Application Protocol WAP which uses an XML markup language called Wireless Markup Language WML to render pages Other languages have been proposed such as Compact HTML CHTML
89. added to lt library gt The createPublisherElement method is a private helper method that simply goes through the tedious DOM steps required to create each XML element One thing that may not seem entirely obvious is the way that text is added to elements such as O Reilly in the lt name gt O Reilly lt name gt tag Element name doc createElement name name appendChild doc createTextNode pub getName pubElem appendChild name The first line is pretty obvious simply creating an empty name element The next line then adds a new text node as a child of the name object rather than setting the value directly on the name This is indicative of the way that DOM represents XML any parsed character data is considered to be a child of a node rather than part of the node itself DOM uses the org w3c dom Text interface which extends from org w3c dom Node to represent text nodes This is often a nuisance because it results in at least one extra line of code for each element you wish to generate The main method in Example 1 4 creates a Library object converts it into a DOM tree then prints the XML text to System out Since the standard DOM API does not provide a standard way to convert a DOM tree to XML we introduce Xerces specific code to convert the DOM tree to text form write the document using Apache Xerces output the document with UTF 8 encoding indent each line org apache xml serialize OutputFormat fmt
90. all of the managers and programmers are listed The pipe operator computes the union of its two operands lt xsl for each select team manager team programmer For each manager or programmer the content of the lt name gt element is printed followed by the value of the ssn attribute which is passed as a parameter to the format ssN template Passing one or more parameters is accomplished by adding xs1 with param as a child of xsl call template To pass additional parameters simply list additional lt xs1 with param elements all as children of xs1 call template At the receiving end xs1 param is used as follows lt xsl template name formatSSN gt lt xsl param name ssn gt In this case the value of the ssn parameter defaults to an empty string if it is not passed In order to specify a default value for a parameter use the select attribute In the following example the zeros are in apostrophes in order to treat the default value as a string rather than as an XPath expression lt xsl param name ssn select 000000000 gt Within the formatSSN template you can see that the substring function selects portions of the social security number string More details on substring and other string formatting functions are discussed later in this chapter 3 2 4 Incrementing Variables Unfortunately there is no standard way to increment a variable in XSLT Once a variable has been defined i
91. am still amazed that an unknown visitor to a web site can become an O Reilly author The other company I would like to thank is Object Computing Inc OCI my employer They have a remarkable group of highly talented software engineers all of whom are always available to answer questions offer advice and inspire me to learn more These people are the reason work for OCI and are the reason this book was possible Finally would like to thank Mark Volkmann of OCI for teaching me about XML in the first place and for answering countless questions during the past five years Chapter 1 Introduction When XML first appeared people widely believed that it was the imminent successor to HTML This viewpoint was influenced by a variety of factors including media hype wishful thinking and simple confusion about the number of new technologies associated with XML The reality is that millions of web sites are written in HTML and no widely used browser fully supports XML and its related standards Even when browser vendors incorporate full support for XML and its family of related technologies it will take years before enough people use these new versions to justify rewriting most web sites in XML Although maintaining compatibility with older browsers is essential companies should not hesitate to move forward with XML and related technologies on the server From the browser perspective HTML will remain dominant on the Web for many years to come
92. author gt lt book gt book publisher oreilly isbn 0 596 00016 2 edition 1 edition publicationDate mm 06 yy 2000 gt lt title gt Java and XML lt title gt lt author gt Brett McLaughlin lt author gt lt book gt lt library gt As shown in library xml a lt 1 ibrary gt consists of publisher elements and lt book gt elements To generate this XML we will use Java classes called Library Book and Publisher These classes are not shown here but they are really simple For example here is a portion of the Book class public class Book private String author private String title public String getAuthor return this author public String getTitle return this title Each of these three helper classes is merely used to hold data The code that creates XML is encapsulated in a separate class called LilbraryDOMCreator which is shown in Example 1 4 Example 1 4 XML generation using DOM package chapl import java io import java util import org w3c dom Document import org w3c dom Element An example from Chapter 1 Creates the library XML file using the DOM API public class LibraryDOMCreator Create a new DOM org w3c dom Document object from the specified Library object param library an application defined class that provides a list of publishers and books return a new DOM document X N
93. be used Of course AcmeTransformer must be a subclass of TransformerFactory for this to work so it is up to vendors to offer support for JAXP If the system property is not specified JAXP next looks for a property file named lib jaxp properties in the JRE directory A property file consists of name value pairs and JAXP looks for a line like this javax xml transform TransformerFactory com foobar AcmeTransformer You can obtain the location of the JRE with the following code String javaHomeDir System getProperty java home Some popular development tools change the value of java home when they are installed which could prevent JAXP from locating jaxp properties JBuilder for instance installs its own version of Java 2 that it uses by default The advantage of creating jaxp properties in this directory is that you can use your preferred processor for all of your applications that use JAXP without having to specify the system property on the command line You can still override this file with the b command line syntax however If jaxp properties is not found JAXP uses the JAR file service provider mechanism to locate an appropriate subclass of TransformerFactory The service provider mechanism is outlined in the JAR file specification from Sun and simply means that you must create a file in the META INF services directory of a JAR file In JAXP this file is called javax xml transform TransformerFactory It contains a single
94. before it can be used by most XML APIs The code shown here does the conversion and will work on Unix Windows and other platforms supported by Java Although you could try to manually prepend the filename with the literal string ile that may not result in portable code The documentation for java io File clearly states that its toURL method generates a system dependent URL so the results will vary when the same code is executed on a non Windows platform In fact on Windows the code actually produces a nonstandard URL with a single slash although it does work within Java programs file C data simple xml Now that we have system identifiers for our two input files an instance of the XSLT processor is created org apache xalan xslt XSLTProcessor processor i org apache xalan xslt XSLTProcessorFactory O jetProcessor J L XSLTProcessor is an interface and XSLTProcessorFactory Is a factory for creating new instances of classes that implement it Because Xalan is open source software it is easy enough to determine that xSLTEnginelmp1 is the class that implements the xSLTProcessor interface although you should try to avoid code that depends on the specific implementation The next few lines of code create XSLT Input Source objects one for the XML file and another for the XSLT file org apache xalan xslt XSLTInputSource xmliInputSource new org apache xalan xslt XSLTInputSource xmlSystemId org apache
95. bufferedServletOut getBuffer public PrintWriter getWriter throws IOException if this outputStream null throw new IllegalStateException The Servlet API forbids calling getWriter after getOutputStream has been called if this printWriter null this printWriter new PrintWriter this bufferedServletOut return this printWriter public ServletOutputStream getOutputStream throws IOException if this printWriter null throw new IllegalStateException The Servlet API forbids calling getOutputStream after getWriter has been called if this outputStream null this outputStream this bufferedServletOut return this outputStream override methods that deal with the response buffer public void flushBuffer throws IOException if this outputStream null this outputStream flush else if this printWriter null this printWriter flush public int getBufferSize return this bufferedServletOut getBuffer length public void reset this bufferedServletOut reset public void resetBuffer this bufferedServletOut reset public void setBufferSize int size this bufferedServletOut setBufferSize size BufferedHttpResponseWrapper is an extension of HttpServlet ResponseWrapper and overrides all methods that affect the Writer or OutputStream back to the client T
96. can see results immediately without waiting for the back end business logic and database access code to be created In the real system static XML will not meet our requirements We need the ability to extract data from a relational database and convert it into XML on the fly as each page is requested This makes the application live making updates to the database immediately visible to users To the XSLT stylesheet developer this is a moot point The XSLT transformations work the same regardless of whether the XML data came from a flat file a relational database or any other source 7 3 1 Domain Classes A domain class is a Java class that represents something in the problem domain That s a fancy way to describe a class that represents the underlying problem you are trying to solve In this example we need to model the discussion forum as a series of Java classes to provide a buffer between the XML and the underlying relational database In addition to representing data about the discussion forum these Java classes can contain business logic Figure 7 6 contains a UML diagram of the classes found in the com oreilly forum domain package These classes do not contain any database access code nor do they have any XML capability Instead they are simply data structures with a few key pieces of functionality This makes it possible for example to rip out the relational database and replace it with some other back end data source without c
97. ck ck ck ck ck ck ck k ck ck k ck k ck ck ck ck ck k KKK KKK KK appointment templat coc ck c ck ck ck ck ck ck ck KK ck ck ck ck ck ck ck ck KEK ck ck ck ck ck ck ck KKK ck ck kk ko ko ko Sk ko ko kx o KKKK KKK KKK KKK gt lt xsl template match appointment gt lt hr gt lt h3 gt Appointment lt h3 gt xsl apply templates select when gt lt table gt Stre lt td gt Subject lt td gt lt td gt lt xsl value of select subject gt lt td gt lt tr gt lt tr gt lt td gt Location lt td gt lt td gt lt xsl value of select location gt lt td gt lt tr gt lt tr gt lt td gt Note lt td gt lt td gt lt xsl value of select note gt lt td gt EE table lt xsl template gt Ckckck ck KKK KKK KKK KKK KKK KK KKK KKK KKK Sk KK SKK CK C Kk CK kk kk Sk KC Sk kk kk KKK KK KKK KK KK when template KKK KKK ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck k ck ck ck ck k ck ck ck kk k ck k ck ck k ck ck ck ck ck ck ck kc ck k kk M lt xsl template match when gt lt p gt lt xsl value of select date month gt lt xsl text gt lt xsl text gt lt xsl value of select date day gt lt xsl text gt lt xsl text gt lt xsl value of select date year gt from lt xsl value of select startTime hour gt lt xsl text gt lt xsl text gt lt xsl value of select startTime minute gt
98. ck k k KKK KKK KKK xx template KCKCKCkCkCk ckck ck kckckckckckckck kc kckck ck ck ck KKK ck k ck ck ck ck ck k ck ck ck ck k ck ck k ck ck ck ck k ck KKK KKK KKK k kk D gt lt xsl template match gt continue the process xsl apply templates select another XPath expression gt you can also include more content here or even include multiple apply templates lt xsl template gt lt xsl stylesheet gt Deciding how to modularize the stylesheet is a subjective process One suggestion is to look for moderately sized chunks of XML data repeated numerous times throughout a document For example a lt customer gt element may contain a name address and phone number Creating a template that matches customer is probably a good idea You may even want to create another template for the lt name gt element particularly if the name is broken down into subelements or if the name is reused in other contexts such as lt employee gt and lt manager gt When you need to produce HTML tables or unordered lists in the result tree two templates instead of one can make the job very easy The first template will produce the lt table gt or lt ul gt element and the second will produce each table row or list item The following fragment illustrates this basic pattern lt the outer template produces the unordered list gt note plural customers gt lt xsl template match customers gt
99. ck ok kk ck ck ck ck kk kk ko ck ko ck ck ck ck ko Sk ko Sk ko kx koX The result tree is XHTML Kok KK KKK KKK ck ck ck kk ck KK ck ck ck ck ck ck ck ck ck k Ck ck ck ck ck ck ck ck k k KK ck k ck k ck ck ck ck ck ck ck ck ck ck ck kc k k k k kk kk xsl output method xml doctype public 2 W3C DTD XHTML 1 0 Transitional EN doctype system http www w3 org TR xhtml1 DTD xhtmll transitional dtd encoding UTF 8 ess KEKE KKK KKK ck ck ck KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK ck ck ck kc ck ck ck kk The navigation category is determined by the meta tag in the source XHTML document The top navigation bar uses this variable KCKCK CK CK CK CK Kk Kk I I IK KK SKK KKK KK KKK KKK KKK S kk S I KK Kk KKK KKK KKK KKK kk kk lt xsl variable name global nav category gt xsl choose xsl when test html head meta name navigationCategory gt lt xsl value of selectz html head meta name navigationCategory content gt xsl when xsl otherwise xsl text unknown xsl text xsl otherwise xsl choose xsl variable 1 KKK KK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK ko ckckock ckckck kc kockckckockckckckckckckockckckokck This template produces the XHTML document CkCck kk ck ckckck ckck ck kck ck kckck ckckck kck ck kckckckck ck kck ck KK KK ck ck ck ck ck KK KK KK KKK KK KK ck ck k k kk kkk lt xsl template match
100. class is used as the key MapKey key new MapKey xmlFileName xsltFileName File xmlFile new File xmlFileName File xsltFile new File xsltFileName Next the value is retrieved from the cache Another helper class MapValue keeps track of the transformation result and when each file was last modified If this is the first request the value will be null Otherwise the isDirty method determines if either file has been updated MapValue value MapValue cache get key if value null value isDirty xmlFile xsltFile this step performs the transformation value new MapValue xml e xsltFile cache put key value return value result l j As the comment indicates constructing a new MapValue causes the XSLT transformation to occur Unless exceptions are thrown the result of the transformation is returned to the caller When compared to the results shown earlier in Table 9 4 this approach to caching is much faster In fact the average response time is less than a millisecond once the initial transformation has been performed This approach is quite easy to implement for applications based on a collection of static files but is significantly more difficult for database driven applications Since more dynamic applications may generate new XML with each invocation a generic utility class cannot simply cache the result of the transformation Stale data is the biggest problem with dynamic caching Wh
101. code beautifier is another option Products such as JIndent http www jindent com can automatically clean up Java code by wrapping long lines inserting spaces and putting braces at the correct locations If you are fortunate enough to have access to a tool like this you can ignore most whitespace issues in the XSLT and rely on JIndent to fix formatting problems later on 8 6 Internationalization with XSLT In this section we explore the key techniques for internationalization i18n using XSLT Although both Java and XSLT offer excellent support for i18n pulling everything together into a working application is quite challenging Hopefully this material will help to minimize some of the common obstacles 8 6 1 XSLT Stylesheet Design In its simplest form i18n is accomplished by providing a separate XSLT stylesheet for each supported language While this is easy to visualize it results in far too much duplication of effort This is because XSLT stylesheets typically contain some degree of programming logic in addition to pure display information To illustrate this point directory xml is presented in Example 8 16 This is a very basic XML datafile that will be transformed using either English or Spanish XSLT stylesheets Example 8 16 directory xml oN lt xml version 1 0 encoding UTF 8 gt lt directory gt lt employee category manager gt lt name gt Joe Smith lt name gt lt phone gt 4 0192 lt phone gt
102. code however For instance we could have searched for common functionality and included that functionality from both stylesheets using xs1 import or xsl include This approach did not work here because although the stylesheets were structured similarly each template produced different output As the web site gets more sophisticated however you will begin to encounter common page elements such as navigation bars that should not be duplicated in multiple places Another approach would be to combine both stylesheets into a single stvlesheet and pass a top level parameter indicating whether to use edit mode or confirm mode In this approach the servlet would pass the parameter to the stylesheet via JAXP s Transformer class and the xsl param element Inside of the stylesheet we would write lots of xsl choose or lt xsl if gt elements to control the output based on the value of the parameter The JAXP code would look something like this javax xml transform Transformer trans trans setParameter personalDataMode edit While this approach has its place it did not make sense for this particular example because every template produced different output It would have resulted in a more complex solution than simply writing two separate stylesheets On the other hand if you encounter a situation where several web pages are almost identical except for a small section that changes passing a stylesheet paramete
103. commas so the entire line is the token firstToken curLine remove redundant quotes firstToken cleanupQuotes firstToken emit the lt value gt element ch startElement value EMPTY_ATTR ch characters firstToken toCharArray 0 firstToken length ch endElement value recursively process the remainder of the line if remainderOfLine null parseLine remainderOfLine ch locate the position of the comma taking into account that a quoted token may contain ignorable commas private int locateFirstDelimiter String curLine if curLine startsWith boolean inQuote true int numChars curLine length for int i l i numChars i char curChar curLine charAt i if curChar inQuote inQuote else if curChar amp amp inQuote return i return 1 else return curLine indexOf remove quotes around a token as well as pairs of quotes within a token private String cleanupQuotes String token StringBuffer buf new StringBuffer int length token length int curIndex 0 if token startsWith amp amp token endsWith curIndex 1 length boolean oneQuoteFound false boolean twoQuotesFound false while curIndex lt length char curChar token charAt curIndex if curChar twoQuotesFound oneQuoteFound true false
104. create the required XML data The next JDOM producer class shown in Example 7 22 is quite simple It merely creates an XML view of an individual message Example 7 22 ViewMessageJDOM java package com oreilly forum xml import com oreilly forum domain import java util Date import org jdom import org jdom output Generate JDOM for the View Message pag y public class ViewMessageJDOM Qparam message the message to view param inResponseTo the message this one is in response to or perhaps null ii public static Element produceElement Message message MessageSummary inResponseTo Element messageElem new Element message messageElem addAttribute id Long toString message getID DayMonthYear d message getCreateDate messageElem addAttribute Integer toString messageElem addAttribute Integer toStrin messageElem addAttribut Integer toStrin d getMonth DNS day g d getDay bag e g year d getYear s Element boardElem BoardSummaryJDOM produceNamelIDElement message getBoard messageElem addContent boardElem if inResponseTo null Element inRespToElem new Element inResponseTo addAttribute id Long toString inResponseTo getID inRespToElem addContent new Element subject setText inResponseTo getSubject messageE
105. databaseURL databaseURL ForumConfig adapterClassName adapterClassName Qreturn the JDBC driver class name SA public static String getJDBCDriverClassName return ForumConfig jdbcDriverClassName return the JDBC database URL ur d public static String getDatabaseURL return ForumConfig databaseURL er public static String getAdapterClassName return ForumConfig adapterClassName return the data adapter implementation class name private ForumConfig The DataException class is a very basic exception that indicates a problem with the back end data source It hides database specific exceptions from the client leaving the door open for nondatabase implementations in the future For example an EJB tier could be added but the EJBs would throw RemoteException and EJBExcept ion instead of SOLException Therefore whenever a specific exception is thrown it is wrapped in an instance of DataException before being propogated to the caller The source code for Dat aExcept ion is found in Appendix B The code for Dat aAdapter shown in Example 7 16 demonstrates how each method throws DataException This class is the centerpiece of the data abstraction layer insulating the domain classes from the underlying database implementation Example 7 16 DataAdapter java package com oreilly forum adapter import com oreilly forum import com or
106. date and time in some other format this approach makes it really easy to issue queries such as SELECT subject FROM Message WHERE createMonth 3 AND createYear 2001 The essage boardiD column is a foreign key that identifies which board a message belongs to The Message msgText column can contain an unlimited amount of text while the remaining fields all contain fixed length text If you are using MySQL Example 7 17 shows a dump file that can be used to easily recreate the database using the import utility that comes with the database Example 7 17 MySQL dump MySQL dump 8 8 E Host localhost Database forum Server version 3 23 23 beta Table structure for table board CREATE TABLE board id bigint 20 DEFAUL 0O NOT NULL name char 80 DEFAUL re NOT NULL description char 255 DEFAULT NOT NULL PRIMARY KEY id s i Dumping data for table board it INSERT INTO board VALUES 0 XSLT Basics How to create and use XSLT stylesheets and processors INSERT INTO board VALUES 1 JAXP Programming Techniques How to use JAXP 1 1 Table structure for table message CREATE TABLE message id bigint 20 DEFAULT 0 NOT NULL inReplyToID bigint 20 DEFAULT 0 NOT NULL createMonth int 11 DEFAULT 0 NOT NULL creat
107. device Grouping cards into decks increases performance because the wireless device can make fewer requests to the server as the user navigates from card to card The first card in this example prompts the user to enter his first name and age Unlike HTML form techniques these values are stored in the WML variables first Name and age This is much better than posting a form to the server because of the limited bandwidth available to wireless devices The age field illustrates another interesting feature of WML that does not exist in HTML input name age format N gt The format attribute shown here indicates that the user can enter any number of numeric digits or decimal points Formats for date entry telephone numbers and other known patterns can also be configured using simple pattern strings defined by the WML specification This is a big advantage over traditional web techniques that require scripting language support to perform client side validation Table 10 1 lists all of the format patterns supported by WML 1 1 1 Not all devices support this feature Table 10 1 WML format strings Format Displays A Uppercase letters symbols and punctuation characters not numbers a Lowercase letters symbols and punctuation characters not numbers N Any number n Any number symbol or punctuation character Same as 7 but includes numbers x Same as a but includes numbers M Any charact
108. does not While differences like these should diminish as vendors have more time to implement the complete WML specification there are no guarantees as to how buttons and lt input gt fields will be displayed In many cases lt do gt tags are mapped to physical buttons on the cell phone keypad rather than displayed as buttons on the screen 10 3 1 1 WMLScript and WBMP Because of bandwidth constraints scripting capability is critical for wireless devices WAP defines a scripting language called WMLScript which is tightly integrated with WML and features a syntax that is very similar to JavaScript With WMLScript form validation and lightweight processing can be performed on the client device greatly reducing the number of requests to a server Wireless Bitmap WBMP is a very simple image format that as expected is optimized for small devices WBMP files are black and white and can be created with a number of free tools There is even a free web site at http www teraflops com wbmp that will convert GIF JPEG and BMP images to WBMP using a browser based interface Again refer to Learning WML amp WMLScript for the complete story on these technologies 10 3 2 Servlets and WML Servlets are important to wireless developers because they can detect the type of client device Different XSLT stylesheets can then be selected for regular web browsers sophisticated PDAs and simple cell phones 10 3 2 1 Identifying the client Detecti
109. each page in the discussion forum application is created using a subclass of Renderer Example 7 27 Renderer java package com oreilly forum servlet import java io import javax servlet import javax servlet http All page renderers must extend from this class ny public abstract class Renderer public abstract void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException The most basic renderer is ErrorRenderer which is shown in Example 7 28 This class displays an error message in a web browser using simple printin statements that generate HTML Unlike all other parts of this application the ErrorRenderer class does not use XML and XSLT The reason for this is that a large percentage of errors occurs because an XML parser is not properly configured on the CLASSPATH If this sort of error occurs this renderer will not be affected I CLASSPATH issues are discussed in great detail in Chapter 9 ErrorRenderer can be written to use XML and XSLT provided that a try catch block catches any transformation errors and reverts to printin statements for error reporting Example 7 28 ErrorRenderer java package com oreilly forum servlet import java io import javax servlet import javax servlet http Shows an error page Since errors are frequently caused by improperly configured JAR files XML And XSLT
110. examples in this chapter the XML will always reside in a text file In future chapters however we will see how to improve performance by dealing with the XML as an in memory object tree This makes sense from a Java XSLT perspective because most web applications will generate XML dynamically rather than deal with a series of static files Since the XML data and XSLT stylesheet are clearly Separated it is very plausible to write several different stylesheets that convert the same XML into radically different formats I Section 2 7 of the XSLT specification covers embedded stylesheets XSLT transformation can occur on either the client or server although server side transformations are currently dominant Since a vast majority of Internet users do not use XSLT compliant browsers at the time of this writing the typical model is to transform XML into HTML on the web server so the browser sees only the resulting HTML In a closed corporate environment where the browser feature set can be controlled moving the XSLT transformation process to the browser can improve scalability and reduce network traffic It should be noted that XSLT stylesheets do not perform the same function as Cascading Style Sheets CSS which you may be familiar with In the CSS model style elements are applied to HTML or XML on the web browser affecting formatting such as fonts and colors CSS do not produce a separate result tree and cannot be applied in advance using a s
111. f T Business Teche Fune Interact The Schedule Java class has a method called get TodaysShows that returns an array of Show objects The array is already sorted which reduces the amount of work that the servlet has to do to generate this page The Schedule and Show classes are used for all of the remaining examples in this chapter Ideally this will help demonstrate that no matter which approach you take keeping business logic and database access code out of the servlet makes it easier to move to new technologies without rewriting all of your code The code for ScheduleServlet java is shown in Example 4 1 This is typical of a first generation servlet generating its output using a series of printin statements Example 4 1 ScheduleServlet java package chap4 import java io import java text SimpleDateFormat import javax servlet import javax servlet http public class ScheduleServlet extends HttpServlet public void doGet HttpServletRequest request HttpServletResponse response throws IOException ServletException SimpleDateFormat dateFmt new SimpleDateFormat hh mm a Show shows Schedule getInstance getTodaysShows response setContentType text html PrintWriter pw response getWriter pw println html head title Today s Shows lt title gt lt head gt lt body gt pw printin lt hl gt Today s Shows lt h1 gt pw println table border 1 cellpad
112. faulty assumption Performance can vary greatly depending on how large the input files are and which features of XSLT are used It is wise to test performance with your application before choosing one set of tools over another 9 3 3 2 Result caching When the XML is highly dynamic and changes with each request XSLT caching may be the best one can hope for But when the same data is requested repeatedly such as on the home page for your company it makes sense to cache the result of the transformation rather than the XSLT stylesheet This way the transformation is performed only when the XML or XSLT actually change Example 9 15 presents a utility class that caches the results of XSLT transformations In this implementation both the XML data and XSLT stylesheet must come from static files If the timestamp of either file changes the transformation is performed again Otherwise a cached copy of the transformation result is returned to the caller Example 9 15 ResultCache java package com oreilly javaxslt util import java io import java util import javax xml transform import javax xml transform stream A utility class that caches XSLT transformation results in memory Qauthor Eric M Burke ud public class ResultCache private static Map cache new HashMap Flush all results from memory emptying the cache EY public static synchronized void flushAll cache clear
113. four unit test methods then setUp and tearbovwn Will each be called four times For our purposes the setUp method locates all of the files that will be used for XSLT transformations These include XML input files the XSLT stylesheet and the XSLT result targets It also performs some simple testing assertNotNull workingDir assert Unable to locate new File this workingDir exists this workingDir These assert methods are part of the JUnit framework causing test failures when the tested condition is not true These are the heart of what programmers write when creating unit tests and can be used in any of the test methods or in the setUp andtearDown methods When an assertion is not true JUnit reports an error message and the line number where the failure occurred This is known as a test failure which is different than a test error An error is reported when JUnit catches an exception that one of the unit tests throws 6 JUnit 3 7 renamed the assert method assert True to avoid conflicts with the new JDK 1 4 assertion facility This first unit test in our example is the test TransformWithTemplates method Because this method name begins with test JUnit can use reflection to locate it The job of this test is to merely perform an XSLT transformation using JAXP s Templates interface delegating to the validateCondensedFile method to do the actual testing This approach is taken because
114. from Chapter 2 and 3 5 1 2 Xalan 1 Implementation The complete code for the Xalan implementation is listed in Example 5 1 As comments in the code indicate this code was developed and tested using Xalan 1 2 2 which is not the most recent XSLT processor from Apache Fully qualified Java class names such as org apache xalan xslt XSLTProcessor are used for all Xalan specific code A Xalan 2 example is not shown here because Xalan 2 is compatible with Sun s JAXP The JAXP version of this program works with Xalan 2 as well as any other JAXP compatible processor Example 5 1 SimpleXalan1 java package chap5 import java io import java net MalformedURLException import java net URL import org xml sax SAXException A simple demo of Xalan 1 This code was originally written using Xalan 1 2 2 It will not work with Xalan 2 public class SimpleXalanl Accept two command line arguments the name of an XML file and the name of an XSLT stylesheet The result of the transformation is written to stdout gr public static void main String args throws MalformedURLException SAXException if args length 2 System err println Usage System err println java SimpleXalanl class get Name xmlFileName xsltFileName System exit 1 String xmlFileName args 0 String xsltFileName gs 1 String xmlSystemId new File xmlFileName toURL toExternal
115. fulfilling the request If the client is a browser the XSLT stylesheet will probably transform the XML into HTML or XHTML For a nonbrowser client however it is conceivable that the XML data is delivered directly without any XSLT transformation 4 3 1 Tradeoffs Scalability is a key motivation for a multitier EJB architecture In such an architecture each tier can execute on a different machine Additional performance gains are possible when multiple servers are clustered on each tier Another motivating factor is reliability If one machine fails a redundant machine can continue processing When updates are made new versions of software can be deployed to one machine at a time preventing long outages Security is improved by strictly regulating access to the data tier via EJB components Yet another motivation for a distributed system is simplicity although a basic EJB application is far more complex than a simple two tier application Yes distributed systems are complex but for highly complex applications this approach simplifies your work by dividing independent tasks across tiers One group of programmers can work on the EJB components while another works on the request handler classes on the web tier Yet another group of designers can work on XML and XSLT while your database expert focuses on the database For simple applications a multitier EJB approach is overkill and will likely harm performance If your web site serves only a fe
116. gt n ct ct ct ll xsl when test monthNumber 4 gt May lt xsl when gt xsl when test SmonthNumber 5 gt Jun lt xsl when gt xsl when test SmonthNumber 6 gt Jul lt xsl when gt xsl when test SmonthNumber 7 gt Aug lt xsl when gt xsl when test monthNumber 8 Sep xsl when xsl when test SmonthNumber 9 gt Oct lt xsl when gt xsl when test monthNumber 10 Nov xsl when xsl when test SmonthNumber 11 gt Dec lt xsl when gt lt xsl choose gt lt xsl template gt lt xsl template name utils printLongMonthName gt xsl param name monthNumber gt lt xsl choose gt xsl when test SmonthNumber 0 gt January lt xsl when gt xsl when test SmonthNumber 1 gt February lt xsl when gt xsl when test SmonthNumber 2 gt March lt xsl when gt xsl when test monthNumber 3 gt April lt xsl when gt xsl when test SmonthNumber 4 gt May lt xsl when gt xsl when test SmonthNumber 5 gt June lt xsl when gt xsl when test S monthNumber 6 gt July lt xsl when gt xsl when test S monthNumber 7 gt August lt xsl when gt xsl when test SmonthNumber 8 gt September lt xsl1 when gt xsl when test monthNumber 9 gt October lt xsl when gt xsl when test SmonthNumber 10 gt November lt xsl when gt xsl when test SmonthNumber 11 gt December lt xsl when gt xsl ch
117. gt xsl with param name url select home xml gt xsl call template xsl call template name navButton xsl with param name category select company xsl with param name displayName select Company xsl with param name url select company xml lt xsl call template gt xsl call template name navButton gt xsl with param name category select products xsl with param name displayName select Products xsl with param name url select products xml gt lt xsl call template gt xsl call template name navButton gt xsl with param name category select jobs xsl with param name displayName select 2 Jobs xsl with param name url select jobs xml xsl call template lt xsl template gt lt KAKKKKKKKKKKK KKK KKK k ck ck ck KKK KKK KKK ck KKK kck ck kck ck ck ck ck ck ck ck ck kck ck ck ck ck ck ck ck ck kk k k kk kk This template produces a button in the top navigation bar KCKCkCKCk Ck ckckckckck ck ck ck ck ckckck ck ck ckck kc kckckckckckckckck ck k ckckck kckck ck ck ck KKK ck ck KKK KKK KKK ck ck kc KK KK xsl template name navButton xsl param name category xsl param name displayName xsl param name url lt xsl choose gt The current category is displayed as text gt xsl when test category global nav category lt xsl value of sel
118. icl saxon trax Result result new com icl saxon trax Result System out The XSLT stylesheet is then compiled resulting in an object that can be used repeatedly from many concurrent threads com icl saxon trax Templates templates processor process xsltInputSource In a typical XML and XSLT web site the XML data is generated dynamically but the same stylesheets are used repeatedly For instance stylesheets generating common headers footers and navigation bars will be used by many pages To maximize performance you will want to process the stylesheets once and reuse the instances for many clients at the same time For this reason the thread safety that Templates offers is critical An instance of the Transformer class is then created to perform the actual transformation Unlike the stylesheet itself the transformer cannot be shared by many clients and is not thread safe If this was a servlet implementation the Transformer instance would have to be created with each invocation of doGet or doPost In our example the code is as follows com icl saxon trax Transformer rans templates newTransformer Js trans transform xmllInputSource sult 5 1 4 SAXON Xalan or TrAX As the previous examples show SAXON and Xalan have many similarities While similarities make learning the various APIs easy they do not result in portable code If you write code directly against either of these interfaces you lock yoursel
119. id 1 name Java Programming gt oN eBoard id name XML Programming gt igeBoard id 3 name XSLT Questions gt lt discussionForumHome gt It is assumed that this data will be generated dynamically as the result of a database query rather than hardcoded as a static XML file Regardless of its origin the XML data says nothing about how to actually display the web page For clarity we will keep the XSLT stylesheet fairly simple at this point The beauty of an XML XSLT approach is that you can beef up the stylesheet later on without compromising any of the underlying XML data structures Even more importantly the Java code that will generate the XML data does not have to be cluttered up with HTML and user interface logic it just produces the basic XML data Once the format of the data has been defined a Java programmer can begin working on the database logic and XML generation code while another team member begins writing the XSLT stylesheets Example 2 2 lists the XSLT stylesheet that produces the home page Don t worry if not everything in this first example makes sense XSLT is after all a completely new language We will cover everything in detail throughout the remainder of this and the next chapter Example 2 2 discussionForumHome xslt lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt xsl output method html match t
120. in Example 6 7 It is responsible for converting PersonalData objects into DOM Document objects By converting to DOM instead of a text XML file we avoid having to parse the XML as it is fed into an XSLT processor Instead we will use the javax xml transform DOMSource Class to pass the DOM tree directly Example 6 7 PersonalDataXML java package chap import javax xml parsers import org w3c dom Responsible for converting a PersonalData object into an XML representation using DOM public class PersonalDataXML param personalData the data to convert to XML param includeErrors if true an extra field will be included in the XML indicating that the browser should warn the user about required fields that are missing return a DOM Document that contains the web page A public Document produceDOMDocument PersonalData personalData boolean includeErrors throws ParserConfigurationException u Docu se Sun s JAXP to create the DOM Document mentBuilderFactory dbf mentBuilder docBuilder ment doc docBuilder newDocument Docu Docu dbf newDocumentBuilder create page the root of the document Element pageElem doc createElement page doc appendChild pageElem if needed if append requiredFieldsMissing includeErrors amp amp personalData isValid pageElem appendChild doc createElement requiredFieldsMissing
121. in earlier chapters concluding with a detailed discussion of XSLT internationalization Other topics include XSLT page layout templates servlet session tracking without cookies browser identification and servlet filters Chapter 9 Offers practical advice for making a wide range of XML parsers XSLT processors and various other Java tools work together Shows how to resolve conflicts with incompatible XML JAR files how to write simple unit tests with JUnit and how to write custom JAXP error handlers Also discusses performance techniques and the relationship between XSLT and EJB Chapter 10 Describes the world of wireless technologies with emphasis on Wireless Markup Language WML Shows how to detect wireless devices from a servlet how to write XSLT stylesheets for these devices and how to test using a variety of cell phone simulators An online movie theater application is developed to reinforce the concepts Appendix A Contains all of the remaining code from the discussion forum example presented in Chapter 7 Appendix B Lists and briefly describes each of the classes in Version 1 1 of the JAXP API Appendix C Contains a quick reference for the XSLT language Lists all XSLT elements along with required and optional attributes and allowable content within each element Also cross references each element with the W3C XSLT specification Conventions Used in This Book Italic is used for e Pathnames filenames and program
122. in this case The first version 1 0 specifies the version of the XSLT specification Although this is the current version at the time of this writing the next version of the XSLT specification is well underway and may be finished by the time you read this You can stay abreast of the latest XSLT developments by visiting the W3C home page at http www w3 org The next attribute declares the XML namespace defining the meaning of the xs1 prefix you see on all of the XSLT elements The prefix s1 is conventional but could be anything you choose This is useful if your document already uses the xs1 prefix for other elements and you do not want to introduce a naming conflict This is really the entire point of namespaces they help to avoid name conflicts In XML lt a book gt and lt b book gt can be discerned from one another because each book has a different namespace prefix Since you pick the namespace prefix this avoids the possibility that two vendors will use conflicting prefixes In the case of XSLT the namespace prefix does not have to be xs1 but the value does have to be http www w3 0rg 1999 XSL Transform The value of a namespace is not necessarily a real web site but the syntax is convenient because it helps ensure uniqueness In the case of XSLT 1999 represents the year that the URL was allocated for this purpose and is not related to the version number It is almost certain that future versions of XSLT will continue to us
123. including stylesheet This can result in problems when two conflicting template rules are included so you must be careful to plan ahead to avoid any conflicts When a conflict occurs the XSLT processor should report an error and halt 3 3 2 xsl import Importing rather than including a stylesheet adds some intelligence to the process When conflicts occur the importing stylesheet takes precedence over any imported stylesheets Unlike lt xsl include gt lt xsl import gt elements must occur before any other element children of xsl stylesheet as shown here lt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt lt xsl import must occur before any other top level elements gt lt xsl import href pageElements xslt lt xsl import href globalConstants xslt gt xsl output method html lt xsl template match gt lt html gt lt html gt lt xsl template gt lt but xsl include can occur anywhere provided it is a top level element gt xsl include href nameFormatting xslt gt lt xsl stylesheet gt For the purposes of most web sites the most common usage pattern is for each page to import or include common stylesheet fragments such as templates to produce page headers footers and other reusable elements on a web site Once a stylesheet has been included or imported its templates can be used as if they were in
124. install XML support into Tomcat 4 0 simply install the required JAR files into the TOMCAT_HOME lib directory These will then be available to all web applications The other option is to install JAR files into the WEB INF lib directory of individual web applications With this approach each application can use different versions of various packages without fear of conflicts 9 2 Testing and Debugging The software development community has shown a renewed interest in testing during the past few years Much of this has been driven by the eXtreme Programming methodology which emphasizes lightweight processes and constant unit testing to promote quality To demonstrate how to test XSLT transformations a few simple files will be used The XML data is shown first in Example 9 4 5 See http www xprogramming com for more information on eXtreme Programming Example 9 4 aidan xml xml version 1 0 encoding UTF 8 lt person gt lt firstName gt Aidan lt firstName gt lt middleName gt Garrett lt middleName gt lt lastName gt Burke lt lastName gt lt birthDate month 6 day 25 year 1999 gt lt person gt Although this data is trivial the same concepts apply to larger more realistic examples The sample XSLT stylesheet is shown in Example 9 5 Example 9 5 condensePerson xslt lt xml version 1 0 encoding UTF 8 gt spec Ck ck Ck ck ck ck ck ck ck ck ck CK KKK KKK ck ck ck Ck ck ck ck ck ck ck ck kk Ck c
125. int cl String xsl LentType tDir null switch clientType case WML CLIENT TYPE xsltDir wml break case XHTML CLIENT TYPE xsltDir xhtml break default throw new IllegalArgumentException Illegal int pageToShow clientType clientType String xsltName null switch pageToShow case HOME_PAGE xsltName home xslt break case THEATERS PAGE xsltName theaters xslt break case SHOWTIMES PAGE xsltName showtimes xslt break default n throw new IllegalArgumentException Illegal pageToShow pageToShow locate a platform dependent path String fullPath getServletContext getRealPath WEB INF xslt xsltDir xsltName return new File fullPath Determines the type of user agent Qreturn either XHTML CLIENT TYPE or WML CLIENT TYPE n private int determineClientType HttpServletRequest req first check for normal web browsers that claim to be mozilla compliant String userAgent req getHeader User Agent if userAgent null amp amp userAgent toLowerCase startsWith mozilla return XHTML CLIENT TYPE Gl if the client accepts wml it must be a WAP compatible device String accept req getHeader Accept if accept null amp amp accept indexOf text vnd wap wml gt 1
126. is to analyze log files to see which pages are requested most often and to focus optimization efforts there 9 3 4 Writing Effective XSLT A big performance hit can be incurred during the XSLT transformation process For large XML documents in particular try to avoid situations where large portions of the tree must be processed repeatedly The operator can be particularly dangerous xsl apply templates select name gt In this statement the entire document is recursively searched for all lt name gt elements beginning at the root The XSLT processor has no way of knowing where lt name gt might appear so it must check every node in the document If the specific path is known a more efficient approach is xsl apply templates select company employee name Variables can also be used to improve performance For example key pieces of data may be copied to the result tree several times Do not do this each time the company owner s name must lect company owner name last gt ct company owner name first gt Instead assign the name to a variable once and reuse that variable throughout the stylesheet This has the added benefit of making the XSLT more readable output the value of the companyOwner variable gt ner gt lt xsl value of select ScompanyOw Another common tip is to write inline code wherever possible Instead of using lt xs1 apply templates to recursively process XML da
127. just copy chap6 war to the TOMCAT HOME webapps directory while Tomcat is not running You can attempt to execute the servlet now but it will probably not work because axp jar xalan jar and crimson jar must be installed in the TOMCAT_HOME lib directory before they can be available for your web application The most difficult aspect of this step is installing the correct versions of these JAR files Depending on which version of Tomcat you are running older versions of jaxp jar and crimson jar may already be found in the TOMCAT_HOME lib directory The safest approach is to download JAXP 1 1 which includes all three of these JAR files and copy them from the JAXP distribution to the TOMCAT_HOME lb directory Once these steps are complete start Tomcat and access the following URL http localhost 8080 chap6 personalData This should bring up the personal information page with a blank form ready for input 6 3 6 Locating Stylesheets with Initialization Parameters As you just saw an easy way to locate stylesheets is simply to place them somewhere underneath the WEB INF directory of a WAR file While this is an ideal solution for solitary web applications there are situations where the same stylesheets are shared across a whole group of web apps In this case embedding the stylesheets into various WAR files is not viable Ideally the stylesheets will be located in a shared directory somewhere but that directory location will not be hardcoded
128. line arg contains a file name on Windows something like C home index xml1 on Unix something like usr home index xml String fileName args 0 File fileObject new File fileName URL fileURL fileObject toURL s String systemID fileURL toExternalForm 3 This code was written on several lines for clarity it can be consolidated as follows String systemID new File fileName toURL toExternalForm Converting from a system identifier back to a filename or a File object can be accomplished with this code URL url new URL systemID String fileName url getFile File fileObject new File fileName And once again this code can be condensed into a single line as follows File fileObject new File new URL systemID getFile Joys 5 3 2 JAXP I O Design The Source and Result interfaces in javax xml transform provide the basis for all transformation input and output in JAXP 1 1 Regardless of whether a stylesheet is obtained via a URI filename or 1nputStream its data is fed into JAXP via an implementation of the Source interface The output is then sent to an implementation of the Result interface The implementations provided by JAXP are shown in Figure 5 3 Figure 5 3 Source and Result interfaces lt lt interface gt gt lt lt interface gt gt Source Result getSystemld String getSystemid String setSystemld systemld String void setSystemld systemld St
129. line that specifies the implementation of TransformerFactory com foobar AcmeTransformer in our fictitious example If you look inside of xalan jar in JAXP 1 1 you will find this file In order to utilize a different parser that follows the JAXP 1 1 convention simply make sure its JAR file is located first on your CLASSPATH Finally if JAXP cannot find an implementation class from any of the three locations it uses its default implementation of TransformerFactory To summarize here are the steps that JAXP performs when attempting to locate a factory 1 Use the value of the javax xml transform TransformerFactory system property if it exists 2 If JRE lib jaxp properties exists then look for a javax xml transform TransformerFactory ImplementationClass entry in that file 3 Use a JAR file service provider to look for a file called META INF services javax xml transform TransformerFactory in any JAR file on the CLASSPATH 4 Use the default TransformerFactory instance The JAXP 1 1 plugability layers for SAX and DOM follow the exact same process as the XSLT layer only they use the javax xml parsers SAXParserFactory and javax xml parsers DocumentBuilderFactory system properties respectively It should be noted that JAXP 1 0 uses a much simpler algorithm where it checks only for the existence of the system property If that property is not set the default implementation is used 5 2 3 The Transformer Class As shown in Example 5
130. lt employee gt lt employ category programmer name Sally Jones lt name gt phone 4 2831 phone lt employee gt lt employ category programmer lt name gt Roger Clark lt name gt phone 4 3345 phone lt employee gt lt directory gt The screen shot shown in Figure 8 6 shows how an XSLT stylesheet transforms this XML into HTML And finally Example 8 17 lists the XSLT stylesheet that produces this output Figure 8 6 English XSLT output Zj Employee Directory Microsoft Internet Explorer L OE x Ele Edi View Favodes ook Help EJ amp 2 9 gi amJ Stop _Rehesh Home Search Favorites History Address sf A C AevedataNaveiifeseneledchaptan chap Be directory xml Qao i Employee Directory Name Category Phone Joe Smith Manager 40192 Sally Jones Programmer 4 2831 Roget Clark Programmer 43345 Example 8 17 directory basic xslt lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl output method html encoding UTF 8 lt xsl template match gt lt html gt lt head gt lt title gt Employee Directory lt title gt lt head gt lt body gt lt hl gt Employee Directory lt h1 gt lt table cellpadding 4 cellspacing 0 border 1 gt lt tr gt lt th gt Name lt th gt lt th gt Category lt th gt lt th gt Phone lt th gt te lt xsl for each select d
131. lt head gt and lt body gt elements Somewhere within this template you must tell the processor to continue searching for additional patterns thus beginning the recursive transformation process In a typical stylesheet lt xsl apply templates gt is used for this purpose instructing the processor to search for additional content in the XML data It should be stressed that this is not the only way to write a stylesheet but it is a very natural way to handle the recursive nature of XML Example 2 4 contains a skeleton XSLT stylesheet that you can use as a starting point for most of your projects Example 2 4 Skeleton stylesheet lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt lt xsl output method html Ckckck KKK KKK KKK KKKK KKK KKK KK KKK KKK KKK KKK KKK kk KC Sk KC Sk kk Sk ks KKK KK KKK KK KK template matches the document and is the starting point CC Ck ck ck ck ck ck ck ck ck ck ck ck Ck Ck ck ck ck ck kk kk CC CC C Ck Ck Ck Ck CK C C S SS Sk ck ck Ck Ck ko ko ko ko Ax kx AG X X gt lt xsl template match gt lt html gt lt head gt lt title gt title goes here lt title gt lt head gt lt body gt lt xsl apply templates select some XPath expression gt lt body gt lt html gt lt xsl template gt HARK KKKKKKKKKKKKKKKKKKKKKKKK kCkCkCk kc kck ck ck ck k k ck ck k KK KKK kCkck kc Ck ck
132. message belongs to one of these boards and may be a response to a previous message This is known as a threaded discussion forum Each message will also contain a subject create date author email and the actual message text When visiting the web site users can read existing messages post new messages or reply to existing messages Only administrators can create new message boards Although XHTML is specified for the reference implementation every effort will be made to facilitate alternatives such as XHTML Basic or WML Other than practical limitations such as bandwidth and database capacity no artificial constraints shall be placed on the number of boards or messages A few features will be omitted to keep this example reasonably sized These include a web based administrative interface user authentication and security and the ability to search the archive Suggestions for implementing these features are mentioned at the end of this chapter 7 1 2 Screen Flow The forum user interface consists of four primary screens as shown in Figure 7 1 Each box represents a different web page that visitors encounter and lines indicate screen to screen flow as the user clicks on links Figure 7 1 Discussion forum screens retur home return home select message Discussion Forum View Month hi y Home select month Show all message View M show all boards and subjects for the return essag months with mess
133. messages Apr 2001 a div div div class box2 lt h2 gt XSLT Basics lt h2 gt lt div gt Writing effective XSLT stylesheets lt div gt div style margin left 2em p lt a href link to post message Post Message lt a gt to XSLT Basics lt p gt lt a href link_to_feb_messages gt Feb 2001 lt a gt lt a href link_to_mar_messages gt Mar 2001 lt a gt lt a href link_to_apr_messages gt Apr 2001 lt a gt lt div gt lt div gt lt div class box2 gt lt h2 gt Sample empty board lt h2 gt lt div gt This board has no messages lt div gt lt div style margin left 2em gt lt p gt lt a href link_to_post_msg gt Post Message lt a gt to Sample empty board lt p gt lt div gt lt div gt lt body gt lt html gt lt div gt and lt span gt tags may be unfamiliar because they were ignored by many HTML authors until CSS became more prevalent Basically a lt div gt tag is wrapped around any number of other elements turning them into a block level element group The lt span gt tag is similar but it is an inline element This means that lt span gt tags will be embedded into the current line while lt div gt tags will wrap to a new line much like lt p gt or lt hi gt tags do The ability to define style classes make lt div gt and lt span gt particularly useful for XHTML Strict which disallows deprecated HTML 4 0 elements such as lt font gt Altho
134. method must be defined for custom servlet output streams public void write int data this bos write data BufferedHttpResponseWrapper calls this method public void reset this bos reset BufferedHttpResponseWrapper calls this method public void setBufferSize int size no way to resize an existing ByteArrayOutputStream this bos new ByteArrayOutputStream size The BufferedServletOutput Stream class extends directly from Servlet OutputStream The only abstract method in ServletOutputStream is write therefore our class must define that method Instead of writing the data to the client however our class writes the data to aByteArrayOutput Stream The remaining methods reset andsetBufferSize are required by the class shown in Example 8 10 Example 8 10 BufferedHttpResponseWrapper java package com oreilly javaxslt util import java io import javax servlet import javax servlet http A custom response wrapper that captures all output in a buffer ud public class BufferedHttpResponseWrapper extends HttpServletResponseWrapper private BufferedServletOutputStream bufferedServletOut new BufferedServletOutputStream private PrintWriter printWriter null private ServletOutputStream outputStream null public BufferedHttpResponseWrapper HttpServletResponse origResponse super origResponse public byte getBuffer return this
135. methods in the data objects themselves that know how to generate a fragment of XML or perhaps an entire document Another approach is to write an XML adapter class for each data object Instead of embedding the XML generation code into the data object the adapter class generates the XML This approach has the advantage of keeping the data objects lightweight and clean but it does result in additional classes to write In either approach it is preferable to return XML as a DOM or JDOM tree rather than raw XML text If the XML is returned as raw text it will have to be parsed right back into memory by the XSLT processor Returning the XML as a data structure allows the tree to be passed directly to the XSLT processor without the additional parsing step Yet another approach is to return XML directly from the EJB components thus eliminating the intermediate data objects Chapter 9 will examine this in detail primarily from a performance perspective The main drawback to consider is that XML tends to be very verbose Sending large text XML files from the application server to the web server may be less efficient than sending serialized Java objects You could compress the data but that would add processor overhead for compression and decompression Regardless of how the XML is generated the final step shown in Figure 4 7 is to pass the XML and stylesheet to the XSLT processor for transformation The result tree is sent directly to the client thus
136. mode In the code shown here both templates have modes so you must include a mode on xsi apply templates in order for one of your templates to be instantiated A complete stylesheet is shown in Example 3 6 In this example the name of a president may occur inside either a table or a list Instead of passing a parameter to the president template two modes of operation are defined In table mode the template displays the name as a row in a table In ist mode the name is displayed as an HTML list item Example 3 6 Template modes lt xml version 1 0 encoding UTF 8 v xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html 1 Demonstrates how to use template modes gt lt xsl template match gt lt html gt px dy gt lt h2 gt Presidents in an HTML Table lt h2 gt lt table border 1 gt r th Last Name lt th gt th First Name lt th gt tr xsl apply templates select president mode table gt lt table gt lt h2 gt Presidents in an Unordered List lt h2 gt lt ul gt lt xsl apply templates select president mode list gt lt ul gt lt body gt lt html gt lt xsl template gt lt l Display a president s name as a table row gt lt xsl template match president mode table gt lt tr gt lt td gt lt xsl value of select name last gt lt td gt lt td gt lt xsl value
137. movie mode createCar produce a card containing showtimes for a movie lt xsl template gt 10 4 The Future of Wireless Looking toward the future two things are inevitable First device capabilities will improve Color displays increased screen resolution increased memory and faster processors can be expected Second bandwidth will improve Migration to Third Generation 3G wireless networks is already underway in many countries offering bandwidth anywhere from 128Kbps to 2Mbps Partly because of these two advancements the WAP Forum and NTT DoCoMo have agreed to migrate towards XHTML Basic for future devices XHTML Basic uses a subset of XHTML Therefore it is far more familiar to web developers than WML Existing web browsers can already display XHTML Basic which is not the case with WML or cHTML XHTML Basic also utilizes CSS to define colors fonts and other presentation styles Newer more capable devices should be able to take advantage of far more style instructions than currently available devices The migration to XHTML Basic will not eliminate the need for technologies such as XSLT however Even though normal web browsers can display the same XHTML Basic web pages that wireless devices use devices such as cellular phones and pagers will always have tiny displays Most web applications will still need to maintain a simplified interface for these devices to minimize the amount of scrolling the user has to do Therefore XSLT
138. msgs hasNext MessageSummary curMsg MessageSummary msgs next Element elem produceMessageElement curMsg msgTree viewMonthElem addContent elem return viewMonthElem Produce a fragment of XML for an individual message This is a recursive function private static Element produceMessageElement MessageSummary msg MessageTree msgTree Element msgElem new Element message msgElem addAttribute id Long toString msg getID msgElem addAttribute day Integer toString msg getCreateDate getDay msgElem addContent new Element subject setText msg getSubject msgElem addContent new Element authorEmail setText msg getAuthorEmail Iterator iter msgTree getReplies msg while iter hasNext MessageSummary curReply MessageSummary iter next recursively build the XML for all replies msgElem addContent produceMessageElement curReply msgTree return msgElem private ViewMonthJDOM The recursive method that produces lt message gt elements is the only difficult code in ViewMonthJDOM Since message elements are nested according to replies the XML forms a recursive tree structure that could be arbitrarily deep JDOM supports this nicely because a JDOM Element can contain other nested Elements The pxroduceMessageElement method is designed to
139. must maintain state information as it waits for the browser to make another request As each browser request arrives it is the controller s job to validate the request and forward commands on to the model The controller then sends the results back to the view This may all sound academic and vague at this point The next few sections will present much more detailed diagrams that show exactly how MVC is implemented for an XSLT driven web site 4 2 3 XSLT Implementation All of the approaches presented up to this point are of course building up to the XSLT approach In many respects the XSLT approach is simultaneously the most powerful and the easiest to understand For a single web page the XSLT approach is probably harder than a servlet or JSP to configure Configuration of the XML parser and XSLT processor can be quite difficult mostly due to CLASSPATH issues But as the complexity of a web application increases the benefits of using XSLT become obvious Figuring out how to tackle these complex web applications is the real goal of this chapter 2 This can be a frustrating experience when the servlet container comes with an older XML parser that uses DOM or SAX Version 1 Most XSLT processors require Version 2 parsers The XSLT approach maps fairly directly to the MVC pattern The XML represents the model the servlet represents the controller and the XSLT produces HTML which represents the view The XSLT stylesheets may contain a m
140. of these XSLT elements the result tree will contain the following XHTML lt xml version 1 0 encoding UTF 8 lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Strict EN http www w3 org TR xhtmll DTD xhtmll strict dtd html xmlns http www w3 0rg 1999 xhtml lt html gt 3 6 3 2 Creating the dependency graph The most interesting and difficult aspect of this stylesheet is its ability to display the complete dependency graph for all Ant build targets The first step is to locate all of the targets that do not have any dependencies As shown in Example 3 13 these targets are named clean prepare and targets for the Tomcat build file They are selected by looking for lt target gt elements that do not have an attribute named depends show all target dependencies as a tree gt lt h3 gt Target Dependency Tree lt h3 gt xsl apply templates select target not depends mode tree gt xsl sort select name gt lt xsl apply templates gt The not depends predicate will refine the list of lt t arget gt elements to include only those that do not have an attribute named depends The lt xsl apply templates gt will instantiate the following template without any parameters lt xsl template match target mode tree gt xsl param name indentLevel select 0 gt lt xsl variable name curName select name gt If you refer to Example 3 14 you will see that this is
141. output jdomDoc sw The parameters for XMLOut putter allow you to specify the amount of indentation for the output along with a boolean flag indicating whether or not linefeeds should be included in the output In the code example no spaces or linefeeds are specified in order to minimize the size of the XML that is produced Now that the St ringWriter contains your XML you can use a StringReader along with javax xml transform stream StreamSource to read the data into JAXP StringReader sr new StringReader sw toString Dip Source xmlSource new javax xml transform stream StreamSource sr The transformation can then proceed just as it did in Example 5 4 The main drawback to this approach is that the XML once converted to text form must then be parsed back in by JAXP before the transformation can be applied 5 4 Stylesheet Compilation XSLT is a programming language expressed using XML syntax This is not for the benefit of the computer but rather for human interpretation Before the stylesheet can be processed it must be converted into some internal machine readable format This process should sound familiar because it is the same process used for every high level programming language You the programmer work in terms of the high level language and an interpreter or compiler converts this language into some machine format that can be executed by the computer Interpreters analyze source code and translate it into machine
142. pack Show the file chooser listing all XML files A private void selectXMLFile this fileChooser setDialogTitle Select XML File this fileChooser setFileFilter this xmlFilter int retVal this fileChooser showOpenDialog this if retVal JFileChooser APPROVE OPTION this xmlFileFld setText this fileChooser getSelectedFile getAbsolutePath Show the file chooser listing all XSLT files private void selectXSLTFile this fileChooser setDialogTitle Select XSLT File this fileChooser setFileFilter this xsltFilter int retVal this fileChooser showOpenDialog this if retVal JFileChooser APPROVE OPTION this xsltFileFld setText this fileChooser getSelectedFile getAbsolutePath private void showErrorDialog String msg JOptionPane showMessageDialog this msg Error JOptionPane ERROR MESSAGE Used with JFileChooser to only show files ending with xml or XML kj class XMLFileFilter extends javax swing filechooser FileFilter public boolean accept File f String name f getName s return f isDirectory name endsWith xml name endsWith XML public String getDescription return XML Files Used with JFileChooser to only show files ending with xslt or XSLT class XSLTFileFilter extends javax swing filechooser FileFilter
143. pathname This allows the St ylesheetCache class to locate the XSLT stylesheet properly Later in the doGet method of the servlet the same method is used to locate the requested XML file ServletContext ctx getServletContext 7 String xmlFileName ctx getRealPath WEB INF xml req getPathInfo Jy As shown back in the source for TemplateServiet it then checks for the existence of this file and sends an error if necessary Otherwise it uses JAXP to perform the XSLT transformation This is where the navigation areas get added to the document More on Caching In the TemplateServiet class the XSLT stylesheets are cached using the com oreilly javaxslt util StylesheetCache class In this particular example however the XML data and XSLT stylesheets are all static files Because these files are not dynamically generated it becomes possible to cache the transformation result yielding the highest possible performance The next chapter discusses a class called ResultCache that makes this possible Using XSLT stylesheets for page layout templates is a useful technique because individual page authors do not have to duplicate headers footers and navigation areas into every page they create By centralizing page layout in one or more standard XSLT stylesheets fewer changes are required to update the look of an entire web site 8 2 Session Tracking Without Cookies Session tracking is an essential part of most web applicat
144. quickly viewed in an XSLT compatible web browser by simply loading the XML page Iterative Design The examples shown in this chapter are the result of several attempts to get the design right As in other areas of software design figuring out what to place in the XHTML XML and XSLT is an iterative process that requires several attempts before the design can be finalized In a nutshell the process works something like this e Prototype the web pages using HTML or XHTML e Create the XML datafile prototypes and optionally create DTDs e Create XSLT stylesheets that transform the XML into XHTML e Desian and create back end data sources and classes that know how to produce the required XML data e Create servlets that tie everything together As each piece of the application is implemented missing or redundant features will manifest themselves in other areas This is where the iterative process comes into effect If some features are not right the first time simply refine the prototypes and repeat various steps in the process until all the pieces fit together The next XML file shown in Example 7 4 contains data for the View Month page Example 7 4 viewMonth xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xslt viewMonth xslt viewMonth month 1 year 2001 gt lt board id 1 gt lt name gt Java Programming lt name gt lt description gt General programmi
145. refers to the actual markup that appears in the XML document So account is a tag that represents an account element in a computer program 1 2 1 SGML XML and Markup Languages Standard Generalized Markup Language SGML forms the basis for HTML XHTML XML and XSLT but in very different ways for each Figure 1 2 illustrates the relationships between these technologies Figure 1 2 SGML heritage metalanguages HTML XHTML XSLT Po markup languages SGML is a very sophisticated metalanguage designed for large and complex documentation As a metalanguage it defines syntax rules for tags but does not define any specific tags HTML on the other hand is a specific markup language implemented using SGML A markup language defines its own set of tags such as n1 and p Because HTML is a markup language instead of a metalanguage you cannot add new tags and are at the mercy of the browser vendor to properly implement those tags XML as shown in Figure 1 2 is a subset of SGML XML documents are compatible with SGML documents however XML is a much smaller language A key goal of XML is simplicity since it has to work well on the Web where bandwidth and limited client processing power is a concern Because of its simplicity XML is easier to parse and validate making it a better performer than SGML XML is also a metalanguage which explains why XML does not define any tags of its own XSLT is a particular markup language implem
146. request handlers and sets up the ForumConfig object amp public void init ServletConfig sc throws ServletException super init sc get initialization parameters from the deployment descriptor web xml String jdbcDriverClassName sc getInitParameter jdbcDriverClassName String databaseURL sc getInitParameter databaseURL String adapterClassName sc getInitParameter adapterClassName ForumConfig setValues jdbcDriverClassName databaseURL adapterClassName try load all request handlers this registry new ReqHandlerRegistry new HomeReqHandler this registry register new PostMsgReqHandler this registry register new ViewMonthReqHandler this registry register new ViewMsgReqHandler catch Exception ex log ex getMessage ex throw new UnavailableException ex getMessage 10 Closes all database connections This method is invoked when the Servlet is unloaded public void destroy super destroy DBUtil closeAllConnections protected void doPost HttpServletRequest request HttpServletResponse response throws IOException ServletException ReqHandler rh this registry getHandler request Renderer rend rh doPost this request response rend render this request response protected void doGet HttpServletRequest request HttpServletResponse response throws IOException Servlet
147. responsible for handling incoming requests from the browser As your web application grows to more and more screens the code gets correspondingly larger Example 6 8 PersonalDataServlet java package chap import java io import java net import javax servlet import javax servlet http import javax xml transform import javax xml transform dom import javax xml transform stream A demonstration servlet that produces two pages In the first page the user is prompted to enter personal information including name phone number and Email In the second page a summary of this information is displayed XSLT is used for all HTML rendering so this servlet does not enforce any particular look and feel ud public class PersonalDataServlet extends HttpServlet private PersonalDataXML personalDataXML new PersonalDataXML Jz private Templates editTemplates private Templates thanksTemplates One time initialization of this Servlet f stylesheet public void init throws UnavailableException TransformerFactory transFact TransformerFactory newInstance String curName null try curName WEB INF xslt editPersonalData xslt URL xsltURL getServletContext getResource curName String xsltSystemID xsltURL toExternalForm this editTemplates transFact newTemplates new StreamSource xsltSystemID curName WEB INF xsl
148. separate CSS file however the HTML is reduced to lt hl gt Some Heading lt h1 gt Because the HTML is now simplified the XSLT stylesheet is also simplified This is why CSS complements XSLT so nicely and should be used whenever possible 9 3 5 Interacting with EJB Enterprise JavaBeans EJB objects are server side components that encapsulate business logic and access to data Because EJBs execute inside of application servers they are typically accessed remotely using Java Remote Method Invocation RMI interfaces This implies that method calls to EJB components occur over a network connection they are much slower than local method calls within the same VM For this reason care must be taken when sending data to and from the application server 9 3 5 1 Sending XML from EJBs From the perspective of Java and XSLT the critical issue is determining where to produce XML There are basically two options available The first is to produce the XML within the EJB container thus providing a pure XML interface to any client wishing to use the beans For instance a bean may have the following additional methods that know how to produce XML public String getLeaderXML throws RemoteException oublic String getTeamMembersXML throws RemoteException public String getProjectInformation throws RemoteException Each of these methods simply returns a St ring that contains XML content Figure 9 9 illustrates how this model works
149. servlet environments where it is desirable to parse an XSLT stylesheet once then cache it in memory as a Templates object The output properties are a read only representation of the lt xs1 output gt stylesheet element public interface Templates Properties getOutputProperties Transformer newTransformer throws TransformerConfigurationException Transformer Instances of this class perform one or more transformations Although Transformer objects can be reused they are not thread safe and therefore cannot be used concurrently Output property names are defined by the Out putKeys class and map to the lt xsl output gt stylesheet element Parameters on the other hand are stylesheet parameters and map to top level lt xsl param gt elements The gecParameter method returns only parameters that have been programmatically set public abstract class Transformer protected Transformer s public abstract void clearParameters public abstract ErrorListener getErrorListener public abstract Properties getOutputProperties public abstract String getOutputProperty String name throws IllegalArgumentException public abstract Object getParameter String name public abstract URIResolver getURIResolver public abstract void setErrorListener ErrorListener listener throws IllegalArgumentException public abstract void setOutputProperties Properties oformat throw
150. servlets check out Jason Hunter s Java Servlet Programming O Reilly Be sure to look for the second edition because so much has changed in the servlet world since this book was first published 6 1 1 Splash Screen Servlet Example Our first servlet example will produce an application splash screen The servlet will receive a request from a browser and output a simple HTML web page Figure 6 1 contains the class diagram for SolashScreenServlet which extends from HttpServiet Figure 6 1 SplashScreenServlet class diagram protocol abstract independent GenericServlet NH abstract specific HttpServlet LN SplashScreenServiet This is what you write getServletinfo doGet When writing servlets you almost always extend from Ht tpServlet In our example we override the doGet method which is called every time the browser issues an HTTP GET request to the server GET requests occur whenever the user types in a URL clicks on a hyperlink or submits an HTML form with GET as the method attribute The other common type of request is POST which is used by HTML forms with POST as the method attribute For example form action someServlet method POST gt form contents lt form gt In the case of POST requests your servlet simply overrides the doPost method instead of doGet Each of these methods takes two parameters HttpServietRequest and HttpServletResponse The r
151. simulated users In the final column lower numbers are better Table 9 3 View month response time Servletcontainer XSLTprocessor Database Threads Average responsetime ms Tomcat 3 2 1 Xalan 2 0 Access 2000 1 130 i E i 5 320 i i 10 760 i i 20 1600 Tomcat 4 0 SAXON 6 2 2 MySQL 1 18 i E 5 150 i i 10 320 i 20 610 This table does not paint the complete picture However it should illustrate the point that in many cases merely changing to different tools and libraries can dramatically improve performance For the measurements shown JMeter was instructed to simulate up to 20 concurrent users with absolutely zero delay between requests JMeter can also be configured to insert fixed or random delays between requests which tends to be much more representative of real world conditions The goal of this test was not to benchmark the performance of the discussion forum but rather to compare the relative performance when switching to different tools 3 Over a period of many hours the discussion forum was restarted with various combinations of servlet containers XSLT processors and databases Although Tomcat 4 0 and SAXON 6 2 2 tend to be slightly faster than Tomcat 3 2 1 and Xalan 2 0 the most dramatic performance delta occurs when switching from Microsoft Access to MySQL 8 Because XSLT processors and servlet containers are changing so fast the actual tool names are not listed here 9 3 2 More Detailed Measurements
152. template match dependentObject gt public class lt xsl value of select SclassName gt lt xsl text gt implements java io Serializable xsl text xsl apply templates select property mode generateField gt lt xsl text gt Construct a new dependent object instance Auf public lt xsl text gt lt xsl value of select className xsl apply templates select property mode generateConstructorParam gt xsl text xsl text xsl apply templates select property mode generateInitializers xsl apply templates select property mode generateGetter gt lt xsl template gt lt l KKKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKK KKK Generate a private field declaration KCKCkCk ck ck ck ck ck k ck kckckckck ck ck ckck kc kckckckckckck ck ck ck kckckck ckckck ck k ck ck k ck ck ck KKK KKK KKK KKK ck k KK lt xsl template match property mode generateField gt private lt xsl value of select type gt lt xsl text gt lt xsl text gt lt xsl value of select name gt lt xsl template gt ede CKkCkck ckckck ck ck ck ck kck ck kck ck ck ck ck ck ckck ck kck ck ck ck ck ck ckck ck ck ck ck ck ck ck k ck ck ck k ck ck ck ck ck ck ck ck ck kk ck k ck kk kkk Generate a get method for a property KCKCk Kk CK Kk SK Kk CK Kk CK Kk SK Kk KK CK SK Kk SK Kk KK SKK Sk CK Ck Ck KKK KKK KKK kck ck KK k D gt lt xsl
153. template match property mode generateGetter public lt xsl value of select type gt xsl text xsl text lt xsl value of select getter gt return this lt xsl value of select name gt lt xsl template gt lt KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKK Generate one of the constructor parameters KKKKKKKKKKKKKKKKKKAKAKKKKKKKKKKKKKKKKKKKKKKKK SK C KC Kk KC KC Ck k ck KKK KK kk gt lt xsl template match property mode generateConstructorParam gt xsl text xml space preserve gt lt xsl value of select type gt xsl text lt xsl text gt lt xsl value of select name gt xsl if test position last gt lt xsl if gt lt xsl template gt lt KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK kk UK KK kk x Sk Kk KG KK k ko k ck kck kckok Generate the initialization code inside of the constructor KCKCkCk ck ck k ck ck kc kckckckckck ck ck ck ck kc kckckckckckck ck ck ck kck ck kc kckck ck k ck ck k ck ck ck ck ck k ck k ck ck ck KKK k ck k kk lt xsl template match property mode generateInitializers lt xsl text xml space preserve gt this lt xsl text gt lt xsl value of select name gt xsl text lt xsl text gt lt xsl value of select name gt lt xsl template gt lt xsl stylesheet gt This stylesheet produces the code for Address java It sta
154. that converts HTML to XHTML It is available at http www w3 org People Raggett tidy Strictly adhering to XHTML DTDs makes it much easier for programmers to write all sorts of programs that manage web site content because page content is consistently structured and can be easily parsed The XSLT stylesheet searches for the lt met a gt tag therefore lt html gt lt head gt and lt meta gt are required elements If the lt met a gt tag is not found the navigation category defaults to unknown and none of the navigation links are highlighted Any content found inside of lt head gt and lt body gt is simply copied to the appropriate location within the result tree document Example 8 2 lists the XSLT stylesheet that inserts the navigation areas Example 8 2 templatePage xslt lt xml version 1 0 encoding UTF 8 gt ches KKK KK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK ko Sk Sk ko ko kx kx kx kx A stylesheet used by every page on a web site This stylesheet defines where the page header and navigation bar are placed Kk KK KK KKK kk ck ck k k ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck k ck ck ck k ck ck KK KK KK ck k ck ck ck ck ck ck ck ck ck ck ck k kc k k k kk kk HH gt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform gt ede ck ck ck ck ck ck ck CK Ck CK Ck Ck ck ck KKK ck ck Ck ck ck ck ck kk kk ck ck ck ck ck ck ck ck
155. that the XSLT model is not really a method call Instead xsl apply templates instructs the processor to scan through the XML document again looking for nodes that match a pattern If matching nodes are found the best matching template is instantiated In the next chapter we will see that XSLT also has xs1 ca11 template which works similarly to a Java method call Let s suppose that your source document contains the following XML school lt name gt SIUC lt name gt lt city gt Carbondale lt city gt lt state gt Illinois lt state gt lt school gt The following template could be used to match the lt school gt element and output its contents template match school gt lt b gt lt xsl value of select name gt is located in lt xsl value of select city gt lt xsl value of select state gt lt b gt xsl template gt The result will be something like lt b gt SIUC is located in Carbondale Illinois lt b gt As you can see elements that do not start with xsi are simply copied to the result tree as is plain text such as is located in We do not show this here but if you try the example you will see that whitespace characters spaces tabs and linefeeds are also copied to the result tree When the destination is HTML it is usually safe to ignore this issue because the browser will collapse that whitespace If you view the actual source code of the generated HTML it can look pretty u
156. the following code xsl apply templates select G node 3 5 3 Transforming Elements and Attributes Once you have typed in the identity transformation and tested it it is time to begin adding additional templates that actually perform the schema evolution In XSLT it is possible for two or more templates to match a pattern in the XML data In these cases the more specific template is instantiated Without going into a great deal of technical detail an explicit match such as lt xsl template match when gt takes precedence over the identity transformation template which is essentially a wildcard pattern that matches any attribute or node To modify specific elements and attributes simply add more specific templates to the existing identity transformation stylesheet In the log file example a key problem is the quantity of XML data written for each lt when gt element Instead of representing the date and time using a series of child elements it would be much more concise to use the following syntax timestamp time 06 35 44 day 15 month 01 year 2000 gt The following template will perform the necessary transformation lt xsl template match when gt lt change when into timestamp and change its child elements into attributes timestamp time hour minute year year month month lt xsl template gt This template can be added to the identity transformation stylesheet and w
157. the JDK 1 1 x version of the java text bDecimalFormat Class For complete information on the syntax of the second argument refer to the JavaDocs for JDK 1 1 x Outputting currencies is a common use for the oxrmat number function The pattern S 0 00 can properly format a number into just about any U S currency Table 3 2 demonstrates several possible inputs and results for this pattern Table 3 2 Formatting currencies using 0 00 Number Result 0 0 00 0 9 0 90 0 919 0 92 10 10 00 1000 1 000 00 12345 12345 12 345 12 The XSLT code to utilize this function may look something like this lt xsl value of select format number amt 440 00 It is assumed that amt is some element in the XML data such as amt gt 1000 lt amt gt The and 0 characters are placeholders for digits and behave exactly as java text DecimalFormat specifies Basically 0 is a placeholder for any digit while is a placeholder that is absent when the input value is 0 l The XSLT specification does not define what happens if the XML data does not contain a valid number Besides currencies another common format is percentages To output a percentage end the format pattern with a character The following XSLT code shows a few examples outputs 0 gt lt xsl value of select format number 0 02 outputs 10 gt lt xsl value of select format number 0 1 0 l outputs L0
158. the Java code from your pages A web page with custom tags may look like Example 4 3 1 Technically programmers create custom actions which are invoked u sing custom JSP tags Example 4 3 JSP with custom tags zu 80 taglib uri 2 my taglib prefix abc gt html head lt title gt JSP Tag Library Demonstration lt title gt lt head gt lt body gt abc standardHeader abc companyLogo lt hl gt Recent Announcements lt h1 gt announcements filter As you can see custom tags look like normal XML tags with a namespace prefix Namespace prefixes are used to give XML tags unique names Because you select the prefix for each tag library you can use libraries from many different vendors without fear of naming conflicts These tags are mapped to Java classes called tag handlers that are responsible for the actual work In fact the JSP specification does not limit the underlying implementation to Java so other languages can be used if the JSP container supports it Using the custom tag approach programmers in your company can produce a set of approved tags for creating corporate logos search boxes navigation bars and page footers Nonprogrammers can focus on HTML layout oblivious to the underlying tag handler code The main drawback to this approach is the current lack of standard tags Although several open source projects are underway to develop custom tag libraries it is unlikely that you
159. the currently selected error 7 private void showErrorDetails int selRow this errorTable getSelectedRow this errorDetailArea setText this errModel getDetailReport selRow Perform an XSLT transformation E public void transform File xmlFile File xsltFile setVisible true try figure out the directory of the XSLT file This will be used to locate the DTD if xsltFile null File xsltDir xsltFile getParentFile if xsltDir isDirectory this xsltURL xsltDir toURL toExternalForm TransformerFactory transFact TransformerFactory newInstance register the table model as an error listener transFact setErrorListener this errModel Transformer trans transFact newTransformer new StreamSource xsltFile check for null because the factory might not throw exceptions when the call to newTransformer fails This is because we registered an error listener that does not throw exceptions if trans null trans setErrorListener this errModel capture the result of the XSLT transformation StringWriter sw new StringWriter trans transform new StreamSource xmlFile new StreamResult sw show the results this resultText sw toString this textOutputArea setText this resultText catch TransformerConfigurationException tce try this errModel fatalError tce catch TransformerExceptio
160. the following variables Bric gt lt xsl variable name firstName select lt xsl variable name lastName select Burke lt xsl variable name middleName select Matthew gt lt xsl variable name fullName select concat S firstName SmiddleName SlastName gt In the first three variables apostrophes are used to indicate that the values are strings Without the apostrophes the XSLT processor would treat these as XPath expressions and attempt to select nodes from the XML input data The third variable u11Name demonstrates how the concat function is used to concatenate two or more strings together The function simply takes a comma separated list of strings as arguments and returns the concatenated results In this case the value for ful iName is Eric Matthew Burke Table 3 3 provides additional examples of string functions The variables in this table are the same ones from the previous example In the first column the return type of the function is listed first followed by the function name and the list of parameters The second and third columns provide an example usage and the output from that example Table 3 3 String function examples Function syntax Example string concat concat firstName string string string SlastName Eric Burke boolean starts with i i hie H a starts with firstName Er string string boolean contains string
161. the second to last template in the stylesheet Since it is broken up into many pieces here you may find it easier to refer to the original code as this description progresses Since the indent Level parameter is not specified it defaults to 0 which makes sense for the top level targets As this template is instantiated recursively the level of indentation increases The curName variable is local to this template and contains the current Ant target name Lines of text are indented using a style attribute div style text indent SindentLevel em gt CSS is used to indent everything contained within the lt div gt tag by the specified number of ems P The value of the current target name is then printed using the appropriate indentation 5 An em is approximately equal to the width of a lowercase letter m in the current font lt xsl value of select ScurName gt If the current lt t arget gt element in the Ant build file has a depends attribute its dependencies are printed next to the target name as part of the report The parseDepends template handles this task This template also part of Example 3 14 is instantiated using xs1 ca11 template gt as shown here lt xsl if test depends gt homp depends on lt xsl text gt lt xsl call template name parseDepends lt xsl wit h param name depends select depends gt lt xsl call template gt lt xsl text gt lt xsl text gt xsl if To continue wit
162. then the template recursively instantiates itself xsl apply templates select message gt lt xsl with param name indent select Sindent 1 gt lt xsl apply templates gt This efficiently selects all lt message gt elements that occur immediately within the current message and increments the indentation by 1 This allows the stylesheet to indent replies appropriately The recursive process continues until no messages remain Another stylesheet viewMsg xsit is responsible for displaying a single message This is a simple XSLT stylesheet and can be found in Appendix A The only remaining stylesheet postMsg xslt is shown in Example 7 10 This stylesheet supports two modes of operation Therefore it is more complicated than the previous examples Example 7 10 XSLT for the Post Reply message page lt xml version 1 0 encoding UTF 8 gt elec KC CK C CK Ck C CK CK C CK CK C CC CC Ck Ck Ck CK C C CK CIC CIC Ck C Ck C Ck CK Ck CK CI S A S Kk Sk Pk kx Mk kx Ax M postMsg xslt Creates the Post New Message XHTML page and the Reply to Message XHTML page CK CC CK Ck C CK CK Ck CK CK CC CK CC Ck CK CK C CC CIC CK Ck C Ck CK Ck CK Ck CK CI S E A S Kk kx Kk kx Mk kx AK M xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl import href utils xslt pass the root directory as a parameter thus allowing this stylesheet to refer to the CSS file g
163. this messageMap put new Long msg getID msg return msg we Post a new message return the newly created messag throws DataException if a database error occurs or if any parameter is illegal ex public Message postNewMessage long boardID String msgSubject String authorEmail String msgText throws DataException BoardSummary boardSum getBoardSummary boardID long msgID getNextMessageID Message msg new MessageImpl msgID new DayMonthYear boardSum msgSubject authorEmail msgText 1 this messageMap put new Long msg getID msg BoardSummaryImpl boardSum messageAdded msg return msg return an iterator of lt code gt BoardSummary lt code gt objects py public Iterator getAllBoards throws DataException return this allBoards iterator public BoardSummary getBoardSummary long boardID throws DataException Iterator iter getAllBoards while iter hasNext BoardSummary curBoard BoardSummary iter next if curBoard getID boardID return curBoard throw new DataException Illegal boardID boardID private synchronized static long getNextMessageID nextMessageID tt return nextMessageID Messagelmpl java shown in Example A 7 is an implementation of the Message interface Example A 7 Messagelmpl java package com oreilly forum domain import j
164. to lt messageBoard gt elements that occur as direct children of lt discussionForumHome gt elements Since our template matches only messageBoard it can be reused for lt messageBoard gt elements that appear anywhere in the XML document For each lt messageBoard gt child the processor looks for the template in your stylesheet that provides the best match Since our stylesheet contains a template that matches the messageBoard pattern exactly it is instantiated for each of the lt messageBoard gt elements The job of this template is to produce a single HTML list item tag for each lt sageBoard element lt xsl template match messageBoard gt li lt a href viewForum id id lt xsl value of select name lt a gt lt li gt lt xsl template gt As you can see the list item must be properly terminated HTML style standalone lt 1 i gt tags are not allowed because they break the requirement that XSLT stylesheets be well formed XML Terminating the element with lt 1i gt also works with HTML so this is the approach you must take The hyperlink is a best guess at this point in the design process because the servlet has not been defined yet Later when we develop a servlet to actually process this web page we will update the link to point to the correct servlet In the stylesheet amp is used to select the values of attributes Curly braces 1 are known as an attribute value template and wil
165. to test actual transformations with both encodings to determine which results in the smallest file for your particular data On a pragmatic note many applications and operating systems particularly Unix and Linux variants offer better support for UTF 8 encoding As nearly every XSLT example in this book has shown the lt xs1 output gt element determines the encoding of the XSLT result tree xsl output method html encoding UTF 16 gt If this element is missing from the stylesheet the XSLT processor is supposed to default to either UTF 8 or UTF 16 encoding I8 The XSLT specification does not say how the processor is supposed to select between UTF 8 and UTF 16 8 6 2 1 Creating the XML and XSLT The XML input data XSLT stylesheet and result tree do not have to use the same character encodings or language For example an XSLT stylesheet may be encoded in UTF 16 but may specify UTF 8 as its output method lt xml version 1 0 encoding UTF 16 lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html encoding UTF 8 gt Even though the first line specifies UTF 16 it is important that the text editor used to create this stylesheet actually uses UTF 16 encoding when saving the file Otherwise tools such as XML Spy http www xmlspy com may report errors as shown in Figure 8 8 Figure 8 8 Error dialog c MempMoo ximl x Your He species an encod
166. to the library element Iterator bookIter library getBooks iterator jus while bookIter hasNext yy d Book book Book bookIter next us Element bookElem createBookElement book root addContent bookElem return doc private Element createPublisherElement Publisher pub Element pubElem new Element publisher pubElem addAttribute id pub getId Elem addContent new Element name setText pub getName o ce o 1j pubElem addContent new Element street setText pub getStreet ge c o xj Elem addContent new Element City setText pub getCity Ira pubElem addContent new Element State setText pub getState O e o xj Elem addContent new Element postal setText pub getPostal return pubElem private Element createBookElement Book book Element bookElem new Element book add publisher oreilly and isbn 1234567 attributes to the book element bookElem addAttribute publisher book getPublisher getid addAttribute isbn book getISBN now add an edition element to book bookElem addContent new Element edition setText Integer toString book getEdition Element pubDate new Element publicationDate pubDate addAttribute mm Integer toString book getPub
167. unique ID for this board f long getID jo return a name for this board String getName return a description for this board String getDescription return an iterator of lt code gt MonthYear lt code gt objects sj Iterator getMonthsWithMessages By design the BoardSummary interface is read only This is an important feature because it means that once an instance of this class is extracted from the back end data source a programmer cannot accidentally call a set method only to discover later that the updates were not saved in the database Technically the client of this class could retrieve an 1c erator of months with messages and then call the remove method on the Iterator instance Although we could take steps to make instances of this interface truly immutable such efforts are probably overkill An early decision made in the design of the discussion forum was to assign a unique long identifier to each domain object These identifiers have absolutely no meaning other than to identify objects uniquely which will make the SQL queries much simpler later on This technique also makes it easy to reference objects from hyperlinks in the XHTML because a simple identifier can be easily converted to and from a string representation 3 The code to actually generate these unique IDs is found in the DBUt i1 class shown in Example 7 18 The next interface shown in Example 7 12 provide
168. which would be painfully slow Any Java programmer knows that application startup time has never been one of the strengths of Java Servlets had to address this issue first What was needed was a new approach in which the JVM was loaded a single time and left running even when no requests came in The term serviet engine referred to the JVM that hosted the servlets often serving a dual role as an HTTP web server 4 1 2 Servlets as CGI Replacements Sun s Java serviet API was originally released way back in 1997 when Java was mosily a client side development language Servlets were originally marketed and used as replacements for CGI programs Developers were quick to adopt servlets because of their advantages over CGI Since the servlet engine can run for as long as the web server runs servlets can be loaded into memory once and kept around for subsequent requests This is easy to accomplish in Java because servlets are really nothing more than Java classes The JVM simply loads the servlet objects into memory hanging on to the references for as long as the web application runs The persistent nature of servlets results in two additional benefits both of which push servlets well beyond the capabilities of basic CGI First state information can be preserved in memory for long periods of time Even though the browser loses its connection to the web server after each request response cycle servlets can store objects in memory until the browser recon
169. will be able to find an existing custom tag for every requirement One persistent problem with a pure JSP approach is that of complex validation Although JSP with custom tags can be an ideal approach for displaying pages the approach falls apart when a JSP is used to validate the input from a complex HTML form In this situation it is almost inevitable that Java code perhaps a lot of it will creep into the page This is where a hybrid approach JSP and servlets which will be covered in the next section is desirable Compared with an XML XSLT approach JSP requires a lot more effort to cleanly separate presentation from the underlying data and programming logic For web sites that are mostly static JSP can be easy for nonprogrammers to create since they work directly in HTML When dynamic content becomes more prevalent your options are to embed lots of Java code into the JSP create custom tags or perhaps write Java beans that output fragments of HTML Embedding code into the JSP is not desirable because of the ugly syntax and maintenance difficulties The other approaches do hide code from the JSP author but some part of your web application to be consistent is still cranking out HTML from Java code either in custom tags or JavaBeans components This still raises serious questions about the ability to make quick changes to your HTML without recompiling and deploying your Java code Another weakness of JSPs in comparison with XML and
170. will continue to be important Appendix A Discussion Forum Code This appendix contains all of the remaining code from the discussion forum example presented in Chapter 7 These are the simple files that did not merit a lot of explanation in the text All of the source code can be downloaded from this book s companion web site at http www oreilly com catalog javaxslt BoardSummarylmpl java 1 shown in Example A 1 provides a default implementation of the BoardSummary interface Example A 1 BoardSummarylImpl java 1 package com oreilly forum domain import com oreilly forum domain import java util An implementation of the BoardSummary interface public class BoardSummaryImpl implements BoardSummary private long id private String name private String description private List monthsWithMessages param monthsWithMessages a list of MonthYear objects gl public BoardSummaryImpl long id String name String description List monthsWithMessages this id id this name name this description description this monthsWithMessages monthsWithMessages public long getID return this id public String getName return this name public String getDescription return this description return an iterator of lt code gt MonthYear lt code gt objects As public Iterator getMonthsWithMessages return this monthsWithMessages iterator
171. 0 5 lt xsl value of select format number 1 0 gt As before the first parameter to the oxmat number function is the actual number to be formatted and the second parameter is the pattern The 0 in the pattern indicates that at least one digit should always be displayed The 5 character also has the side effect of multiplying the value by 100 so it is displayed as a percentage Consequently 0 15 is displayed as 15 and 1 is displayed as 100 To test more patterns the XML data shown in Example 3 8 can be used This works in conjunction with numberFormatting xslt to display every combination of format and number listed in the XML data Example 3 8 numberFormatting xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href numberFormatting xslt lt numberFormatting gt lt formatSamples gt lt add more format elements to test more combinations gt lt format gt S 0 00 lt format gt lt format gt lt format gt lt format gt 0 lt format gt lt format gt 0 0 lt format gt lt format gt 0 lt format gt lt format gt 0 0 lt format gt lt formatSamples gt lt numberSamples gt add more number elements to test more combinations mber 10 number number 1 number number 0 number number 0 000123 number number gt 0 1 lt number gt number gt 0 9 lt number gt mber gt 0 91 lt number gt num
172. 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt xsl output method html encoding UTF 8 gt Isolate locale specific content gt lt xsl variable name lang pageTitle select Employee Directory lt xsl variable name lang nameHeading select Name gt lt xsl variable name lang categoryHeading select Category gt lt xsl variable name lang phoneHeading select Phone gt lt xsl variable name lang manager select Manager gt lt xsl variable name lang programmer select Programmer gt lt xsl variable name lang other select Other gt lt xsl template match gt lt html gt lt head gt title xsl value of select S lang pageTitle gt lt title gt head lt body gt lt h1 gt lt xsl value of select 1lang pageTitle h1 lt table cellpadding 4 cellspacing 0 border 1 gt lt tr gt lt th gt lt xsl value of select lang nameHeading gt lt th gt lt th gt lt xsl value of select S lang categoryHeading gt lt th gt lt th gt lt xsl value of select 1lang phoneHeading th lt tr gt lt xsl for each select directory employee gt lt tr gt lt td gt lt xsl value of select name gt lt td gt lt td gt lt xsl choose gt xsl when test category manager gt lt xsl value of select S lang manager gt lt xsl when gt xsl when te
173. 4 createDate getDay stmt setInt 5 createDate getYear stmt setString 6 Long toString board getID stmt setString 7 msgSubject stmt setString 8 authorEmail DBUtil setLongString stmt 9 msgText stmt executeUpdate return new MessagelImpl newMsgID createDate board msgSubject authorEmail msgText inReplyToID catch SQLException sqe sge printStackTrace s throw new DataException sqe finally DBUtil close stmt con Since this is not a book about relational database access using Java we will not focus on the low level JDBC details found in this class The SQL code is intentionally simple to make this class portable to several different relational databases The database URL and JDBC driver class name are retrieved from the ForumConfig Class instead of hardcoded into the class private static String dbURL ForumConfig getDatabaseURL fre Construct the data adapter and load the JDBC driver public JdbcDataAdapter throws DataException try Class forName ForumConfig getJDBCDriverClassName s catch Exception ex ex printStackTrace throw new DataException Unable to load JDBC driver ForumConfig getJDBCDriverClassName J a Creating connections with the DBUt i1 class is another common pattern Connection con null try con DBUtil getConnection dbURL As mentioned earlier this approach leaves the door open for connect
174. 8 6 Example 8 6 Session tracking XSLT stylesheet lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform gt hes XC CC CK CK Ck Ck Ck Ck CK CK KKK KKK KEK KKK KKK KKK KKK KKK KKK Ck CK KKK C KKK KEK KKK KKK KKK KKK KKK global sessionID Used for URL rewriting to implement VW session tracking without cookies CK CK CK Ck kk Ck Kk Sk Kk C CK Ck Ck Ck CK Sk Kk CK Ck Ck kk kk kk Sk kk SK kk Ck kk Ck Pk ck Ck kk Ck kk kc KKK KKK KKK KKK xsl param name global sessionID gt lt This stylesheet produces XHTML xsl output method xml indent yes encoding UTF 8 doctype public W3C DTD XHTML 1 0 Transitional EN doctype system http www w3 org TR xhtmll DTD xhtml1l transitional dtd d EE ck ck 0k ck ck ck 0k ck KKK Ck Ck ck ck ck ck ck ck ck 0k ck ck ck ck ck ck ck Ck ck ck ck koc ck ck ck kk ck ck ck ck ck ck kk kk kk Sk ko ck ko ck ko ck Sk ko ko ko ko ko This template produces the skeletal XHTML document CK CK CK Ck Ck Ck Ck Ck ck CK kk Kk Ck kk Ck CK CK CK CK Sk CK Ck Sk Ck Sk kk Sk Kk Sk kk Ck kk Ck kk Ck Ck Ck kk ck KKK KKK ck ck KK KK lt xsl template match gt lt html xmlns http www w3 0rg 1999 xhtml lt head gt lt title gt Shopping Example lt title gt lt head gt lt body gt Create a form for this page gt lt form method post action chap8 shopping global sessionID g
175. Altova s XML Spy http www xmlspy com After downloading and unzipping the Xalan distribution from Apache simply add xalan jar and erces jar to your CLASSPATH The transformation can then be initiated with the following command java org apache xalan xslt Process IN discussionForumHome xml XSL discussionForumHome xslt This will apply the stylesheet sending the resulting HTML content to standard output Adding OUT filename to the command will cause Xalan to send the result tree directly to a file To see the complete list of Xalan options just type java org apache xalan xslt Process For example the TT option allows you to see trace which templates are being called Xalan s IN and x51 parameters accept URLs as arguments rather than as file names A simple filename will work if the files are in the current working directory but you may need to use a full URL syntax such as file path file ext when the file is located elsewhere In Chapter 5 we will show how to invoke Xalan and other XSLT processors from Java code which is far more efficient because a separate Java Virtual Machine JVM does not have to be invoked for each transformation Although it can take several seconds to start the JVM the actual XSLT transformations will usually occur in milliseconds Another option is to find a web browser that supports XSLT which allows you to edit your stylesheet and hit the Reload button to view the transformation 2 2 T
176. BoardSummarylmpl java 2 shown in Example A 2 is an alternate implementation of the BoardSummary interface This class is used by the fake data implementation which is useful for testing purposes when a database is not available Example A 2 BoardSummarylImpl java 2 package com oreilly forum fakeimpl import com oreilly forum domain import java util public class BoardSummaryImpl implements BoardSummary private long id private String name private String description a list of MonthYear objects private List monthsWithMessages public BoardSummaryImpl long id String name String description this id id this name name this description description this monthsWithMessages new ArrayList public void messageAdded Message msg DayMonthYear createDate msg getCreateDate update the monthsWithMessages list Iterator iter this monthsWithMessages iterator while iter hasNext MonthYear curMonth MonthYear iter next iy if createDate getMonth curMonth getMonth amp amp createDate getYear curMonth getYear return this monthsWithMessages add createDate public long getID return this id public String getName return this name public String getDescription return this description public Iterator getMonthsWithMessages return this monthsWithMessages iterator DataException java shown
177. C Ck Ck Ck kk S S M Ax x KG M KA ko kock The main template creates the deck and the home card CK CK Kk CK CK CK Ck SK Kk CK Kk CC Kk SK Kk CK CK SK Kk SK Ck KK SKK kk SK Kk SK KC KC KC Kk C KKK KKK KKK ko kk gt lt xsl template match movies gt wml call a template to produce the splash screen gt xsl call template name createSplashCard gt card id home title Home newcontext true gt lt p align center gt Please select your city lt select name city multiple false gt lt xsl apply templates select city gt lt select gt lt p gt lt p gt lt em gt lt a href movieguide action theaters amp amp city city gt Show Theaters a lt em gt lt p gt lt card gt wml lt xsl template gt sem kk ck Ck Ck Ck Ck Ck Ck Ck Ck Sk Ck Ck Ck Kk Ck SK Ck Ck Ck Ck Ck Ck Ck CK ck Ck Ck kk Ck kk Ck kk Ck kk Ck kk Ck kk ck kk Sk kk Sk ko Sk ke ko kv kx ko ko Produce a single option element for a city KKK KK KK KKK k ck ck k ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck KKK KKK KKK k ck ck ck ck ck ck ck ck ck k k kc k k KK KK KK lt xsl template match city gt lt option value id gt lt xsl value of select name gt lt option gt lt xsl template gt 1 CC CK CK CK CC Ck Ck Ck CK CK CCS C Ck C Ck C C CK CI SCC CK CC Ck Ck Ck CK Ck CK CI CK C Ck Ck Ck Ck Sk S E M Ax x AG M KA KKK Create t
178. CkCckckCkckck kc kckckckck ck ck ck ckck ck ck ck kc kckck ck k ck ck ck ck KK ck ck k KKK KKK KKK KKK gt target name transform description Perform an XSLT transformation lt style processor trax basedir chapters chap9 destdir builddir style condensePerson xslt in chapters chap9 aidan xml1 out builddir aidan_condensed xml gt lt pass a stylesheet parameter gt lt param name includeMiddle expression yes gt lt style gt target lt project gt All Ant build files are XML and have a lt project gt root element This specifies the default target as well as the base directory Each of the targets is specified using lt t arget gt elements which can have dependencies on each other Targets in turn contain tasks which are responsible for performing individual units of work The CLASSPATH used by various tasks can be defined once and reused throughout the build file The lt path gt element is emphasized in Example 9 3 including several JAR files from the ib directory For instance lt pathelement path lib servlet 2 3 jar This illustrates two key points about defining a consistent development environment First it is a good idea to rename JAR files to include version numbers This is a great way to avoid conflicts and unexpected errors because different versions of most tools use the same filenames for JAR files By renaming them it is easier to keep track of what is install
179. D throws SQLException List monthsWithMessages new ArrayList ResultSet rs stmt executeQuery Statement stmt SELECT DISTINCT createMonth createYear FROM Message WHERE boardID boardID while rs next monthsWithMessages add new MonthYear rs getInt 1 rs getInt 2 return monthsWithMessages private Message insertMessage BoardSummary board String msgSubject String authorEmail String msgText throws DataException long inReplyToID avoid overflowing the max database column lengths if msgSubject length gt ForumConfig MAX MSG SUBJECT LEN msgSubject msgSubject substring 0 ForumConfig MAX MSG SUBJECT LEN if authorEmail length gt ForumConfig MAX EMAIL L authorEmail authorEmail substring 0 ForumConfig MAX EMAIL LEN DayMonthYear createDate new DayMonthYear Connection con null PreparedStatement stmt null try con DBUtil getConnection dbURL eal z as long newMsgID DBUtil getNextID Message con stmt con prepareStatement INSERT INTO Message id inReplyToID createMonth createDay createYear boardID subject authorEmail msgText VALUES 7 2 9 9 9 2 2 42 stmt setString 1 Long toString newMsgID stmt setString 2 Long toString inReplyToID stmt setInt 3 createDate getMonth stmt setInt
180. Document object in a single line of code new XMLOutputter true UTF 8 output doc System out The three arguments to xMLOut putter indicate that it should use two spaces for indentation include linefeeds and encode its output using UTF 8 1 2 4 4 JDOM and DOM interoperability Current XSLT processors are very flexible generally supporting any of the following sources for XML or XSLT input e a DOM tree or output from a SAX parser e any Java InputStream or Reader e aURI file name or java io File object JDOM is not directly supported by some XSLT processors although this is changing fast 4 For this reason it is typical to convert a JDOM Document instance to some other format so it can be fed into an XSLT processor for transformation Fortunately the JDOM package provides a class called DoMOut putter that can easily make the transformation As this book went to press Version 6 4 of SAXON was released with beta support for transforming JDOM trees Additionally JDOM beta 7 introduces two new classes JDOMSource and JDOMResult that interoperate with any JAXP compliant XSLT processor org jdom output DOMOutputter outputter new org jdom output DOMOutputter org w3c dom Document domDoc outputter output jdomDoc The DOM Document object can then be used with any of the XSLT processors or a whole host of other XML libraries and tools JDOM also includes a class that can convert a Document into a time it seems like
181. Exception RegHandler rh this registry getHandler request Renderer rend rh doGet this request response rend render this request response ForumServiet overrides the init method to perform one time initialization before any client requests are handled This is where context initialization parameters are read from the deployment descriptor and stored in the ForumConfig instance String jdbcDriverClassName sc getInitParameter jdbcDriverClassName String databaseURL sc getInitParameter databaseURL String adapterClassName sc getInitParameter adapterClassName ForumConfig setValues jdbcDriverClassName databaseURL adapterClassName The init method then sets up instances of each type of request handler These are registered with the RegHandlerRegistry class which has the ability to locate request handlers later on In the destroy method which is called when the servlet is unloaded any outstanding database connections are closed public void destroy super destroy DBUtil closeAllConnections While this currently has no real effect the code was put in place because a future version of the software may use database connection pooling This allows the application to close all connections in the pool just before exiting The only remaining methods in the servlet are doGet and doPost _ which are virtually identical All these methods do is locate
182. FORUM DTD WML 1 1 EN doctype system http www wapforum org DTD wml 1 1 xml KKK KK KKK Ck Ck KKK KKK Ck Ck KKK KKK KK KKK KKK KKK KKK KKK KKK KK KK KKK KKK KKK KKK KKK KKK HK The main template creates the deck and the movies card CK CK Kk KC CK Kk SK CK CK Kk CK C Kk SK Kk CK KKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKK KKK kc ko k ko kk D gt lt xsl template match movies gt lt wml gt lt generate the WML template gt lt template gt do type prev label Back name common_prev gt lt prev gt lt do gt lt template gt lt card id movies title Movies gt 1 shadow the template in this card do type prev name common_prev gt lt noop gt lt do gt lt select the theater that matches the city_id and theater_id stylesheet parameters gt lt xsl apply templates select city gid city id theater Qid theater id card generate more cards one per movie xsl apply templates select city Qgid city id theater id theater_id movie mode createCard gt wml xsl template ee KKKEKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Show more information about a theater KKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKAKKKKKKKKKKKAKKKKKKKKKKKKKKKKK KKK KKK KKK lt xsl template match theater gt lt p gt lt big gt lt xsl value of select name gt lt big gt lt p gt lt p gt Select a mov
183. Form E String xsltSystemId new File xsltFileName toURL toExternalForm 3 org apache xalan xslt XSLTProcessor processor org apache xalan xslt XSLTProcessorFactory getProcessor org apache xalan xslt XSLTInput Source xmllInputSource new org apache xalan xslt XSLTInputSource xmlSystemId org apache xalan xslt XSLTInputSource xsltInputSource new org apache xalan xslt XSLTInputSource xsltSystemId org apache xalan xslt XSLTResultTarget resultTree 1ew org apache xalan xslt XSLTResultTarget System out processor process xmlInputSource xsltInputSource resultTree The code begins with the usual list of imports and the class declaration followed by a simple check to ensure that two command line arguments are provided If all is OK then the XML file name and XSLT file name are converted into system identifier values String xmlSystemId new File xmlFileName toURL toExternalForm js String xsltSystemId new File xsltFileName toURL toExternalForm jus System identifiers are part of the XML specification and really mean the same thing as a Uniform Resource Identifier URI A Uniform Resource Locator URL is a specific type of URI and can be used for methods that require system identifiers as parameters From a Java programming perspective this means that a platform specific filename such as C data simple xml needs to be converted to file C data simple xml
184. ID select id gt lt div class box2 gt lt h2 gt lt xsl value of select name gt lt h2 gt lt div gt lt xsl value of select description gt lt div gt lt div style margin left 2em gt lt create a link so the user can post a new message to this board gt lt p gt lt a href forum main postMsg mode postNewMsg amp boardID id gt Post Message lt a gt to lt xsl value of select name gt lt p gt For each month that has messages show the month name and year number as a link lt xsl for each select messages gt lt ahref forum main viewMonth boardID SboardID amp month month amp y ear year gt xsl call template name utils printShortMonthName gt xsl with param name monthNumber select month gt xsl call template lt xsl text gt xsl text lt xsl value of select year gt lt a gt put a pipe character after all but the last month xsl if test position last xsl text lt xsl text gt lt xsl if gt xsl for each div lt div gt lt xsl template gt lt xsl stylesheet gt This stylesheet opens with the usual lt xs1 stylesheet gt tag and then proceeds to import utils xslt This is a stylesheet that contains common templates for formatting dates Since these utilities are needed on just about every page they are defined a common file that is imported as shown her
185. IResolver OutputKeys TransformConfigurationException lt lt interface gt gt ErrorListener lt lt ITOl gt gt TransformerFactoryConfigurationError As you can see this is a small package indicative of the fact that JAXP is merely a wrapper around the tools that actually perform transformations The entry point is TransformerFactory which creates instances of Transformer as we have already seen as well as instances of the Templates abstract class A Templates object represents a compiled stylesheet and will be covered in detail later in this chapter The advantage of compilation is performance the same Templates object can be used over and over by many threads without reparsing the XSLT file 3 The exact definition of a compiled stylesheet is vague XSLT processors are free to optimize cached stylesheets however they see fit The URIResolver is responsible for resolving URIs found within stylesheets and is generally something you will not need to deal with directly It is used when a stylesheet imports or includes another document and the processor needs to figure out where to look for that document For example xsl import href commonFooter xslt ErrorListener as you may guess is an interface that allows your code to register as a listener for error conditions This interface defines the following three methods void error TransformerException ex void fatalError TransformerException ex void wa
186. Language WML Using Java for such a task requires skilled programmers who understand APIs such as DOM SAX or JDOM For web sites in particular it is desirable to simplify the page generation process so nonprogrammers can participate XSLT is explicitly designed for XML transformations With XSLT XML data can be transformed into any other text format including HTML XHTML WML and even unexpected formats such as Java source code In terms of complexity and sophistication XSLT is harder than HTML but easier than Java This means that page authors can probably learn how to use XSLT successfully but will require assistance from programmers as pages are developed XSLT processors are required to interpret and execute the instructions found in XSLT stylesheets Many of these processors are written in Java making Java an excellent choice for applications that must interoperate with XML and XSLT For web sites that utilize XSLT Java servlets and EJBs are still required to intercept client requests fetch data from databases and implement business logic XSLT may be used to generate each of the XHTML web pages but this cannot be done without a language like Java acting as the coordinator This book explains the most important concepts behind the XSLT markup language but is not a comprehensive reference on that subject Instead the focus is on interoperability with Java with particular emphasis on servlets and web applications Every concept is back
187. Loader java Native method java lang ClassLoader defineClass ClassLoader java 486 java security SecureClassLoader defineClas en cureClassLoader ja va 111 java net URLClassLoader defineClass URLClassLoader java 248 ee Maia ERE QUUM e LLL eap dp du e 56 java net URLClassLoader 1 run URLClassLoader java 195 By making the stack trace depth larger it is more likely that some of your code will show up somewhere in the report This makes the report much larger however These traces are useful because they show which methods are called leading up to each hotspot Companies that have the budget to do so should definitely consider purchasing a tool such as JProbe or Optimizelt Although the JVMPI interface offers much of the same functionality that these tools offer JVMPI output is entirely textual requiring quite a bit of manual detective work to isolate problems The commercial profiling tools also require some analysis but present the results in a graphical format that is substantially easier to navigate 9 3 2 3 Unit testing The effectiveness of simpler approaches to measurement should not be dismissed Often the easiest technique is to simply write a 15 line Java program that tests a specific piece of functionality For instance you might want to start with a short Java program that performs an XSLT transformation as shown in Chapter 5 Next use System currentTimeInMillis to measure the time immediately before and a
188. M tree offering better memory utilization and performance 5 3 5 1 The approach It turns out that writing a SAX parser is quite easy All a SAX parser does is read an XML file top to bottom and fire event notifications as various elements are encountered In our custom parser we will read the CSV file top to bottom firing SAX events as we read the file A program listening to those SAX events will not realize that the data file is CSV rather than XML it sees only the events Figure 5 4 illustrates the conceptual model 14 Our examples use SAX 2 Figure 5 4 Custom SAX parser CSV File Burke Eric M SAX Events Result Burke Jennifer LP PUstom say gt prxStr TT gt Tree Burke Aidan G Ser Essor 4 i s XSLT Stylesheet In this model the XSLT processor interprets the SAX events as XML data and uses a normal stylesheet to perform the transformation The interesting aspect of this model is that we can easily write custom SAX parsers for other file formats making XSLT a useful transformation language for just about any legacy application data In SAX org xml sax XMLReader is a standard interface that parsers must implement It works in conjunction with oxc xmi sax ContentHandler Which is the interface that listens to SAX events For this model to work your XSLT processor must implement the ContentHandler interface so it can listen to the SAX events that the xMLReader generates In the case of JAXP javax xml trans
189. MessageTree java package com oreilly forum domain k import java util Arranges a collection of MessageSummary objects into a tree Py public class MessageTree private List topLevelMsgs new ArrayList map ids to MessageSummary objects private Map idToMsgMap new HashMap map reply to ids to lists of MessageSummary objects private Map replyIDToMsgListMap new HashMap Construct a new message tr from an iterator of MessageSummary objects public MessageTree Iterator messages while messages hasNext stor ach message in a map for fast retrieval by ID MessageSummary curMsg MessageSummary messages next this idToMsgMap put new Long curMsg getID curMsg build the inverted map that maps reply to IDs to lists of messages Long curReplyID new Long curMsg getInReplyTo List replyToList List this replyIDToMsgListMap get curReplyID if replyToList null replyToList new ArrayList this replyIDToMsgListMap put curReplyID replyToList replyToList add curMsg build the list of top level messages A top level messag fits one of the following two criteria its reply to ID is 1 its reply to ID was not found in the list of messages This occurs when a message is a reply to a previous month s message Iterator iter this replyIDToMsgListMap keySet iterator while iter hasNext Lon
190. OM 2 or XSLT transformations applications requesting any of these new features may see one of these exceptions when JAXP 1 0 is installed instead of JAXP 1 1 As mentioned earlier the filename jaxp jar is used with Versions 1 0 and 1 1 of JAXP Therefore special care must be taken to ensure that the newer copy is present instead of the old one Since JAXP 1 1 is backwards compatible with Version 1 0 the older version can be safely replaced without breaking currently installed applications that depend on it The easiest exception to debug is java lang ClassNotFoundException This may occur when JAXP 1 1 is listed on the CLASSPATH However an XSLT processor or XML parser is not listed To remedy this situation merely add a JAXP compliant parser and XSLT processor to the CLASSPATH 9 1 1 4 Java optional packages The Java VM does not simply load classes based on the CLASSPATH environment variable Before searching the CLASSPATH the VM attempts to load classes from an optional package directory An installed optional package is a JAR file located in the Java 2 Runtime Environment s lib ext directory or in the jre lib ext directory of the Java 2 SDK If an installed optional package is not located the VM then searches for download optional packages These are JAR files that are explicitly referenced by the Class Path manifest header of another JAR file For example a manifest might contain the following line Class Path jaxp jar
191. PMMPPPPPTIPIIIIIIITTMIPM a helper class that represents a value in the cache map KALULE TATA STATA TATA ATTA TATA ATTA TATA AAT TAA ATA TTT static class MapValue long xmlLastModified when the XML file was modified long xsltLastModified when the XSLT file was modified String result MapValue File xmlFile File xsltFil e throws TransformerException this xmlLastModified xmlFile lastModified this xsltLastModified xsltFile lastModified TransformerFactory transFact TransformerFactory newlInstance Transformer trans transFact newTransformer new StreamSource xsltFile StringWriter sw new StringWriter trans transform new StreamSource xmlFile new StreamResult sw this result sw toString return true if either the XML or XSLT file has been modified more recently than this cache entry T boolean isDirty File xmlFile File return this xmlLastModified thas The key to this class is its transform method This method takes filenames of an XML file and XSLT stylesheet as arguments and returns the transformation result as a St ring If any error occurs a TransformerException Is thrown St atic synchronized a String transform String xmlFileName String xsltFileName Y throws TransformerException The cache is implemented using a java util Map data structure which requires key value pairs of data The MapKey helper
192. R xslt The system id is optional but can be helpful when displaying error messages or warnings public interface Result public static final String PI_DISABLE_OUTPUT_ESCAPING javax xml transform disable output escaping public static final String PI ENABLE OUTPUT ESCAPING javax xml transform enable output escaping String getSystemId ys void setSystemId String systemIQd Source This is a generic interface implemented by DoMSource SAXSource and StreamSource The system id is particularly important for Source because it allows the processor to resolve relative URI references within the XML and XSLT inputs Cl URI references are found in elements such as lt xs1 import gt and lt xsl include gt f public interface Source String getSystemId void setSystemId String systemIQd SourceLocator Instances of this interface are useful when reporting locations of error messages and warnings Application programmers retrieve SourceLocator instances from TransformerException s getLocator method public interface SourceLocator int getColumnNumber s int getLineNumber String getPublicId s String getSystemId Js Templates These instances represent compiled transformation instructions Whether a particular XSLT processor actually compiles stylesheets is implementation dependent However Templates objects are guaranteed to be thread safe This makes them ideal for
193. S Layout Page and Navigation are responsible for rendering a view back to the browser When compared to a pure XML XSLT approach frameworks have the advantage of value added features If you remove all of the non web features such as database connection pooling and object to relational mapping tools you will see that the underlying modelview controller architecture is very easy to implement You should be wary of any framework that provides too much non web related functionality because many of these features should be placed on the application server instead of the web server anyway The remainder of this chapter is devoted to showing you how to structure a complex web application without committing yourself to a specific framework 4 2 2 Model View Controller Cleanly separating data and presentation logic is important What exactly are the benefits First and foremost when data is completely isolated from the user interface changes can be made to the visual appearance of an application without affecting the underlying data This is particularly important in web applications that have to support multiple incompatible browsers or even WML XHTML Basic or HTML It is much harder to adapt to new user interface requirements when data and presentation are mixed Programming logic should also be separated from data and presentation logic To a certain extent programming logic must depend in part on both data and presentation But you can gener
194. SAX as well as an entirely new plugability layer for performing transformations JAXP 1 1 also refines the algorithm used for locating implementation classes for the three supported plugability layers This algorithm is discussed in Chapter 5 in the Introduction to JAXP 1 1 section Package javax xml parsers The classes in this package support parsing using Simple API for XML SAX 2 and Document Object Model DOM Level 2 These classes do not perform the actual parsing work instead they delegate to plugable parser implementations such as Apache s Crimson or Xerces DocumentBuilder Instances of this class define an API for parsing XML from a variety of input sources as well as for creating new DOM Document objects from scratch The Document Builder instance should be obtained from the Document BuilderFactory instance Once an instance has been obtained the newDocument method can be used to construct new DOM Document objects without resorting to the implementation of specific code public abstract class DocumentBuilder orotected DocumentBuilder s public abstract DOMImplementation getDOMImplementation jy public abstract boolean isNamespaceAware public abstract boolean isValidating public abstract Document newDocument ja public Document parse InputStream is String systemId throws SAXException IOException oublic Document parse String uri throws SAXException IOException public Document parse File f
195. SLT approach and a pure Java approach is that XSLT does not require break statements between x51 when elements In XSLT the lt xsi when gt elements are evaluated in the order in which they appear and the first one with a test expression resulting in true is evaluated All others are skipped If no lt xs1 when gt elements match then lt xsl otherwise gt if present is evaluated Since xs1 if has no corresponding xs1 e1se xsl choose can be used to mimic the desired functionality as shown here xsl choose xsl when test condition gt if condition gt xsl when lt xsl otherwise gt lt else condition xsl otherwise lt xsl choose gt As with other parts of XSLT the XML syntax forces a lot more typing than Java programmers are accustomed to but the mechanics of i e1se are faithfully preserved 3 2 Parameters and Variables As in other programming languages it is often desirable to set up a variable whose value is reused in several places throughout a stylesheet If the title of a book is displayed repeatedly then it makes sense to store that title in a variable rather than scan through the XML data and locate the title repeatedly It can also be beneficial to set up a variable once and pass it as a parameter to one or more templates These templates often use xs1 if Or xsi choose to produce different content depending on the value of the parameter that was passed 3 2 1
196. SLT can then convert that XML into HTML without a great deal of custom coding resulting in less work for your development team 1 3 3 Nonbrowser Clients While web sites typically deliver HTML to browsers web applications may be asked to interoperate with applications other than browsers It is typical to provide feature rich Swing GUI clients for use within a company while remote workers access the system via an XHTML interface through a web browser An XML approach is key in this environment because the raw XML can be sent to the Swing client while XSLT can be used to generate the XHTML views from the same XML data If your XML is not in the correct format XSLT can also be used to transform it into another variant of XML For example a client application may expect to see lt name gt Eric Burke lt name gt But the XML data on the web tier deals with the data as lt firstName gt Eric lt firstName gt lt lastName gt Burke lt lastName gt In this case XSLT can be used to transform the XML into the simplified format that the client expects 1 3 3 1 SOAP Sending raw XML data to clients is a good approach because it interoperates with any operating system hardware platform or programming language Allowing Visual Basic clients to extract XML data from a web application allows existing client software to be salvaged while enabling remote access to enterprise data using a more portable solution such as Java But defining a custom
197. ST ME Once extracted the manifest can be viewed with any text editor Example 9 1 shows the content of the manifest from Version 1 0 of jaxp jar Example 9 1 Version 1 0 jaxp jar manifest contents Manifest Version 1 0 Specification Title Java API for XML Parsing Interfaces Specification Vendor Sun Microsystems Created By 1 4 Sun Microsystems Inc Specification Version 1 0 0 javax xml parsers e Version 1 0 0 SE ication Title Java API for XML Parsing S Fication Vendor Sun Microsystems S true SE Fication Version 1 0 0 Pac ge Vendor Sun Micr stems Inc Package Title javax xml parsers This manifest makes it quite easy to identify the contents of this JAR file Although Sun s products tend to be very good about this the manifest contents are entirely optional and many other products omit all manifest information 9 1 1 2 Sealing violations The dreaded sealing violation is one of the more cryptic exceptions encountered Example 9 2 shows a stack trace that is displayed when a sealing violation occurs Example 9 2 Sealing violation stack trace Exception in thread main java lang SecurityException sealing violation at java net URLClassLoader defineClass URLClassLoader java 234 at java net URLClassLoader access 100 URLClassLoader java 560 at java net URLClassLoader 1 run URLClassLoader java 195 at java security AccessController doPrivileged Native Method at jav
198. StreamSource xsltFile The Source interface is used to read both the XML file and the XSLT file Unlike the SAX Input Source class or Xalan s xsiTInputSource class Source is an interface that can have many implementations In this simple example we are using St reamSource which has the ability to read from a File object an InputStream a Reader or a system ID Later we will examine additional Source implementations that use SAX and DOM as input Just like Source Result is an interface that can have several implementations In this example a StreamResult sends the output of the transformations to System out javax xml transform Result result new javax xml transform stream StreamResult System out Next an instance of TransformerFactory is created javax xml transform TransformerFactory transFact javax xml transform TransformerFactory newInstance ey The TransformerFactory is responsible for creating Transformer and Template objects In our simple example we create a Transformer object javax xml transform Transf trans orme transFact newTransfo r erixsltSourse e Transformer Objects are not thread safe although they can be used multiple times For a simple example like this we will not encounter any problems In a threaded servlet environment however multiple users cannot concurrently access the same Transformer instance JAXP also provides a Templates interface which represents a stylesheet that can be accessed by
199. String msgSubject String authorEmail String msgText throws DataException Message inReplyToMsg this getMessage origMsgID return insertMessage inReplyToMsg getBoard origMsgID msgSubject authorEmail msgText we Post a new message Qreturn the newly created messag throws DataException if a database error occurs or if any parameter is illegal public Message postNewMessage long boardID String msgSubject String authorEmail String msgText throws DataException BoardSummary board this getBoardSummary boardID return insertMessage board 1 msgSubject authorEmail msgText If no messages exist for the specified board and month return an empty iterator return an iterator of lt code gt MessageSummary lt code gt objects throws DataException if the boardID is illegal or a database error occurs public Iterator getAllMessages long boardID MonthYear month throws DataException List allMsgs new ArrayList x F X X Connection con null Statement stmt null try con DBUtil getConnection dbURL stmt con createStatement BoardSummary boardSum this getBoardSummary boardID stmt ResultSet rs stmt executeQuery SELECT id inReplyToID createDay Subject authorEmail FROM Message WHERE createMonth month getMonth AND createYear month getYear n
200. T processors into a book is futile because the market is maturing too fast Some of the currently popular Java based processors are listed here but a quick web search for XSLT Processors would be prudent before you decide to standardize on a particular tool as new processors are constantly appearing We will see how to use Xalan in the next chapter a few other choices are listed here 1 4 1 1 XT XT was one of the earliest XSLT processors written by James Clark If you read the XSLT specification you may recognize him as the editor of the XSLT specification As the XSLT specification evolved XT followed a parallel path of evolution making it a leader in terms of standards compliance At the time of this writing however XT had not been updated as recently as some of the other Java based processors Version 19991105 of XT implements the W3C s proposed recommendation PR xslt 19991008 version of XSLT and is available at http www jclark com xml xt html Like the other processors listed here XT is free 1 4 1 2 LotusXSL LotusXSL is a Java XSLT processor from IBM Alphaworks available at http www alphaworks ibm com In November 1999 IBM donated LotusXSL to Apache forming the basis for Xalan LotusXSL continued to exist as a separate product However it is currently a thin wrapper around the Xalan processor Future versions of LotusXSL may add features above and beyond those offered by Xalan but there doesn t seem to be a compelling rea
201. The creat eLeftNavbar template on the other hand simply copies some static content to the result Finally the contents of the lt body gt tag are copied from the original document to the result tree xsl copy of select html body html body text Unlike the lt head gt the lt body gt is not copied directly Instead all elements and text within the body are copied This prevents the following invalid XHTML from being produced lt tr gt lt td gt lt body gt lt body gt lt td gt lt tr gt The createTopNavbar named template is used to create the row of links in the top navigation area For each navigation category it calls the navButton template xsl call template name navButton gt xsl with param name category select home xsl with param name displayName select Home xsl with param name url select home xml xsl call template The category parameter allows the navButton template to determine if the displayName parameter should be displayed as a hyperlink or text The code to do this is emphasized in the navButton template in Example 8 2 and is not repeated here None of this works without a servlet driving the process In this example all XHTML pages are stored in the web application s WEB INF directory and saved with xm filename extensions Remember that these are the original web pages and do not contain any navigation areas They are stored in the WEB INF directory to ensur
202. The servlet API has a nice class called RequestDispatcher that allows server side forwarding and including This is the normal mechanism for interaction between the servlet and JSP Figure 4 3 illustrates this design at a high level Figure 4 3 Hybrid JSP servlet approach validates request Browser Web Tier RequestDispatcher renders response This approach combines the best features of servlets with the best features of JSPs The arrows indicate the flow of control whenever the browser issues a request The job of the servlet is to intercept the request validate that the form data is correct and delegate control to an appropriate JSP Delegation occurs via javax servlet RequestDispatcher which is a standard part of the servlet API The JSP simply renders the page ideally using custom tags and no Java code mixed with the HTML The main issue with this approach becomes evident when your web site begins to grow beyond a few pages You must make a decision between one large servlet that intercepts all requests a separate servlet per page or helper classes responsible for processing individual pages This is not a difficult technological challenge but rather a problem of organization and consistency This is where web frameworks can lend a helping hand 4 2 The Universal Design Despite the proliferation of APIs frameworks and template engines most web application approaches seem to be consolidating around the idea of mo
203. This requires skilled developers who know how to interact with Enterprise JavaBeans or relational databases Since skilled Java developers are a scarce and expensive resource it makes sense to let them work on the back end data sources and business logic while web page developers and less experienced programmers work on the HTML user interface As we will see in Chapter 4 this can be difficult with traditional Java servlet approaches because Java code is often cluttered with HTML generation code 1 1 2 Keeping Data and Presentation Separate HTML does not separate data from presentation For example the following fragment of HTML displays some information about a customer In it data fields such as Aidan and Burke are clearly intertwined with formatting elements such as lt t r gt and lt td gt lt h3 gt Customer Information lt h3 gt lt table border 1 cellpadding 2 cellspacing 0 gt lt tr gt lt td st Name lt td gt lt td gt Aidan lt td gt lt tr gt lt tr gt lt td gt Last Name lt td gt lt td gt Burke lt td gt lt tr gt Pos GEO gt lt table Traditionally this sort of HTML is generated dynamically using print in statements in a servlet or perhaps through a JavaServer Page JSP Both require Java programmers and neither technology explicitly keeps business logic and data separated from the HTML generation code To support multiple incompatible browsers you have to be careful to avoid duplication of
204. To resolve this problem when using InputStream the javax xml transform Source interface provides the setSystemId method This allows the XSLT processor to resolve URI references in the stylesheet see Chapter 5 For this servlet we avoid this issue by using a URL instead of an InputStream The URL is converted into a system identifier which makes it possible to create a St reamSource instance That is in turn used to create a Templates instance for this stylesheet URL xsltURL getServletContext getResource curName String xsltSys temID xsltURL toExternalForm js this editTemplates transFact newTemplates new StreamSource xsltSystemID The same process is repeated for the second stylesheet followed by basic exception handling curName WEB INF xslt confirmPersonalData xslt XSltURL getServletContext getResource curName xsltSystemID xsltURL toExternalForm 3 this thanksTemplates transFact newTemplates new StreamSource xsltSystemID catch TransformerConfigurationException tce log Unable to compile stylesheet tce throw new UnavailableException Unable to compile stylesheet catch MalformedURLException mue log Unable to locate XSLT file curName throw new UnavailableException Unable to locate XSLT file curName The log method causes messages to be written to one of Tomcat s log files found in the TOMCAT HOME lo
205. UTF 16 gt UTF 16 lt br gt lt td gt lt tr gt lt table gt lt p gt lt input type submit name submitBtn value Submit gt lt p gt lt form gt lt body gt lt html gt The servlet LanguageDemo java is shown in Example 8 24 This servlet accepts input from the j18n html web page and then applies the XSLT transformation Example 8 24 LanguageDemo java servlet package chap8 import java io import javax servlet import javax servlet http import javax xml transform import javax xml transform stream Allows any combination of English Spanish and Chinese XML and XSLT ur public class LanguageDemo extends HttpServlet public void doPost HttpServletRequest req HttpServlet Response res throws ServletException IOException ServletContext ctx getServletContext these are all required parameters from the HTML form String xmlLang req getParameter xmlLanguage String xsltLang req getParameter xsltLanguage String charEnc req getParameter charEnc convert to system dependent path names String xmlFileName ctx getRealPath WEB INF xml numbers xmlLang xml String xsltFileName ctx getRealPath WEB INF xslt numbers xsltLang xslt do this BEFORE calling HttpServletResponse getWriter res setContentType text html charset charEnc try Source xmlSource new Strea
206. XSLT becomes obvious when you try to test your web application With JSP it is virtually impossible to test your code outside the bounds of a web browser and servlet container In order to write a simple automated unit test against a JSP you have to start a web server and invoke your JSPs via HTTP requests With XML and XSLT on the other hand you can programmatically generate the XML data without a web browser or server This XML can then be validated against a DTD or schema You can also test the XSLT stylesheets using command line tools without deploying to a servlet container or starting a web server The result of the transformation can even be validated again with a DTD if you use XHTML instead of HTML 4 1 4 Template Engines Before moving on let s discuss template engines A quick search on the Internet reveals that template engines are abundant each claiming to be better than JSP for various reasons For the most part template engines have a lot in common with JSP particularly if you restrict yourself to custom tags There are some differences however e Template engines typically forbid you from embedding Java code into pages Although JSP allows Java code along with HTML it is not considered good form e Most template engines are not compiled so they do not have the same problems that JSP has with error messages They also start up faster on the first invocation which can make development easier The effect on end users is minima
207. a lot of Java code and the HTML itself This places additional burdens on Java developers who should be working on more important problems There are ways to keep programming logic separate from the HTML generation but extracting meaningful data from HTML pages is next to impossible This is because the HTML does not clearly indicate how its data is structured A human can look at HTML and determine what its fields mean but it is quite difficult to write a computer program that can reliably extract meaningful data Although you can search for text patterns such as First Name followed by ca this approach fails as soon as the presentation is modified For example changing the page as follows would cause this approach to fail 1 This approach is commonly known as screen scraping tr td Full Name lt td gt lt td gt Aidan Burke lt td gt lt tr gt 1 1 3 The XSLT Solution XSLT makes it possible to define clearly the roles of Java XML XSLT and HTML Java is used for business logic database queries and updates and for creating XML data The XML is responsible for raw data while XSLT transforms the XML into HTML for viewing by a browser A key advantage of this approach is the clean separation between the XML data and the HTML views In order to support multiple browsers multiple XSLT stylesheets are written but the same XML data is reused on the server In the previous example the XML data for the customer did not contain
208. a child element to something else By adding several consecutive xsl sort elements you can accomplish multifield sorting Each sort can be in ascending or descending order and the data type for sorting is either number or text The sort order defaults to ascending Some examples of xs1 sort include xsl sort select first gt xsl sort select last order descending gt xsl sort select term from order descending data type number xsl sort select name first data type text case order upper first In the last line the case oraer attribute specifies that uppercase letters should be alphabetized before lowercase letters The other accepted value for this attribute is 16wer first According to the specification the default behavior is language dependent 2 5 3 Looping and Sorting Examples The easiest way to learn about looping and sorting is to play around with a lot of small examples The code in Example 2 9 applies numerous different looping and sorting strategies to our list of presidents Comments in the code indicate what is happening at each step Example 2 9 Looping and sorting lt xml version 1 0 encoding UTF 8 gt xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl output method html lt xsl template match gt html body hl Sorting Examples lt h1 gt xsl apply templates select presidents gt body html
209. a net URLClassLoader findClass URLClassLoader java 188 at java lang ClassLoader loadClass ClassLoader java 297 at sun misc LauncherSAppClassLoader loadClass Launcher java 286 at java lang ClassLoader loadClass ClassLoader java 253 at java lang ClassLoader loadClassInternal ClassLoader java 313 at java lang Class forName0 Native Method at java lang Class forName Class java 120 at javax xml transform TransformerFactory newInstance TransformerFactory ja va 117 at Test main Test java 17 This exception is hard to diagnose because the error message is not very descriptive and the stack trace consists mostly of internal Java classes According to the stack trace line 17 of Test java caused the problem Here it is TransformerFactory transFact TransformerFactory newInstance Actually this line of code is perfectly correct The problem lies in the CLASSPATH instead The key to understanding this error is the sealing violation description This indicates that one or more sealed JAR files are on the CLASSPATH in the wrong order A sealed JAR file has a manifest entry Sealed true as shown in Example 9 1 7 The package sealing mechanism was introduced in Java Version 1 2 to enforce version consistency Whenever a package is sealed all classes in that package must be loaded from the same JAR file If some of the classes are loaded from one JAR file and others from another an instance of java lang SecurityException
210. a sealing violation exception may occur if the existing CLASSPATH contains the newer crimson jar but an older version of parser jar is still present The best approach to fully configure Tomcat 3 2 x for XML support is as follows e Remove jaxp jar and parser jar from the TOMCAT_HOME lib directory e Install the following files from the JAXP 1 1 distribution into the TOMCAT_HOME lib directory jaxp jar crimson jar and xalan jar Of course JAXP 1 1 supports other tools besides Crimson and Xalan If you prefer simply replace crimson jar and xalan jar with competing products that are JAXP 1 1 compatible 9 1 3 2 Configuring Tomcat 4 0 x Tomcat 4 0 improves upon Tomcat 3 2 x configuration issues in two key ways First the user s existing CLASSPATH is no longer appended to Tomcat s CLASSPATH This helps to avoid situations where code works for one developer who happens to have some critical file on her CLASSPATH but fails for other developers who have slightly different personal CLASSPATH configurations Secondly Tomcat 4 0 no longer places JAXP JAR files in a location visible to web applications This means that if XML support is required you must install the proper XML JAR files before anything will work This is far better than the old Tomcat model because it avoids unexpected collisions with XML libraries used internally by Tomcat Instead if you forget to install XML support you simply see a java lang NoClassDefFoundError To
211. a will be generated dynamically as the result of a database query In this case it does not make sense to write the database query results to an XML file and then parse it into the XSLT processor Instead it is desirable to pipe the XML data directly into the processor using SAX or DOM In fact we will even see how to read nonXML data and transform it using XSLT 5 3 1 System Identifiers Files and URLs The simple examples presented earlier in this chapter introduced the concept of a system identifier As mentioned before system identifiers are nothing more than URIs and are used frequently by XML tools For example javax xml transform Source one ofthe key interfaces in JAXP has the following API blic interface Source String getSystemId void setSystemId String systemId The second method set Systemid _ is crucial By providing a URI to the Source the XSLT processor can resolve URIs encountered in XSLT stylesheets This allows XSLT code like this to work lt xsl import href commonFooter xslt gt When it comes to XSLT programming you will use methods in java io File and java net URL to convert platform specific file names into system IDs These can then be used as parameters to any methods that expect a system ID as a parameter For example you would write the following code to convert a platform specific filename into a system ID public static void main String args assume that the first command
212. ac ud remove xsltFileName The first method merely removes everything from the Map while the second removes a single stylesheet Whether you use these methods is up to you The 1usn211 method for instance should probably be called from a servlet s dest roy method to ensure proper cleanup If you have many servlets in a web application each servlet may wish to flush specific stylesheets it uses via the flush method If the xsitFileName parameter is not found the Map implementation silently ignores this request The majority of interaction with this class occurs via the newTrxansftormer method which has the following signature public static synchronized Transformer newTransformer String xsltFileName throws TransformerConfigurationException The parameter an XSLT stylesheet filename was chosen to facilitate the last accessed feature We use the java io File class to determine when the file was last modified which allows the cache to automatically reload itself as edits are made to the stylesheets Had we used a system identifier or Inout Stream instead of a filename the auto reload feature could not have been implemented Next the File object is created and its LastModified flag is checked File xsltFile new File xsltFileName determine when the file was last modified on disk long xslLastModified xsltFile lastModified The compiled stylesheet represented by an instance of MapEnt ry is then retrie
213. ack http www w3 org TR xslt fallback xsl for each xsl for each select node set expression Content Any number of lt xsl sort gt followed by template gt xsl for each See XSLT specification section 8 Repetition http www w3 org TR xsltz for each xsl if xsl if test boolean expression gt lt Content template gt lt xsl if gt See XSLT specification section 9 1 Conditional Processing with lt xsl if gt http www w3 org TR xsit section Conditional Processing with xsl if xsl import xsl import href uri reference See XSLT specification section 2 6 2 Stylesheet Import http www w3 org TR xsltzzimport xsl include xsl include href uri reference gt See XSLT specification section 2 6 1 Stylesheet Inclusion http www w3 org TR xslt include xsl key xsl key name gname match pattern use expression gt See XSLT specification section 12 2 Keys http www w3 org TR xslt key xsl message xsl message terminate yes or no gt lt Content template gt lt xsl message gt See XSLT specification section 13 Messages http www w3 org TR xsit message xsl namespace alias xsl namespace alias stylesheet prefix prefix or default result prefix prefix or default gt
214. after a slash character following the servlet mapping HttpServletRequest includes a method called get PathiInfo that returns any path information that is present Example 7 30 ReqHandlerRegistry java package com oreilly forum servlet import java util import javax servlet http A utility class that locates request handler instances based on extra path information public class RegqHandlerRegistry private ReqHandler defaultHandler private Map handlerMap new HashMap ysis public ReqHandlerRegistry ReqHandler defaultHandler this defaultHandler defaultHandler public void register ReqHandler handler this handlerMap put handler getPathInfo handler public ReqHandler getHandler HttpServletRequest request RegHandler rh null String pathInfo request getPathInfo if pathInfo null int firstSlashPos pathInfo indexOf int secondSlashPos firstSlashPos gt 1 pathInfo indexOf firstSlashPos l 1 String key null if firstSlashPos gt 1 if secondSlashPos gt 1 key pathInfo substring firstSlashPostl secondSlashPos else key pathInfo substring firstSlashPos 1 else key pathInfo if key null amp amp key length gt 0 rh ReqHandler this handlerMap get key return rh null rh this defaultHandler Throughout the discussion forum application URLs take on the fo
215. ageElem Since lt page gt is the root element it is the only thing added directly to our document All remaining elements will be added as children or descendents of lt page gt Even though we are not adding anything else directly to the doc object we must continue using it as the factory for creating the remaining elements if needed append requiredFieldsMissing if includeErrors amp amp personalData isValid pageElem appendChild doc createElement requiredFieldsMissing Since DOM can be tedious the children of lt personalData gt are created in a helper method called addElem Element personalDataElem doc createElement personalData pageElem appendChild personalDataElem use a private helper function to avoid some of DOM s tedious code addElem doc personalDataElem firstName personalData getFirstName true You can refer back to Example 6 7 for the complete implementation of the addElem method A sample of its output is firstName required true gt Eric lt firstName gt The final piece of code PersonalDataServlet java is presented in Example 6 8 This is a basic approach to servlet development that works for smaller programs such as this but has a few scalability problems that we will discuss later in this chapter Although we have removed all ofthe HTML and XML generation from this servlet it is still
216. ages through a Servlet because the Servlet container prevents direct access to anything under WEB INF div lt body gt lt html gt Figure 8 2 XHTML output with navigation areas 3 Home Page Netscape DJ x Fie Edit Yew Go Window Help Home Search Netscape Print t ki P Bookmarks Jj oan Fr ocalhost 8080 chap8 templote hoene xri E What s Related B WebMail B Contac E People Ej YelwPages E Downoad 4 Channel Home Company Products Jobs Left Navigation Area Welcome to the Home Page This is a normal XHTML page that authors create The guidelines are as follows Each page must be valid XHTML Each page must have a meta tag that indicates the navigalion category The templatePage xslt stylesheet will add the top and side navigation bars Pages are published to the WEB INF aml directory of a web app This forces chents to access pages through a Servlet because the Servlet container prevents direct access to anything under hitp jflocalhost 8080 chap8 temelatejproducts xml Since XSLT is used to insert the appropriate navigation areas all pages must be well formed XML This is a good practice and anyone who knows HTML should be able to make the transition to XHTML P Programmers can provide scripts for page authors to run that validate the XML against one of the XHTML DTDs reporting errors before pages are published to the web site 2 HTML TIDY is a free tool
217. ages specified month post new Post New or Reply To Message reply to cancel Creating a graphical layout of the web pages as shown here is sometimes called storyboarding a common user interface design technique that has its roots in the animation television and motion picture industries Such high level diagrams typically start as hand drawn sketches on paper with the intent of capturing the overall application flow This is a good place to start because it shows how everything fits together without delving too deeply into technical design details The Discussion Forum Home page is the starting point and displays the list of all message boards For each message board a list of months with messages is displayed From this screen the user can either click on a month to view a list of message subjects or click on a link to post a new message The user can always return to the home page from any other page in the application The View Month page shows message subjects for a particular month in a given board These messages are displayed in a tree that shows the message subject author and create date The structure of the tree represents threads of discussion with replies indented underneath the original messages From this page the user can either select a message to view or click on a link to visit the Post New Message page The View Message screen shows details for an individual message From this page vi
218. ake the pages look presentable The strict variant of XHTML does not allow most of the HTML 4 0 formatting tags but instead encourages the use of CSS Example 7 1 contains the complete CSS file used by the discussion forum 1H See http www w3 org TR xhtml1 for more information on XHTML Strict Example 7 1 forum css body font family Verdana Geneva Arial Helvetica sans serif boxl border 3px solid Navy text align center padding 4px margin 2px background color 4c0c0c0 box2 border 1px solid Navy padding 4px margin 2px background color FFFFCC h1 font size 22pt font weight normal margin Opx Opx Opx Opx h2 font size 18pt font weight normal margin Opx Opx Opx 0px h3 font size l4pt font weight normal margin Opx Opx 0px 0px ul margin top Opx msgSummaryLine font size smaller font weight normal a hover background color yellow error font weight bold color red Each of the XHTML web pages refers to this CSS file using the following syntax lt link type text ss rel ylesheet href forum forum css This is a great MCN because it keeps the size of the XSLT stylesheets and each XHTML page much smaller Changes to fonts and colors can be made in the single CSS file and are immediately reflected throughout the web application The primary obstacle at this time is noncompliant web browsers Althou
219. al get Calendar DAY OF MONTH ireturn the month number for a given date f public synchronized static int getMonth Date date cal setTime date return cal get Calendar MONTH return the year number for the given date m public synchronized static int getYear Date date cal setTime date return cal get Calendar YEAR private DateUtil DayMonthYear java shown in Example A 5 is a helper class that groups a day month and year together It also supports comparisons for sorting purposes Example A 5 DayMonthYear java package com oreilly forum domain import java util Date Represents a day month and year 7 public class DayMonthYear extends MonthYear private int day public DayMonthYear this new Date public DayMonthYear Date date super date this day DateUtil getDayOfMonth date public DayMonthYear int day int month int year super month year this day day public int getDay return this day public boolean equals Object obj if obj instanceof DayMonthYear DayMonthYear rhs DayMonthYear obj return super equals obj amp amp this day rhs day return false public int hashCode return super hashCode this day public int compareTo Object obj DayMonthYear rhs DayMonthYear obj int comparison super compareTo obj if comparison 0 if this day lt rhs day return
220. alData personalData boolean includeErrors String xsltFileName throws IOException ServletException try org w3c dom Document domDoc this personalDataXML produceDOMDocument personalData includeErrors Transformer trans StylesheetCache newTransformer xsltFileName response setContentType text html PrintWriter writer response getWriter trans transform new DOMSource domDoc new StreamResult writer catch Exception ex showErrorPage response ex If any exceptions occur this method can be showed to display the stack trace in the browser window Ry private void showErrorPage HttpServletResponse response Throwable throwable throws IOException PrintWriter pw response getWriter pw println html body hl An Error Has Occurred lt hi gt lt pre gt throwable printStackTrace pw pw println pre body c html A helper method that retrieves the PersonalData object from the HttpSession n private PersonalData getPersonalData HttpServletRequest request HttpSession session request getSession true PersonalData pd PersonalData session getAttribute chap6 PersonalData if pd null pd new PersonalData session setAttribute chap6 PersonalData pd return pd One key difference in this example is its reliance on the com oreilly javaxslt util StylesheetCache class This will of course
221. ally isolate business logic which depends on the data and presentation logic which depends on the user interface Figure 4 4 illustrates these dependencies Figure 4 4 Dependencies User Interface Presentation Logic Business Logic The arrows indicate dependencies For example if your underlying data changes then the business logic will probably have to change However that does not always flow up and break your presentation logic In general if changes are sweeping it is hard to avoid affecting upper layers but minor changes can almost always be encapsulated If the implementation of your business logic changes however there is no reason to change the underlying data Likewise you should be able to make changes to the presentation logic without breaking the business logic Later in this chapter we will see how Java XML and XSLT can be utilized to satisfy these dependencies The dominant pattern in scalable web sites is model view controller The MVC pattern originated with Smalltalk 80 as a way to develop graphical user interfaces in an object oriented way The basics are simple GUI components represent the view and are responsible for displaying visual information to the user The model contains application data The controller is responsible for coordinating between the model and the view It intercepts events from the view components queries the model for its current state makes modifications to the model and notifies the
222. always set the content type before getting the writer In future examples we will occasionally use text xmi as the content type but only when sending raw XML data to the client The remainder of SolashScreenServlet simply prints out an HTML response pw println lt html gt pw printin lt head gt lt title gt Splash Screen lt title gt lt head gt pw printin lt body gt pw pri n center style border lpx navy solid gt pw pri n to Java and XSLT h1 pw pri n y and Associates lt h3 gt pw pri n ition 2001 lt p gt lt hr gt OW pri n a nextURL gt Click here to continue lt a gt pw printin lt div gt pw println lt body gt pw println lt html gt As you can see the next URL parameter is used to create a hyperlink to the next page This is why a value of nu11 is unacceptable for this example This approach works fine for simple examples but quickly gets out of hand for complex pages This is because all but the most basic web pages require hundreds if not thousands of lines of HTML to create fancy tables colors and graphics For reasons discussed in Chapter 5 hardcoding that HTML into the servlet is simply unacceptable in a sophisticated web application 6 2 WAR Files and Deployment In the servlet model Web Application Archive WAR files are the unit of deployment WAR files enable portability across a wide range of servlet con
223. ame this lastName lastName getter methods omitted If two threads invoke the set Name method at roughly the same time the following scenario can occur 1 Thread A sets the first name to Bill but is interrupted by thread B 2 Thread B sets the first and last names to George and Bush 3 Thread A regains control and sets the last name to Clinton At this point the person s name is George Clinton which is clearly not what was intended Although you could make the setName method synchronized you would also have to make any get methods synchronized as well Another option is to make this an immutable object An immutable object cannot be modified so multiple threads cannot concurrently alter it The Person class can be modified as follows public class Person private String firstName private String lastName public Person String firstName String lastName Bc ee firstName this lastName lastName oe public String getFirstName return this firstName public String getLastName return thi a stName Since instances of the Person class cannot be modified its methods do not have to be synchronized This makes the objects fast and allows them to be read by many threads concurrently The only drawback is that you cannot make changes to these objects once they are constructed The simple fix is to create a brand new Person object whenever a change needs to be made Thi
224. amp Location Location Exception Cause the actual data private List exceptionList null return a detailed text report of the exception at the specified row public String getDetailReport int row if this exceptionList null row 0 row gt this exceptionList size return TransformerException te TransformerException this exceptionList get row SourceLocator loc te getLocator may be null buffer the report StringWriter sw new StringWriter PrintWriter pw new PrintWriter sw pw println te getClass getName pw printin oce eene ug if loc null pw println Line Number null SourceLocator pw println Column Number null SourceLocator pw println Public ID null SourceLocator pw println System ID null SourceLocator else pw println Line Number loc getLineNumber pw println Column Number loc getColumnNumber pw println Public ID loc getPublicId pw println System ID loc getSystemId pw println Message amp Location te getMessageAndLocation pw printin Location te getLocationAsString pw println Exception te getException if te getException null te getException printStackTrace pw pw println Cause te getCause if te getCause
225. amp nbsp lt xsl text gt lt xsl value of select middle gt lt xsl text disable output escaping yes gt amp amp nbsp lt xsl text gt lt xsl value of select last gt br lt xsl template gt lt xsl stylesheet gt Notice that when applying a sort to lt xsl apply templates gt that element can no longer be an empty element Instead one or more lt xs1 sort gt elements are added as children of xsl apply templates You should also note that sorting cannot occur in the lt xsl template match name gt element The reason for this is simple at the lt xs1 apply templates end you have a list of nodes to sort By the time the processing reaches lt xsl template match name the search has narrowed down to a single lt name gt so there is no node list left to sort 2 6 Outputting Dynamic Attributes Let s assume we have an XML document that lists books in a personal library and we want to create an HTML document with links to these books on Amazon com In order to generate the hyperlink the href attribute must contain the ISBN of the book which can be found in our original XML data An example of the URL we would like to generate is as follows lt a href http www amazon com exec obidos ASIN 0596000162 Java and XML lt a gt One thought is to include lt xsl value of select isbn gt directly inside of the attribute However XML does not allow you to insert the less than lt chara
226. an do the job A web application on the other hand is typically a custom application intended to perform a specific business or technical function They are often written as replacements for existing systems in an effort to enable browser based access When replacing existing systems developers are typically asked to duplicate all of the existing functionality using a web browser and HTML This is difficult at best because of HTML s limited support for sophisticated GUI components Most of the screens in a web application are dynamically generated and customized on a per user basis while many pages on a typical web site are static Java XML and XSLT are suitable for web applications because of the high degree of modularity they offer While one programmer develops the back end data access code a graphic designer can be working on the HTML user interface Yet another servlet expert can be working on the web tier while someone else is defining and creating the XML data Programmers and graphic designers will typically work together to define the XSLT stylesheets although the current lack of interactive tools may make this more of a programming task Another reason XML is suitable for web applications is its unique ability to interoperate with back end business systems and databases Once an XML layer has been added to your data tier the Web tier can extract that data in XML form regardless of which operating system or hardware platform is used X
227. and does not require a human being to interact as the test is running For instance requiring a user to type in specific values into HTML form fields and then look at the resulting web page is clearly not automated Also a test that merely displays a long text report is not automated because it requires a knowledgeable person to read over the report and inspect it for errors By automating tests every developer can run an entire suite of tests by executing a command line program The test suite then reports exactly which tests failed and where so the problems can be fixed immediately A key philosophy behind a successful unit testing methodology is the idea that every test must always run at 100 percent success Now when programmers change an XSLT stylesheet or XML code and a test suddenly fails they know that their changes were likely the source of the problem When broken tests are left in the project for long periods of time developers will probably stop running the testing suite because it becomes too difficult to manually filter through all of the error reports caused by the broken tests It is important to adopt a policy in which every developer runs the suite of unit tests before checking any modified code into a shared code repository such as CVS For XSLT transformations performing a transformation and then validating against a DTD or Schema is the easiest kind of testing Once the structure of the result is validated addi
228. andard Edition SDK JDOM beta6 http www jdom org Open source alternative to DOM JUnit 3 7 http www junit org Open source unit testing framework Tomcat 4 0 http jakarta apache org Open source servlet container Xalan Included with JAXP 1 1 XSLT processor There are certainly other tools most notably the SAXON XSLT processor available from http users iclway co uk mhkay saxon This can easily be substituted for Xalan because of the vendor independence that JAXP offers All of the examples as well as JAR files for the tools listed in Table P 1 are available for download from http www javaxslt com and from the O Reilly web site at http www oreilly com catalog javaxslt The included README txt file contains instructions for compiling and running the examples Organization This book consists of 10 chapters and 3 appendixes as follows Chapter 1 Provides a broad overview of the technologies covered in this book and explains how XML XSLT Java and other APIs are related Also reviews basic XML concepts for readers who are familiar with Java but do not have a lot of XML experience Chapter 2 Introduces XSLT syntax through a series of small examples and descriptions Describes how to produce HTML and XHTML output and explains how XSLT works as a language XPath syntax is also introduced in this chapter Chapter 3 Continues with material presented in the previous chapter covering more sophisticated XSLT lan
229. andler EJB Business data Data Object XML Presentation data This diagram is much closer to the true physical model of a multitier web application that uses XSLT The arrows indicate the overall flow of a single request originating with the client This client is typically a web browser but it could be a cell phone or some other device The client request goes to a single servlet and is handed off to something called RequestHandler In the pattern outlined here you create numerous subclasses of Request Handler Each subclass is responsible for validation and presentation logic for a small set of related functions One manageable strategy is to design one subclass of Request Handler for each web page in the application Another approach is to create fine grained request handlers that handle one specific task which can be beneficial if the same piece of functionality is invoked from many different screens in your application The request handler interacts with the application server via EJB components The normal pattern is to execute commands on session beans which in turn get their data from entity beans The internal behavior of the EJB layer is irrelevant to the web tier however Once the EJB method call is complete one or more data objects are returned to the web tier From this point the data object must be converted to XML The conversion to XML can be handled in a few different ways One common approach is to write
230. another consideration Today direct access to a MySQL database may be the preferred approach In the future a full EJB solution with some other database may be desired Or we may choose to store messages in flat files instead of any database at all All of these capabilities are achieved by using an abstract class called Dat aAdapter This class is shown in Figure 7 7 along with several related classes Figure 7 7 Data adapter design lt lt utility gt gt abstract ForumContig DataAdapter Se MAX_BOARD_NAME_LEN gatinstance DataAdapter MAX BOARD DESC LEN exception lt lt throw gt gt getMessage use MAX MSG SUBJECT LEN DataException lt Chri m replyToMessage 0554205025 405 86 gt MAX_EMAIL_LEN postNewMessage _ getAllMessages getAliBoards getBoardSummary setValues getJDBCDriverClassName getDatabaseURL getAdapterClassName utility DBUtil close FakeDataAdapter J bcDataAdapter use s getConnection closeAliConnections setLongString getLongString getNextID The Dat aAdapter class defines an interface to some back end data source As shown in the class diagram FakeDataAdapter and JdbcDataAdapter are subclasses These implement the data tier using flat files and relational databases respectively It is easy to imagine someone creating an RUBDataAdapter at some point in the future ForumConfig is used to determine which sub
231. ans that compilation running and debugging will all work properly within the JBuilder IDE But once the application is executed outside of JBuilder it will probably fail This is because the Java 2 SDK contains the older JAXP 1 0 JAR file and its older XML parser Merely adding the newer JAXP related JAR files to the CLASSPATH will probably introduce a sealing exception rather than fix the problem because the VM will still load files from the installed optional package directory before searching the CLASSPATH One way to fix this problem is to replace jaxp jar and parser jar with the same JAR files found in JBuilder s directory Another option is to update the JAVA HOME environment variable and PATH to point to JBuilder s version of Java 9 1 2 Ant Configuring JAR files and the CLASSPATH on a single developer s machine can be difficult keeping an entire team of developers in sync requires support from tools For this reason it is critical that every team member use the same build process when testing and integrating code changes In this section we take a brief look at Apache s Ant As discussed in Chapter 3 Apache s Ant is a Java based build tool that is an excellent alternative to make Ant is good for numerous reasons including BI These notes apply to Ant 1 3 Newer versions of Ant may handle JAR files differently e ts XML build files are easier to create than Makefiles e It is written in Java and is quite portable e Build
232. any consideration for ease of development or maintainability by nonexperts These decisions are hard and are often subjective based on individual experience and preferences The goal of this chapter is to look at the highlights of several popular technologies for web application development using Java and see how each measures up to an XSLT based approach The focus is on architecture which implies a high level viewpoint without emphasis on specific implementation details Although XSLT offers a good balance between performance maintainability and flexibility it is not the right solution for all applications It is hoped that the comparisons made here will help you decide if XSLT is the right choice for your web applications 4 1 Traditional Approaches Before delving into more sophisticated options let s step back and look at a few basic approaches to web development using Java For small web applications or moderately dynamic web sites these approaches may be sufficient As you might suspect however none of these approaches hold up as well as XML and XSLT when your sites get more complex 4 1 1 CGI Common Gateway Interface CGI is a protocol for interfacing external applications which can be written in just about any language with web servers The most common language choices for CGI are C and Perl This interface is accomplished in a number of ways depending on the type of request For example parameters associated with an HTTP GET
233. any formatting instructions lt customer gt lt firstName gt Aidan lt firstName gt lt lastName gt Burke lt lastName gt lt customer gt Since XML contains only data it is almost always much simpler than HTML Additionally XML can be created using a Java API such as JDOM http www jdom org This facilitates error checking and validation something that cannot be achieved if you are simply printing HTML as text using PrintWriter and printin statements in a servlet Best of all the XML generation code has to be written only once The XML data can then be transformed by any number of XSLT stylesheets in order to support different browsers alternate languages or even nonbrowser devices such as web enabled cell phones 1 2 XML Review In a nutshell XML is a format for storing structured data Although it looks a lot like HTML XML is much more strict with quotes properly terminated tags and other such details XML does not define tag names so document authors must invent their own set of tags or look towards a standards organization that defines a suitable XML markup language A markup language is essentially a set of custom tags with semantic meaning behind each tag XSLT is one such markup language since it is expressed using XML syntax The terms element and tag are often used interchangeably and both are used in this book Speaking from a more technical viewpoint element refers to the concept being modeled while tag
234. application The JDOM producer and XSLT stylesheet actually do most of the work distinguishing between the various modes of operation 7 5 Finishing Touches That about does it for the code walkthrough Since this is a moderately large application downloading the code from this book s web site is much easier than typing everything in by hand Do not forget that several additional classes are listed in Appendix B 7 5 1 Deployment A deployment descriptor and WAR file are required to deploy and test the application The deployment descriptor web xml is shown in Example 7 39 Example 7 39 Deployment descriptor lt xml version 1 0 encoding ISO 8859 1 lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 2 EN http java sun com j2ee dtds web app 2 2 dtd web app lt servlet gt servlet name forumServlet servlet name servlet class com oreilly forum servlet ForumServlet servlet class init param param name jdbcDriverClassNamec param name MySQL version is commented out lt param value gt org gjt mm mysql Driver lt param value gt gt lt param value gt sun jdbc odbc JdbcOdbcDriver lt param value gt init param init param param name databaseURL param name MySQL version is commented out lt param value gt jdbc mysql localhost 3306 forum lt param value gt gt lt param value gt jdbc odbc forum lt param value
235. ar This command assumes that the WAR file will be placed in the parent of your current working directory the forward slash works on Windows as well as Unix clients Once the WAR file has been created you can view its contents by changing to its directory and issuing the following command jar tvf appname war This shows the table of contents for the WAR file which must match the structure shown in Figure 6 2 The topmost directory in the WAR file is publicly accessible to web browsers and should contain your JSP and HTML files You can also create subdirectories which will also be visible to the client A common practice is to create an images directory for storing your graphic files The WEB INF directory is always hidden from clients that access your web application The deployment descriptor web xml is located here as are the classes and lib directories As Figure 6 2 indicates the classes directory becomes available to your application s ClassLoader Any JAR files contained in the ib directory are also available to your code making it very easy to deploy third party libraries along with a web application The folder other directories can be anything you want and will also be hidden from clients since it resides under the WEB INF directory Although clients cannot see any of these directories and files directly your servlet can access these resources programmatically and then deliver that content 6 2 2 Deployment Descriptor
236. are abstract and are written in terms of interfaces defined in the com oreilly forum domain package For example a message can be retrieved by its ID public abstract Message getMessage long msgID throws DataException By writing this code in terms of the Message interface a future programmer could easily write a new class that implements Message in a different way Throughout the Dat a2 dapter class a DataException occurs when an id is invalid or when the underlying database fails The downloadable discussion forum implementation comes with a fake implementation of DataAdapter as well as a JDBC based implementation The fake implementation is listed in Appendix B The database implementation has been tested on Microsoft Access as well as MySQL and should work on just about any relational database that includes a JDBC driver Figure 7 8 shows the physical database design that the JdbcDat aAdapter class uses Figure 7 8 Database design id PK inReplyToID createMonth createDay createYear boardID FK subject authorEmail msgText description The database is quite simple Each table has an id column that defines a unique identifier and primary key for each row of data Message inReplyToID contains a reference to another message that this one is in reply to or 1 if this is a top level message The create date for each message is broken down into month day and year Although the application could store the
237. are not used by this class If XML and XSLT were used then the same CLASSPATH issue that caused the original exception to occur would probably cause this page to fail as well public class ErrorRenderer extends Renderer private String message private Throwable throwable F F F X public ErrorRenderer Throwable throwable this throwable throwable getMessage lye public ErrorRenderer String message this null message public ErrorRenderer Throwable throwable String message this throwable throwable this message message public void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException response setContentType text html PrintWriter pw response getWriter j just show a simple error page for now pw println lt html gt pw println body pw println p pw println this message pw println p if this throwable null pw printin lt pre gt this throwable printStackTrace pw pw println lt pre gt pw println body html XSLTRenderHelper shown in Example 7 29 is a utility class used by all remaining renderers This class does the low level XSLT transformations eliminating a lot of duplicated code in each of the renderers XSLTRenderHelper also maintains a cache of stylesheet filenames so they d
238. are rendered The XML is used only for data so you can use the stylesheets to include graphics render the output in a foreign language or combine page fragments from other sources such as headers and footers into your web pages The lt requiredFieldsMissing gt element is optional If omitted the XSLT stylesheet will not display error messages about missing fields This is useful when the data is generated the first time because all fields will be blank and you probably don t want to show a bunch of error messages In our servlet the doGet method is called when the user first requests this web page so it is here where we disable this element It is important to mention that this XML is used only for documentation purposes and for testing the XSLT stylesheets Once you move into a production environment the XML will be generated dynamically using the PersonaliData and PersonalDataxXML classes so this static file will not be required You will probably want to hang on to your static XML however as this will make it easier to experiment with changes to the XSLT The XSLT stylesheet that creates the HTML form is shown in Example 6 4 The stylesheets are substantially longer than the XML data which is typical In a more simplistic approach to servlet development all of this logic would be hardcoded into the source code as a series of print in statements making the servlet much larger and less flexible Example 6 4 editPersonalD
239. ata xslt lt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xmlns http www w3 org 1999 xhtml xsl output method xml indent yes encoding UTF 8 doctype public W3C DTD XHTML 1 0 Transitional EN doctype system http www w3 org TR xhtml1 DTD xhtml1l transitional dtd gles ck ck ck ck ck ck ke ke ke ke ke ck ck ck ck ck ck ck ck ck ck ck ck ck ke ke cock ck ck ck ck ck ck KKK KKK KKK cec ck ck ck ck ck ck ckckck ckck ck ko kck ck c Top level template Creates the framework for the XHTML page CK CKCkck ckCckck k ck ck ck ck ck ck kck ck k ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck ck kck ck ck ck ck ck ck ck ck kk ck k ck k k kk kkk lt xsl template match gt lt html gt lt head gt lt title gt Edit Personal Information lt title gt lt head gt lt body gt xsl apply templates select page personalData gt body lt html gt lt xsl template gt Sess KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Match the lt personalData gt element KKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKAKKKKKKKKKKKKK KK KKK KKK KK KKK KK k D lt xsl template match personalData gt lt h3 gt Personal Information lt h3 gt lt xsl if test requiredFieldsMissing gt lt div style color red font size larger Error one or more required fields are missing div xsl if lt i gt Fields mark
240. ava and XSLT Eric M Burke Publisher O Reilly First Edition September 2001 ISBN 0 596 00143 6 528 pages By GiantDino Learn how to use XSL transformations in Java programs ranging from stand alone applications to servlets Java and XSLT introduces XSLT and then shows you how to apply transformations in real world situations such as developing a discussion forum Copyright transforming documents from one form to another and generating Table of Contents content for wireless devices Index Full Description About the Author Reviews Reader reviews Errata ava and XSLT Preface Audience Software and Versions Organization Conventions Used in This Book How to Contact Us Acknowledgments 1 Introduction 1 1 Java XSLT and the Web 1 2 XML Review 1 3 Beyond Dynamic Web Pages 1 4 Getting Started 1 5 Web Browser Support for XSLT 2 XSLT Part 1 The Basics 2 1 XSLT Introduction 2 2 Transformation Process 2 3 Another XSLT Example Using XHTML 2 4 XPath Basics 2 5 Looping and Sorting 2 6 Outputting Dynamic Attributes 3 XSLT Part 2 Beyond the Basics 3 1 Conditional Processing 3 2 Parameters and Variables 3 3 Combining Multiple Stylesheets 3 4 Formatting Text and Numbers 3 5 Schema Evolution 3 6 Ant Documentation Stylesheet 4 Java Based Web Technologies 4 1 Traditional Approaches 4 2 The Universal Design 4 3 XSLT and EJB 4 4 Summary of Key Approaches 5 XSLT Processingwith Java 5 1 A
241. ava util An implementation of the Message interfac js public class MessageImpl extends MessageSummaryImpl implements Messag private String text Construct a new instance of this class ey public MessageImpl long id DayMonthYear createDate BoardSummary board String subject String authorEmail String text long inReplyTo super id createDate board subject authorEmail inReplyTo this text text ireturn the text of this message 2g public String getText return this text MessageSummarylmpl java shown in Example A 8 is an implementation of the MessageSummary interface Example A 8 MessageSummarylmpl java package com oreilly forum domain import java util Implementation of the MessageSummary interface T public class MessageSummaryImpl implements MessageSummary private long id private BoardSummary board private String subject private String authorEmail private DayMonthYear createDate private long inReplyTo public MessageSummaryImpl long id DayMonthYear createDate BoardSummary board String subject String authorEmail long inReplyTo this id id this createDate createDate this board board this subject subject this authorEmail authorEmail this inReplyTo inReplyTo public long getInReplyTo return this inReplyTo public long getID return this id
242. be stored in the same way that shorter strings are stored In some databases these are referred to as CLOB columns MS Access uses the MEMO type while MySQL uses the TEXT data type Since this is an area where databases can be implemented differently the code is placed into the DBUt i 1 class for consistency If a special concession has to be made for a particular database it can be made in one place rather than in every SQL statement throughout the application Finally the JdbcDat aAdapter class is presented in Example 7 19 This is the relational database implementation of the Dat aAdapter class and should work with just about any relational database Example 7 19 JdbcDataAdapter java package com oreilly forum jdbcimpl import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import java sql import java util An implementation of the DataAdapter that uses JDBC public class JdbcDataAda ter extends DataAdapter private static String dbURL ForumConfig getDatabaseURL x Construct the data adapter and load the JDBC driver Ay public JdbcDataAdapter throws DataException try Class forName ForumConfig getJDBCDriverClassName catch Exception ex ex printStackTrace throw new DataException Unable to load JDBC driver ForumConfig getJDBCDriverClassName iparam msgID must be a valid message identifier
243. ber gt 0 919 lt number gt number gt 1 lt number gt number gt 10 lt number gt number gt 100 lt number gt number gt 1000 lt number gt number gt 10000 lt number gt number gt 12345 12345 lt number gt lt number gt 55555 55555 lt number gt lt numberSamples gt lt numberFormatting gt S G NAA KAKA KAKA AKA AAKAAAHKAAAA ii z The stylesheet numberFormatting xslt is shown in Example 3 9 Comments in the code explain what happens at each step To test new patterns and numbers just edit the XML data and apply the transformation again Since the XML file references the stylesheet with lt xm1 stylesheet you can simply load the XML into an XSLT compliant web browser and click on the Reload button to see changes as they are made Example 3 9 numberFormatting xslt lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt xsl output method html lt xsl template match gt lt html gt lt body gt lt loop over each of the sample formats gt lt xsl for each select numberFormatting formatSamples format gt lt h2 gt show the format as a heading gt lt xsl value of select gt lt 7 h2 gt lt table border 1 cellpadding 2 cellspacing 0 gt lt tr gt lt th gt Number lt th gt lt th gt Result lt th gt lt tr gt pass the format as a parameter to the template that shows each n
244. book and are important for programmers to understand The chapter concludes with advice for internationalization using XSLT and Java 8 1 XSLT Page Layout Templates In many cases dynamically generated highly interactive web applications are overkill A small company may need only a static web site that displays job openings new product announcements and other basic information Corporate intranets present another common scenario In a typical intranet a large number of departments and individual project teams may be responsible for various web sites within the corporation Many of these groups are composed of nonprogrammers who can create basic XHTML pages but are not technical enough to write XML XSLT and servlets In either scenario consistent look and feel are essential XSLT is very effective for defining consistent page layout In the approach outlined here web page authors create XHTML pages using whatever tools they are familiar with These pages should not use frames or include navigation areas As Figure 8 1 shows an XSLT stylesheet is used to insert navigation areas on the top and left sides of input XHTML pages This is why individual pages should not attempt to insert their own navigation areas Figure 8 1 XSLT template layout Top Navigation i input XHTML XSLT stylesheet ten copy ef input Navigation XHTML page output XHTML page Since the top navigation area is dynamic page authors must also include a lt
245. both doGet and doPost When the visitor first visits this web site an HTTP GET request causes the doGet method to be called which shows a form that allows the user to enter his or her information When they hit the submit button on the web page the doPost method validates all form fields and shows the confirmation page if everything is valid If one or more fields are missing the form is redisplayed with an error message init doGet doPost converts PersonalData Uu into DOM tree The PersonalData Class simply holds data that the user has entered and is located via the HttpSession Each visitor gets his or her own copy of Ht tpSession therefore they get their own copy of PersonalData In order to convert this data to XML a separate helper class called PersonalDataXML was created The decision to use a separate helper class for XML generation was not arbitrary Many people like to put code directly into classes like PersonalData such as a get XML _ method that performs this task By placing the XML generation logic into a totally separate class however it will be easier to migrate to a technology like JDOM without breaking current clients in any way A new class called PersonalDataJDOM could be added to the system while preserving all of the existing code This approach also keeps the PersonalData class smaller since all it has to do is hang on to the data The first web page is shown in Figure 6 5 A
246. cation is probably the biggest change because new database tables may be required to associate messages with users For web based administration tools additional request handlers and renderers need to be written These tools also need to be integrated with the security and authentication mechanism otherwise any user can run the administrative tools Searching is beyond the abilities of XML and XSLT and is best handled by a dedicated search engine technology This could be as simple as embedding a few lines of HTML into each page that links to a search engine such as Google Another approach is to write custom search code that integrates more directly with the underlying database Finally the whole issue of supporting alternate client user interfaces will be discussed in the next chapter In a nutshell this will involve detecting the client browser type and selecting an appropriate XSLT stylesheet 10 Even though all pages are generated dynamically many web crawlers such as Google index every page in the application Chapter 8 Additional Techniques This chapter presents solutions to a few commonly encountered problems that were not covered in previous chapters such as implementing session tracking without browser cookies detecting the browser type and using XSLT as a rudimentary code generator None of these techniques are remarkably difficult to implement or use However they all build upon the technologies presented throughout this
247. cell phones kr public class MovieServlet extends HttpServlet currently supports two types of clients could b xpanded later private static final int XHTML CLIENT TYPE 1 private static final int WML CLIENT TYPE 2 three pages in this web app private static final int HOME PAGE 100 private static final int THEATERS PAGE 101 private static final int SHOWTIMES PAGE 102 This a servlet supports GET and POST public void doGet HttpServletRequest req HttpServletResponse res throws IOException ServletException doPost req res public void doPost HttpServletRequest req HttpServletResponse res try showtimes throws IOException ServletException String action req getParameter action String city req getParameter city String theater req getParameter theater default to the home page int pageToShow HOME_PAGE if theaters equals action amp amp city null city is a required parameter for a theater list pageToShow THEATERS PAGE else if showtimes equals action amp amp city null amp amp theater null city and theater are required parameters for rj pageToShow SHOWTIMES PAGE set the content type of the response int clientType determineClientType req switch clientType
248. ch pattern name qname priority number mode qname Content Any number of lt xsl param gt followed by template gt lt xsl template gt See XSLT specification section 5 3 Defining Template Rules http www w3 org TR xslt section Defining Template Rules xsl text xsl text disable output escaping yes or no Content PCDATA xsl text See XSLT specification section 7 2 Creating Text http www w3 org TR xslt section Creating Text xsl transform xsl transform version number id id extension element prefixes tokens exclude result prefixes tokens gt Content Any number of lt xsl import gt followed by top level elements gt lt xsl transform gt See XSLT specification section 2 2 Stylesheet Element http www w3 org TR xslt stylesheet element lt XSl value of gt lt xsl value of select string expression disable ouput escaping yes or no gt See XSLT specification section 7 6 1 Generating Text with lt xsl value of gt http www w3 org TR xslt value of xsl variable xsl variable name qname select expression gt lt Content template gt xsl variable See XSLT specification section 11 Variables and Parameters http www w3 org TR xslit variables xslI when xsl when
249. chnology Figure 1 3 illustrates the typical interaction between SAX parsers and DOM implementations Figure 1 3 DOM and SAX interaction document DOM Implementation root idm org xml sax DOM Tree ContentHandler pr StartDocument SE nodi Edd eA soe startElement Element PRL A Games characters endElement Node Node i parse endDocurnent serialize T 7T serialize XML file Le ona S Vendor Specific Serializer Roten Although it is important to understand how these pieces fit together we will not go into detailed parsing syntax in this book As we progress to more sophisticated topics we will almost always be generating XML dynamically rather than parsing in static XML data files For this reason let s look at how DOM can be used to generate a new document from scratch Example 1 3 contains XML for a personal library Example 1 3 library xml lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE library SYSTEM library dtd gt lt library gt This is an XML comment publisher id oreilly gt lt name gt O Reilly lt name gt lt street gt 101 Morris Street lt street gt lt city gt Sebastopol lt city gt lt state gt CA lt state gt lt postal gt 95472 lt postal gt lt publisher gt book publisher oreilly isbn 1 56592 709 5 gt edition 1 edition publicationDate mm 10 yy 1999 gt title XML Pocket Reference lt title gt author Robert Eckstein lt
250. cific text 8 6 3 3 Web page and servlet The user begins with the web page that was shown in Figure 8 9 The HTML source for this page is listed in Example 8 23 The language and encoding selections are posted to a servlet when the user clicks on the Submit button Example 8 23 i18n html html head title Internationalization Demo lt title gt lt head gt lt body gt lt form method post action chap8 languageDemo gt table border 1 gt lt tr valign top gt td XML Language lt td gt lt td gt lt input type radio name xmlLanguage checked checked value english gt English lt br lt input type radio name xmlLanguage value spanish Spanish lt br gt lt input type radio name xmlLanguage value chinese gt Chinese lt td gt lt tr gt lt tr valign top gt lt td gt XSLT Language lt td gt lt td gt lt input type radio name xsltLanguage checked checked value english gt English lt br gt lt input type radio name xsltLanguage value spanish gt Spanish lt br gt lt input type radio name xsltLanguage value chinese gt Chinese lt td gt lt tr gt lt tr valign top gt lt td gt Character Encoding lt td gt lt td gt lt input type radio name charEnc value ISO 8859 1 gt ISO 8859 1 lt br gt lt input type radio name charEnc value UTF 8 checked checked gt UTF 8 br gt lt input type radio name charEnc value
251. ck here to change your answer i nossos As you can see in the picture the second card displays the values that were entered in the first card 3 Here is some of the code again 3 Notice that this particular device does not honor the lt em gt tag when the age is displayed Hello there S firstName e This demonstrates how to utilize WML variables something that is not possible with HTML The e at the end of the variable name is optional and instructs the device to perform URL escaping of the text before displaying it This is useful if the user enters spaces and other characters such as lt that may cause problems with the WML Hyperlinks in WML look just like hyperlinks in HTML lt p gt Click lt a href home gt here lt a gt to The trickiest part about WML is the wide variety of devices that may be in use Figure 10 3 shows these same two cards on a cellular phone that has a smaller display Figure 10 3 Another cell phone simulator zT 10 x CES ee ml File View Bookmarks Help File View Bookmarks Help eue 2220 filewc Jevsdataijavaxs exarr ie IIC fcvsdatafjavaxsTl exarr ERICSSON Mie You claim o be 30 years old can tis possibly be tue Click here to change As you can see the first card does not fit on the display so the user has to scroll On the second card the phone honors the emphasis em tag when displaying the age while the first browser in Figure 10 2
252. ckckckckckckckckckck ck ckck ck ck ck ck kk xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl import href utils xslt gt xsl param name rootDir select docroot gt xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public z W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtmll DTD xhtmll strict dtd Se CkCkckckck ck kCck ck ckck ck ck ckck ck ck ck ck ckck ck ck ckck ck ck ck ck kck ck kck ck k ck ck ck k ck k ck ck ck kckck kk kk kkkk Create the XHTML web page KKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKKKKKKK KKK kck KKK kk xsl template match html xmlns http www w3 0rg 1999 xhtml head title Discussion Forum Home lt title gt link href SrootDir forum css rel stylesheet type text css gt lt head gt lt body gt lt div class box1 gt lt hl gt Discussion Forum Home lt h1 gt lt div gt lt xsl apply templates select home board gt lt body gt lt html gt lt xsl template gt Se CkCk ckCckck ck kckck ck ck ck ck ckck ck KKK ck ck ck ck ck ck ck KKK ck ck ck ck ck ck ck kck ck ck ck ck ck ck ck ck kk ck k ck k kk kk Output a box for each board in the discussion forum CK CK CK Ck CK CK CC C0 CC CK CC Ck Ck Ck CK CK CC C CK Ck C Ck Ck Ck Ck 0k C Sk S A Kk Kk Ck ko ko Sk kv kx A kx Xo ko lt xsl template match board gt lt xsl variable name board
253. class of Dat aAdapter to instantiate and the DBUt i1 class encapsulates a few commonly used JDBC functions The source code for ForumConfig is shown in Example 7 15 This is a simple class that places configurable application settings in a single place As shown later in this chapter all configurable settings are stored in the servlet s deployment descriptor so they do not have to be hardcoded The first thing the servlet does is read the values and store them in ForumConfig I6 JNDI could also be used for this purpose However JNDI requires more configuration and may make it harder to deploy to some ISPs Example 7 15 ForumConfig java package com oreilly forum Define application wide configuration information The Servlet must call the setValues method before any of the get methods in this class can be used u public class ForumConfig maximum sizes of various fields in the database public static final int MAX BOARD NAME LEN 80 public static final int MAX_BOARD_DESC_LEN 255 public static final int MAX MSG SUBJECT LEN 80 public static final int MAX EMAIL LEN 80 private static String jdbcDriverClassName private static String databaseURL private static String adapterClassName public static void setValues String jdbcDriverClassName String databaseURL String adapterClassName ForumConfig jdbcDriverClassName jdbcDriverClassName ForumConfig
254. code with each execution In this case of XSLT this requires that the stylesheet be read into memory using an XML parser translated into machine format and then applied to your XML data Performance is the obvious problem particularly when you consider that stylesheets rarely change Typically the stylesheets are defined early on in the development process and remain static while XML data is generated dynamically with each client request A better approach is to parse the XSLT stylesheet into memory once compile it to machine format and then preserve that machine representation in memory for repeated use This is called stylesheet compilation and is no different in concept than the compilation of any programming language 5 4 1 Templates API Different XSLT processors implement stylesheet compilation differently so JAXP includes the javax xml transform Templates interface to provide consistency This is a relatively simple interface with the following API public interface Templates java util Properties getOutputProperties javax xml transform Transformer newTransformer throws TransformerConfigurationException The getOutputProperties method returns a clone of the properties associated with the xsl output element such as method xm1 indent yes and encoding UTF 8 You might recall that java util Properties a Subclass of java util Hashtable provides key value mappings from property names to property values Si
255. cter inside of an attribute value won t work gt a href lt xsl value of select isbn gt gt Java and XML lt a gt We also need to consider that the attribute value is dynamic rather than static XSLT does not automatically recognize content of the href attribute as an XPath expression since the lt a gt tag is not part of XSLT There are two possible solutions to this problem 2 6 1 lt xsl attribute gt In the first approach xs1 attribute is used to add one or more attributes to elements In the following template an href attribute is added to an lt a gt element lt xsl template match book gt lt li gt lt a gt the href attribute is generated below gt xsl attribute name href gt lt xsl text gt http www amazon com exec obidos ASIN lt xsl text gt lt xsl value of select isbn gt xsl attribute lt xsl value of select title gt ex lt xsl template gt The lt li gt tag is used because this is part of a larger stylesheet that presents a bulleted list of links to each book The lt a gt tag as you can see is missing its href attribute The lt xsl attribute gt element adds the missing href Any child content of lt xsl attribute gt Is added to the attribute value Because we do not want to introduce any unnecessary whitespace xsl text is used Finally xs1 va1ue of is used to select the isbn attribute 2 6 2 Attribute Value Templates Using x
256. d a corresponding template was instantiated The lt xsl apply templates gt element tells the XSLT processor to begin a new search for elements in the source XML document that match the discussionForumHome messageBoard pattern and to instantiate an additional template that matches As we will see shortly the transformation piotees is recursive and must be driven by XSLT elements such as lt xsil apply templates gt Simply including one or more lt xsl template gt elements in a stylesheet does not mean that they will be instantiated In this e the lt xsl apply templates gt element tells the XSLT processor to first select all lt discussionForumHome gt ao of the current node ENG current node is or the top of the Paaa so it only selects the lt discussionForumHome gt element that occurs at the document s root level If another i scussionForumHome gt element i is deeply nested within the XML document it will not be abd by this pattern Assuming that the processor locates the lt discussionForumHome gt element it then searches for all of its lt messageBoard gt children The select attribute in xs1 apply templates does not pava to be the same as the match attribute in lt xsl template gt Although the stylesheet presented in ae 2 2 could have specified xs1 template match discussionForumHome messageBoard gt for the second template this would limit the reusability of the template Specifically it could only be applied
257. d is responsible for returning a renderer that displays the XHTML form while the doPost method is responsible for processing the form submission Because the XHTML form contains several required fields and buttons the doPost method is far more complex than doGet As the code reveals almost all of this complexity is introduced because of error checking and validation logic The doPost method checks for illegal impossible parameters first returning an error page if any problems occur Next it checks to see what the user typed in If the user left a required field blank the parameter value will be an empty string rather than nu11 Of course leading and trailing spaces must be trimmed in case the user hit the space bar msgSubject msgSubject trim authorEmail authorEmail trim ye msgText msgText trim If any of these fields are empty the PostMsgRenderer is returned with form field values pre filled return new PostMsgRenderer board inResponseToMsg true msgSubject authorEmail msgText This gives the user an opportunity to fill in missing values and try to submit the form again If all is well an instance of ViewMsgRenderer is returned This allows the user to view the message that was just submitted The source code for oscMsgRenderer is shown in Example 7 38 Example 7 38 PostMsgRenderer java package com oreilly forum servlet import com oreilly forum import com orei
258. d note that XPath uses a single character for comparisons instead of as Java does A portion of the HTML for our list ends up looking like this li Washington George lt 1li gt li style font weight bold gt Adams John li lt li gt Jefferson Thomas lt li gt lt li style font weight bold gt Madison James lt 1li gt lt li gt Monroe James lt li gt lt li style font weight li Jackson Andrew lt 1i remaining HTML omit bold gt Adams John nbsp Quincy lt 1li gt lt li gt Bush George current president lt li gt The name output has been improved from the previous chapter and now uses lt xs1 if gt to determine if the middle name is present lt xsl template match name gt lt xsl value of select last gt xsl text lt xsl text gt lt xsl value of select first gt xsl if test middle gt lt xsl text gt disable output escaping yes gt amp amp nbsp lt xsl text gt lt xsl value of select middle gt xsl if lt xsl template gt In this case lt xsl if test middle gt checks for the existence of a node set rather than for a boolean value If any lt middie gt elements are found the content of lt xs1 it gt is instantiated The test does not have to be this simplistic any of the XPath location paths from the previous chapter would work here as well As written here if any middle elements are found the first one is printed Later in Examp
259. d using DOM Provides implementations of Source and Result DOMSource and DOMResult Supports SAX2 transformations Defines SAX versions of Source and Result SAXSource and SAXResult Also defines a subclass of TransformerFactory that allows SAX2 events to be fed into an XSLT processor javax xml transform sax Defines I O stream implementations of Source and Result StreamSource and StreamResult javax xml transform stream The heart of JAXP XSLT support lies in the javax xml transform package which lays out the mechanics and overall process for any transformation that is performed This package mostly consists of interfaces and abstract classes except for OutputKeys and a few exception and error classes Figure 5 2 presents a UML class diagram that shows all of the pieces in this important package Figure 5 2 javax xml transform class diagram exception TranstormerException create Templates a compiled and Transforms stylesheet lt lt interface gt gt Templates lt lt creale gt gt lt lt abstratt gt gt Transformer H lt lt Creale gt gt lt lt abstract gt gt TransformFactory lt lt interface gt gt Result ecreate lt lt interface gt gt SourceLocator interface Source os line and transformations column of error lt lt interface gt gt lt lt utility gt gt lt lt exception gt gt UR
260. ded or imported this one This stylesheet was designed to be reused by other stylesheets so it does not include a template that matches the root node For large web sites the ability to import or include stylesheets is crucial It almost goes without saying that every web page on a large site will contain the same navigation bar footer and perhaps a common heading region Standalone stylesheet fragments included by other stylesheets should generate all of these reusable elements This allows you to modify something like the copyright notice on your page footer in one place and those changes are reflected across the entire web site without any programming changes 3 3 1 lt xsl include gt The xsi include element allows one stylesheet to include another It is only allowed as a top level element meaning that lt xs1 include gt elements are siblings to xs1 template elements in the stylesheet structure The syntax of xs1 include is xsl include href uri reference gt When a stylesheet includes another the included stylesheet is effectively inserted in place of the xsl include element Actually the children of its lt xsl stylesheet gt element are inserted into the including document It is possible to include many other stylesheets and for those stylesheets to include others Inclusion is a relatively simple mechanism because the resulting stylesheet behaves exactly as if you had typed all included elements into the
261. del view controller MVC Clean separation between data presentation and programming logic is a key goal of this design Most web frameworks implement this pattern and the hybrid approach of JSP and servlets follows it XSLT implementations also use this pattern which leads to the conclusion that model view controller is truly a universal approach to development on the web tier 4 2 1 Web Frameworks A framework is a value added class library that makes it easier to develop certain types of applications For example an imaging framework may contain APIs for reading writing and displaying several image formats This makes it much easier to build applications because someone else already figured out how to structure your application Servlet frameworks are no different Now that servlets JSP and hybrid approaches have been available for a few years common architectural patterns are emerging as best practices These include separation of Java code and HTML generation using servlets in conjunction with JSP and other variations Once basic patterns and themes are understood it becomes desirable to write common frameworks that automate the mundane tasks of building web applications The most important tradeoff you make when selecting a framework is vendor lock in versus open standards At this time there are no open standards for frameworks Although there are numerous open source frameworks none is backed by a standards organization or ev
262. ding 3 pw println cellspacing 0 gt pw printin lt tr gt lt th gt Channel lt th gt lt th gt From lt th gt pw printin lt th gt To lt th gt lt th gt Title lt th gt lt tr gt for int i 0 i shows length i pw println tr pw print lt td gt pw print shows i getChannel rs pw println td pw print lt td gt pw print dateFmt format shows i getStartTime LINS pw printin lt td gt pw print lt td gt pw print dateFmt format shows i getEndTime pw printin lt td gt pw print lt td gt pw print shows i getTitle Die pw printin lt td gt pw printin lt tr gt pw println lt table gt pw println body pw printin lt html gt If you are interested in the details of servlet coding be sure to read Chapter 6 For now focus on how the HTML is generated All of those printin statements look innocuous enough in this short example but a real web page will have thousands of printin statements resulting in code that is quite difficult to maintain over the years Generally you will want to factor that code out into a series of methods or objects that generate fragments of the HTML However this approach is still tedious and error prone The main problems are development scalability and future maintainability The code becomes increasingl
263. doPost HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException if the user hit the Cancel button return to the home page if request getParameter cancelBtn null return new HomeRenderer lots of error checking follows if request getParameter submitBtn null servlet log Expected submitBtn parameter to be present return new ErrorRenderer Invalid request a null parameter indicates either a hack attempt or a syntax error in the HTML String mode request getParameter mode String msgSubject request getParameter msgSubject String authorEmail request getParameter authorEmail String msgText request getParameter msgText if mode null msgSubject null authorEmail null msgText null return new ErrorRenderer Invalid request one of these may be null String origMsgIDStr request getParameter origMsgID String boardIDStr request getParameter boardID if origMsgIDStr null amp amp boardIDStr null return new ErrorRenderer Invalid request long origMsgID 0 long boardID 0 try origMsgID origMsgIDStr null Long parseLong origMsgIDStr 0 boardID boardIDStr null Long parseLong boardIDStr 0 catch NumberFormatException nfe return new ErrorRenderer
264. e SAX InputSource Xalan own class XSLTInputSource InputSource xmllInputSource org xml sax InputSource xmlSystemId InputSource xsltInputSource org xml sax InputSource xsltSystemId com icl saxon trax new compiled styles n trax Result result Result System out heet essor process xsltI transformer that ca n trax Transformer orm xmllInputSource n trax Templates templates nputSource n be used for a single trans templates newTransformer result The SAXON implementation starts exactly as the Xalan implementation does Following the class declaration the command line parameters are validated and then converted to system IDs The XML and XSLT system IDs are then wrapped in org xml sax InputSource objects as follows org xml sax InputSou new org xml org xml sax InputSou new org xml rce xmlInputSource sax InputSource xmlSystemId rce xsltInputSource sax InputSource xsltSystemId This code is virtually indistinguishable from the Xalan code except Xalan uses XSLTInputSource instead of Input Source As mentioned before XSLTInput Source is merely a subclass of Input Source that adds support for reading from a DOM Node SAXON also has the ability to read from a DOM node although its approach is slightly different Creating a Result object sets up the destination for the XSLT result tree which is directed to em out in this example oyok com
265. e error occurs RJ public Message getMessage long msgID throws DataException Message msg Message this messageMap get new Long msgID if msg null return msg throw new DataException Invalid msgID If no messages exist for the specified board and month return an empty iterator return an iterator of lt code gt MessageSummary lt code gt objects Qthrows DataException if the boardID is illegal or a database error occurs a7 public Iterator getAllMessages long boardID MonthYear month throws DataException this is slow but works fine for a fake implementation List msgs new ArrayList Iterator iter this messageMap values iterator while iter hasNext MessageSummary curMsg MessageSummary iter next if curMsg getBoard getID boardID amp amp month containsInMonth curMsg getCreateDate msgs add curMsg return msgs iterator Add a reply to an existing message e throws DataException if a database error occurs or if any parameter is illegal y public Message replyToMessage long origMsgID String msgSubject String authorEmail String msgText throws DataException MessageSummary origMsg getMessage origMsgID long msgID getNextMessageID Message msg new MessageImpl msgID new DayMonthYear origMsg getBoard msgSubject authorEmail msgText origMsgID
266. e Referring back to the code in Example 6 8 the init method used the following to locate the stylesheets curName WEB INF xslt editPersonalData xslt URL xsltURL getServletContext getResource curName As this code illustrates the locations of the stylesheets are entirely relative to their position in the WAR file Therefore your servlet will still work as the web application is moved onto a production web server The deployment descriptor listed in Example 6 9 has been expanded to include the new PersonalDataServiet class The lines that have changed from our first iteration are emphasized Example 6 9 Expanded deployment descriptor lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 2 EN http java sun com j2ee dtds web app 2 2 dtd web app servlet servlet name personalDataServlet servlet name servlet class chap6 PersonalDataServlet servlet class servlet lt servlet gt servlet name splashScreenc servlet name servlet class chap6 SplashScreenServlet servlet class servlet servlet mapping servlet name personalDataServlet servlet name url pattern personalData url pattern servlet mapping servlet mapping servlet name splashScreenc servlet name url pattern splash url pattern servlet mapping lt web app gt 6 3 5 H
267. e This stylesheet also takes a parameter named rootDir allowing the web application to specify the location of the document root directory xsl param name rootDir select docroot The select attribute defines a default value for this parameter if none was specified During the stylesheet development process the XSLT is tested using a static XML file This is done outside of a web application so the parameter is not specified and the root directory defaults to docroot This makes it possible to locate the CSS file during development when developers are working from a static directory structure on their file systems Later when the XSLT stylesheet is deployed to a web application and the servlet is running the servlet can specify a different value for this parameter that indicates a directory relative to the web application context This is a useful technique whenever a stylesheet has to reference external resources such as CSS files JavaScript files or images Next the lt xsi output gt element is used to set up XHTML output The XHTML 1 0 Strict DTD is used which eliminates many deprecated HTML 4 0 features Because the strict DTD does away with many formatting tags a CSS file is required to make the pages look presentable All the XSLT needs to do is produce HTML code that references the external stylesheet as shown here html xmlns http www w3 org 1999 xhtml head title Discussion Forum Home lt title gt
268. e ErrorlListener interface is emphasized the remaining code is used to present errors in a Swing table The Swing JTable component displays rows and columns of data getting its information from an underlying javax swing table TableModel interface javax swing table AbstractTableModel is an abstract class that implements TableModel serving as the base class for application defined table models as shown here As you can see ErrorListenerModel extends from AbstractTableModel Since our table model implements the ErrorListener interface it can be attached to a JAXP Transformer When transformation problems occur warning error or fatalError is called Since these methods have the same signature they all delegate to the report method Comments in the code indicate which types of problems are supposed to call each method although XSLT processors are not consistent in the way they report errors The report method simply adds the TransformerException object to a private list of exceptions and then triggers a Swing event to indicate that the JTable should redraw its contents When the JTable receives this event it asks the ErrorListenerModel for the row count column count and values at individual cells within the table model This functionality is contained within the getRowCount getColumnCount andgetvalueat methods all of which are defined in the TableModel interface Our class also has an additional method ca
269. e actual CSV parsing read each line of the file until EOF is reached String curLine null while curLine br readLine null curLine curLine trim ee if curLine length y gt 0 create the lt line gt element ch startElement ine EMPTY ATTR parseLine curLine ch ch endElement line And finally we must indicate that the parsing is complete emit csvFile ch endElement csvFile ch endDocument js The remaining methods in CSVxXMLReader are not discussed in detail here because they are really just responsible for breaking down each line in the CSV file and checking for commas quotes and other mundane parsing tasks One thing worth noting is the code that emits text such as the following lt value gt Some Text Here lt value gt SAX parsers use the characters method on ContentHandler to represent text which has this signature public void characters char ch int start int length Although this method could have been designed to take a St ring using an array allows SAX parsers to preallocate a large character array and then reuse that buffer repeatedly This is why an implementation of ContentHandler cannot simply assume that the entire ch array contains meaningful data Instead it must read only the specified number of characters beginning at the start position Our parser uses a relatively straightforward approach simply converti
270. e does not have to be hardcoded into your application For additional examples see Section 6 3 6 later in this chapter Another important class is javax servlet ServletContext This class does a lot more than ServletConfig and its instance is shared among a group of servlets Use ServletConfig to obtain a reference to the ServletContext config is an instance of ServletConfig ServletContext ctx config getServletContext Later in this book we will focus on ServletContext s ability to locate resources in a portable way You may be familiar with the getResource and getResourceAsStream methods on java lang Class These methods allow you to locate files and directories based on the system CLASSPATH ServletContext provides its own getResource and getResourceAsStream methods but they are not based on CLASSPATH Instead the directory locations are based on the location of the current web application For example you can write something such as context getResource WEB INF stylesheets home xslt to load a stylesheet from the current WAR file Regardless of where Tomcat was installed this approach will always locate the stylesheet without hardcoding a path name such as C pathl 6 3 Another Servlet Example In our next example the servlet will utilize DOM and XSLT to create its web pages This achieves our goal of separation between data and presentation making it possible to fully customize the HTML output wi
271. e examples shown in previous chapters ServletContext is utilized to locate these files in a portable manner String fullPath getServletContext getRealPath WEB INF xslt xsltDir xsltName Last but not least the XSLT transformation is performed using the JAXP API 10 3 3 5 XSLT stylesheets This application consists of six XSLT stylesheets Three of these stylesheets are listed here and are used to generate the three WML decks The other three are used to generate XHTML and can be downloaded along with the rest of the examples in this book The first stylesheet shown in Example 10 10 is responsible for creating the home deck Example 10 10 Home page XSLT lt xml version 1 0 encoding UTF 8 gt 1 CK CK Ck CK Ck C CK CK Ck CK CK C CC CC Ck CK CK Ck CC CC C CC Ck Ck Ck CK CK CC CC C Ck Ck 0k CK S S E S Sk Kk Kk Kk Kk Sk Kk Mk ko Ax Produces the home page for WML enabled devices Kk kk kk kk ck ck ck ck ck ck ck KK KK ck ck ck ck ck ck ck ck ck ck ck k ck ck ck Ck ck ck ck k k k ck kk kk k ck ck ck ck ck ck ck k ck ck kck k KK k k kk kk xsl stylesheet version 1 0 xmlns xsl 2 http www w3 0rg 1999 XSL Transform xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public WAPFORUM DTD WML 1 1 EN doctype system http www wapforum org DTD wml 1 1 xml ie CC CK CK CK CC Ck Ck Ck CK CK CC CCS CK Ck CK CC CC CI SCC CC Ck Ck Ck Ck CK CK CI CCS
272. e installed These and many other fonts are included with Windows 2000 but are not automatically installed unless the appropriate language settings are selected under the regional options window This window can be found in the Windows 2000 Control Panel A good source for font information on other versions of Windows is Fontboard at http www geocities com fontboard Sun Solaris users should start at the Sun Global Application Developer Corner web site at http www sun com developers gadc This offers information on internationalization support in the latest versions of the Solaris operating system For other versions of Unix or Linux a good starting point is the Netscape 6 Help menu The International Users option brings up a web page that provides numerous sources of fonts for various versions of Unix and Linux on which Netscape runs 8 6 3 1 XML data Each of the three XML datafiles used by this example follows the format shown in Example 8 20 As you can see the XML data merely lists translations from English to another language All three files follow the same naming convention numbers english xml numbers spanish xml and numbers chinese xml Example 8 20 numbers spanish xml xml version 1 0 encoding UTF 8 numbers language gt Espafiol Spanish lt language gt number english one gt uno lt number gt number english two gt dos lt number gt number english three gt tres lt number gt number en
273. e it was finally promoted to a W3C Recommendation but IE had already shipped using the older version of the specification Although Microsoft has done a good job updating its MSXML parser with full support for the final XSLT Recommendation millions of users will probably stick to IE 5 0 or 5 5 for quite some time making it very difficult to perform portable XSLT transformations on the client For IE 5 0 or 5 5 users the MSXML parser is available as a separate download from Microsoft Once downloaded installed and configured using a separate program called xmiinst the browser will be compliant with Version 1 0 of the XSLT recommendation This is something that developers will want to do but probably very few end users will have the technical skills to go through these steps At the time of this writing Netscape had not introduced support for XSLT into its browsers We hope this changes by the time this book is published Although their implementation will be released much later than Microsoft s it should be compliant with the latest XSLT Recommendation Yet another alternative is to utilize a browser plug in that supports XSLT although this approach is probably most effective within the confines of a corporation In this environment the browser can be controlled to a certain extent allowing client side transformations much sooner than possible on public web sites Because XSLT transformation on the client will likely be mired in browser co
274. e of the XSLT stylesheet for this particular filter instance It is also possible to specify multiple lt filter gt elements using the same filter class but different filter names This allows the same web application to utilize a single filter with many different configurations Finally the deployment descriptor lists several explicit mappings for this filter In the examples shown the filter is applied to static XML files It can just as easily be applied to a servlet or JSP however 8 4 3 Closing Thoughts on Filters Using filters for XSLT transformations is an interesting concept primarily because it allows different stylesheets to be applied to XML from many different sources using the web application deployment descriptor To use a different stylesheet merely change the deployment descriptor One interesting approach is using JSP to generate pure XML then applying a filter to transform that XML into XHTML for the client Filters do suffer drawbacks and probably are not the best solution for most applications First and foremost the filter API is available only in Version 2 3 of the servlet specification many existing servlet containers do not support filters at all In the case of XSLT transformations a custom ServletOutputStream must be written to capture the response output and downcasts are required because there is no HTTP specific filter class Because some servlet containers may cache the response for performance reasons workaro
275. e resulting node set Once again discussion of XSLT and XPath tends to sound overly technical until you see a few basic examples Let s start with a basic fragment of XML message header the context node gt lt subject gt Hello World lt subject gt date mm 03 dd 01 yy 2002 gt lt sender gt pres whitehouse gov lt sender gt lt recipient gt burke_e ociweb com lt recipient gt lt recipient gt burke_e yahoo com lt recipient gt lt recipient gt aidan burke com lt recipient gt lt header gt lt body gt lt body gt lt message gt If the lt header gt is the context node then child sub ject will select the lt subject gt node child recipient will select the set of all lt recipient gt nodes and child will select all children of lt header gt The asterisk character is a wildcard that represents all nodes of the principal node type Each axis has a principal node type which is always element unless the axis is attribute Or namespace If dace is the context node then attribute yy will select the yy attribute and attribute will select all attributes of the lt date gt element Without any predicates a location step can result in zero or more nodes Adding a predicate simply filters the resulting node set generally reducing the size of the resulting node set Adding additional predicates applies additional filters For example child recipient position 1 will initially
276. e that clients cannot access them directly Instead clients must use a servlet called TemplateServiet to request all pages This servlet locates the XML file performs the XSLT transformation using templatePage xsit and sends the result tree back to the client browser The entire process is transparent to clients because they see only the results of the transformation Table 8 1 shows the complete structure of the WAR file that supports this example Table 8 1 WAR file contents File Description WEB INF web xml The deployment descriptor see Example 8 3 WEB The servlet that drives the XSLT transformation INF classes chap8 TemplateServlet class see Example 8 4 WEB INF lib javaxslt jar Contains the St ylesheetCache class WEB INF xml company xml An example web page WEB INF xml home xml An example web page see Example 8 1 WEB INF xml jobs xml An example web page WEB INF xml products xml An example web page WEB INF xslt templatePage xslt The XSLT stylesheet see Example 8 2 The deployment descriptor web xml is shown in Example 8 3 Example 8 3 Deployment descriptor lt xml version 1 0 encoding ISO 8859 1 gt lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 2 EN http java sun com j2ee dtds web app 2 2 dtd lt web app gt lt servlet gt servlet name template servlet name servlet class chap8 TemplateServlet servlet class servlet servlet mapping servle
277. e this same URL S Even the slightest typo in the namespace will render the stylesheet useless for most processors The text must match http www w3 org 1999 XSL Transform exactly or your stylesheet will not be processed Spelling or capitalization errors are a common mistake and should be the first thing you check when things are not working as you expect The next line of the stylesheet simply indicates that the result tree should be treated as an HTML document instead of an XML document xsl output method html In Version 1 0 of XSLT processors are not required to fully support this element Xalan does however so we will include this in all of our stylesheets Since the XSLT stylesheet itself must be written as well formed XML some HTML tags are difficult to include Instead of writing lt hr gt you must write lt hr gt in your stylesheet When the output method is html processors such as Xalan will remove the slash character from the result tree which produces HTML that typical web browsers expect The remainder of our stylesheet consists of two templates Each matches some pattern in the XML input document and is responsible for producing output to the result tree The first template is repeated as follows xsl template matchz lt html gt lt head gt lt title gt Discussion Forum Home Page lt title gt lt head gt lt body gt hl Discussion Forum Home Page lt t lt h3 gt Plea
278. e tree looking for patterns in the data 2 2 2 Recursive Processing with Templates Most transformation in XSLT is driven by two elements xs1 template and lt xsl apply templates In XSLT lingo a node can represent anything that appears within your XML data Nodes are typically elements such as message or element attributes such as 1i 123 Nodes can also be XML processing instructions text or even comments XSLT transformation begins with a current node list that contains a single entry the root node This is the XML document and is represented by the pattern Processing proceeds as follows e For each node X in the current node list the processor searches for all xsl template match pattern elements in your stylesheet that potentially match that node From this list of templates the one with the best match is selected BI See section 5 5 of the XSLT specification for conflict resolution rules e The selected lt xsl template match pattern gt is instantiated using node X as its current node This template typically copies data from the source document to the result tree or produces brand new content in combination with data from the source e fthe template contains lt xsl apply templates select newPattern gt anew current node list is created and the process repeats recursively The select pattern is relative to node X rather than the document root As the XSLT transformation process conti
279. eDay int 11 DEFAULT 0 NOT NULL createYear int 11 DEFAULT 0 NOT NULL boardID bigint 20 DEFAULT 0 NOT NULL subject varchar 80 DEFAULT NOT NULL authorEmail varchar 80 DEFAULT NOT NULL msgText text DEFAULT OT NULL PRIMARY KEY id KEY inReplyToID inReplyToID KEY createMonth createMonth KEY createDay createDay KEY boardID boardID The bBUt i1 class shown in Example 7 18 consists of utility functions that make it a little easier to work with relational databases from Java code Example 7 18 DBUtil java package com oreilly forum jdbcimpl import java io import java sql import java util Helper methods for relational database access using JDBC public class DBUtil a map of table names to maximum ID numbers private static Map tableToMaxIDMap new HashMap Close a statement and connection public static void close Statement stmt Connection con if stmt null try stmt close catch Exception ignoredl if con null try con close catch Exception ignored2 return a new Connection to the database public static Connection getConnection String dbURL throws SQLException NOTE implementing a connection pool would be a worthy enhancement return DriverManager getConnection dbURL Close any connections that are still open The Servlet will
280. eam methodin javax servlet ServletResponse public interface ServletResponse ServletOutputStream getOutputStream throws IOException additional methods Here is how javax servlet ServletResponseWrapper defines the same method public class ServletResponseWrapper implements ServletResponse private ServletResponse response public ServletResponseWrapper ServletResponse response this response response default implementation delegates to the wrapped response public ServletOutputStream getOutputStream throws IOException return this response getOutputStream additional methods behave the same way To modify the response sent to the client browser the custom wrapper subclass must override the getOutputStream method as follows public class MyResponseWrapper extends ServletResponseWrapper public ServletOutputStream getOutputStream throws IOException cannot return the ServletOutputStream from the superclass because that object does not allow us to capture its output Therefore return a custom subclass of ServletOutputStream return new MyServletOutputStream ServletOutputStream is an abstract class and does not provide methods that allow it to be modified Instead programmers must create custom subclasses of ServletOutputStream that allow them to capture the output and make any necessary modifications This is what makes modificatio
281. ean isIgnoringComments public boolean isIgnoringElementContentWhitespace public boolean isNamespaceAware public boolean isValidating public abstract DocumentBuilder newDocumentBuilder throws ParserConfigurationException public static DocumentBuilderFactory newInstance ys public abstract void setAttribute String name Object value throws IllegalArgumentException public void setCoalescing boolean coalescing public void setExpandEntityReferences boolean expandEntityRef public void setIgnoringComments boolean ignoreComments public void setIgnoringElementContentWhitespace boolean whitespace public void setNamespaceAware boolean awareness public void setValidating boolean validating FactoryConfigurationError This indicates that the class for a parser factory could not be located or instantiated If this error occurs something is not installed correctly on the system Refer to Chapter 5 for information on the algorithm that JAXP uses to locate parser implementations public class FactoryConfigurationError extends Error public FactoryConfigurationError public FactoryConfigurationError public FactoryConfigurationError public FactoryConfigurationError public Exception getException public String getMessage String msg Exception e Exception e String msg 1 1 ParserConfigurationException According t
282. ear Date date this DateUtil getMonth date DateUtil getYear date Construct a new object with the given month and year iparam month a zero based month just like java util Calendar y public MonthYear int month int year this month month this year year Compare this MonthYear object to another ui public int compareTo Object obj MonthYear rhs MonthYear obj first compare year if this year lt rhs year return 1 else if this year gt rhs year return 1 then month if this month rhs month return 1 else if this month gt rhs month return 1 return 0 ireturn true if the specified date occurs sometime during this month 7 public boolean containsInMonth DayMonthYear date return date getMonth this month amp amp date getYear this year return the month number starting with O0 for January x4 public int getMonth return this month return the year number 7 public int getYear return this year public boolean equals Object obj if obj instanceof MonthYear MonthYear rhs MonthYear obj return this month rhs month amp amp this year rhs year return false public int hashCode return this month this year The viewMsg xsit XSLT stylesheet shown in Example A 10 displays a web page for a single message Example A 10
283. eb site at http www oreilly com Acknowledgments would like to thank my wife Jennifer for tolerating my absence during the past six months as have locked myself in the basement researching writing and thinking also feel fortunate that my two year old son Aidan goes to bed early a vast majority of this book was written well after 8 30 P M Coming up with a list of people to thank is a difficult job because so many have influenced the material in this book only hope that do not leave anyone out All of the technical reviewers did an amazing amount of work each offering a unique perspective and useful advice The official reviewers were Dean Wette Kevin Heifner Paul Jensen Shane Curcuru and Tim Brown would also like to thank Weiqi Gao Shu Zhu Santosh Shanbhag and Suman Ganesh for help with the internationalization example in Chapter 8 A technical article by Dan Troesser inspired my servlet filter implementation and Justin Michel and Brent Roberts reviewed some of the first chapters that wrote There are two companies that really want to thank O Reilly has this little link on their home page called Write for Us This book came into existence because casually clicked on that link one day and decided to submit a proposal Although my original idea was not accepted Mike Loukides and exchanged several emails after that in a virtual brainstorming session and eventually the proposal for this book emerged
284. ect displayName xsl when All other categories are displayed as hyperlinks gt xsl otherwise lt a href Surl gt lt xsl value of select displayName lt a gt xsl otherwise xsl choose xsl template eec ACKCKCkck kCckck ck ckck ck ck ck ck kckck ck ckck ck k ck ck ck ckck KKK ck ck ck ck ck ck ck kck ck ck ck ck ck ck ck ck kk ck ck ck ck ck ck ck ck k ck k kk kk This template creates the left navigation area KCKCKCKCk Ck ckckckck ck kc kckckckckck ck ck ck ck ck ckckckckckckckck ck ck k ck ck kc kckck ck k ck ck k ck ck ck KKK ck ck ck KKK ck ck k KK kk gt xsl template name createLeftNavbar Left Navigation Area xsl template lt xsl stylesheet gt This stylesheet is quite simple in concept First it sets up the global nav category variable The stylesheet uses XPath to check for the existence of a lt met a gt tag that contains a navigationCategory attribute lt xsl variable name global nav category gt lt xsl choose gt xsl when test html head meta name navigationCategory gt lt xsl value of select html head meta name navigationCategory content gt lt xsl when gt lt xsl otherwise gt lt xsl text gt unknown lt xsl text gt lt xsl otherwise gt xsl choose xsl variable The first part of the XPath expression used by xs1 when locates any mec a gt tags html head meta Next a predicate is used t
285. ed by working examples all of which work on widely available free tools Audience Java programmers who want to learn how to use XSLT comprise the target audience for this book Java programming experience is essential and basic familiarity with XML terminology is helpful but not required Since so many of the examples revolve around web applications and servlets Chapter 4 and 6 are devoted to this topic offering a fast paced tutorial to servlet technology Chapter 2 and Chapter 3 contain a detailed XSLT tutorial so no prior knowledge of XSLT is required This book is particularly well suited for readers who may have read a lot about these technologies but have not used everything together in a complete application Chapter 7 for example presents the implementation of a web based discussion forum from start to finish Fully worked examples can be found in every chapter ranging from an Ant build file documentation stylesheet in Chapter 3 to internationalization techniques in Chapter 8 Software and Versions Keeping up with the latest technologies is always a challenge particularly when writing about XML related tools The set of tools listed in Table P 1 is sufficient to run just about every example in this book Table P 1 Software and versions Tool URL Description Crimson Included with JAXP 1 1 XML parser from Apache JAXP 1 1 http java sun com xml Java API for XML Processing JDK 1 2 x http java sun com Any Java 2 St
286. ed methods an entity bean can provide a single method to retrieve an instance of Address This reduces load on the network and database and makes the code somewhat easier to understand As you can see the Address class is very straightforward It has a constructor that initializes all fields and a series of get methods Although Address is small some dependent objects may have dozens of fields These are tedious to write at best resulting in a typing exercise rather than programming creativity XSLT can help by acting as a simple code generator minimizing the tedious part of the programmer s job AdaressDO xml shown in Example 8 14 contains the data that will feed into our code generator Example 8 14 AddressDO xml lt xml version 1 0 encoding UTF 8 gt lt dependentObject class Address gt lt property name street type String getter getStreet gt lt property name city type String getter getCity lt property name state type String getter getState gt lt property name zip type String getter getZip gt dependentObject The XML data is obviously much shorter than the generated code and the difference is magnified for larger dependent objects with many fields The lt dependentOb ject gt element contains a list of property elements each of which defines the field name datatype and get method name Now that the data is captured in a well defined XML format a DTD or Schema can be used to pe
287. ed on the system The only drawback to this approach is that build files must be manually updated whenever new versions of JAR files are installed Second this particular Ant build file defines its own CLASSPATH rather than relying on the developer s CLASSPATH Relying on the CLASSPATH environment variable introduces problems because each developer on a team may have a completely different set of JAR files defined in his environment By encoding everything in the Ant build file everyone will compile and test with the same setup The following target shows how the build file compiles the application target name compile depends prepare description lt javac srcdir comn ep include vaxslt swingtrans Ww ys sspath refid thirdparty class path So to execute this target simply type ant compile from the command prompt Since this target depends on the prepare target the build directory will be created before the code is compiled Fortunately the lt javac gt task is smart enough to compile only source code files that have changes since the last build making Ant much faster than manually typing javac java The srcdir and destdir attributes are relative to the basedir that was specified in the project element Since Ant always uses forward slashes as path separators these relative directories will work on Windows and Unix Linux systems As you might guess the includes attribute defines a filter that li
288. ed that this is the output from Version 1 6 Alpha of JMeter so later versions may change significantly The GUI interface has been completely rewritten for Version 1 6 and many features are unfinished as this book is being written On this display the dots represent actual response times the top line represents the average response time and the bottom line represents the standard deviation from average Of the measurements shown on the graph the average response time is the most useful The numbers to the right are in milliseconds so we can see that the average response time for this web application is 151 milliseconds When using a tool such as JMeter it is best to leave the stress test running for several minutes until the average response time stabilizes It generally takes much longer for the first few tests to run because Java is loading classes starting threads and allocating memory Over time performance will fluctuate as the garbage collector runs and VMs such as HotSpot optimize code Unless the application has memory leaks or simply cannot keep up with demand the response time should eventually level off Table 9 3 shows how the View Month page from the discussion forum example in Chapter 7 fared when tested with JMeter In this table worst case and best case scenarios are shown Other combinations of servlet container XSLT processor and database are not shown The number of threads in the fourth column indicates the number of
289. ed to the list of presidents so far Since we almost always want to display the name of a president or vice president name formatting templates should be broken out into a separate stylesheet Example 3 7 shows a stylesheet designed for reuse by other stylesheets Example 3 7 nameFormatting xslt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html lt Show a name formatted like Burke Eric Matthew lt xsl template match name mode lastFirstMiddle gt lt xsl value of select last gt xsl text lt xsl text gt output escaping yes gt amp nbsp lt xsl text gt lt xsl value of select gt xsl for each lt xsl template gt lt fou Show a name formatted like Eric Matthew Burke gt lt xsl template match name mode firstMiddleLast gt lt xsl value of select first gt lt xsl for each select middle gt xsl text disable output escaping yes gt amp nbsp lt xs lt xsl value of select gt xsl for each xsl text disable output escaping yes amp amp nbsp xsl text xsl value of select last gt lt xsl template gt lt xsl stylesheet gt The code in Example 3 7 uses template modes to determine which template is instantiated Adding additional templates would be simple and those changes would be available to any stylesheet that inclu
290. ed with are required lt i gt form action chap6 personalData method post gt lt table border 0 cellpadding 2 cellspacing 0 gt Select all immediate children such as firstName lastName daytimePhone etc xsl apply templates table lt div align center gt lt hr gt lt input type submit name submitBtn value Submit gt lt div gt lt form gt lt xsl template gt lt i KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKKKK Output a new row in the table for each field KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKK KKK kk lt xsl template match firstName lastName daytimePhone eveningPhone email gt lt tr gt xsl if test required true and requiredFieldsMissing and faa poss xsl attribute name style gt lt xsl text gt color red font weight bold lt xsl text gt xsl attribute xsl if td lt xsl choose gt xsl when test name firstName gt First Name lt xsl when gt xsl when test name lastName gt Last Name lt xsl when gt xsl when test name daytimePhone gt Daytime Phone lt xsl when gt xsl when test name eveningPhone gt Evening Phone xsl when xsl when test name email gt Email xsl when xsl choose td i lt input type text name name value gt 0
291. efill elements were not part of the original prototype but it was quickly determined that these were needed if the user did not provide information for all required fields When the Post New Message page is first displayed these XML elements are not present After the user clicks on the Submit button however these elements are inserted into the XML if a field is missing and the page needs to be redisplayed And finally the XML for the View Message page is shown in Example 7 6 Example 7 6 viewMsg xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xslt viewMsg xslt gt message id 5 month 1 day 4 year 2001 gt lt board id 1 gt lt name gt Java Programming lt name gt lt board gt lt inResponseTo id 4 gt lt subject gt Test Subject lt subject gt lt inResponseTo gt lt subject gt Re Test Subject lt subject gt lt authorEmail gt burke_e yahoo com lt authorEmail gt lt text gt This is a test of the message text lt text gt lt message gt A quick study of this data reveals that postMsg xml and viewMsg xml have many similarities A few modifications to either XML file will enable us to reuse the same JDOM code later when producing these pages The alternative is to keep these pages separate which results in at least one additional Java class later on The advantage of keeping these files separate is so that the XML generation code does not
292. eilly forum domain import java util Defines an interface to a data source ai public abstract class DataAdapter private static DataAdapter instance return the singleton instance of this class public static synchronized DataAdapter getInstance throws DataException if instance null String adapterClassName ForumConfig getAdapterClassName try Class adapterClass Class forName adapterClassName instance DataAdapter adapterClass newInstance catch Exception ex throw new DataException Unable to instantiate adapterClassName return instance iparam msgID must be a valid message identifier ireturn the message with the specified id throws DataException if msgID does not exist or a database error occurs Ky public abstract Message getMessage long msgID throws DataException Add a reply to an existing message Qthrows DataException if a database error occurs or if any parameter is illegal Ry public abstract Message replyToMessage long origMsgID String msgSubject String authorEmail String msgText throws DataException Post a new message return the newly created messag throws DataException if a database error occurs or if any parameter is illegal public abstract Message postNewMessage long boardID String msgSubject String authorEmail String msgText
293. elp keep data and presentation separate As you know supporting different transformations is a matter of writing different XSLT stylesheets Figuring out which stylesheet to apply is the only missing piece For web applications the User Agent HTTP header offers the solution HTTP requests consist of a header followed by content the header contains name value pairs of data allowing the client and server to exchange additional information with each other The text shown in Example 8 7 contains the complete HTTP request issued by Netscape 6 0 when running on Windows 2000 Example 8 7 Netscape 6 HTTP request GET HTTP 1 1 Host localhost 80 User Agent Mozilla 5 0 Windows U Windows NT 5 0 en US m18 Gecko 20001108 Netscape6 6 0 Accept Accept Language en Accept Encoding gzip deflate compress identity Keep Alive 300 Connection keep alive For the purposes of browser detection the value of User Agent must be parsed to determine what kind of browser is requesting information from the servlet Based on this information the servlet can select an appropriate XSLT stylesheet that supports the particular strengths and weaknesses of the browser in question Unfortunately there are hundreds of variations of User Agent and browser vendors do not rigorously adhere to any standard format The common browsers can be identified however with a small amount of parsing logic Table 8 2 lists some of the more common browsers you mig
294. emainingTokens gt xsl call template lt xsl when gt lt xsl otherwise gt lt xsl text gt lt xsl text gt lt xsl otherwise gt xsl choose Ideally these descriptions will help clarify some of the more complex aspects of this stylesheet The only way to really learn how this all works is to experiment changing parts of the XSLT stylesheet and then viewing the results in a web browser You should also make use of a command line XSLT processor and view the results in a text editor This is important because browsers may skip over tags they do not understand so you might not see mistakes until you view the source Chapter 4 Java Based Web Technologies In a perfect world a single web development technology would be inexpensive easy to maintain offer rapid response time and be highly scalable It would also be portable to any operating System or hardware platform and would adapt well to future requirement changes It would support access from wireless devices standalone client applications and web browsers all with minimal changes to code No perfect solution exists nor is one likely to exist anytime soon If it did many of us would be out of work A big part of software engineering is recognizing that tradeoffs are inevitable and knowing when to sacrifice one set of goals in order to deliver the maximum value to your customer or business For example far too many programmers focus on raw performance metrics without
295. ement session tracking This is easy to check because the javax servlet http HttpServletRequest interface provides the isRequestedSessionlIdFromCookie method When this method returns true cookies are enabled and the remaining steps can be ignored The code in Example 8 5 shows what a serviet s doGet method looks like when implementing session tracking Example 8 5 Session tracking code public void doGet HttpServletRequest req HttpServletResponse res throws ServletException IOException try retrieve current settings from the session HttpSession session req getSession true Cart cart Cart session getAttribute shoppingCart if cart null cart new Cart session setAttribute shoppingCart cart produce the DOM tree Document doc CartDOMProducer createDocument cart prepare the XSLT transformation Transformer trans StylesheetCache newTransformer this xsltFileName allow cookieless session tracking if req isRequestedSessionIdFromCookie String sessionID session getId trans setParameter global sessionID jsessionid sessionID send the web page back to the user res setContentType text html trans transform new javax xml transform dom DOMSource doc new StreamResult res getWriter ae as catch ParserConfigurationException pce throw new ServletException pce catch TransformerConfigurationExcept
296. en Sun s Java Community Process The low level servlet and JSP APIs are very well defined and widely implemented Java standard extensions But a framework can offer much more sophisticated features such as enhanced error checking database connection pooling custom tag libraries and other value added features As you add more framework specific features however your flexibility to choose another framework or vendor quickly diminishes One typical framework is Turbine which is one of many different frameworks supported by Apache Turbine is a large framework with many value added features including e Database connection pooling integration with object to relational mapping tools and relational database abstractions e Integration with numerous template engines e Role based security and access control lists e Web browser detection e Integration with JavaMail This is only a short list of Turbine s features At its core however the compelling reason to use a framework like Turbine is the underlying object model The fundamental approach of Turbine is to cleanly separate validation logic the servlet itself and page rendering into distinctly different modules In fact Turbine uses a single servlet so your validation and rendering logic have to go elsewhere The approach is to define helper classes called actions which are responsible for validation of incoming requests Once an action has validated the inbound request other classes such a
297. en the result of an XSLT transformation is stored in memory and the underlying database changes the cache must be refreshed for users to see the correct data Let s suppose that we want to add result caching to the discussion forum application presented in Chapter 7 Since messages cannot be modified once they have been posted this should be fairly easy to implement for the View Message page One easy approach is to keep a cache of a fixed number of messages Whenever a user views a message the generated web page is added to the cache If the cache exceeds a specified number of messages the oldest entries can be flushed For more dynamic pages such as the Month View page the database must be queried to determine when the most recent message was posted for that particular message board If the most recently posted message is newer than the cached web page the transformation must be performed again using the updated data As you might guess this sort of caching must be done on a case by case basis because it is very tightly coupled to the database design Web applications relying on URL rewriting for session tracking may not be able to cache transformation results This is because as outlined in Chapter 8 every URL must be dynamically encoded with the jsessionid when cookies are disabled As with any other type of optimization the benefits of caching must be carefully weighed against the costs of added complexity The best approach
298. enever possible to optimize performance Since each instance of Templates is thread safe it is desirable to maintain a single copy shared by many clients This reduces the number of times your stylesheets have to be parsed into memory and compiled as well as the overall memory footprint of your application The code shown in Example 5 10 illustrates a custom XSLT stylesheet cache that automates the mundane tasks associated with creating Templates instances and storing them in memory This cache has the added benefit of checking the 1ast Modified flag on the underlying file so it will reload itself whenever the XSLT stylesheet is modified This is highly useful in a web application development environment because you can make changes to the stylesheet and simply click on Reload on your web browser to see the results of the latest edits Example 5 10 StylesheetCache java package com oreilly javaxslt util import java io import java util import javax xml transform import javax xml transform stream A utility class that caches XSLT stylesheets in memory public class StylesheetCache map xslt file names to MapEntry instances MapEntry is defined below private static Map cache new HashMap Flush all cached stylesheets from memory emptying the cache Ef public static synchronized void flushAll cache clear Flush a specific cached stylesheet from memory pa
299. ent count vicePresident gt 1 name ul Presidents named John were ul xsl apply templates select presidents president name child first John ul Presidents elected between 1800 and 1850 were ul xsl apply templates select presidents president term 8from gt 1800 and term from amp lt 1850 name gt lt ul gt lt body gt lt html gt lt xsl template gt lt xsl template match name gt lt li gt lt xsl value of select first gt xsl text lt xsl text gt lt xsl value of select middle gt xsl text lt xsl text gt lt xsl value of select last gt lt li gt lt xsl template gt lt xsl stylesheet gt In the first lt xsl apply templates gt element the location path is as follows presidents president position 3 name This path consists of three location steps separated by slash characters but the final step is what we want to select This path is read from left to right so it first selects the lt presidents gt children of the current context The next step is relative to the lt presidents gt context and selects all lt oresident gt children It then filters the list according to the predicate The third president element is now the context and its lt name gt children are selected Since each president has only one lt name gt the template that matches name is instantiated only once This location path shows
300. ent is bound to an empty string The example shown in item 3 is equivalent to n lt xsl variable name empty select 3 2 1 2 Using variables To use a variable refer to the variable name with a 5 character In the following example an XPath location path is used to select the name of the last president This text is then stored in the lastPresident variable Xxxsl variable name lastPresident select president position last 1 name Later in the same stylesheet the Last President variable can be displayed using the following fragment of code lt xsl value of select SlastPresident gt Since the select attribute of xsl value of expects to see an XPath expression lastPresident is treated as something dynamic rather than as static text To use a variable within an HTML attribute value however you must use the attribute value template AVT syntax placing braces around the variable reference lt a href ShomePage gt Click here to return to the home page a Without the braces the variable would be misinterpreted as literal text rather than treated dynamically The primary limitation of variables is that they cannot be changed It is impossible for example to use a variable as a counter in an xs1 or each loop This can be frustrating to programmers accustomed to variables that can be changed but can often be overcome with some ingenuity It usually comes down to passing a param
301. ented using XML and will be covered in detail in the next two chapters XHTML like XSLT is also an XML based markup language XHTML is designed to be a replacement for HTML and is almost completely compatible with existing web browsers Unlike HTML however XHTML is based strictly on XML and the rules for well formed documents are very clearly defined This means that it is much easier for vendors to develop editors and programming tools to deal with XHTML because the syntax is much more predictable and can be validated just like any other XML document Many of the examples in this book use XHTML instead of HTML although XSLT can easily handle either format XHTML Basics XHTML is a W3C Recommendation that represents the future of HTML Based on HTML 4 0 XHTML is designed to be compatible with existing web browsers while complying fully with XML This means that a properly written XHTML document is always a well formed XML document Furthermore XHTML documents must adhere to one or more of the XHTML DTDs therefore XHTML pages can be validated using today s XML parsers such as Apache s Crimson XHTML is designed to be modular therefore subsets can be extracted and utilized for wireless devices such as cell phones XHTML Basic also a W3C Recommendation is one such modularization effort and will likely become a force to be reckoned with in the wireless space Here is an example XHTML document lt xml version 1 0 encoding UTF 8
302. equest HttpServletResponse response throws IOException ServletException return new HomeRenderer s All of the request handlers must override the get PathInfo method This determines the path info portion of the URL so each request handler must return a unique string The renderer for the home page shown in Example 7 32 is also quite simple As with the home request handler this renderer is simple because it has only one mode of operation Like other renderers this class gets some data from the database using the Dat aAdapter class asks a JDOM producer to convert the data into XML and then tells xSLTRenderHelper which XSLT stylesheet to use when performing the transformation Example 7 32 HomeRenderer java package com oreilly forum servlet import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import com oreilly forum xml import java io import java util import javax servlet import javax servlet http import org jdom Shows the home page Ry public class HomeRenderer extends Renderer public void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException try get the data for the home page DataAdapter adapter DataAdapter getInstance an iterator of BoardSummary objects Iterator boards adapter getAllBoards yo
303. equest contains information from the client to the servlet and the response allows the servlet to send data back to the client This correlates directly to the request response nature of HTTP itself Example 6 1 contains the complete source code for our simple servlet Example 6 1 SplashScreenServlet java package chap6 import java io import javax servlet import javax servlet http A simple Servlet example that displays a Splash Screen for a web application ai public class SplashScreenServlet extends HttpServlet public String getServletInfo return Shows an application splash screen protected void doGet HttpServletRequest request HttpServletResponse response throws IOException ServletException demonstrate how to get parameters from the request String nextURL request getParameter nextURL if nextURL null nextURL response setContentType text html PrintWriter pw response getWriter pw println html pw printin lt head gt lt title gt Splash Screen lt title gt lt head gt pw printin lt body gt pw println div align center style border lpx navy solid gt pw println hl Welcome to Java and XSLT lt h1 gt pw println h3 O Reilly and Associates lt h3 gt pw println p First Edition 2001 lt p gt lt hr gt pw println a href nextURL Click here to continue
304. er public abstract boolean getFeature String name public abstract URIResolver getURIResolver public static TransformerFactory newInstance hrows TransformerFactoryConfigurationError c abstract mplates newTemplates Source source hrows TransformerConfigurationException c abstract Transformer newTransformer Source source hrows TransformerConfigurationException c abstract Transformer newTransformer hrows TransformerConfigurationException c abstract void setAttribute String name Object value hrows IllegalArgumentException c abstract void setErrorListener ErrorListener listener hrows IllegalArgumentException public abstract void setURIResolver URIResolver resolver t ct Gh cboct publ publ publ publ publ PE e E Beer Gk pecct esa TransformerFactoryConfigurationError This error is typically seen when a transformer factory class cannot be instantiated This is a good indicator of CLASSPATH problems public class TransformerFactoryConfigurationError extends Error public TransformerFactoryConfigurationError String msg public TransformerFactoryConfigurationError Exception e public TransformerFactoryConfigurationError Exception e String msg public TransformerFactoryConfigurationError public Exception getException public String getM
305. er but the device should try to default to uppercase entry m Any character but the device should try to default to lowercase entry f Any number of the specified characters is one of the format codes shown in this table Must appear at the end of the format string n is a number from 1 to 9 specifying the number of characters that can be entered is f S P one of the format codes shown in this table Must appear at the end of the format string Displays a specific character in the field For instance NNN NN NNNN specifies a data c format for U S social security numbers allowing the user to enter a number such as 333 22 4444 The first card in Example 10 1 finishes with a ao tag do type accept gt go href hello gt do This causes a button to appear which acts like a hyperlink to the he11o URL when the user clicks on it This is a reference to the second card in the deck Therefore the server is not contacted when this particular button is clicked Figure 10 2 shows how one particular device displays the first and second cards Figure 10 2 Cell phone simulator FARIGOS WapIDt oj x File View Bookmarks Help 6 f le tC fcvsdatafjavaxsit examplesichaptersicnaptOwmimelloworl wml Z wossoius DE File View Bookmarks Help le C fevedatalyavaxsil examples chapters tnaptO wmimelloworlc wami You claim to be 30 years old can this possibly be true Cli
306. er database domain objects JDOM producers and XSLT stylesheets This task lies in the servlet implementation and related classes In an XSLT driven web application the servlet itself really does not do all that much Instead it acts as a mediator between all of the other actions taking place in the application Figure 7 9 shows the UML class diagram for the com oreilly forum servlet package This design consists of a few key classes along with numerous subclasses of Renderer and ReqHandler These subclasses are very repetitive in nature which is indicative of the highly structured application design that XML and XSLT facilitate Figure 7 9 Servlet design HttpServlet ForumServlet ReqHandlerRegistry render getHandler abstract Renderer lt lt Call gt gt init destroy render doGet doPost te locate abstract ReqHandler lt lt Call gt gt doGet doPost e euseoo 5 ulilitys XSLTRenderHelper HomeRegHandler lt lt USE gt gt aaa po 9 gt render PostMsgRedqHandler lt lt US gt gt i Anreise ViewMonth ReqHandler ViewMonthRenderer ViewMsgRenderer ViewMsgReqHandler A single servlet design has been adopted for this application In this approach the ForumServlet intercepts all inbound requests from clients The requests are then delegated to subclasses of ReqHandler which handle requests for individual pages Once the
307. er getErrorHandler return this errorHandler public void parse String systemId throws IOException SAXException parse new InputSource systemId Creating the subclass CSVXMLReader involves overriding the parse method and actually scanning through the CSV file emitting SAX events as elements in the file are encountered While the SAX portion is very easy parsing the CSV file is a little more challenging To make this class as flexible as possible it was designed to parse through any CSV file that a spreadsheet such as Microsoft Excel can export For simple data your CSV file might look like this Burke Eric M Burke Jennifer L Burke Aidan G The XML representation of this file is shown in Example 5 6 The only real drawback here is that CSV files are strictly positional meaning that names are not assigned to each column of data This means that the XML output merely contains a sequence of three lt value gt elements for each line so your stylesheet will have to select items based on position Example 5 6 Example XML output from CSV parser lt xml version 1 0 encoding UTF 8 gt lt csvFile gt line lt value gt Burke lt value gt lt value gt Eric lt value gt lt value gt M lt value gt lt line gt lt line gt lt value gt Burke lt value gt lt value gt Jennifer lt value gt lt value gt L lt value gt lt line gt lt line gt lt value gt Burke lt value gt lt val
308. er the encoding that was specified in the lt xs1 output gt element shown earlier in Example 8 21 Finally the servlet performs the transformation sending the result tree to a Writer obtained from HttpServletResponse note res getWriter will use the encoding type that was specified earlier in the call to res setContentType trans transform xmlSource new StreamResult res getWriter yee As the comment indicates the servlet container should set up the Writer to use the correct character encoding as specified by the Content Type HTTP header I UTF 16 works under Tomcat 3 2 x but fails under Tomcat 4 0 beta 5 Hopefully this will be addressed in later versions of Tomcat 8 6 4 118n Troubleshooting Checklist Here are a few things to consider when problems occur First rule out obvious problems e Visit a web site that uses the language you are trying to produce For example http www chinadaily com cn has an option to view the site in Chinese This will confirm that your browser loads the correct fonts e Test your application with English XML data and XSLT stylesheets to verify that the transformations are performed correctly e Perform the XSLT transformation on the command line Save the result to a file and view with a Unicode compatible text editor If all else fails view with a binary editor to see how the characters are being encoded e Verify that your XML parser supports the encodings you are tr
309. er url openStream else Quotes are used as delimiters when the values contain commas lt pre gt a b etu eG fug hy i lt pre gt This throw new SAXException Invalid InputSource object ch startDocument emit csvFile ch startElement csvFile EMPTY ATTR read each line of the file until EOF is reached String curLine null while curLine br readLin null curLine curLine trim i if curLine length gt 0 create the lt line gt element SAX events are delivered to the ContentHandler that was registered via lt code gt setContentHandler lt code gt ch startElement ine EMPTY ATTR output data from this line parseLine curLine ch close the line element ch endElement line emit lt csvFile gt ch endElement csvFile ch endDocument Break an individual line into tokens This is a recursive function that extracts the first token then recursively parses the remainder of the line private void parseLine String curLine ContentHandler ch throws IOException SAXException String firstToken null String remainderOfLine null int commaIndex locateFirstDelimiter curLine if commaIndex gt 1 firstToken curLine substring 0 commaIndex trim remainderOfLine curLine substring commaIndex 4l trim else no
310. erhead and still does not ensure that all threading issues will be resolved For example concurrent modifications to a shared resource such as a file or a static field are not prevented in any way 6 5 2 Thread Safety Tips Most servlet threading problems occur when two or more threads make changes to the same resource This might mean that two threads try to modify a file or perhaps several threads all update the value of a shared variable at the same instant This causes unpredictable behavior and can be very hard to diagnose Another type of thread problem is deadlock where two threads are in contention for the same resource each holding a lock that the other thread needs Yet another problem is performance As mentioned earlier synchronizing access to a method can introduce significant performance penalties The best overall approach to servlet thread safety is to avoid the SingleThreadModel interface and synchronizing access to the service method This way your servlet can handle multiple client requests at the same time This also means that you must avoid situations where more than one thread can modify a shared resource concurrently The following tips should offer some guidance 6 5 2 1 Tip 1 Local variables are thread safe Object fields in a servlet are often bad news Consider the following code public class HomeServlet extends HttpServlet private Customer currentCust request throws IOException sion t
311. ervlet frameworks e The XSLT approach In the hybrid approach the servlet is the controller and the JSP is the view It is assumed that the data will be retrieved from a database or Enterprise JavaBeans EJB components which act as the model A good framework may make the distinction between model view and controller more explicit Instead of using the servlet as a controller a common pattern is to use a single servlet that delegates work to helper classes that act as controllers Each of these classes is equivalent to ConcreteController in Figure 4 5 and has knowledge of specific web pages and data Although originally intended for Smalltalk GUIs MVC has always been one of the most frequently used patterns in all sorts of GUIs from Motif to Java On the web MVC is also prevalent although a few mechanics are slightly different In a web environment we are restricted to the HTTP protocol which is stateless With each click of a hyperlink the browser must establish a new connection to the web server Once the page has been delivered the connection is broken It is impossible for the server to initiate a conversation with the client so the server merely waits until the next request arrives Implementing MVC in this stateless architecture results in looser coupling between the controller and the view In a GUI environment the controller immediately notifies the view of any changes to the underlying model In a web environment the controller
312. ervletContext ctx servlet getServletContext xsltFileName ctx getRealPath WEB INF xslt xsltBaseName filenameCache put xsltBaseName xsltFileName write the JDOM data to a StringWriter StringWriter sw new StringWriter XMLOutputter xmlOut new XMLOutputter false UTF 8 xmlOut output xmlJDOMData sw response setContentType text html Transformer trans StylesheetCache newTransformer xsltFileName pass a parameter to the XSLT stylesheet trans setParameter rootDir forum trans transform new StreamSource new StringReader sw toString new StreamResult response getWriter catch IOException ioe throw ioe catch Exception ex throw new ServletException ex private XSLTRenderHelper XSLTRenderHelper performs the XSLT transformation by first converting the JDOM Document into a St ring of XML and then reading that St ring back into a JAXP compliant XSLT processor This is not necessarily the most efficient way to integrate JDOM with JAXP but it works reliably with some beta versions of JDOM By the time you read this JDOM will have more standardized APIs for integrating with JAXP Another utility class RegHandlerRegistry is shown in Example 7 30 This class is responsible for locating instances of RegHandler based on path information found in the request URL Basically path information is any text that occurs
313. es a text indent in ems In Cascading Style Sheets one em is supposed to be equal to the width of the lowercase letter m in the current font Finally the person template is invoked recursively passing in Slevel 1 as the parameter Although this does not increment an existing variable it does pass a new local variable to the template with a larger value than before Other than tricks with recursive processing there is really no way to increment the values of variables in XSLT 3 2 5 Template Modes The final variation on templates is that of the mode This feature is similar to parameters but a little simpler sometimes resulting in cleaner code Modes make it possible for multiple templates to match the same pattern each using a different mode of operation One template may display data in verbose mode while another may display the same data in abbreviated mode There are no predefined modes you make them up The mode attribute looks like this lt xsl template match name mode verbose gt display the full name lt xsl template gt lt xsl template match name mode abbreviated gt omit the middle name xsl template In order to instantiate the appropriate template a mode attribute must be added to lt xsl apply templates as follows at lt xsl apply templates select president nam mode verbose gt If the mode attribute is omitted then the processor searches for a matching template that does not have a
314. es such as concurrency deployment and performance 5 1 A Simple Example Let s start with perhaps the simplest program that can be written For this task we will write a simple Java program that transforms a static XML data file into HTML using an XSLT stylesheet The key benefit of beginning with a simple program is that it isolates problems with your development environment particularly CLASSPATH issues before you move on to more complex tasks Two versions of our Java program will be written one for Xalan and another for SAXON A JAXP implementation will follow in the next section showing how the same code can be utilized for many different processors CLASSPATH Problems CLASSPATH problems are a common culprit when your code is not working particularly with XML related APIs Since so many tools now use XML it is very likely that a few different DOM and SAX implementations reside on your system Before trying any of the examples in this chapter you may want to verify that older parsers are not listed on your CLASSPATH More subtle problems can occur if an older library resides in the Java 2 optional packages directory Any JAR file found in the jre lib ext directory is automatically available to the JVM without being added to the CLASSPATH You should look for files such as jaxp jar and parser jar which could contain older incompatible XML AP Is If you experience problems remove all JAR files from the optional packages director
315. es that this element does not contain any content although it may contain attributes An attribute is a name value pair such as from 1797 Another requirement for well formed XML is that all attribute values be enclosed in quotes or apostrophes Most presidents had middle names some did not have vice presidents and others had several vice presidents For our example XML file these are known as optional elements Ulysses Grant for example had two vice presidents He also had a middle name president term from 1869 to 1877 gt lt name gt lt first gt Ulysses lt first gt lt middle gt Simpson lt middle gt lt last gt Grant lt last gt lt name gt lt party gt Republican lt party gt lt vicePresident gt lt name gt lt first gt Schuyler lt first gt lt last gt Colfax lt last gt lt name gt lt vicePresident gt lt vicePresident gt lt name gt lt first gt Henry lt first gt lt last gt Wilson lt last gt lt name gt lt vicePresident gt lt president gt Capitalization is also important in XML Unlike HTML all XML tags are case sensitive This means that lt president gt is not the same as PRESIDENT It does not matter which capitalization scheme you use provided you are consistent As you might guess since XHTML documents are also XML documents they too are case sensitive In XHTML all tags must be lowercase such as lt html gt lt body gt and lt head gt
316. essage URIResolver In most cases the JAXP provides a UR T Resolver instance By creating a custom implementation however applications can define how relative URI references in XSLT stylesheets are resolved For instance the UR 1 Resolver defines how xs1 include href header xsit gt locates header xsit public interface URIResolver Source resolve String href String base throws TransformerException Package javax xml transform dom This package defines how to perform transformations using DOM DOMLocator This interface allows applications to locate the DOM node where an error occurs Since TransformerException returns instances of SourceLocator applications must downcast to obtain DOMLocator objects public interface DOMLocator extends SourceLocator Node getOriginatingNode DOMResult This class allows transformation results to be stored in a DOM tree If the default constructor is used the XSLT processor creates a DOM Document node Otherwise applications can specify a DOM Document DocumentFragment Of Element node as the constructor parameter The FEATURE constant is used with TransformerFactory getFeature to determine if the factory supports DOMResult public class DOMResult implements Result public static final String FEATURE http javax xml transform dom DOMResult feature lic DOMResult Node node lic DOMResult Node node String systemId lic DOMResult s
317. etailed information on character encodings The most comprehensive character encoding is called ISO IEC 10646 This is also known as the Universal Character Set UCS and allocates a 32 bit number for each character Although this allows UCS to uniquely identify every character in every language it is not directly compatible with most computer software Also using 32 bits to represent each character results in a lot of wasted memory Unicode is the official implementation of ISO IEC 10646 and currently uses 16 bit characters You can learn more about Unicode at http www unicode org UCS Transformation Formats UTFs are designed to support the UCS encoding while maintaining compatibility with existing computer software and encodings UTF 8 and UTF 16 are the most common transformation formats and all XML parsers and XSLT processors are required to support both If you deal mostly with English text UTF 8 is the most efficient and easiest to use Because the first 128 UTF 8 characters are the same as the US ASCII characters existing applications can utilize many UTF 8 files transparently When additional characters are required however UTF 8 encoding will use up to three bytes per character UTF 16 is more efficient than UTF 8 for Chinese Japanese and Korean CJK ideographs When using UTF 16 each character requires two bytes while many will require three bytes under UTF 8 encoding Either UTF 8 or UTF 16 should work However it is wise
318. etaining portability First released in March 2000 Sun s JAXP 1 0 utilized XML 1 0 XML Namespaces 1 0 SAX 1 0 and DOM Level 1 JAXP is a standard extension to Java meaning that Sun provides a specification through its Java Community Process JCP as well as a reference implementation JAXP 1 1 follows the same basic design philosophies of JAXP 1 0 adding support for DOM Level 2 SAX 2 and XSLT 1 0 A tool like JAXP is necessary because the XSLT specification defines only a transformation language it says nothing about how to write a Java XSLT processor Although they all perform the same basic tasks every processor uses a different API and has its own set of programming conventions JAXP is not an XML parser nor is it an XSLT processor Instead it provides a common Java interface that masks differences between various implementations of the supported standards When using JAXP your code can avoid dependencies on specific vendor tools allowing flexibility to upgrade to newer tools when they become available The key to JAXP s design is the concept of plugability layers These layers provide consistent Java interfaces to the underlying SAX DOM and XSLT implementations In order to utilize one of these APIs you must obtain a factory class without hardcoding Xalan or SAXON code into your application This is accomplished via a lookup mechanism that relies on Java system properties Since three separate plugability layers are used you can
319. eter to a template instead of using a global variable and then recursively calling the template again with an incremented parameter value An example of this technique will be presented shortly Another XSLT trick involves combining the variable initialization with lt xs1 choose gt Since variables cannot be changed you cannot first declare a variable and then assign its value later on The workaround is to place the variable definition as a child of lt xsi1 variable gt perhaps using lt xsl choose gt as follows lt xsl variable name midName gt lt xsl choose gt lt xsl when test middleName gt lt xsl value of select middleName gt lt xsl when gt lt xsl otherwise gt lt xsl text gt lt xsl text gt lt xsl otherwise gt lt xsl choose gt xsl variable This code defines a variable called midName If the lt middleName gt element is present its value is assigned to midName Otherwise a blank space is assigned 3 2 2 lt xsl call template gt and Named Templates Up until this point all of the templates have been tightly coupled to the actual data in the XML source For example the following template matches an employee element therefore employee must be contained within your XML data lt xsl template match employee gt content perhaps display the name and SSN for the employee lt xsl template gt But in many cases you may wish to use this template for types of elements other than l
320. f JAXP it encapsulates differences between various XML parsers allowing Java programmers to use a consistent API regardless of which parser they use As we will see in Chapter 5 JAXP 1 1 adds a consistent wrapper around various XSLT processors in addition to standard SAX and DOM parsers JAXP provides a bocumentBuilderFactory to construct a Document Builder which is then used to construct new Document objects The Document class is a part of DOM so most of the remaining code is defined by the DOM specification In DOM new XML elements must always be created using factory methods such as createElement 0nan instance of Document These elements must then be added to either the document itself or one of the elements within the document before they actually become part of the XML create the library document root element Element root doc createElement library doc appendChild root At this point the 1 ibrary gt element is empty but it has been added to the document The code then proceeds to add all lt pub1isher gt children add publisher children to the library element shers Iterator publisherIter library getPublishers iterator while publisherIter hasNext Publisher pub Publisher publisherIter next ee Element pubElem createPublisherElement doc pub root appendChild pubElem For each instance of Publisher a lt publisher gt Element is created and then
321. f into that particular implementation unless you want to rewrite your application The other option is to write a facade around both processors presenting a consistent interface that works with either processor behind the scenes The only problem with this approach is that as new processors are introduced you must update the implementation of your facade It would be very difficult for one individual or organization to keep up with the rapidly changing world of XSLT processors But if the facade was an open standard and supported by a large enough user base the people and organizations that write the XSLT processors would feel pressure to adhere to the common API rather than the other way around TrAX was initiated in early 2000 as an effort to define a consistent API to any XSLT processor Since some of the key people behind TrAX were also responsible for implementing some of the major XSLT processors it was quickly accepted that TrAX would be a de facto standard much in the way that SAX is 5 2 Introduction to JAXP 1 1 TrAX was a great idea and the original work and concepts behind it were absorbed into JAXP Version 1 1 If you search for TrAX on the Web and get the feeling that the effort is waning this is only because focus has shifted from TrAX to JAXP Although the name has changed the concept has not JAXP provides a standard Java interface to many XSLT processors allowing you to choose your favorite underlying implementation while r
322. f the servlet container so a unit test can simply create the XML and validate it against a DTD or XML Schema Tools such as XML Spy make it easy to create XSLT stylesheets and test them interactively against sample XML files long before they are ever deployed to a servlet container XML Spy is available from http www xmlspy com If you are looking for alternatives a directory of XML tools can be found at http www xmlsoftware com The XSLT processor is another piece of the puzzle that is not tied to the servlet in any way Because the processor is an independent component additional unit tests can perform transformations by applying the XSLT stylesheets to the XML data again without any interference from a web server or servlet container If your stylesheets produce XHTML instead of HTML the output can be easily validated against one of the W3C DTDs for XHTML JUnit an open source unit testing tool can be used for all of these tests It can be downloaded from http www junit org 4 3 XSLT and EJB Now that the options for web tier development have been examined let s look at how the web tier interacts with other tiers in large enterprise class systems A typical EJB architecture involves a thin browser client a servlet driven web tier and EJB on an application server tier Figure 4 7 expands upon the conceptual XSLT model presented earlier Figure 4 7 XSLT and EJB architecture Presentation logic Business Logic RequestH
323. face that all custom filters must implement It defines the following three methods void init FilterConfig config void destroy void doFilter ServletRequest req ServletResponse res FilterChain chain The init anddestroy methods are virtually identical to the init and destroy methods found in any servlet init is called when the filter is first loaded and the FilterConfig parameter provides access to the ServletContext and to a list of initialization parameters The code in Example 8 11 demonstrates each of these features destroy as expected is called once when the filter is unloaded This gives the filter a chance to release resources The doFilter method is called whenever a client request is received The filter participates ina FilterChain set up by the servlet container which allows multiple filters to be attached to one another If this filter wishes to block the request it can simply do nothing Otherwise it must pass control to the next resource in the chain chain doFilter req res Although the next entry in the chain might be another filter it is probably a servlet or a JSP Either way the filter does not have to know this Simply calling doFilter req res merely passes control to the next entry in the chain To modify the request or response the filter must modify the ServletRequest and or ServletResponse object Unfortunately these are both interfaces and their implementation cla
324. fective XSLT stylesheets Post Message to XSLT Basics Mar 2001 Apr 2001 Sample empty board This board has no messages Post Message to Sample empty board The complete XHTML source code for the home page is shown in Example 7 2 As shown the actual hyperlinks are not valid because the design for the servlets has not been completed and the final URLs are probably unknown at this point At any rate this is only prototype code because the actual XHTML web pages are dynamic and will be produced as the result of an XSLT transformation from XML data Example 7 2 Home page XHTML source lt xml version 1 0 encoding UTF 8 lt DOCTYPE html PUBLIC W3C DTD XHTML 1 0 Strict EN http www w3 org TR xhtml1 DTD xhtmll strict dtd lt html xmlns http www w3 0rg 1999 xhtml head title Discussion Forum Home lt title gt lt link href docroot forum css rel stylesheet type text css gt lt head gt lt body gt lt div class boxl lt h1l gt Discussion Forum Home lt h1 gt lt div gt lt div class box2 gt lt h2 gt Java Programming lt h2 gt lt div gt General programming questions about Java lt div gt div style margin left 2em p lt a href link to post message Post Message lt a gt to Java Programming lt p gt a href link to feb messages Feb 2001 a lt a href link to mar messages Mar 2001 lt a gt a href link to apr
325. form sax TransformerHandler is used for this purpose Obtaining an instance of TransformerHandler requires a few extra programming steps First create a TransformerFactory as usual TransformerFactory transFact TransformerFactory newInstance jus As before the TransformerFactory is the JAXP abstraction to some underlying XSLT processor This underlying processor may not support SAX features so you have to query it to determine if you can proceed if transFact getFeature SAXTransformerFactory FEATURE If this returns false you are out of luck Otherwise you can safely downcast to a SAXTransformerFactory and construct the TransformerHandler instance SAXTransformerFactory saxTransFact SAXTransformerFactory transFact create a ContentHandler don t specify a stylesheet Without a stylesheet raw XML is sent to the output TransformerHandler transHand saxTransFact newTransformerHandler ys In the code shown here a stylesheet was not specified JAXP defaults to the identity transformation stylesheet which means that the SAX events will be transformed into raw XML output To specify a stylesheet that performs an actual transformation pass a Source to the method as follows cce xsltSource new StreamSource myXsltSystemIQd ransformerHandler transHand saxTransFact newTransformerHandler xsltSource 5 3 5 2 Detailed CSV to SAX design Before delving into the complete example program let s step back and
326. formation as text private String resultText private JTabbedPane tabPane new JTabbedPane private JTextArea textOutputArea new JTextArea 30 70 private XMLOutputPanel xmlOutputPanel new XMLOutputPanel private private JTable errorTable new JTable this errModel private JT private String xsltURL rrorListenerModel errModel new ErrorListenerModel xtArea errorDetailArea new JTextArea 10 70 Construct a new instance and layout the GUI components public TransformerWindow super XSLT Transformation add the tab pane to the frame Container cp getContentPane cp add this tabPane BorderLayout CENTER add individual tabs this tabPane add Text Output new JScrollPane this textOutputArea this tabPane add Transformation Problems createErrorPanel this tabPane add XML Output this xmlOutputPanel listen to new tab selections this tabPane addChangeListener new ChangeListener public void stateChanged ChangeEvent evt tabChanged this textOutputArea setEditable false 1 listen to selection changes on the table of errors this errorTable getSelectionModel addListSelectionListener new ListSelectionListener public void valueChanged ListSelectionEvent evt if l evt getValuelsAdjusting showErrorDetails H pack Show details for
327. former trans templates newTransformer s do two transformations using the same Transformer trans transform new StreamSource this aidanXMLFile new StreamResult this aidanCondensedXMLFile trans transform new StreamSource this johnXMLFile new StreamResult this johnCondensedXMLFile validate both files validateCondensedFile this aidanCondensedXMLFile Aidan Garrett Burke 6 25 1999 validateCondensedFile this johnCondensedXMLFile John Fitzgerald Kennedy 5 29 1917 Another unit test public void testTransformer throws Exception Transformer trans this transFact newTransformer new StreamSource this condenseXSLTFile trans transform new StreamSource this aidanXMLFile new StreamResult this aidanCondensedXMLFile validateCondensedFile this aidanCondensedXMLFile Aidan Garrett Burke 6 25 1999 a helper method used by each of the unit tests private void validateCondensedFile File file String expectedName String expectedBirthDate try first do a simple validation against the DTD SAXBuilder builder new SAXBuilder true validate Document doc builder build file now perform some additional checks Element nameElem doc getRootElement getChild name assertEquals Name was not correct expectedName nameElem getText Element birthDateElem doc getRootElement getChild birthDate assertE
328. fter each transformation Then simply experiment with different XSLT stylesheets to see which approaches offer the best performance Similar standalone tests can be written for various database access routines key pieces of business logic and code that generates XML Since JUnit reports the time spent in each unit test you may want to combine these performance metrics with meaningful unit tests Regardless of how these individual test routines are written it is critical that the first runs are ignored This is because the results will be greatly skewed by Java class loading and initialization time A good approach is to execute the unit test once before recording the system time Then execute the test many thousands of times recording the overall time at the end of the runs The average response time calculated by dividing the total time by the number of runs will be much more accurate than taking a few isolated measurements Another point to consider is caching In a real application data may change with every single request making it difficult to cache the transformation result Unit tests that repeatedly transform the same file are not a good representation of real world behavior because the processor may cache the transformation result and report artificially high performance 9 3 3 Using XSLT Processors Effectively Measuring performance is the first step towards making Java and XSLT applications faster Once the bottlenecks have been l
329. g org apache tools ant taskdefs XSLTLiaison When omitted defaults to trax includes The comma separated list of file patterns to include no includesfile The name of a file that contains include patterns no excludes The comma separated list of file patterns to exclude no excludesfile The name of a file that contains exclude patterns no defaultexcludes May be yes or no defaults to yes no in A single XML file input no out A single output filename no The pattern attributes such as includes and excludes work just like other patterns in Ant Basically these allow the task to filter which files are included and excluded from the transformations When omitted all files in the base directory are included Here is how an entire directory of XML files can be transformed lt style basedir xmlfiles includes xml destdir build doc style report xslt extension html As shown back in Example 9 3 parameters can be passed using nested lt param gt elements This element has required name and expression attributes style basedir xmlfiles includes xml destdir build doc style report xslt extension html lt param name reportType expression detailed gt style 9 1 3 Tomcat Apache s Tomcat is a Servlet and JSP container and has been mentioned throughout this book It is available from http jakarta apache org tomcat Tomcat is fairly easy to install and configure e Download the latest T
330. g all of the information in a single table Once again this is accomplished with a different XSLT stylesheet that converts the XML to XHTML instead of WML Figure 10 8 Showtimes XHTML output 5 9i4 Qudzvdu dv Adress 21 http flocalhost 8090 chap1 0 movieguide7action showtinessiity stiithester of alon E ea Links EJCustomee Links FreeHotmal Windows Windows Meda Showtimes for O Fallon Cine in St Louis Movie Times Raiders of the Lost Ark 10 15a 3 30 12 30 5 45 7 15 10 30 Indiana Jones and The Temple of Doom 1 30 4 00 6 00 Back to the Future 2 4 00 6 00 8 00 10 00 Select a different theater E Local intranet Although WML does define a lt table gt element it has almost no chance of fitting on a cell phone display and is not widely supported by currently available devices 10 3 3 4 Serviet implementation This application uses a single servlet listed in Example 10 9 This servlet has three primary functions e Parse request parameters and determine which page to display next e Identify the client type e Perform the appropriate XSLT transformation Example 10 9 MovieServlet java package chap10 import java io import javax servlet import javax servlet http import javax xml transform import javax xml transform stream A servlet that shows schedules for movie theaters in various cities Supports normal web browser clients as well as WAP enabled PDAs and
331. g curReplyToID Long iter next if curReplyToID longValue 1 this idToMsgMap containsKey curReply TOID List msgsToAdd List this replyIDToMsgListMap get curReplyTOoID this topLevelMsgs addAll msgsToAdd Collections sort this topLevelMsgs public Iterator getTopLevelMessages return this topLevelMsgs iterator return an iterator of Me re replies x to the specified public Iterator getReplies Mess List replies List thi new Long msg getI if replies null Collections sort replies return replies iterator else return Collections EMPTY_LIST iterator 3 The MessageTree class helps organize a list of messages according to threads of discussion If you look back at the code for MessageSummary you will see that each message keeps track of the message that it is in reply to public interface MessageSummary extends Comparable long getInReplyTo If the message is a top level message then the reply to id is 1 Otherwise it always refers to some other message Since a message does not have a corresponding method to retrieve a list of replies the MessageTree class must build this list for each message This leads to the three data structures found in the MessageTree class private List topLevelMsgs new ArrayList private Map idToMsgMap new HashMap private Map replyIDToMsgListMap new HashMap When the Mes
332. g the browser to determine which encoding to expect In our example the three possible character encodings result in the following possible content types text html charset ISO 8869 1 text html charset UTF 8 text html charset UTF 16 Content Typ Content Typ Content Tyrp 0 O0 D Next the servlet uses the javax xml transform Source interface and the javax xml transform stream StreamSource class to read from the XML and XSLT files Source xmlSource new StreamSourc e new File xmlFileName Source xsltSource new StreamSource new File xsltFileName By using java io File the StreamSource will correctly determine the encoding of the XML and XSLT files by looking at the XML declaration within each of the files The St reamSource constructor also accepts Input St ream Or Reader as parameters Special precautions must be taken with the Reader constructors because Java Reader implementations use the default Java character encoding which is determined when the VM starts up The Input St reamReader is used to explicitly specify an encoding as follows Source xmlSource new StreamSource new InputStreamReader new FileInputStream xmlFileName UTF 8 For more information on how Java uses encodings see the JavaDoc package description for the java lang package Our servlet then overrides the XSLT stylesheet s output encoding as follows trans setOutputProperty OutputKeys ENCODING charEnc This takes precedence ov
333. gets The output for this graph is shown in Example 3 13 Example 3 13 Target dependencies clean all depends on clean dist prepare tomcat depends on prepare j2ee depends on tomcat j2ee dist depends on j2ee main depends on tomcat webapps dist depends on main webapps dist zip depends on dist all depends on clean dist webapps depends on prepare dist depends on main webapps dist zip depends on dist all depends on clean dist main depends on tomcat webapps dist depends on main webapps dist zip depends on dist all depends on clean dist targets This is actually the output from the Ant build file included with Apache s Tomcat The list of top level targets is shown at the root level and dependent targets are indented and listed next The targets shown in parentheses list what each target depends on This tree view is created by recursively analyzing the dependencies which appear in the Ant build file as follows target name all Figure 3 1 shows a portion of the output dependency graph The output concludes build file Figure 3 1 depends clean dist in a web browser A table listing all targets follows the with a table of all global properties defined in the Ant Antdoc sample output A Ant Project Summary Tomcat Microsoft Internet Explorer E Hi file gdt wew Favorites Joos Help oo o Lnks address ETE cist mp depends on dist all depends on clean
334. gh support for CSS is gradually improving web pages must be tested on a variety of browsers to identify formatting problems A common theme presented throughout this book is the separation of data and presentation that XSLT supports CSS expands upon this theme by separating XHTML content from many aspects of its visual presentation CSS and XSLT are very different technologies that complement one another nicely Most of the code in a CSS file is fairly self explanatory For example the n2 style applies to n2 elements in the XHTML One style element that many programmers may not be familiar with is box2 2px background color FFFFCC The dot in box2 indicates a style class definition Here is how the box2 style class is used in the XHTML lt div class box2 gt Messages for March 2001 lt div gt The advantage of a style class is that it can be applied to any element in the XHTML In this case a thin border and yellow background are applied to any element that has the box2 class The web page designers should create basic representations of every page in the application at this point The home page is shown in Figure 7 2 Figure 7 2 Home page prototype F Discussion Forum Home Microsoft internet Explorer BG Ble Edit Yew Favorites Tools Help Java Programming General programming questions about Java Post Message to Java Programming Feb 2001 Mar 2001 Apr 2001 XSLT Basics Writing ef
335. given month This page may contain hundreds of messages displaying key information found in the MessageSummary interface But the text of each message could contain thousands of words so it was decided that the text should be retrieved later when a message is displayed in its entirety For this page an instance of a class that implements Message can be created These are the sorts of design decisions that cannot be made in complete isolation Regardless of how cleanly XSLT and XML separate the presentation from the underlying data model heavily used web pages should have some influence on design decisions made on the back end The trick is to avoid falling into the trap of focusing too hard on early optimization at the expense of a clean design In this case the potential for large numbers of very long messages was significant enough to warrant a separate interface for Message The three reference implementation classes are Messagelmpl Message Summarylmp1 and BoardSummary Impl These are basic Java classes that hold data and are listed in Appendix B The JDBC data adapter layer see Section 7 3 2 will create and return new instances of these classes which implement the interfaces in this package If creating a new back end data source in the future it is possible to reuse these classes or write brand new classes that implement the appropriate interfaces The final class in this package MessageTree is listed in Example 7 14 Example 7 14
336. glish four gt cuatro lt number gt number english five gt cinco lt number gt number english six gt seis lt number gt number english seven gt siete lt number gt number english eight gt ocho lt number gt n m AUN WBA UN BR AW UA umber gt ber gt number english nine gt nueve lt lt number english ten gt diez lt nu lt numbers gt 8 6 3 2 XSLT stylesheets The numbers_english xsit stylesheet is shown in Example 8 21 and follows the same pattern that was introduced earlier in this chapter Specifically it isolates locale specific data as a series of variables Example 8 21 numbers_english xslt lt xml version 1 0 encoding UTF 8 gt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html encoding UTF 8 gt lt xsl variable name lang pageTitle gt XSLT in English lt xsl variable gt lt xsl variable name lang tableCaption gt Here is a table of numbers xsl variable lt xsl variable name lang englishHeading 5English xsl variable lt xsl template match gt lt html gt head title xsl value of select Slang pageTitle gt lt title gt lt head gt lt body gt xsl apply templates select numbers gt lt body gt lt html gt lt xsl template gt lt xsl template match numbers gt hl xsl value of select lang pageTitle gt lt h1 gt lt xsl va
337. gly An alternative to simply including is located in is to use Technically elements that do not belong to the XSLT namespace are simply copied to the result tree the namespace prefix might not be x51 xsl text is located in lt xsl text gt This provides explicit control over how whitespace and linefeeds are treated xsl value oft copies the value of something in the XML source tree to the result tree In this case the current node is school SO lt xsl value of select name selects the text content of the lt name gt element contained within lt schoo1 gt This is the simplest usage of XPath which will be introduced shortly XPath is not limited to the current node so it can also be used to locate elements in other parts of the source document It can even select attributes processing instructions or anything else that can occur in XML 2 2 3 Built in Template Rules All XSLT processors must include four built in template rules that have lower precedence than any other rules so they can be overridden by simply writing a new template rule that matches the same pattern The best way to think about built in rules is to assume they are always in the background ready to be applied if no other rule is found that matches a node The first rule allows recursive processing to continue in case an explicit rule does not match the current node or the root node lt xsl template match gt l apply templates
338. gs directory The UnavailableException simply indicates that this servlet is unavailable so it will not be loaded into memory The user will see an error page in their browser at this point If the init method completes successfully the servlet will be available to handle requests from clients In this servlet the doGet and doPost methods have been implemented therefore both HTTP GET and POST protocols are supported When the user first enters the application they will click on a hyperlink type a URL into their browser or visit a saved bookmark In all of these cases the browser issues an HTTP GET request that ultimately causes the doGet method to be invoked protected void doGet HttpServletRequest request oGe See ee Response response throws IOException ServletException PersonalData personalData getPersonalData request the third parameter false indicates that error messages should not be displayed when showing the page showPage response personalData false this editTemplates The first thing the doGet method does is retrieve the instance of PersonalData associated with this particular user The appropriate code has been factored out into the getPersonalData helper method since this same functionality is required by the doPost method as well You can refer back to Example 6 8 to see how getPersonalData is implemented It basically uses Ht tpSession to locate the appro
339. gt init param init param lt param name gt adapterClassName lt param name gt Relational database version is commented out lt param value gt com oreilly forum jdbcimpl JdbcDataAdapter lt param value gt gt lt param value gt com oreilly forum fakeimpl FakeDataAdapter lt param value gt lt init param gt lt servlet gt lt servlet mapping gt lt servlet name gt forumServlet lt servlet name gt url patte lt servlet mapping gt 1 gt main lt url pattern gt web app The deployment descriptor contains context initialization parameters for the data adapter layer The default settings utilize a fake data adapter allowing the discussion forum to function without creating any sort of database Once this is up and running you will want to create a relational database and configure the appropriate parameter values as shown in web xml 7 5 2 Ideas for Enhancements A few key features were omitted to keep this chapter reasonably sized as you can see this is already far longer than any other chapter in the book Some ideas for enhancements include e Database connection pooling e Web based administration tools e Authentication of users e The ability to search the entire archive e Alternate client user interfaces such as XHTML Basic or WML Any one of these features can be added without fundamentally changing the existing architecture User authenti
340. gt lt xsl comment gt See XSLT specification section 7 4 Creating Comments http www w3 org TR xslt section Creating Comments xsl copy xsl copy use attribute sets qnames gt Content template gt lt xsl copy gt See XSLT specification section 7 5 Copying http www w3 org TR xslt copying xsl copy of xsl copy of select expression gt See XSLT specification section 11 3 Using Values of Variables and Parameters with lt xsl copy of gt http www w3 org TR xslt copy of xsl decimal format xsl decimal format name qname decimal separator char grouping separator char infinity string minus sign char NaN string percent char per mille char zero digit char digit char pattern separator char gt See XSLT specification section 12 3 Number Formatting http www w3 org TR xslt format number lt Xxsl element gt lt xsl element name qname namespace uri reference use attribute sets qnames gt i Content template gt lt xsl element gt See XSLT specification section 7 1 2 Creating Elements with lt xsl element gt http www w3 org TR xslt section Creating Elements with xsl element xsl fallback xsl fallback Content template gt xsl fallback See XSLT specification section 15 Fallb
341. guage features such as conditional logic parameters and variables text and number formatting and producing XML output This chapter concludes with a more sophisticated example that produces summary reports for Ant build files Chapter 4 Offers comparisons between popular web development technologies comparing each with the Java and XSLT approach The model view controller architecture is discussed in detail and the relationship between XSLT web applications and EJB is touched upon Chapter 5 Shows how to use XSLT processors with Java applications and servlets Older Xalan and SAXON APIs are mentioned but the primary focus is on Sun s JAXP Key examples show how to use XSLT and SAX to transform non XML files and data sources how to improve performance through caching techniques and how to interoperate with DOM and JDOM Chapter 6 Provides a detailed review of Java servlet programming techniques Shows how to create web applications and WAR files how to deploy XML and XSLT files within these web applications and how to perform XSLT transformations from servlets Chapter 7 Implements a complete web application from start to finish In this chapter a web based discussion forum is designed and implemented using Java XML and XSLT techniques The relationship between CSS and XSLT is presented and XHTML Strict is used for all web pages Chapter 8 Covers important Java and XSLT programming techniques that build upon concepts presented
342. h bugs and eggs Whether they take their eggs sunny side up or over easy is still a matter of great debate Female ermines give birth to only one litter per year The mating season is in the late spring but after fertilization the ermine embryos stop developing and do not implant in the uterus for several months Once implantation occurs gestation takes only about a month and the babies are born in the spring of the year following fertilization Ermines can live up to eight years but their lifespan in the wild tends to be only a year or less Their main killer is starvation dependent as they are on fluctuating rodent populations but they are also preyed upon by hawks owls and humans Ermine fur which is harvested from both M erminea and its cousin M frenata the long tailed weasel is specifically the fur of an ermine in winter At this time of year their fur is stark white except for a small black tip on the tail leading to the black flecked white fur robes favored by stylish monarchs all over the world Matt Hutchinson was the production editor and copyeditor for Java and XSLT Susan Carlson Greene proofread the book and Leanne Soylemez and Emily Quill provided quality control John Bickelhaupt wrote the index James Carter provided production assistance Ellie Volckhausen designed the cover of this book based on a series design by Edie Freedman The cover image is a 19th century engraving from the Dover Pictorial Archive Em
343. h param name depends select SremainingTokens gt lt xsl call template gt lt xslsit gt lt xsl template gt iem C Ck OK C Ck C Ck S Ck KC Ck KC Ck C Ck KC Ck Ck Ck Ck Ck Ck Ck Ck kk Ck Ck kk Ck kk Ck Sk kk E kx kx Sk ke x UG Ko kx ko ko koko k This template will begin a recursive process that forms a dependency graph of all targets KCKCK CK Kk CK CK CK Ck CK Kk CK CK SK Ck CK CK KICK SKK Kk Kk SKK Ck SK KC Ck KC Sk KC kk k ck Kk k ck ck KKK kk lt xsl template match target mode tree gt lt xsl param name indentLevel select 0 gt lt xsl variable name curName select name gt lt div style text indent indentLevel em gt lt xsl value of select curName lt if the depends attribute is present show the list of dependencies gt xsl if test depends gt lt xsl text gt depends on lt xsl text gt xsl call template name parseDepends gt xsl with param name depends select depends gt xsl call template xsl text xsl text xsl if div set up the indentation lt xsl variable name nextLevel select SindentLevel 1 gt search all other target elements that have depends attributes lt xsl for each select target depends gt lt Take the comma separated list of dependencies and clean it up See the comments for the fixDependency template gt lt xsl variable name correc
344. h the dependency graph the target template must instantiate itself recursively Before doing this the indentation must be increased Since XSLT does not allow variables to be modified a new variable is created lt xsl variable name nextLevel select SindentLevelti gt When the template is recursively instantiated next Level will be passed as the value for the ndent Level parameter xsl apply templates select mode tree gt xsl with param name indentLevel select SnextLevel gt d eie cise The remainder of the template is not duplicated here but is emphasized in Example 3 14 The basic algorithm is as follows e Use lt xs1 for each gt to select all targets that have dependencies Instantiate the fixDependency template to replace commas with characters e Recursively instantiate the target template for all targets that depend on the current target 3 6 3 3 Cleaning up dependency lists The final template in the Antdoc stylesheet is responsible for tokenizing a comma separated list of dependencies inserting pipe characters between each dependency XS template name fixDependency 1 is xsl param name depends gt The depends parameter may contain text such as a b c The template tokenizes this text producing the following output lalb c Since XSLT does not have an equivalent to Java s St ringTokenizer class recursion is required once again The technique is to process the tex
345. hange data if the message is corrupted in any way the receiving System must reject the message altogether or risk making the wrong assumptions This is important for XSLT programmers to understand because XSLT itself is expressed using XML When writing stylesheets you must always adhere to the basic rules for well formed documents All well formed XML documents must have exactly one root element In Example 1 1 the root element is lt presidents gt This forms the base of a tree data structure in which every other element has exactly one parent and zero or more children Elements must also be properly terminated and nested Pj ge lt first gt E n ngton lt last gt Although whitespace spaces tabs and linefeeds between elements is typically irrelevant it can make documents more readable if you take the time to indent consistently Although XML parsers preserve whitespace it does not affect the meaning of the underlying elements In this example the lt first gt tag must be terminated with a corresponding lt first gt The following XML would be illegal because the tags are not properly nested name lt first gt George lt last gt Washington lt first gt lt last gt lt name gt XML provides an alternate syntax for terminating elements that do not have children formally known as empty elements The lt term gt element is one such example term from 1797 to 1801 gt The closing slash indicat
346. hanging to the XML generation logic Figure 7 6 Key domain classes monthsWithMessages inReplyTo lt lt interface gt gt einterface BoardSummary MessageSummary LN getiD long getID long DayMonthYea getName String getSubjact String createDate getDescription String geAuthorEmail String BoardSummarylmpl interface Message MessageSummarylmpl lt cutility gt gt Text Stri getText String lt lt utility gt gt i soris a collection of Messagelmpl messages into a hierarchy BoardSummary MessageSummary and Message are the key interfaces that describe the basic discussion forum capabilities For each interface an associated 1 1 class provides a basic implementation that contains get and set methods which are not shown here The MonthYear DayMonthYear and DateUtil classes are designed to represent and manipulate dates in an easy way and are listed in Appendix B Finally the MessageTree class encapsulates some business logic to sort a collection of messages into a hierarchical tree based on message replies and creation dates The BoardSummary interface shown in Example 7 11 contains data that will eventually be used to build the discussion forum home page Example 7 11 BoardSummary java package com oreilly forum domain import java util Iterator Information about a message board ur public interface BoardSummary return a
347. have to be cluttered up with a lot of i e 1 se statements to figure out the mode of operation it is in 7 2 3 XSLT Stylesheets Yet another member of the development team can be assigned to the task of creating XSLT stylesheets although he or she will have to wait until the XML and XHTML prototypes are complete More often than not the person designing the XML will be the one creating the initial XSLT stylesheets At this point in the process a tool such as XML Spy can be invaluable The ability to edit the XSLT stylesheet and click on the Refresh button in an IDE makes development a snap Alternately an XSLT compatible web browser can quickly display changes as stylesheets are edited As explained in Chapter 1 Microsoft s Internet Explorer 5 x supports XSLT provided that the updated msxm l parser is installed using the xmlinst utility gt 12 XML Spy is a commercial XML editor that works nicely for XSLT development It is available at http www xmlspy com 3 As this is written IE 6 0 is in beta testing It supports the latest XSLT specification The Mozilla browser will also support XSLT at some point Example 7 7 shows the XSLT for the discussion forum home page Example 7 7 XSLT for the home page lt xml version 1 0 encoding UTF 8 KKEAKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK home xslt k k Transforms the home page into XHTML KKEKKKKKKKKK KKK KKK KKK KKK KKK KKK ckckckckckckckckockck
348. he Home JDOM class the constructor is private This prevents instantiation of the class another decision made in the name of efficiency Since each of the JDOM producer classes for the discussion forum are stateless and thread safe the produceElement method can be static This means that there is no reason to create instances of the JDOM producers because the same method is shared by many concurrent threads Additionally there is no common base class because each of the produceElement methods accept different types of objects as parameters Other JDOM Options The static method technique shown in this chapter is certainly not the only way to produce JDOM data You may prefer to create custom subclasses of JDOM s Element class In your subclass the constructor can take a domain object as a parameter So instead of calling a static method to produce XML you end up writing something like Iterator boards Element homeElem new HomeElement boards Yet another option is to embed the JDOM production code into the domain objects In this approach your code would resemble this BoardSummary board Element elem board convertToJDOM js This approach is probably not the best because it tightly couples the JDOM code with the domain classes It also will not work for cases where the XML data is produced from a group of domain objects instead of from a single object Regardless of the technique follo
349. he appropriate stylesheet Figure 6 7 Confirmation page FID MM Intern PS E3 Ele Edt wew Favorkes Tools Help Bak gt Q i A Asearch ijFavortes Hetey Address e hrosiocahostooonichasejpersonabats 1 Go uns Thank You Your Information First Name Fric Last Name Bumke Daytime Phone 636 123 4567 Evening Phone Email burke_e yahoo com Chek here to edit this information lE Done 6 3 2 XML and Stylesheets Deciding how to structure your XML can have significant impact on your ability to customize the output of a web application In our current example the same XML file is used for all web pages This XML is shown in Example 6 3 Example 6 3 Example XML output lt xml version 1 0 encoding UTF 8 lt page gt lt the next element is optional lt requiredFieldsMissing lt personalData gt lt firstName required true gt Eric lt firstName gt lt lastName required true gt Burke lt lastName gt lt daytimePhone required true gt 636 123 4567 lt daytimePhone gt lt eveningPhone gt lt email required true gt burke_e yahoo com lt email gt lt personalData gt lt page gt As you can see the XML is very minimal None of the captions such as First Name are included because they are all specified in the XSLT stylesheets Even the asterisk character is omitted giving the XSLT author complete control over how things
350. he document root xsl template matchz html head title Discussion Forum Home Page lt title gt head body hl Discussion Forum Home Page lt h1 gt select a message board to view lt h3 gt u 1 lt xsl apply templates select discussionForumHome messageBoard gt lt ul gt lt body gt lt html gt lt xsl template gt match a lt messageBoard gt element gt lt xsl template match messageBoard gt li lt a href viewForum id id gt lt xsl value of select name gt The filename extension for XSLT stylesheets is irrelevant In this book sit is used Many stylesheet authors prefer xsl The first thing that should jump out immediately is the fact that the XSLT stylesheet is also a well formed XML document Do not let the xsi namespace prefix fool you everything in this document adheres to the same basic rules that every other XML document must follow Like other XML files the first line of the stylesheet is an XML declaration lt xml version 1 0 encoding UTF 8 gt g Unless you are dealing with internationalization issues this will remain unchanged for every stylesheet you write This line is immediately followed by the document root element which contains the remainder of the stylesheet xsl stylesheet cSion 1 0 xmlns xsl http www w3 org 1999 XSL Transform gt The xsi stylesheet element has two attributes
351. he framework for the XHTML page kckckckckckckckckckckckckckckckckckckckokokokckckokckckckckckckckckckckckokckckokckckckckckckckckckckck ck kck ck KK kk gt lt xsl template match gt lt html gt lt head gt lt title gt Personal Data Summary lt title gt lt head gt lt body gt lt xsl apply templates select page personalData gt lt body gt lt html gt lt xsl template gt lt le KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Match the lt personalData gt element KCKCkCkCkCkCk ck ck k ck ck kc KKK KKK KKK KKK KK KKK ck ck ck ck ck ck ck k ck ck k ck k kck ck ck KKK ck ck KKK KKK KK D gt xsl template match personalData lt h2 gt Thank You h2 lt h3 gt Your Information lt h3 gt lt table border 0 cellpadding 2 cellspacing 0 gt Select all immediate children such as firstName lastName daytimePhone etc gt xsl apply templates lt table gt lt p gt lt a href chap6 personalData gt Click here to edit this information lt a gt lt p gt lt xsl template gt lt a CkCkckCckck ck kck ck ck ck ck KKK ck kck ck ck KKK KKK KK KK KKK ck ck ck ck ck ck KKK KKK ck k ck ck ck ck ck kk ck k kk kk Output a new row in the table for each field KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKAKKKK ck k k kk xsl template match firstName lastName daytimePhone eveningPhone email gt
352. he splash screen CK CK Kk CK CK CK Kk SK KK CK Kk CK C Kk SK Kk CK CK CK CK Ck SK Kk KK SKK SK KK Kk SK KK SK KC S KG kk k kc k ck kc ko k ko kk D gt lt xsl template name createSplashCard gt lt card id splash title ABC Theaters ontimer home gt lt timer value 15 gt lt p align center gt lt big gt Welcome to ABC Theaters lt big gt lt p gt p Mmmm Popcorn p do type accept gt go href home gt do card lt xsl template gt lt xsl stylesheet gt This is actually a very simple stylesheet The critical feature is the lt xs1 output gt element which specifies the XML output method and the WML DTD This application adheres to Version 1 1 of WML for maximum compatibility with existing cell phones although newer versions of WML are available For these versions use the newer DTDs found at http www wapforum org The only marginally difficult part of the stylesheet is the following line lt a href movieguide action theaters amp city city gt Show Theaters lt a gt This creates the hyperlink to the next deck passing parameters for the action and city The ampersand character must be written as amp for the XML parser to handle this attribute correctly Although the city syntax looks a lot like an XSLT Attribute Value Template it is actually a WML variable This is how the selected city is sent to the servlet when the user clicks on the hyperl
353. his allows us to fully capture and control the response before anything is sent back to the client browser According to the servlet API either getWriter of getOutputStream can be called but not both This custom response wrapper class cannot know which is needed so it must support both This is definitely an area where the servlet filtering API can make things a lot easier for programmers Very little of this is currently documented in the servlet specification Perhaps this will improve by the time this book is published However there are currently very few examples that show how to capture and modify the response Hopefully this will improve as more containers are upgraded to support the servlet 2 3 specification The primary class in this example is shown in Example 8 11 This is the actual filter that performs XSLT transformations Example 8 11 Servlet filter for XSLT transformations package com oreilly javaxslt util import java io import javax servlet import javax servlet http import javax xml transform import javax xml transform stream A utility class that uses the Servlet 2 3 Filtering API to apply an XSLT stylesheet to a servlet response Qauthor Eric M Burke public class StylesheetFilter implements Filter private FilterConfig filterConfig private String xsltFileName This method is called once when the filter is first loaded f public void init
354. his almost completes the stylesheet xs1 copy simply copies the lt message gt element to the result tree but does not copy any of its attributes or children We can explicitly add new attributes using lt xsl attribute gt and explicitly create new child elements using lt xs1 element gt xsl apply templates then tells the processor to continue the transformation process for the children of message One problem right now is that the lt t ype gt element has been converted into an attribute but has not been removed from the document The identity transformation still copies the lt t ype gt element to the result tree without modification To fix this simply add an empty template as follows lt xsl template match type gt The complete schema evolution stylesheet simply contains the previous templates Without duplicating all of the code here is its overall structure lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt lt xsl output method xml version 1 0 encoding UTF 8 indent yes gt 1 the identity transformation gt lt xsl template match 8 node lt xsl template gt locate message elements gt lt xsl template match message gt lt xsl template gt locate when elements gt lt xsl template match when gt lt xsl template gt suppress the type element
355. his bst e Vest Olive 1E SL Charies 12 TIMEPORT The final deck is shown in Example 10 8 As mentioned earlier this consists of several cards one per movie Example 10 8 Showtimes WML lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE wml PUBLIC WAPFORUM DTD WML 1 1 EN http www wapforum org DTD wml_ 1 1 xml wml template do name common prev label Back type prev gt prev do lt template gt lt card title Movies id movies gt do name common prev type prev gt noop do p lt big gt O Fallon Cine lt big gt lt p gt lt p gt Select a movie lt p gt lt p gt lt a href jonesl gt Raiders Lost Ark lt a gt lt br gt lt a href jones2 gt Temple of Doom lt a gt lt br gt lt a href back2future2 gt Back 2 Future 2 lt a gt lt br gt lt p gt lt p gt lt em gt a href movieguide action theaters amp amp city stl Change theater a em lt p gt lt card gt card title Showtimes id jones1 gt lt p gt lt em gt Raiders of the Lost Ark lt em gt lt p gt p 10 15a 3 30 12 30 5 45 715 10 30 lt p gt card card title Showtimes id jones2 gt lt p gt lt em gt Indiana Jones and The Temple of Doom lt em gt lt p gt lt p gt 1 30 4 00 6 00 lt p gt lt card gt lt card title Showtimes id back2future2 gt lt p gt lt em gt Back to the Future 2 lt em gt lt p gt
356. his sort of error First one of the XSLT stylesheets may have a bug making it forget to pass one of these required parameters If this is the case a developer should theoretically catch this error during development and testing The second possibility is that someone is manually keying in parameters without using the standard XHTML user interface This could be a hacker attacking the site by probing for an application error so we simply deny the request Standalone GUI applications do not have to contend with such issues because the user interface can prevent illegal user input But web applications are essentially wide open for the entire world to see so developers must adopt a highly defensive style of programming If suppressing hack attempts is not a priority the code could simply redirect the user to the home page when an illegal request occurs It might be a good idea to write a log file entry that contains the requesting user s IP address and any other relevant information when errors occur Log entries can be very useful when diagnosing application bugs as well ViewMonthRenderer is shown in Example 7 34 This is another simple class that displays an entire month s worth of messages in a given board Although the XHTML display can be quite complex for this page the JDOM producer and XSLT stylesheet handle the real work keeping the Java code to a minimum Example 7 34 ViewMonthRenderer java package com oreil
357. hough the transformation is fast it does take time to generate the DOM DOM is also memory intensive and may not be the best choice for large documents In most cases the DOM data will be generated dynamically as the result of a database query or some other operation see Chapter 1 Once the DOM is generated simply wrap the Document object ina DOMSource as follows org w3c dom Document domDoc createDomDocument Je Source xmlSource new javax xml transform dom DOMSource domDoc The remainder of the transformation looks identical to the file based transformation shown in Example 5 4 JAXP needs only the alternate input Source object shown here to read from DOM 5 3 5 JAXP SAX I O XSLT is designed to transform well formed XML data into another format typically HTML But wouldn t it be nice if we could also use XSLT stylesheets to transform nonXML data into HTML For example most spreadsheets have the ability to export their data into Comma Separated Values CSV format as shown here Burke Eric M Burke Jennifer L Burke Aidan G One approach is parsing the file into memory using DOM to create an XML representation of the data and then feeding that information into JAXP for transformation This approach works but requires an intermediate programming step to convert the CSV file into a DOM tree A better option is to write a custom SAX parser feeding its output directly into JAXP This avoids the overhead of constructing the DO
358. how to perform basic numeric comparisons presidents president term from amp lt 1800 name Since the less than lt character cannot appear in an XML attribute value the it entity must be substituted In this particular example we use the abbreviated syntax to represent the attribute axis 2 4 5 Abbreviated Syntax Using descendant child parent and other axes is very verbose requiring a lot of typing Fortunately XPath supports an abbreviated syntax for many of these axes that requires a lot less effort The abbreviated syntax has the added advantage in that it looks like you are navigating the file system so it tends to be somewhat more intuitive Table 2 2 compares the abbreviated syntax to the verbose syntax The abbreviated syntax is almost always used and will be used throughout the remainder of this book Table 2 2 Abbreviated syntax Abbreviation Axis Z4 descendant self parent MI attribute child In the last row the abbreviation for the child axis is blank indicating that chila is an implicit part of a location step This means that vicePresident name is equivalent to child vicePresident child name Additional explanations follow e vicePresident selects the vicePresident children of the context node e vicePresident name selects all name children of vicePresident children of the context node e name selects all name descendants of the context node e selects the context node e
359. howtimes 3 city city id Shows all movies for a specific theater in the given city theater theater id 10 3 3 2 XML data To keep things simple for the theater owners this application produces all pages from a single XML datafile on the server The DTD for this file is shown in Example 10 4 Example 10 4 Movie theater DTD lt ELEME movies moviedef city lt ELEMENT moviedef shortName longName gt lt ELEME city name theatert gt lt ELEME name PCDATA gt lt ELEME shortName PCDATA gt lt ELEME longName PCDATA gt lt ELEMENT theater name moviet gt lt ELEMENT movie times gt lt ELEME times PCDATA gt lt ATTLIST city id ID REQUIRED gt lt ATTLIST movie ref IDREF REQUIRED gt lt ATTLIST moviedef id ID REQUIRED gt lt ATTLIST theater id ID REQUIRED gt It is worth pointing out the difference between a lt moviedef gt and lt movie gt element Basically a lt moviedef gt defines a short and long description for a movie in a single place Since the same movie is likely to be listed in many different theaters it makes sense to define the mov edet once and then refer to it from other parts of the document using lt movie gt elements Example 10 5 contains a portion of an example XML datafile that adheres to this DTD This is the data displayed in the upcoming screen shots
360. hreads of discussion Here is another look at a portion of the viewMonth xml file presented earlier in this chapter lt viewMonth month 1 year 2001 gt lt board id 1 gt name Java Programming lt name gt description General programming questions about Java lt description gt board message id 1 day 1 gt lt subject gt First test message lt subject gt lt authorEmail gt burke_e yahoo com lt authorEmail gt lt message id 2 day 2 gt lt subject gt Re First test message lt subject gt lt authorEmail gt aidan nowhere com lt authorEmail gt lt message gt lt message gt lt message id 3 day 4 gt lt subject gt Another test message lt subject gt lt authorEmail gt burke_e yahoo com lt authorEmail gt lt message gt lt viewMonth gt In the XSLT stylesheet the first part of the recursive process selects all lt message gt elements occurring immediately below the lt viewMonth gt element xsl apply templates select viewMonth message gt This selects messages with ids 1 and 3 causing the following template to be instantiated lt xsl template match message gt lt xsl param name indent select 0 gt This template takes a parameter for the level of indentation If the parameter is not specified as in this first usage it defaults to 0 This code is followed by very basic XSLT code to produce a one line summary of the current message and
361. href movieguide action theaters amp amp city city gt Show Theaters lt a gt This is actually the final URL used by the finished application rather than a prototype URL During the prototyping phase the following link is more appropriate lt a href theaters wml gt Show Theaters lt a gt By using URLs to static WML files it is at least possible to navigate from page to page before the servlet is written Figure 10 5 shows how these first two pages look on a cell phone simulator Figure 10 5 Home page output Ejeszem weite PATE Edessztm wapibe PIT ES File View Bookmarks Help Ffe View Bookmarks Help seer eiseeu e fr BGO hag 1 Ormoveguide x p eosDichapt movieguide RIZ IG ERICSSON E ERICSSON E Sarees Piae select your ety E The image to the left shows the splash screen which is replaced by the image on the right after 1 5 seconds On this particular phone the user navigates with the up and down arrows making selections by clicking on the telephone s YES button The next WML page shown in Example 10 7 shows a list of theaters for the current city In this example the list uses a series of hyperlinks This can also be done using a select tag as shown in the previous example However the user can see the entire list when hyperlinks and lt br gt tags are used Of course on smaller displays the user will typically have to scroll down to see all items Example 10 7
362. ht encounter Table 8 2 Common User Agent values User Agent Browser Lynx 2 8rel 3 libwww FM 2 14 Lynx 2 8rel3 Mozilla 4 0 compatible MSIE 4 0 Windows NT TUS Explorer Mozilla 4 0 compatible MSIE 5 5 Windows NT 5 0 DES Explorer Mozilla 4 08 en WinNT U Nav Netscape 4 08 Mozilla 5 0 Windows U Windows NT 5 0 en US m18 Gecko 20001 108 Netscape 6 6 0 Netscape 6 Mozilla 3 0 compatible Opera 3 0 Windows 95 NT4 v3 1 The first browser Lynx is listed because it is the most common text only browser Whenever the User Agent begins with Lynx your web application can select an XSLT stylesheet that omits all graphics from the web page The three most popular browsers are clearly Microsoft Internet Explorer Netscape Navigator and Opera Software s Opera Of these three browsers Navigator was available first and its User Agent always begins with Mozilla In the early days of web development many sites checked for this and only provided fancy versions of their web sites to Netscape browsers When Microsoft Internet Explorer became available it had to begin its User Agent string with Mozilla to maintain compatibility with many existing web sites Therefore you cannot simply check for Mozilla to determine the browser type As you can see in Table 8 2 Microsoft browsers include the text MSIE followed by the version number making them easily identifiable A more recent entry Opera also begins with Mozilla The U
363. ic String getSystemId public void setHandler ContentHandler handler public void setLexicalHandler LexicalHandler handler public void setSystemId String systemId SAXSource This allows output from a SAX parser to be fed into an XSLT processor for transformation It is also used to build Templates or Transformer objects using TransformerFactory public class SAXSource implements Source public static final String FEATURE http javax xml transform sax SAXSource feature public SAXSource XMLReader reader InputSource inputSource public SAXSource InputSource inputSource public SAXSource public InputSource getInputSource public String getSystemId public XMLReader getXMLReader s public void setInputSource InputSource inputSource public void setSystemId String systemId public void setXMLReader XMLReader reader public static InputSource sourceToInputSource Source source SAXTransformerFactory This is a subclass of TransformerFactory that adds SAX specific methods To create an instance of this class create a TransformerFactory instance and downcast if transFact getFeature SAXTransformerFactory FEATURE returns true public abstract class SAXTransformerFactory extends TransformerFactory public static final String FEATURE http javax xml transform sax SAXTransformerFactory feature public static final String FEATURE_XMLFILTER
364. ie lt p gt lt p gt lt xsl apply templates select movie gt lt p gt lt p gt lt em gt lt a href movieguide action theaters gamp city Scity_id gt Change theater lt a gt lt em gt lt p gt lt xsl template gt 1 Ck Ck Ck ck ck ck ck ckockckockockck ck ck ckckckck ck ck ck ckckockockckckckckckckckckckck ckockckockockckckckckckckckckck ck ck KKK KKK ckckckckck ck ck kc kk Show more information about a movie in the main card KCKCkCKCK Ck Kk SK Kk KK CK CK Kk KICK CK CK CK CK CK CK CK CK CK CK SKK Kk SKK KC S KG KKK KKK ck ck kc KK kk lt xsl template match movie gt lt xsl variable name curId select ref gt the hyperlink text is the shortName from the lt moviedef gt a href ScurId gt lt xsl value of select movies moviedef id ScurId shortName gt lt a gt lt br gt lt xsl template gt lt lt CK Ck Ck KKK KKK KKK KKK CC Ck ck Ck Ck KKK KKK KEKE CK Ck Ck Ck Ck Ck KKK KKK KKK KR ck Ck ck ck Ck Ck Ck Ck Ck KKK KKK ko kc ko KKK Create a card for a movie that lists showtimes KCKCKCkCKkCkCkCckckCk ck ck ck ck kckckck ck KKK kc kck kck ck ck ck ck ck ckck kc kckck ck ck k ck ck ck ck ck ck ck k ck kck ck ck ck ck ck ck ck ck kc KKK KK lt xsl template match movie mode createCard gt lt xsl variable name curId select ref gt lt card id ScurId title Showtimes gt lt p gt lt em gt lt xsl value of select movie
365. ilableException Unable to locate XSLT stylesheet this xsltFileName 30 public void doGet HttpServletRequest req HttpServletResponse res throws ServletException IOException try use the ServletContext to locate the XML file ServletContext ctx getServletContext String xmlFileName ctx getRealPath WEB INF xml req getPathInfo verify that the file exists if new File xmlFileName exists res sendError HttpServletResponse SC NOT FOUND xmlFileName else res setContentType text html load the XML file Source xmlSource new StreamSource new BufferedReader new FileReader xmlFileName use a cached version of the XSLT Transformer trans StylesheetCache newTransformer xsltFileName trans transform xmlSource new StreamResult res getWriter catch TransformerConfigurationException tce throw new ServletException tce catch TransformerException te throw new ServletException te This is a fairly basic servlet whose sole purpose is to locate XML files and perform XSLT transformations The init method is used to locate templatePage xsit from the WEB INF xslt directory ServletContext ctx getServletContext ja this xsltFileName ctx getRealPath WEB INF xslt templatePage xslt As discussed in earlier chapters the getRealPath method converts the path into a system specific
366. ill take precedence whenever a when element is encountered Instead of using lt xs1 copy gt this template produces a new lt t imestamp gt element AVTs are then used to specify attributes for this element effectively converting element values into attribute values The AVT syntax hour is equivalent to selecting the lt hour gt child of the lt when gt element You may notice that XSLT processors do not necessarily preserve the order of attributes This is not important because the relative ordering of attributes is meaningless in XML and you cannot force the order of XML attributes The next thing to tackle is the lt message gt element As mentioned earlier we would like to convert the text attribute to an element and the lt t ype gt element to an attribute Just like before add a new template that matches the lt message gt element which will take precedence over the identity transformation Comments in the code explain what happens at each step locate message elements gt lt xsl template match message copy the current out not its attributes xsl copy change the type element to an attribute gt xsl attribute name type gt lt xsl value of select type gt xsl attribute 2 change the text attribute to a child node gt xsl element name g instructions gt lt xsl apply templates gt xsl copy lt xsl template gt T
367. imes will probably rank very high on this list while a method that consumes one second but is only called once will be much further down on the list Example 9 14 Partial JVMPI output rank self accum count trace method 1 13 70 13 70 20 31 java lang ClassLoader defineClass0 2 7 53 21 23 11 19 java util zip ZipFile getEntry 3 5 3 UNE 8 35 java io Win32FileSystem getBooleanAttributes 4 30 828 6 26 java util zip ZipFile read 5 34 25 5 92 java util zip Inflater inflateBytes 6 37 67 5 6 java assLoader findBootstrapClass 7 40 41 4 22 java util zip ZipFile getEntry 8 43 15 4 143 org apache xalan templates StylesheetRootnewTransformer 9 2 74 45 89 4 14 java util zip ZipFile open 10 1 37 47 26 2 4 java net URLClassLoader defineClass The actual file will grow to many megabytes in size depending on how large an application is and how long the profiler runs As expected a difficult task is filtering through a file of this size to find bottlenecks that are actually caused by an application s code rather than by the Java class libraries A majority of the JVMPI output file consists of stack traces A number identifies each trace and the depth command line option affects how many lines are displayed for each stack trace The fifth column of data in Example 9 14 contains the trace number making it possible to search through the file for the actual stack trace TRACE 31 java lang ClassLoader defineClass0 Class
368. impor Cr CU CT T T T 1 Show th A4 com oreilly forum com oreilly forum domain com oreilly forum xml javasio javax servlet javax servlet http org jdom view message pag public class ViewMsgRenderer extends Renderer privat Message message private MessageSummary inResponseTo public ViewMsgRenderer Message message MessageSummary inResponseTo this message message this inResponseTo inResponseTo public void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException convert the data into XML a JDOM Document Document doc new Document ViewMessageJDOM produceElement this message this inResponseTo apply the appropriate stylesheet XSLTRenderHelper render servlet doc viewMsg xslt response The next class Post MsgReqHandler is shown in Example 7 37 In the docet method the mode parameter indicates whether the user is trying to post a new message or reply to an existing message The doGet method is invoked as a result of an HTTP GET request such as the user clicking on a hyperlink or typing in a URL Example 7 37 PostMsgReqHandler java package com oreilly forum servlet import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import java io import javax servlet
369. in Example 6 2 The only caveat is that newer versions of the servlet specification such as Version 2 3 use a different version number in the deployment descriptor Unless you are using 2 3 features however you should stick with 2 2 to remain compatible with as many servlet containers as possible A servlet definition lists the fully qualified package and class name of the servlet class as well a name for that servlet Whenever another section in the deployment descriptor wishes to reference this particular servlet it uses the name specified here et anf n 0 0o 00 5 o0 0 bg KH e r2 0 a Ss N nA H A 1 ar OF ct o As you can see in Example 6 2 the servlet mapping uses this name in order to associate a URL pattern with this particular servlet This pattern will show up in the address that users type into their web browsers when they access this servlet In this case the URL to SplashScreenServlet is http hostname port chap6 splash This is the form that Tomcat defaults to having the following components hostname port Typically Localhost 8080 although Tomcat can be configured to run on any port number chap6 The name of your web application which is deployed in chap6 war for this example splash Part of the URL pattern for the servlet Wildcards in the URL pattern indicate that any text will match Since the deployment descriptor listed splash as the pattern any of the fo
370. in Example A 3 is a generic exception that occurs when something goes wrong with the underlying database This prevents database specific code from creeping into the application making it possible to migrate to other data sources in the future Example A 3 DataException java package com oreilly forum adapter An exception that indicates some operation with the back end data source failed mf public class DataException extends Exception private Throwable rootCause Wrap a DataException around another throwable nf public DataException Throwable rootCause super rootCause getMessage Ws this rootCause rootCause Construct an exception with the specified detail message ud public DataException String message super message return a reference to the root exception or null EPA public Throwable getRootCause return this rootCause DataUtil java shown in Example A 4 is a simple utility method that deals with dates Example A 4 DateUtil java package com oreilly forum domain import java util Misc utility functions for dates Methods are synchronized because the same Calendar instance is shared y public final class DateUtil private static Calendar cal Calendar getInstance he return the day of the month for a given date NF public synchronized static int getDayOfMonth Date date cal setTime date return c
371. inates the intermediate step of JDOM or DOM production because the SAX events are fed directly into JAXP for transformation 5 3 6 Feeding JDOM Output into JAXP The DOM API is tedious to use so many Java programmers opt for JDOM instead The typical usage pattern is to generate XML dynamically using JDOM and then somehow transform that into a web page using XSLT This presents a problem because JAXP does not provide any direct implementation of the avax xml Source interface that integrates with JDOM P There are at least three available options 3 As this is being written members of the JDOM community are writing a JDOM implementation of javax xml Source that will directly integrate with JAXP e Use org jdom output SAXOutputter to pipe SAX 2 events from JDOM to JAXP e Use org jdom output DOMOutputter to convert the JDOM tree to a DOM tree and then use javax xml transform dom DOMSource to read the data into JAXP e Use org jdom output XMLOutputter to serialize the JDOM tree to XML text and then use java xml transform stream StreamSource to parse the XML back into JAXP 5 3 6 1 JDOM to SAX approach The SAX approach is generally preferable to other approaches Its primary advantage is that it does not require an intermediate transformation to convert the JDOM tree into a DOM tree or text This offers the lowest memory utilization and potentially the fastest performance In support of SAX JDOM offers the org jdom output SAXOut
372. ing UTF 16 that does not match the actual encoding of the fie This He wall instead be interpreted according to the Unicode UTF 8 encoding that you have selected as the default in the settings dialog When pou cave the file t wil be saved according to the encoding specilication in the XML daclaration To further complicate matters there are actually two variants of UTF 16 In UTF 16 Little Endian UTF 16LE encoding the low byte of each two byte character precedes the high byte As expected the high byte precedes the low byte in UTF 16 Big Endian UTF 16BE encoding Fortunately XML parsers can determine the encoding of a file by looking for a byte order mark In UTF 16LE the first byte of the file should start with OXFFFE In UTF 16BE files the byte order mark is OXFEFF For the upcoming Chinese example the NJStar Chinese word processor http www njstar com was used to input the Chinese characters This is an example of an editor that has the ability to input ideographs and store files in various encodings The Windows NT version of Notepad can save files in Unicode UTF 16LE format and the Windows 2000 version of Notepad adds support for UTF 8 and UTF 16BE If all else fails encoded text files can be created with Java using the java io OutputStreamWriter class as follows FileOutputStream fos new FileOutputStream myFile xml the OutputStreamWriter specifies the encoding of the file PrintWriter pw new PrintWriter new
373. inimal amount of logic potentially blurring the line between view and controller Figure 4 6 represents a conceptual view of how the XSLT approach maps to MVC Figure 4 6 XSLT conceptual model Servlet Controller XML T XSLT Stylesheets View request response e HTML One weakness common to every approach other than XSLT is the HTML centric viewpoint In every example presented thus far it was assumed that we generated HTML What happens when the requirement to support cellular phones arises It is very likely that these devices will not use HTML Instead they will use WML XHTML Basic or some other technology that has not been invented yet For now consider that you would have to write brand new servlets or JSPs to support these devices when using traditional approaches Any programming logic embedded into JSP pages would be duplicated or would have to be factored out into common helper classes In a pure servlet approach the hardcoded HTML generation logic would have to be completely rewritten XSLT offers an elegant solution simply create a second stylesheet Instead of transforming XML into HTML this new stylesheet transforms XML into WML You can even support different web browsers with the XSLT approach Again just write different stylesheets for browser specific functions Since XSLT stylesheets can import and include functionality from other stylesheets much of the code can be shared and reused across a
374. ink With ordinary XHTML this can only be accomplished using a form or a scripting language 4 Recall from Chapter 2 that XSLT AVTs are written like Svar The stylesheet shown in Example 10 11 is responsible for creating a list of theaters in a city Example 10 11 Movie listing XSLT lt xml version 1 0 encoding UTF 8 gt ales CC KKK KKK KKK KKK KKK KKK KEK CK CK C KKK KKK KKK KKK KKK KEK KKK KKK KKK Ck Ck KKK KKK KKK KKK ck ckock Produces a list of theaters for WML enabled devices ck ck oko kk kk Sk Ck Ck Ck Ck ck ck ck ck ck KKK KKK KKK KKK Ck Ck ck ck ck ck ck ck ck kk 0k Sk S e Mk Mk ke ke ke ko ko ko ko koc ko k xsl stylesheet version 1 0 xmins xsl http www w3 org 1999 XSL Transform gt lt xsl param name city_id select st1 gt xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public WAPFORUM DTD WML 1 1 EN doctype system http www wapforum org DTD wml 1 1 xml lt KKK ck ck KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKK KKKKKKK KKK KKKKKEK The main template creates the deck and the theaters card CK CK CK Ck Ck ck Ck Ckckck ck ckck ck ck ck ck ck ck ckck kc kckckckckckckck ck ck kckckck kckckck Ckokck ck ck k ckck kc kckckck k ck ck ck ck ck ck k KKK k lt xsl template match movies gt lt wml gt lt card id theaters title Theaters gt lt select the appropriate city gt
375. installed in a different directory The best approach is to use a relative pathname such as WEB INF so the stylesheets can be located regardless of where your web application is deployed A relative pathname has to be relative to some starting location so we use the ServletContext class ServletContext has the ability to locate resources relative to the deployed directory of the current web application so you can avoid absolute pathnames in your code The details of mapping the relative pathname to the absolute pathname are taken care of by the servlet container thus making your code more portable In this example chap6 war is deployed to Tomcat s webapps directory Tomcat will expand it into the webapps chap6 directory which contain subdirectories that match the directory structure of the WAR file We start by assigning the current XSLT filename to the curName variable using the following pathname try curName WEB INF xslt editPersonalData xslt Two options are available at this point The ServletContext can provide either an Input Stream or a URL both of which represent the XSLT stylesheet If you use an InputStream however the XSLT processor sees your stylesheet as a stream of bytes It will not know where this datastream originated so it will not automatically know how to resolve URI references This becomes a problem if your stylesheet imports or includes another stylesheet because this other stylesheet will not be located
376. into any servlets The simple way to accomplish this is via initialization parameters These are name value pairs of strings specified in the deployment descriptor and retrieved via the Servlet or ServletContext Servlet initialization parameters are tied to specific servlets and context initialization parameters are tied to an entire web application For the purposes of specifying the XSLT stylesheet location it makes sense to use context parameters These can be specified in the deployment descriptor as follows lt web app gt context param param name xslt directory param name param value C dev xslt param value context param lt servlet gt lt servlet gt lt web app gt And the values of these parameters can be retrieved using the following methods on the javax servlet ServletContext interface public interface ServletContext if the parameter name does not exist return null String getInitParameter String name r Enumeration getInitParameterNames Nes remaining methods omitted So in order to locate the stylesheet one might write the following code in a serviet s init method public class MyServlet extends HttpServlet private String xsltDirectory public void init ServletConfig config throws ServletException super init config this xsltDirectory config getServletContext getInitParameter xslt_directory if this xsltDirectory null throw new Una
377. ion API for XML TrAX More information on TrAX is coming up in the JAXP discussion In a nutshell TrAX provides a uniform API that should work with any XSLT processor Example 5 2 SimpleSaxon java package chap5 import java io import java net MalformedURLException import java net URL import org xml sax SAXException A simple demo of SAXON This code was originally written using SAXON 5 5 1 x public class SimpleSaxon Accept two command line arguments the name of an XML file and the name of an XSLT stylesheet is written to public static vo throws MalformedURLI The result of the transformation stdout id main String args Exception IOException SAXException if args length 2 System err println Usage System err println java SimpleSaxon class getName 9 xnlFileName xsltFileName System exit 1 String xmlFileName args 0 String xsltFileName args 1 String xmlSystemId new File xmlFileName toURL toExternalForm String xslts File xsltFileName t ystemId new oOURL toExternalForm jas com icl saxon trax Processor processor com icl saxon trax Processor newInstance xslt unlike Xa uses its org xml sax new org xml sax new com icl saxo new create a com icl saxo proc create a transformation com icl saxo trans transf lan SAXON uses th
378. ion sending the result tree to the original servlet response The deployment descriptor is listed in Example 8 12 Example 8 12 Filter deployment descriptor lt xml version 1 0 encoding ISO 8859 1 lt DOCTYPE web app PUBLIC Sun Microsystems Inc DTD Web Application 2 3 EN http java sun com j2ee dtds web app 2 3 dtd web app filter filter name xsltFilter filter name lt filter class gt com oreilly javaxslt util StylesheetFilter lt filter class gt init param param name xsltPath param name param value WEB INF xslt templatePage xslt param value init param lt filter gt filter mapping lt filter name gt xsltFilter lt filter name gt lt url pattern gt home xml lt url pattern gt filter mapping filter mapping filter name xsltFilter filter name url pattern company xml url pattern filter mapping filter mapping filter name xsltFilter filter name lt url pattern gt jobs xml lt url pattern gt filter mapping filter mapping filter name xsltFilter filter name lt url pattern gt products xml lt url pattern gt filter mapping lt web app gt As the first few lines of the deployment descriptor indicate filters require Version 2 3 of the web application DTD The filter initialization parameter is specified next inside of the lt fiilter gt element This provides the nam
379. ion pooling in a future implementation When the pool is written it only needs to be added to the DBUt i1 class in a single place When connections and statements are no longer needed they should always be closed in a finally block finally DBUtil close stmt con As mentioned earlier this ensures that they will be closed because finally blocks are executed regardless of whether an exception occurs 7 3 3 JDOM XML Production The discussion forum code presented up to this point can extract data from a relational database and create instances of Java domain classes The next step is to convert the domain objects into XML that can be transformed using XSLT For this task we use the JDOM class library As mentioned in earlier chapters JDOM is available at http www jdom org and is open source software Although the DOM API can also be used JDOM is somewhat easier to work with which results in cleaner code 8 For a DOM example see the LibraryDOMCreator class shown in Example 1 4 The basic pattern relies on various JDOM producer classes each of which knows how to convert one or more domain objects into XML This approach capitalizes on the recursive nature of XML by having each class produce a JDOM Element instance Some of these Element instances represent entire documents while others represent a small fragment of XML These fragments can be recursively embedded into other Element instances to build up more complex
380. ion tce throw new ServletException tce catch TransformerException te throw new ServletException te The critical lines of code are emphasized The first of these checks to see if the session was not obtained using a cookie if req isRequestedSessionIdFromCookie For the very first request the cookie will not be present because the servlet has not had a chance to create it For all subsequent requests the cookie will be missing if the user has disabled cookies in the browser Under either scenario the session identifier is obtained from the HttpSession Instance String sessionID session getId yee The servlet API takes care of generating a random session identifier you are responsible for preserving this identifier by passing it as a parameter to the stylesheet This is done as follows trans setParameter global sessionID i jsessionid sessionID This servlet also takes the liberty of prefixing the session identifier with jessionid This makes the XSLT stylesheet simpler because it does not have to check if the session ID is an empty string or not As implemented here the value of global sessionID can be appended to all URLs a href whatever global sessionID gt click here lt a gt The end result is that if cookies are enabled the URL will be unaffected Otherwise it will be properly encoded to use session tracking A larger XSLT example follows in Example
381. ions By nature the HTTP protocol is connectionless This means that each time users click on a hyperlink or submit an XHTML form the browser establishes a new connection to the web server Once the request is sent and the response is received the connection between browser and server is broken This presents a problem for servlet authors Although the browser and web server do not maintain a persistent connection between page views applications must maintain state information for each user Stateful applications make technologies like shopping carts possible for instance With each request from the browser the servlet must reestablish the identity of the user and locate his session information 8 2 1 Servlet Session Tracking API The traditional servlet approach to session tracking utilizes the javax servlet http HttpSession interface This interface allows a web application to store information about a user that persists across page requests The interface is easy to use mapping attribute names to attribute values The code shown here is part of a servlet that uses HttpSession public void doGet HttpServletRequest req HttpServletResponse res throws ServletException IOException retrieve an instance of HttpSession for this user The true parameter indicates that the object should be created if it does not exist HttpSession session req getSession true retrieve the cart for this user Cart cart Cart
382. ions Code that is highlighted will be discussed in the next several paragraphs Example 3 1 xsl if2 examples lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl output method html Ckckckck ck ck ck ck ck ck kckck ck ck k ck ck ck kckck ck ck k KKK ck ck ck ck k ck ck k ck ck ck ck ck ck ck k ck ck ck ck ck ck k kkk template KCKCkCk ckck ck ck ck kckckckckck ck ck k ck ck kc kckck ck kckck k ck KKK ck ck ck ck k ck ck ck ck ck ck KKK KK kk lt xsl template match gt lt html gt lt body gt hl Conditional Processing Examples lt h1 gt xsl apply templates select presidents gt lt body gt lt html gt lt xsl template gt CkCkckck ck kck ck ck ck KCk ck ck kCk ck ck k ck ck k ck k ck kCk kk ck ck ck k ck k kCk ck ck ck ck ck ck k ck KKK ck ck KK KK presidents template KCKCkCkCckck ck ck ck ck ckckckckckckck ck ck ck kc kckck ck ck kck k ck ck k ck ck k ck ck k ck ck ck KKK KKK KK kk lt xsl template match presidents gt lt h3 gt List of lt xsl value of select count president gt Presidents lt h3 gt lt ul gt lt xsl for each select president gt lt li gt 1 display every other row in bold gt xsl if test position mod 2 0 gt xsl attribute name style gt xsl text font weight bold lt xsl text gt lt xsl attrib
383. irectory employee gt SEES td xsl valu td lt td gt lt xsl choose gt xsl when test category manager gt lt xsl text gt Manager lt xsl text gt lt xsl when gt xsl when test category programmer gt lt xsl text gt Programmer lt xsl text gt lt xsl when gt lt xsl otherwise gt lt xsl text gt Other lt xsl text gt lt xsl otherwise gt lt xsl choose gt lt td gt lt td gt xsl valu td lt tr gt lt xsl for each gt lt table gt lt body gt lt html gt lt xsl template gt lt xsl stylesheet gt of select name gt of select phone gt In this stylesheet all locale specific content is highlighted This is information that must be changed to support a different language As you can see only a small portion of the XSLT is specific to the English language and is embedded directly within the stylesheet logic The entire stylesheet must be rewritten to support another language Fortunately there is an easy solution to this problem XSLT stylesheets can import other stylesheets templates and variables in the importing stylesheet take precedence over conflicting items in the imported stylesheet By isolating locale specific content we can use xs1 import to support multiple languages while reusing all of the stylesheet logic Example 8 18 shows a revised version of our XSLT stylesheet Example 8 18 directory_en xslt lt xml version
384. is not always the root of performance problems XML parsers have a significant impact on performance along with many other factors such as database access time time spent processing business logic and network latency Obsessing over performance can be a dangerous trap to fall into Focusing too heavily on optimization techniques often results in code that is difficult or impossible to understand and maintain From a strictly technical viewpoint the fastest technology sounds great From a business viewpoint time to market and maintainability are often far more important than runtime performance metrics An application that meets performance requirements and is easy to maintain over the years makes better business sense than a highly tuned cryptic application that runs fast but cannot be modified because the original author quit the company and nobody can figure out the code 9 3 1 Stress Testing with JMeter One good way to measure overall application throughput is to simulate how real users use an application Apache s JMeter is designed to perform this task for web applications measuring response time as the number of concurrent users increases JMeter is written in Java and can display response time graphically as shown in Figure 9 8 Figure 9 8 JMeter output lB x bre Help iy Root e Text flan Graph Results TheeedGroup View Rena Graph Rents apn v data 231 f Web Testing ViorkBench e aman It should be not
385. is thrown Figure 9 2 illustrates the problem 2 t is also possible to seal individual packages within a JAR file Refer to the Java 2 Standard Edition documentation for more information Figure 9 2 Sealing violation 1 application loads a o application tries to load SAX 1 class such as a SAX 2 class such as org xml sax SAXException org xml sax ContentHandler sealing violation provided with JAXP 1 0 In this diagram parser jar is listed on the CLASSPATH before crimson jar This is a problem because Java applications search JAR files in the order in which they appear on the CLASSPATH Once the org xml sax SAXException class has been loaded by the JVM any additional classes or interfaces in the ox5 xm1 sax package must be loaded from parser jar because it is sealed When the application requests an instance of ContentHandler the class loader attempts to load the requested class file from crimson jar which triggers the SecurityException shown in Example 9 2 The simple fix to this problem is to remove parser jar from the CLASSPATH which will load all classes in the org xm1 sax package from crimson jar 9 1 1 3 Other exceptions and errors Other various configuration exceptions defined by JAXP are javax xml transform TransformerConfigurationException and avax xml parsers Factory ConfigurationError These may occur when an older version of jaxp jar is still listed on the CLASSPATH Since JAXP 1 0 is not aware of SAX 2 D
386. it http www motorola com e Nokia WAP Toolkit http www nokia com e Openwave Software Development Kit http developer openwave com 10 1 1 Why Not HTML HTML is used by nearly every web site and can theoretically be used by wireless devices as well All that is needed is a web browser a big display lots of processing power and sufficient bandwidth Maybe not 10 1 1 1 Problems with HTML Consider this web page lt boDY gt hl align center gt Welcome to our home page lt h1 lt ul gt lt LI gt first item lt LI gt second item lt Li gt third item Believe it or not Netscape 4 x Netscape 6 and IE 5 5 all display this page perfectly without a single warning or error Browsers are incredibly forgiving of errors in HTML because vendors and end users want these browsers to display all web pages properly Since only a tiny fraction of web sites are written using well formed HTML browsers must be written to silently recover from a wide range of errors A browser that fails to display poorly written HTML is not acceptable in the marketplace because it fails on so many pages Nonprogrammers may view this as a benefit because it allows them to create web sites without too much concern for capitalization quotes or properly nested tags What they do not realize is that browsers are much more complex than they really need to be Writing HTML parsers to handle every conceivable form of poorly written HTML resul
387. ith its two import statements The javax xml parsers package contains the JAXP interfaces and the org w3c dom package contains the standard DOM interfaces and classes import javax xml parsers import org w3c dom The key to this class is its public API which allows a PersonalData object to be converted into a DOM Document object public Document produceDOMDocument PersonalData personalData boolean includeErrors throws ParserConfigurationException The includeErrors parameter indicates whether or not to include the lt requiredFieldsMissing gt element in the result If this method throws a ParserConfigurationException the most likely cause is a CLASSPATH problem This frequently occurs when an older version of JAXP is present When using JAXP it takes a few lines of code to obtain the appropriate implementation of the DocumentBuilder abstract class By using the factory pattern our code is safely insulated from vendor specific DOM implementations use Sun s JAXP to create the DOM Document DocumentBuilderFactory dbf DocumentBuilderFactory newInstance s DocumentBuilder docBuilder dbf newDocumentBuilder Yu Document doc docBuilder newDocument ee Once the doc object has been created we use it to create all remaining elements in the XML data For example the lt page gt element is created first create lt page gt the root of the document Element pageElem doc createElement page doc appendChild p
388. k ck ck ck kk ok ck ko ck ko ck ck ck ko Sk Sk Sk ko ko ko koX Transforms an XML file representing a person into a more concise format CkCkck ckckck ck kck ck ckck ck ck ckck ck kck ck ckck ck ck ckck ck ck ck ck ok ck ck ck ck ck ck ck ck ck kk ck k kc ck k ck k kk kkkk xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl param name includeMiddle select 2 yes xsl output method xml version 1 0 encoding UTF 8 indent yes doctype system condensed dtd gt match an existing lt person gt element lt xsl template match person gt produce a new lt person gt element in a condensed form xsl element name person gt xsl element name name gt xsl value of select firstName xsl text xsl text xsl if test SincludeMiddle yes lt xsl value of select middleName gt xsl text lt xsl text gt fxslsif xsl value of select lastName lt xsl element gt lt 3 element name pirthDate l value of select birthDate month gt l text xsl text l value of select birthDate day gt l text xsl text value of select birthDa lt xsl element gt lt xsl element gt lt xsl template gt lt xsl stylesheet gt NAA AAD X 0 H Q ct e year gt The job of this stylesheet is to transform XML data into a more concise format as shown in Example 9 6 E
389. ke this body bgcolor yellow text green link navy vlink red gt body content lt body gt In this particular example the xs1 attribute set was used only once so its value is minimal It is possible for one stylesheet to include another however as we will see in the next chapter In this way you can define the xs1 attribute set in a fragment of XSLT included in many other stylesheets Changes to the shared fragment are immediately reflected in all of your other stylesheets Chapter 3 XSLT Part 2 Beyond the Basics As you may have guessed this chapter is a continuation of the material presented in the previous chapter The basic syntax of XSLT should make sense by now If not it is probably a good idea to sit down and write a few stylesheets to gain some basic familiarity with the technology What we have seen so far covers the basic mechanics of XSLT but does not take full advantage of the programming capabilities this language has to offer In particular this chapter will show how to write more reusable modular code through features such as named templates parameters and variables The chapter concludes with a real world example that uses XSLT to produce HTML documentation for Ant build files Ant is a Java build tool that uses XML files instead of Makefiles to drive the compilation process Since XML is used XSLT is a natural choice for producing documentation about the build process 3 1 Conditional Proce
390. ko ck k kk lt xsl template match property name mode tableRow gt lt tr gt lt td gt lt xsl value of select name gt lt td gt lt td gt lt xsl choose gt lt xsl when test not value gt xsl text disable output escaping yes gt amp amp nbsp lt xsl text gt xsl when xsl otherwise lt xsl value of select value gt lt xsl otherwise gt xsl choose td tr xsl template e C Ck OK Ck Ck C Ck Ck CC CK Ck KC Ck CC Ck CK C Ck Ck Sk Ck Ck Ck kk kk Sk kk kk Sk KK M Kx M Kk ko ko ko oko ko target template mode tableRow Print a target name and its list of dependencies in a table row KCKCkCkCkCkCk ck ck k ck ck kc kckckckck ck ck ck ck ck k ck ck kc kckck ck ck ck ck k ck ck ck ck ck k ck k kck ck ck ck kck ck k ck ck ck KKK KK D gt lt xsl template match target mode tableRow gt lt tr valign top gt lt td gt lt xsl value of select name gt lt td gt lt td gt lt xsl choose gt xsl when test depends gt xsl call template name parseDepends xsl with param name depends select depends gt xsl call template xsl when xsl otherwise xsl otherwise xsl choose td td xsl if test description gt lt xsl value of select description gt lt xsleit gt lt xsl if test not description gt xsl text xsl text xsl if td tr xsl template
391. l From a deployment perspective you do not need a Java compiler on the web server as you do with JSP e Template engines come with an existing library of tags or simple scripting languages JSP does not provide any standard tags although numerous libraries are available from other vendors and open source projects The JSP API is open so you can create your own custom tags with a fair amount of effort Template engines have their own unique mechanisms for integrating with underlying Java code e JSP has the backing of Sun and is pretty much available out of the box on any servlet container The main benefit of a standard is the wide availability of documentation knowledgeable people and examples There are many implementations of JSP to choose from 4 1 5 The Hybrid Approach Since JSP now has custom tags you can remove hide actually all of the Java code when rendering or generating a page to send to the browser When a complex HTML form is posted to the JSP however you still have problems You must verify that all fields are present verify that the data is within bounds and clean up the data by checking for null values and trimming all strings Validation is not particularly difficult but it can be tedious and requires a lot of custom code You do not want to embed that code directly into a JSP because of the debugging and maintenance issues The solution is a hybrid approach in which a servlet works in conjunction with a JSP
392. l Java business logic As discussed in previous chapters an initial challenge faced with XSLT and servlets is the initial configuration Getting started with a web application is typically harder than client only applications because there are more pieces to assemble With a Swing application for instance you can start with a single class that has amain method But with a web application you must create an XML deployment descriptor in addition to the servlet package everything up into aWAR file and properly deploy to a servlet container When errors occur you see something like HTTP 404 File not found which is not particularly helpful The goal of this chapter is to introduce servlet syntax with particular emphasis on configuration and deployment issues Once servlet syntax has been covered integration with XSLT stylesheets and XML is covered illustrated by the implementation of a basic web application By the time you have worked through this material you should have confidence to move on to the more complicated examples found in the remainder of this book 6 1 Servlet Syntax Servlet architecture was covered in Chapter 4 along with comparisons to many other approaches The architecture of a system is a mile high view ignoring implementation details so you can focus on the big picture We now need to dig into the low level syntax issues to proceed with the really interesting examples in later chapters For a complete discussion of
393. l be discussed in Chapter 3 If you look back at Example 2 1 you will see that each message board has two attributes id and name lt messageBoard id 1 name Java Programming When the stylesheet processor is executed and the result tree generated we end up with the HTML shown in Example 2 3 The HTML is minimal at this point which is exactly what you want Fancy changes to the page layout can be added later the important concept is that programmers can get started right away with the underlying application logic because of the clean separation between data and presentation that XML and XSLT provide Example 2 3 discussionForumHome html html lt head gt lt title gt Discussion Forum Home Page lt title gt lt head gt lt body gt lt hl gt Discussion Forum Home Page lt h1 gt lt h3 gt Please select a message board to view lt h3 gt lt ul gt lt li gt lt a href viewForum id 1 gt Java Programming lt a gt lt li gt lt li gt lt a href viewForum id 2 gt XML Programming lt a gt lt li gt lt li gt lt a href viewForum id 3 gt XSLT Questions lt a gt lt li gt lt ul gt lt body gt lt html gt 2 1 2 Trying It Out To try things out download the examples for this book and locate discussionForumHome xml and discussionForumHome xsit They can be found in the chap1 directory If you would rather type in the examples you can use any text editor or a dedicated XML editor such as
394. l hinder scalability as more and more clients wait for their turn to access the underlying data source 6 5 2 4 Tip 4 Understand the Templates interface Multiple threads can share implementations of javax xml transform Templates Therefore instances can be stored as object fields on a servlet public class MyServlet extends HttpServlet private Templates homePageStylesheet But instances of javax xml transform Transformer are not thread safe they should be declared as local variables within the doGet or doPost method public class MyServlet extends HttpServlet private Templates homePageStylesheet public void init throws UnavailableException create the Templates instance protected void doGet Transformer trans homePageStylesheet newTransformer use this Transformer instance a local variable Chapter 7 Discussion Forum Up until now the examples in this book have been short and to the point The goal of this chapter is to show how a much more sophisticated web application is designed and implemented from the ground up This is the culmination of everything covered so far combining XML servlets XSLT JDBC JAXP and JDOM into a fully functioning web based discussion forum As with the other examples in this book the full source code is available from the companion web site Walking the line between textbook quality and real world examples is difficult First and foremost the goal of thi
395. l variable name global yearNum select viewMonth year gt Sees Ck Ck Ck ck ck ck koc Cck ck kk ko kk Ck kk kk Ck kk Ck kk kk Ck kk ko kk kk ko ko Sk Sk Ck ko Sk Sk Mk Sk Mk ko kx ko ko ko Create the XHTML web page KCKCKCkCkCkCk ck ck kc kck kc kckckckck ck ck ck ck ck k ck ck kc kckck ck ck ck ck k ck ck ck ck ck ck ck ck ck ck ck ck ck ck KKK kk D lt xsl template match gt html xmlns http www w3 0rg 1999 xhtml head title lt xsl value of select Sglobal boardName gt lt title gt lt reference an external CSS file to keep this XSLT stylesheet smaller gt lt link href SrootDir forum css rel stylesheet type text css gt lt head gt lt body gt lt div class boxl hl lt xsl value of select global boardName h1 div div class box2 gt xsl text Messages for xsl text xsl call template name utils printLongMonthName gt xsl with param name monthNumber select global monthNum xsl call template xsl text lt xsl text gt lt xsl value of select Sglobal yearNum gt lt div gt lt Quick Actions gt lt h3 gt Quick Actions lt h3 gt lt ul gt lt li gt lt a href postMsg mode po stNewMsg amp amp boardID global boardID gt Post lt a gt a new message lt li gt lt li gt Return to the a href home gt home page lt a gt lt li gt lt ul gt
396. le 3 7 xsl for each will be used to print all middle names for presidents such as George Herbert Walker Bush Checking for the existence of an attribute is very similar to checking for the existence of an element For example xsl if test someAttribute gt execute this code if someAttribute is present xsl if Unlike most programming languages lt xs1 if gt does not have a corresponding else or otherwise clause This is only a minor inconvenience because the xs1 choose element provides this functionality Bl 2 51 choose requires a lot of typing 3 1 2 lt xsl choose gt lt xsl when gt and lt xsl otherwise gt The XSLT equivalent of Java s switch statement is lt xsl choose gt which is virtually identical in terms of functionality lt xs1 choose gt must contain one or more lt xs1 when gt elements followed by an optional xs1 otherwise element Example 3 2 illustrates how to use this feature This example also uses xs1 variable which will be covered in the next section 2 Java s switch statement only works with char byte short or int Example 3 2 xsl choose lt xsl template match presidents gt lt h3 gt Color Coded by Political Party lt h3 gt lt ul gt lt xsl for each select president gt lt xsl variable name color gt lt define the color value based on political party xsl choose xsl when test party Democratic gt xsl text bl
397. le system or web site 2 4 1 How XSLT Uses XPath XSLT uses XPath in three basic ways e To select and match patterns in the original XML data Using XPath in this manner is the focus of this chapter You see this most often in lt xsl template match pattern gt and xsl apply templates select node set expression ln either case XPath syntax is used to locate various types of nodes e To support conditional processing We will see the exact syntax of lt xs1 if gt and xsl choose in the next chapter both of which rely on XPath s ability to represent boolean values of t rue and false e To generate text A number of string formatting instructions are provided giving you the ability to concatenate strings manipulate substrings and convert from other data types to strings Again this will be covered in the next chapter 2 4 2 Axes Whenever XSLT uses XPath something in the XML data is considered to be the current context node XPath defines seven different types of nodes each representing a different part of the XML data These are the document root elements text attributes processing instructions comments and nodes representing namespaces An axis represents a relationship to the current context node which may be any one of the preceding seven items A few examples should clear things up One axis is chi id representing all immediate children of the context node From our earlier schedule xml example the child axi
398. lem addContent inRespToElem messageElem addContent new Element subject SetText message getSubject yJ messageElem addContent new Element authorEmail setText message getAuthorEmail yg messageElem addContent new Element text SetText message getText s return messageElem private ViewMessageJDOM The JDOM producer shown in Example 7 23 is also quite simple Its job is to create XML for a BoardSummary object This class is unique because it is not designed to create an entire XML document Instead the elements produced by BoardSummaryJDOM are embedded into other XML pages in the application For example the home page shows a list of all lt board gt elements found in the system each of which is generated by BoardSummaryJDOM As you design your own systems you will certainly find common fragments of XML that are reused by several pages When this occurs write a common helper class rather than duplicate code Example 7 23 BoardSummaryJDOM java package com oreilly forum xml import com oreilly forum domain import java util import org jdom Produces JDOM for a BoardSummary object ud public class BoardSummaryJDOM public static Element produceNameIDElement BoardSummary board produce the following board id 123 gt lt name gt the board name lt name gt description board descriptio
399. licationMonth pubDate addAttribute yy Integer toString book getPublicationYear bookElem addContent pubDate bookElem addContent new Element title setText book getTitle bookElem addContent new Element author setText book getAuthor return bookElem public static void main String args throws IOException Library lib new Library LibraryJDOMCreator ljc new LibraryJDOMCreator Document doc ljc createDocument lib Write the XML to System out indent two spaces include newlines after each element new XMLOutputter true UTF 8 output doc System out The JDOM example is structured just like the DOM example beginning with a method that converts a Library object into a JDOM Document public Document createDocument Library library The most striking difference in this particular method is the way in which the Document and its Elements are created In JDOM you simply create Java objects to represent items in your XML data This contrasts with the DOM approach which relies on interfaces and factory methods Creating the Document is also easy in JDOM Element root new Element library JDOM supports the lt DOCTYPE gt DocType dt new DocType library library dtd Document doc new Document root dt As this comment indicates JDOM allows you to refer to a DTD while DOM does not
400. lize space substring before depends gt xsl when xsl otherwise xsl value of select normalize space depends xsl otherwise xsl choose xsl variable 1 define a variable that contains everything after the first comma gt lt xsl variable name remainingTokens select normalize space substring after depends xsl text xsl text lt xsl value of select firstToken gt xsl choose xsl when test remainingTokens xsl call template name fixDependency gt xsl with param name depends select SremainingTokens gt xsl call template xsl when xsl otherwise lt xsl text gt lt xsl text gt xsl otherwise xsl choose lt xsl template gt lt xsl stylesheet gt 3 6 3 1 Specifying XHTML output One of the first things this stylesheet does is set the output method to mi because the resulting page will be XHTML instead of HTML The doct ype public and doctype system are required for valid XHTML and indicate the strict DTD in this case xsl output method xml doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtml11 DTD xhtmll strict dtd indent yes encoding UTF 8 gt The remaining XHTML requirement is to declare the namespace of the lt html gt element lt xsl template match gt lt html xmlns http www w3 0rg 1999 xhtml lt html gt lt xsl template gt Because
401. lled get Det ailReport which is used to produce a text report of a TransformerException object This method is worth studying because it shows which methods are available when dealing with transformation problems As the code in Example 9 9 shows many of the fields may be nu11 Some XSLT processors may provide a lot of detailed error reporting while others may simply leave these fields nuil 9 2 3 A Custom XSLT Transformer GUI In this section an XSLT transformer GUI is developed This is a simple Swing application that allows an XML file to be transformed using an XSLT stylesheet The results of the transformation are then shown in a text area along with a JTable that shows all errors using the ErrorListenerModel class shown in Example 9 9 XML validation of the transformation result is also provided Given that the stylesheet produces XML this tool will attempt to parse and validate the result tree This is a great way to make sure that your XSLT is producing valid XHTML for example because the result can be validated against one of the XHTML DTDs as soon as each transformation is performed The Ant build file shown earlier in Example 9 3 contains a run target that can be used to execute this application by typing ant run 9 2 3 1 Screen shots The first window to appear is shown in Figure 9 5 This window is always displayed and allows the user to select the XML and XSLT input files 7 These screen shots show the Macintosh
402. llow data such as a social security number to be passed into the template Example 3 3 contains a complete stylesheet that demonstrates how to pass the ssn parameter into a named template Example 3 3 namedTemplate xslt lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html lt xsl template match gt lt html gt lt body gt lt h3 gt Team Members lt h3 gt lt ul gt lt xsl for each select team manager team programmer gt lt xsl sort select name gt lt li gt lt xsl value of select name gt lt xsl text gt ssn lt xsl text gt xsl call template name formatSSN gt xsl with param name ssn select ssn gt xsl call template lt li gt lt xsl for each gt lt ul gt lt body gt lt html gt lt xsl template gt lt a named template that formats a 9 digit SSN by inserting characters gt lt xsl template name formatSSN gt lt xsl param name ssn gt lt xsl value of select substring ssn 1 3 xsl text xsl text lt xsl value of select substring S ssn 4 2 xsl text xsl text lt xsl value of select substring ssn 6 xsl template xsl stylesheet This stylesheet displays the managers and programmers in a list sorted by name The xsl for each element selects the union of tcam manager and team programmer so
403. llowing URLs also invoke SplashScreenServlet e http localhost 8080 chap6 splash e http localhost 8080 chap6 splash whatever html e http localhost 8080 chap6 splash a b c 6 2 3 Deploying SplashScreenServlet to Tomcat The simple steps for getting SolashScreenServlet up and running are to compile the code create the deployment descriptor listed in Example 6 2 and create the WAR file using the jar utility The WAR file contents for this servlet are shown in Figure 6 3 Figure 6 3 SplashScreenServlet WAR file w chap6 war F index html WEB INF xinl e classes EJ chap6 SplashScreenServlet class Once you have created chap6 war be sure to execute jar tvf chap6 war to confirm that the contents are structured properly The final step is to simply copy the entire JAR file to Tomcat s webapps directory If a WAR file is copied into the webapps directory while 4 Tomcatis running it will not be recognized Simply restart Tomcat to begin using the web application Once the WAR file has been copied you can execute startup bat or startup sh in Tomcat s bin directory and then enter http localhost 8080 chap6 splash into your favorite web browser If you see error messages check to see that the JAVA HOME and TOMCAT HOME environment variables are properly set You can also look in Tomcat s webapps directory to see if the WAR file is properly expanded When a web application is first invoked Tomcat expands the WAR file in
404. llowing form http hostname port forum main home In this URL forum represents the web application and is the name of the WAR file The next part of the URL main is a mapping to ForumServlet Since the WAR file and servlet will not change this part of the URL remains constant The remaining data nome is path information This is the portion of the URL that ReqgHandierRegistry uses to locate instances of RegHandler If the path information is nu11 or does not map to any request handlers the default request handler is returned This simply returns the user to the home page The first real request handler HomeReqHandler is shown in Example 7 31 This class is quite simple and merely returns an instance of HomeRenderer The code is simple because the home page does not have any modes of operation other than to display all message boards Other request handlers are more complex because they must process HttpServietRequest parameters Example 7 31 HomeReqHandler java package com oreilly forum servlet import java io import javax servlet import javax servlet http This is the default request handler in the app The first inbound request generally goes to an instance of this class which returns the home page renderer public class HomeReqHandler extends ReqHandler protected String getPathInfo return home protected Renderer doGet HttpServlet servlet HttpServlet Request r
405. lly forum domain import com oreilly forum xml import java io import java util import javax servlet import javax servlet http mport org jdom Show the web page that allows a user to post or reply to a message E public class PostMsgRenderer extends Renderer private MessageSummary inResponseToMsg private BoardSummary board private String msgSubject private String authorEmail private String msgText private boolean showError This constructor indicates that the user is replying to an existing message public PostMsgRenderer Message inResponseToMsg this board inResponseToMsg getBoard n this inResponseToMsg inResponseToMsg this showError false this msgSubject Re inResponseToMsg getSubject this authorEmail StringTokenizer st new StringTokenizer inResponseToMsg getText n StringBuffer buf new StringBuffer buf append n append n gt Original Message s append n Posted by append inResponseToMsg getAuthorEmail append on append inResponseToMsg getCreateDate toString buf append n while st hasMoreTokens String curLine st nextToken buf append gt buf append curLine buf append n o amp Fh Fh Fh Fh Fh buf append this msgText buf toString This constructor indicates that the user is posting
406. look at a more detailed design diagram The conceptual model is straightforward but quite a few classes and interfaces come into play Figure 5 5 shows the pieces necessary for SAX based transformations Figure 5 5 SAX and XSLT transformations lt lt interface gt gt org xmi sax XMLReader The SAX event listener interface abstract abstract lt lt inte com oreilly javaxslt util org xml sax javax xml transform AbstractXML Reader ContentHandler TransformerFactory setContentHandler ContentHandler lt lt interface gt gt lt lt abstract gt gt javax_xmil transform sax lt lt create gt gt javax xml transform sax TransformHandler e SAXTransformFactory com oreilly javaxslt util CSVXMLReader parse InputSource setResult Result new TransformerHandier Source TransformerHandler This class parses CSV files and emits SAX events The InputSource provides the location of the CSV file einterface interface javax xml transform javax xml transform Transform Result This diagram certainly appears to be more complex than previous approaches but is similar in many ways In previous approaches we used the TransformerFactory to create instances of Transformer in the SAX approach we start with a subclass of TransformerFactory Before any work can be done you must verify that your particular implementation supports SAX based transformations The reference i
407. loyment issues can make it difficult to debug and test your applications The best advice is to start small writing a very basic application that proves your environment is configured correctly before moving on to more sophisticated examples Apache s Tomcat is probably the best servlet container for beginners because it is free easy to configure and is the official reference implementation for Sun s servlet API A servlet container is the server that runs servlets Chapter 6 covers the essentials of the servlet API but for all the details you will want to pick up a copy of Java Servlet Programming by Jason Hunter O Reilly You definitely want to get the second edition because it covers the dramatic changes that were introduced in Version 2 2 of the servlet API 1 4 1 Java XSLT Processor Choices Although this book uses primarily Sun s JAXP and Apache s Xalan many other XSLT processors are available Processors based on other languages may offer much higher performance when invoked from the command line primarily because they do not incur the overhead of a Java Virtual Machine JVM at application startup time When using XSLT from a servlet however the JVM is already running so startup time is no longer an issue Pure Java processors are great for servlets because of the ease with which they can be embedded into the web application Simply adding a JAR file to the CLASSPATH is generally all that must be done Putting an up to date list of XSL
408. lt tr gt lt td gt lt xsl choose gt xsl when test name firstName gt First Name lt xsl when gt xsl when test name lastName gt Last Name xsl when xsl when test name 2 daytimePhone Daytime Phone lt xsl when gt xsl when test name eveningPhone gt Evening Phone xsl when xsl when test name email gt Email xsl when xsl choose td td b xsl value of select gt lt b gt td SES lt xsl template gt xsl stylesheet 6 3 3 Source Code The first piece of source code to examine is shown in Example 6 6 The PersonalData class is simply a data holder and does not contain any XML code or database code By keeping classes like this simple you can easily write standalone unit tests that verify if your code is written properly If this code were written as part of the servlet instead of a standalone class it would be very difficult to test outside of the web browser environment Example 6 6 PersonalData java package chap A helper class that stores personal information XML generation is intentionally left out of this class This class ensures that its data cannot be null nor can it contain extra whitespace xf public class PersonalData private String firstName private String lastName private String daytimePhone private String eveningPhone private String email public PersonalData this m
409. lt xsl template match type gt lt xsl stylesheet gt 3 5 4 The Result File Now that the stylesheet is complete it can be applied to all of the existing XML log files using a simple shell script or batch file The resulting XML file is shown in Example 3 12 Example 3 12 Result of the transformation lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href schemaChange xslt gt log message type ERROR gt text input parameter was null lt text gt timestamp time 03 12 18 day 15 month 01 year 2000 lt where gt lt class gt com foobar util StringUtil lt class gt lt method gt reverse String lt method gt lt where gt lt message gt lt message type WARNING gt lt text gt cannot read config file lt text gt timestamp time 06 35 44 day 15 month 01 year 2000 gt lt where gt class com foobar servlet MainServlet class lt method gt init method lt where gt lt message gt message type ERROR gt lt text gt negative duration is not allowed lt text gt timestamp time 10 01 49 day 17 month 01 year 2000 gt lt where gt lt class gt com foobar util DateUtil lt class gt lt method gt getWeek int lt method gt lt where gt lt message gt lt log gt 3 6 Ant Documentation Stylesheet Apache s Ant has taken the Java development community by storm supplementing traditional Java IDEs a
410. lue of select 1lang tableCaption table border 1 gt lt tr gt th xsl value of select lang englishHeading gt lt th gt lt th gt lt xsl value of select language gt lt th gt lt tr gt xsl apply templates select number gt lt table gt lt xsl template gt lt xsl template match number gt lt tr gt lt td gt lt xsl value of select english gt lt td gt lt td gt lt xsl value of select gt lt td gt lt tr gt lt xsl template gt lt xsl stylesheet gt As you can see the default output encoding of this stylesheet is UTF 8 This can and will be overridden by the servlet however The Spanish stylesheet numbers spanish xslt is shown in Example 8 22 Example 8 22 numbers_spanish xslt lt xml version 1 0 encoding UTF 8 gt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform gt lt xsl import href numbers_english xslt gt lt xsl variable name lang pageTitle gt XSLT en Espafiol xsl variable lt xsl variable name lang tableCaption gt Aqu esta un vector de n meros xsl variable lt xsl variable name lang englishHeading Ingl s xsl variable xsl stylesheet The Chinese stylesheet numbers chinese xslt is not listed here because it is structured exactly like the Spanish stylesheet In both cases numbers english xslt is imported and the three variables are overridden with language spe
411. lumnName int column return this exceptionList null Transformation Problems COLUMN NAMES column return true if any errors occurred public boolean hasErrors return this exceptionList null This is part of the javax xml transform ErrorListener interface Indicates that a warning occurred Transformers are required to continue processing after warnings unless the application throws TransformerException public void warning TransformerException te throws TransformerException report te This is part of the javax xml transform ErrorListener interface Indicates that a recoverable error occurred public void error TransformerException te throws TransformerException report te This is part of the javax xml transform ErrorListener interface Indicates that a non recoverable error occurred public void fatalError TransformerException te throws TransformerException report te adds the exception to exceptionList and notifies the JTable that the content of the table has changed private void report TransformerException te if this exceptionList null nis exceptionList new ArrayList T CT nis exceptionList add te fireTableStructureChanged else nis exceptionList add te H q nt row this exceptionList size 1 super fireTableRowsInserted row row Code related to th
412. ly forum servlet import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import com oreilly forum xml import java io import javax servlet import javax servlet http import org jdom Renders a page that shows all messages in a given month y public class ViewMonthRenderer extends Renderer private BoardSummary board private MonthYear month public ViewMonthRenderer BoardSummary board MonthYear month this board board this month month public void render HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException try convert the data into XML a JDOM Document Document doc new Document ViewMonthJDOM produceElement this board this month apply the appropriate stylesheet XSLTRenderHelper render servlet doc viewMonth xslt response catch DataException de throw new ServletException de ViewMsgRegHandler shown in Example 7 35 requires a parameter named msg ID As before if this parameter is invalid an error page is displayed to the user Otherwise an instance of ViewMsgRenderer is returned to the servlet Example 7 35 ViewMsgReqHandler java package com oreilly forum servlet import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import java io import javax se
413. ly specify both the XML document and the XSLT document as parameters to the processor Because of this capability the processing instruction shown does not force that particular stylesheet to be used From a development perspective including this line quickly displays your work because you simply load the XML document into a compatible web browser and the stylesheet is loaded automatically In this book the xml stylesheet processing instruction uses t ype text xs1 However some processors use type text xml which does not work with Microsoft Internet Explorer The XSLT specification contains one example which uses text xml Figure 2 3 shows the XHTML output from an XSLT transformation of schedule xml As you can see the stylesheet is capable of producing content that does not appear in the original XML data such as Subject It can also selectively copy element content and attribute values from the XML source to the result tree nothing requires every piece of data to be copied Figure 2 3 XHTML output File Edit Wew Favortes Tools Help LJ Eric Burke s Schedule Appointment 03 15 2001 from 09 30 until 10 30 Subject Intermew potenhal new hire Location Rm 103 Note Ask Bob for an updated resume Appointment 03 15 2001 from 15 30 until 16 30 Subject Dr Appointment Location 1532 Mam Street Note amp Done L My Computer The XSLT stylesheet that produces this output is shown in Example 2 6 As me
414. ly that tools will begin offering native support for JDOM making extra conversions unnecessary The details of all these techniques are covered in Chapter 5 1 3 Beyond Dynamic Web Pages You probably know a little bit about servlets already Essentially they are Java classes that run on the web tier offering a high performance portable alternative to CGI scripts Java servlets are great for extracting data from a database and then generating XHTML for the browser They are also good for validating HTTP POST or GET requests from browsers allowing people to fill out job applications or order books online But more powerful techniques are required when you create web applications instead of simple web sites 1 3 1 Web Development Challenges When compared to GUI applications based on Swing or AWT developing for the Web can be much more difficult Most of the difficulties you will encounter can be traced to one of the following e Hypertext Transfer Protocol HTTP e HTML limitations e browser compatibility problems e concurrency issues HTTP is a fairly simple protocol that enables a client to communicate with a server Web browsers almost always use HTTP to communicate with web servers although they may use other protocols such as HTTPS for secure connections or even FTP for file downloads HTTP is a request response protocol and the browser must initiate the request Each time you click ona hyperlink your browser issues a new request t
415. m String systemId public StreamSource Reader reader public StreamSource Reader reader String systemId public StreamSource String systemId public StreamSource File f public StreamSource public InputStream getInputStream public String getPublicId public Reader getReader public String getSystemId public void setInputStream InputStream inputStream public void setPublicId String systemId public void setReader Reader reader public void setSystemId File f public void setSystemId String systemId Appendix C XSLT Quick Reference This appendix provides a quick reference to the XSLT markup language Each element is listed in alphabetical order along with a reference to the appropriate section in Version 1 0 of the XSLT specification available at http www w3 org TR xslt Attributes are shown along with their allowable values and square brackets indicate optional attributes Values enclosed in curly braces are treated as attribute value templates and quoted values are literals XML style comments indicate which elements allow content and the allowable type of that content xsl apply imports xsl apply imports See XSLT specification section 5 6 Overriding Template Rules http www w3 org TR xslt apply imports xsl apply templates xsl apply templates select node set expression mode qname
416. m domain import org jdom Produce JDOM for the Post Message page kf public class PostMessageJDOM public static Element produceElement BoardSummary board MessageSummary inResponseToMsg boolean showError String subject String authorEmail String msgText Element messageElem new Element postMsg reuse the BoardSummaryJDOM class to produce a fragment of the XML messageElem addContent BoardSummaryJDOM produceNameIDElement board if inResponseToMsg null Element inRespTo new Element inResponseTo addAttribute id Long toString inResponseToMsg getID inRespTo addContent new Element subject setText inResponseToMsg getSubject messageElem addContent inRespTo if showError messageElem addContent new Element error addAttribute code ALL FIELDS REQUIRED Element prefill new Element prefill prefill addContent new Element subject setText subject prefill addContent new Element authorEmail SetText authorEmail prefill addContent new Element message setText msgText messageElem addContent prefill return messageElem private PostMessageJDOM 7 4 Serviet Implementation We are almost finished The remaining piece of the puzzle is to coordinate activity between the web brows
417. mSource new File xmlFileName Source xsltSource new StreamSource new File xsltFileName TransformerFactory transFact TransformerFactory newlInstance Transformer trans transFact newTransformer xsltSource trans setOutputProperty OutputKeys ENCODING charEnc note res getWriter will use the encoding type that was specified earlier in the call to res setContentType trans transform xmlSource new StreamResult res getWriter catch TransformerConfigurationException tce throw new ServletException tce catch TransformerException te throw new ServletException te After getting the three request parameters for XML XSLT and encoding the servlet converts the XML and XSLT names to actual filenames String xmlFileName ctx getRealPath WEB INF xml numbers_ xmlLang xml String xsltFileName ctx getRealPath WEB INF xslt numbers xsltLang xslt Because the XML files and XSLT stylesheets are named consistently it is easy to determine the filenames The next step is to set the content type of the response do this BEFORE calling HttpServletResponse getWriter res setContentType text html charset charEnc This is a critical step that instructs the servlet container to send the response to the client using the specified encoding type This gets inserted into the Content Type HTTP response header allowin
418. ma Colby produced the cover layout with QuarkTM XPress 4 1 using Adobe s ITC Garamond font David Futato designed the interior layout based on a series design by Nancy Priest Neil Walls converted the files from Microsoft Word to FrameMaker 5 5 6 using tools created by Mike Sierra The heading font is Bitstream Bodoni the text font is ITC New Baskerville and the code font is Constant Willison The illustrations that appear in the book were produced by Robert Romano and Jessamyn Read using Macromedia FreeHand 9 and Adobe Photoshop 6 This colophon was written by Leanne Soylemez
419. ment gt lt appointment gt lt when gt lt date month 03 day 15 year 2001 gt lt startTime hour 15 minute 30 gt lt endTime hour 16 minute 30 gt lt when gt lt subject gt Dr Appointment lt subject gt lt location gt 1532 Main Street lt location gt lt appointment gt lt appointment gt lt when gt lt date month 03 day 16 year 2001 gt lt startTime hour 11 minute 30 gt lt endTime hour 12 minute 30 gt lt when gt lt subject gt Lunch w Boss lt subject gt lt location gt Pizza Place on First Capitol Drive lt location gt lt appointment gt lt schedule gt As you can see the XML document uses both attributes month 03 and child elements to represent its data XSLT has the ability to search for and transform both types of data as well as comments processing instructions and text In our current document the appointments are stored in chronological order Later we will see how to change the sort order using lt xsl sort gt Unlike the earlier example the second line of Example 2 5 contains a reference to the XSLT stylesheet lt xml stylesheet type text xsl href schedule xslt gt This processing instruction is entirely optional When viewing the XML document in a web browser that supports XSLT this is the stylesheet that is used If you apply the stylesheet from the command line or from a server side process however you normal
420. met a gt tag in every XHTML page that is published meta name navigationCategory content home gt This tag allows the top navigation area to visually highlight the category that the current page belongs to The XSLT stylesheet selects this tag and generates the appropriate XHTML for the navigation area As shown in Figure 8 2 the sample stylesheet uses hyperlinks for each of the navigation categories This same approach also works for fancy graphical navigation areas H1 You can extend this technique by adding a second lt met a gt tag for subcategories Since a single stylesheet controls page layout changes to this stylesheet are visible across the entire web site The code for the home page is listed in Example 8 1 The required elements are emphasized Example 8 1 home xml lt xml version 1 0 encoding UTF 8 html head lt title gt Home Page lt title gt lt meta name navigationCategory content home gt lt head gt lt body gt lt hl gt Welcome to the Home Page lt h1 gt lt div gt This is a normal XHTML page that authors create The guidelines are as follows ul lt li gt Each page must be valid XHTML li lt li gt Each page must have a meta tag that indicates the navigation category lt li gt li The templatePage xslt stylesheet will add the top and side navigation bars li ul Pages are published to the WEB INF xml directory of a web app This forces clients to access p
421. method as synchronized In this approach your doGet method would be declared as follows protected syn oid d request et HttpServletRec TO eption throws i The synchronized keyword will require that any thread wishing to invoke this method first obtain a lock on the servlet object Once the first client obtains the lock and begins to execute the method all others must wait their turn If the doGet method takes 0 5 seconds to execute then a load of a mere 100 users will result in nearly a minute long wait for many visitors to your site since each waits in a queue for access to the lock This is almost never a viable option so another choice is to declare that your servlet implements the javax servlet SingleThreadModei interface as follows public class MyServlet extends HttpServlet implements SingleThreadModel The SingleThreadMode1 interface is a marker interface meaning that it does not declare any methods It merely indicates to the servlet container that your servlet is not thread safe and can handle only one request at a time in its service method A typical servlet container will maintain a pool of serviet instances in this case allowing each instance to handle a single request at a time This is somewhat better than merely synchronizing the doGet or doPost method However it does mean that multiple copies of the servlet will be instantiated This results in higher memory ov
422. mine which mode of operation the user was in For this task the servlet looks for a request parameter called mode Legal values for this parameter are replyToMsg and postNewMsg Since the user is submitting an XHTML form the easiest way to pass this data is via a hidden form field named mode Here is the code that does the work choose stMsg inResponseTo N den name origMsgID ostMsg inResponseTo id gt l when test lt input i ridden name mode value replyToMsg gt all lt input type hidden name mode value postNewMsg gt lt xsl otherwise gt lt xsl choose gt The stylesheet also inserts a hidden form field that contains the original message ID whenever the mode is replyToMsg On the servlet side the code looks something like this public void doGet HttpServletRequest request HttpServletResponse response String mode request getPar if replyToMsg equals String origMsgID est getParameter origMsgID 7 3 Making the XML Dynamic At this point in the process we have specified what each web page looks like the XML data for each page and the XSLT stylesheets to perform the necessary transformations The next step is to figure out where the XML actually comes from During the design and prototyping process all XML data is created as a collection of static text files This makes development of the XSLT stylesheets much easier because the stylesheet authors
423. mits which files are included in the build The last target in this build file performs an XSLT transformation using Ant s lt style gt task which is described next 9 1 2 3 Transforming using Ant s style task Of particular interest to XSLT developers is Ant s lt style gt task This is a core task that performs one or more XSLT transformations Ant s JAXP JAR files must be updated as described earlier for this task to work Here is a simple example of this task style basedir destdir style sample xslt processor trax in company xml out report txt gt This will look in the project s base directory for the specified XML and XSLT files placing the output into report txt The processor is trax which means the same thing as JAXP 1 1 Ant will use the first JAXP compliant processor found on the CLASSPATH Table 9 2 lists the complete set of attributes for the style task Table 9 2 Ant style attributes Attribute Description Required basedir The directory where XML files are located yes destdir The directory where the result tree should be placed yes CERE The default filename extension for the result of the extension no transformation s style The XSLT stylesheet filename yes Specifies which XSLT processor is used Legal values are trax for a TrAX compliant processor xslp for the XSL P processor and xalan for Xalan Version 1 x May also contain the name of pnus a class that implements n
424. mmon API to XML parsers and XSLT processors A Java replacement for make Ant build files provide a consistent way for every member of the development team to compile and test code An integrated development environment such as Borland s JBuilder An open source unit testing framework Some individual tools are much more powerful when used in the context of an overall development environment JUnit is much more effective when used in combination with Ant because Ant ensures that every developer on the team is compiling and testing with the same settings This means that unit tests executed by one developer should work the same way for everyone else Without Ant unit tests that succeed for one developer may fail for others since they may be using different versions of some tools 9 1 1 CLASSPATH Issues The migration from first generation XML parsers and XSLT processors has been a somewhat painful experience for Java developers Although the newer APIs are great older JAR files linger throughout many applications and directories causing more than their fair share of configuration difficulties This section describes some of the most common problems and offers advice for configuring several popular tools 9 1 1 1 JAR hell A common complaint against Microsoft Windows systems is known as DLL Hell This refers to problems that occur when two applications require different versions of the same DLL file Installing a new application may
425. mpatibility issues for several years the role of Java with respect to XSLT will continue to be important One use will be to detect the browser using a Java servlet and then deliver the appropriate stylesheet to the client only if a compliant browser is in use Otherwise the servlet will drive the transformation process by invoking the XSLT processor on the web server Once we finish with XSLT syntax in the next two chapters the role of Java and XSLT will be covered throughout the remainder of this book Chapter 2 XSLT Part 1 The Basics Extensible Stylesheet Language XSL is a specification from the World Wide Web Consortium W3C and is broken down into two complementary technologies XSL Formatting Objects and XSL Transformations XSLT XSL Formatting Objects a language for defining formatting such as fonts and page layout is not covered in this book XSLT on the other hand was primarily designed to transform a well formed XML document into XSL Formatting Objects Even though XSLT was designed to support XSL Formatting Objects it has emerged as the preferred technology for all sorts of transformations Transformation from XML to HTML is the most common but XSLT can also be used to transform well formed XML into just about any text file format This will give XML and XSLT based web sites a major leg up as wireless devices become more prevalent because XSLT can also be used to transform XML into Wireless Markup Language or some other s
426. mplementation of JAXP does support this although other implementations are not required to do so In the following code fragment the sec Feature method of TransformerFactory will return true if you can safely downcast to a SAXTransformerFactory instance TransformerFactory transFact TransformerFactory newInstance ys if transFact getFeature SAXTransformerFactory FEATURE downcast is allowed SAXTransformerFactory saxTransFact SAXTransformerFactory transFact If gec Feature returns false your only option is to look for an implementation that does support SAX based transformations Otherwise you can proceed to create an instance of TransformerHandler IransformerHandler transHand saxTransFact newTransformerHandler myXsltSource This object now represents your XSLT stylesheet As Figure 5 5 shows TransformerHandler extends org xml sax ContentHandler SO it knows how to listen to events from a SAX parser The series of SAX events will provide the fake XML data so the only remaining piece of the puzzle is to set the Result and tell the SAX parser to begin parsing The TransformerHandler also provides a reference to a Transformer which allows you to set output properties such as the character encoding whether to indent the output or any other attributes of lt xsl output gt 5 3 5 3 Writing the custom parser Writing the actual SAX parser sounds harder than it really is The process basically involve
427. mplished by reverting to vendor specific code The workhorse of this class is the createDocument method which takes a Library asa parameter and returns an org w3c dom Document object This method could throw a ParserConfigurat ionExcept ion Which indicates that Sun s Java API for XML Parsing JAXP could not locate an XML parser public Document createDocument Library library throws javax xml parsers ParserConfigurationException n The Library Class simply stores data representing a personal library of books In a real application the Library class might also be responsible for connecting to a back end data source This arrangement provides a clear separation between XML generation code and the underlying database The sole purpose of LibraryDOMCreator is to crank out DOM trees making it easy for one programmer to work on this class while another focuses on the implementation of Library Book and Publisher The next step is to begin constructing a DOM Document object javax xml parsers DocumentBuilderFactory dbf javax xml parsers DocumentBuilderFactory newInstance Js javax xml parsers DocumentBuilder docBuilder dbf newDocumentBuilder Ys Document doc docBuilder newDocument This code relies on JAXP because the standard DOM API does not provide any support for creating a new Document object in a standard way Different parsers have their own proprietary way of doing this which brings us to the whole point o
428. n User ees bd getUserAgentString pw println Supports CSS bd isCssOK pw println JavaScript bd isJavascriptOK yey pw println Browser Name bd getBrowserName pw printin Platform 07 bd getBrowserPlatform pw println Version bd getBrowserVersion 8 4 Servlet Filters Version 2 3 of the Java servlet specification adds a new feature called filters A filter is an object that intercepts requests to a servlet JSP or static file in a web application The filter has the opportunity to modify the request before passing it along to the underlying resource and can capture and modify the response before sending it back to the client Since filters can be specified declaratively using the web application deployment descriptor they can be inserted into existing web applications without altering any of the existing code 8 4 1 Filter Overview Servlet filters are useful for many purposes including logging user authentication data compression encryption and XSLT transformation Many filters can be chained together each performing one specific task For the purposes of this book XSLT transformations are the most interesting use of filters Figure 8 5 illustrates the general filter architecture Figure 8 5 Servlet filters servlet Container request request Servlet response response Client a could also be a Filter static file or JSP javax servlet Filter is an inter
429. n Garre at chaps SampleUnxTest validateCondensedF ile SampleUndzTes java 1 33 at Chap SarnpleUneTest tesfTransforr ith Templates SamaleUnitTest java 103 Finished 0 311 seconds Exit The rectangular area to the left of U is a progress bar that expands as tests are executed When dozens or hundreds of tests are executed the progress bar gives a good visual indication of how many tests have executed It also changes from green to red when errors or failures occur so programmers know exactly when something went wrong The scrolling list in the middle of the screen shows individual test errors and failures and the text area near the bottom of the screen shows details for the selected error The GUI interface is great for interactive testing while the command line interface is more appropriate for batch mode automated tests These are the sorts of tests that execute as part of a nightly build process We now move past unit testing software into the realm of custom application error handling using JAXP error listeners 9 2 2 JAXP 1 1 Error Listeners When performing XSLT transformations using JAXP errors are typically reported to System err While this is sufficient for command line transformations some custom applications require more control over the error reporting process For this class of applications the javax xml transform ErrorListener interface is provided By implementing this interface an application can capture and
430. n ignored catch TransformerException te try this errModel fatalError te catch TransformerException ignored catch Exception unexpected System err println The XSLT processor threw an unexpected exception unexpected printStackTrace show the error tab if this errModel hasErrors this tabPane setSelectedIndex 1 the user clicked on a different tab private void tabChanged try setCursor Cursor getPredefinedCursor Cursor WAIT CURSOR int sellndex this tabPane getSelectedIndex String selTab this tabPane getTitleAt selIndex when the XML tab is selected set the text on the XML panel Although the text may not be XML we won t know that until it is parsed if XML Output equals selTab this xmlOutputPanel setXML this resultText this xsltURL finally setCursor Cursor getPredefinedCursor Cursor DEFAULT_CURSOR a helper method to create the panel that displays errors private JComponent createErrorPanel JSplitPane splitPane new JSplitPane JSplitPane VERTICAL SPLIT this errorTable setAutoResizeMode JTable AUTO RESIZE OFF int size this errorDetailArea getFont getSize this errorDetailArea setEditable false this errorDetailArea setFont new Font Monospaced Font PLAIN size 2 splitPane setTopComponent new JScrollPane this errorTable
431. n lt description gt board Element boardElem new ment board boardElem addAttribute id Long toString board getID 2 boardElem addContent new Element name setText board getName boardElem addContent new Element description setText board getDescription return boardElem public static Element produceElement BoardSummary board Element boardElem produceNameIDElement board add the list of messages Iterator iter board getMonthsWithMessages i while iter hasNext onthYear curMonth MonthYear iter next ys Element elem new Element messages elem addAttribute month Integer toString curMonth getMonth 3 7 elem addAttribute year Integer toString curMonth getYear boardElem addContent elem return boardElem private BoardSummaryJDOM The final JDOM producer Post MessageJDOM is shown in Example 7 24 The produceElement method takes numerous arguments that allow the method to produce XML for posting a new message or replying to an existing message Also values for the message subject author email and message text may be pre filled in the XML The application takes advantage of this capability whenever it must redisplay an HTML form to a user with its values filled in Example 7 24 PostMessageJDOM java package com oreilly forum xml import com oreilly foru
432. n of the servlet response so difficult 8 4 2 XSLT Transformation Filter The previous discussion introduced a lot of concepts about servlet filters without a lot of details Next a complete example for performing XSLT transformations using a filter is presented Hopefully this will illustrate some of the issues mentioned so far The basic goal is to create a servlet filter that performs XSLT transformations A servlet JSP or static XML file will provide the raw XML data The filter will intercept this XML before it is sent to the client browser and apply an XSLT transformation The result tree is then sent back to the browser Example 8 9 is the first of three classes that comprise this example This is a custom subclass of ServietOutputStream that captures its output in a byte array buffer The XML data is queued up in this buffer as a first step before it is transformed Example 8 9 BufferedServletOutputStream java package com oreilly javaxslt util import java io import javax servlet A custom servlet output stream that stores its data in a buffer rather than sending it directly to the client author Eric M Burke Aj public class BufferedServletOutputStream extends ServletOutputStream the actual buffer private ByteArrayOutputStream bos new ByteArrayOutputStream return the contents of the buffer public byte getBuffer return this bos toByteArray This
433. nException SAXNotSupportedException public boolean isNamespaceAware public boolean isVa public static SAXPa SAXParser newSAXParser publ publ publ publ ic abstract tory lidating Cur s ee rserFactory newInstance throws ParserConfigurationException ic abstract void setFeature String name throws ParserConfigurationException SAXNotSupportedException ic void s tNamespaceAwar String name SAXNotRecognizedExcept ion SAXException boolean value SAXNotRecognizedException boolean awareness ic void setValidating boolean validating Package javax xml transform This package defines an API for performing transformations Although these are common XSLT transformations the API is flexible enough to support other transformation technologies Like the javax xml parsers package the classes and interfaces in this package hide vendor specific implementation code JAXP 1 1 ships with Xalan as its reference implementation for transformations different processors can be plugged in ErrorListener This interface allows applications to implement custom error handling If an error listener is not registered errors are written to System err More details on this interface can be found in Chapter 9 public interface ErrorListener void error TransformerException exception throws TransformerException void fatalError TransformerExcep
434. names e New terms where they are defined e Internet addresses such as domain names and URLs Constant width is used for e Anything that appears literally in a Java program including keywords datatypes constants method names variables class names and interface names e All Java code listings e HTML XML and XSLT documents tags and attributes Constant width italic is used for e General placeholders that indicate that an item is replaced by some actual value in your own program Constant width bold is used for e Command line entries e Emphasis within a Java or XML source file How to Contact Us We have tested and verified the information in this book to the best of our ability but you may find that features have changed or even that we have made mistakes Please let us know about any errors you find as well as your suggestions for future editions by writing to O Reilly amp Associates Inc 101 Morris Street Sebastopol CA 95472 800 998 9938 in the U S or Canada 707 829 0515 international local 707 829 0104 FAX There is a web page for this book which lists errata examples or any additional information You can access this page at http www oreilly com catalog javaxslt To comment or ask technical questions about this book send email to bookquestions oreilly com For more information about books conferences software Resource Centers and the O Reilly Network see the O Reilly w
435. nce a clone or deep copy is returned you can safely modify the Properties instance and apply it to a future transformation without affecting the compiled stylesheet that the instance of Templates represents The newlransformer method is more commonly used and allows you to obtain a new instance of a class that implements the Transformer interface It is this Transformer object that actually allows you to perform XSLT transformations Since the implementation of the Templates interface is hidden by JAXP it must be created by the following method on javax xml transform TransformerFactory public Templates newTemplates Source source throws TransformerConfigurationException As in earlier examples the Source may obtain the XSLT stylesheet from one of many locations including a filename a system identifier or even a DOM tree Regardless of the original location the XSLT processor is supposed to compile the stylesheet into an optimized internal representation Whether the stylesheet is actually compiled is up to the implementation but a safe bet is that performance will continually improve over the next several years as these tools stabilize and vendors have time to apply optimizations Figure 5 6 illustrates the relationship between Temp1ates and Transformer instances Figure 5 6 Relationship between Templates and Transformer One Transformer instance per concurrent user Instances can be reused for fulure transformations Each Tem
436. nd java com oreilly javaxslt util SimpleCSVProcessor presidents csv CSVvToHTMLTable xslt As before the results are sent to System out and contain code for an HTML table This stylesheet will work with any CSV file parsed with impieCSVProcessor not just presidents xml Now that the concept has been proved you can add fancy formatting and custom output to the resulting HTML without altering any Java code just edit the stylesheet or write a new one 5 3 5 5 Conclusion Although writing a SAX parser and connecting it to JAXP does involve quite a few interrelated classes the resulting application requires only two command line arguments and will work with any CSV or XSLT file What makes this example interesting is that the same approach will work with essentially any data source The steps are broken down as follows 1 Create a custom SAX parser by implementing org xml sax XMLReader or extending com oreilly javaxslt util AbstractXMLReader 2 n your parser emit the appropriate SAX events as you read your data 3 Modify SimpleCSVProcessor to utilize your custom parser instead of CSVXMLReader For example you might want to write a custom parser that accepts a SQL statement as input rather than a CSV file Your parser could then connect to a database issue the query and fire SAX events for each row in the ResultSet This makes it very easy to extract data from any relational database without writing a lot of custom code This also elim
437. nd outright replacing Makefiles on most Java development projects Ant is a build tool similar to the make utility only it uses XML files instead of Makefiles In addition to a portable build file based on XML Ant itself is written in Java and has few platform specific dependencies Finally since Ant can reuse the same running instance of the Java Virtual Machine for nearly every step of the build process it is blazingly fast Ant can be downloaded from http jakarta apache org and is open source software 3 6 1 Ant Basics Ant is driven by an XML build file which consists of one project This project contains one or more targets and targets can have dependencies on one another The project and targets are represented as lt project gt and lt target gt in the XML build file lt oroject gt must be the document root element It is common to have a prepare target that builds the output directories and a compile target that depends on the prepare target If you tell Ant to execute the compile target it first checks to see that the prepare target has created the necessary directories The structure of an Ant build file looks like this lt xml version 1 0 gt lt project name SampleProject default compile basedir gt global properties gt lt property name srcdir value src gt lt property name builddir value build gt lt target name prepare description Creates the output directories gt
438. nderer Once the renderer is created the servlet asks it to render its content The renderer then asks the appropriate JDOM producer to create the XML data and performs the transformation using an XSLT stylesheet The result of the transformation is sent back to the client browser One request handler might map to several renderers For example suppose the user is trying to post a new message and submits this information to the Post MsgReqHandler Class If the request handler determines that some required fields are missing it can return an instance of the PostMsgRenderer class This allows the user to fill in the remaining fields On the other hand if a database error occurs an instance of ErrorRenderer can be returned Otherwise ViewMsgRenderer is returned when the message is successfully posted Because request handlers and renderers are cleanly separated renderers can be invoked from any request handler The code for ForumServlet is shown in Example 7 25 As already mentioned this is the only servlet in the application Example 7 25 ForumServlet java package com oreilly forum servlet import com oreilly forum ForumConfig import com oreilly forum jdbcimpl DBUtil import java io import java util import javax servlet import javax servlet http The single servlet in the discussion forum hy public class ForumServlet extends HttpServlet private RegHandlerRegistry registry Registers all
439. nding method doGet doPost Since the doGet method is called from its parent class it can be protected If you do not override the doGet method the default behavior in Ht coserviet is to return an error page back to the client If you also want to support POST you must override the doPost method One common technique is to have the doGet method call the doPost method or vice versa This allows the same servlet to support both GET and POST without duplicating any code The doGet implementation is very straightforward The first thing it does is check for the existence of a parameter called next URL This is part of the request that the browser issues to the servlet For example typing the following URL into your browser will include the next URL parameter http localhost 8080 chap6 splash nextURL http www oreilly com If the next URL parameter is not specified its value will be nu11 For this reason servlets must always check for 511 when getting parameters from the request String nextURL request getParameter nextURL if nextURL null nextURL In our example nu11 causes an error so we replace next URL with a forward slash character As you might guess this is a relative URL that points to the root directory In the case of a servlet running on Tomcat the root directory will point to Tomcat s home page This is not the same as the root directory on your file system In T
440. ne an XML parser or XSLT processor reference implementations do include these tools These reference implementations are open source Apache XML tools so complete source code is available 11 Crimson and Xalan 5 2 1 JAXP 1 1 Implementation You guessed it we will now reimplement the simple example using Sun s JAXP 1 1 Behind the scenes this could use any JAXP 1 1 compliant XSLT processor this code was developed and tested using Apache s Xalan 2 processor Example 5 3 contains the complete source code Example 5 3 SimpleJaxp java package chap5 import java io A simple demo of JAXP 1 1 public class SimpleJaxp Accept two command line arguments the name of an XML file and the name of an XSLT stylesheet The result of the transformation is written to stdout public static void main String args throws javax xml transform TransformerException if args length 2 System err println Usage System err println java SimpleJaxp class getName xnlFileName xsltFileName System exit 1 File xmlFile new File args 0 File xsltFile new File args 1 javax xml transform Source xmlSource new javax xml transform stream StreamSource xmlFile javax xml transform Source xsltSource new javax xml transform stream StreamSource xsltFile javax xml transform Result result new javax xml transform stream StreamResult System out reat i i rmer
441. nects for the next page Secondly since Java has built in threading capability it is possible for numerous clients to share the same servlet instance Creating additional threads is far more efficient than spawning additional external processes making servlets very good performers Early versions of the Java servlet API did not specify the mechanism for deployment i e installation onto servers Although the servlet API was consistent deployment onto different servlet engines was completely vendor specific With Version 2 2 of the servlet API however proprietary servlet engines were dropped in favor of a generic servlet container specification The idea of a container is to formalize the relationship between a serviet and the environment in which it resides This made it possible to deploy the same servlet on any vendor s container without any changes Along with the servlet container came the concept of a web application A web application consists of a collection of servlets static web pages images or any other resources that may be needed The standard unit of deployment for web applications is the Web Application Archive WAR file which is actually just a Java Application Archive JAR file that uses a standard directory structure and has a war file extension In fact you use the jar command to create WAR files Along with the WAR file comes a deployment descriptor which is an XML configuration file that specifies all configuration as
442. new Element Channel setText Integer toString show getChannel e addContent new Element from setText this dateFmt format show getStartTime e addContent new Element to setText this dateFmt format show getEndTime ee ee e addContent new Element title setText show getTitle return e You might be wondering why this JDOM code is that much better than the servlet code which also used Java to programmatically produce output The difference is fundamental and important With this JDOM example printin statements are not used Instead a data structure representing the television schedule is created By virtue of the JDOM API the data structure is guaranteed to produce well formed XML We could very easily add a DTD writing a unit test that validates the integrity of the generated data structure In addition to ensuring the integrity of the data the JDOM code will typically be much smaller than the servlet or JSP code In this basic web page the servlet and JSP were quite small because the HTML did not contain any significant formatting or layout In a real world web page however the servlet and JSP will continue to grow in complexity as the HTML layout gets more sophisticated while the JDOM code remains exactly the same Although the XSLT stylesheet will get larger as the HTML gets more complex this is arguably less of a problem because the presentation logic is completely separated f
443. nfig file gt lt type gt WARNING lt type gt lt when gt lt year gt 2000 lt year gt month gt 01 lt month gt lt day gt 15 lt day gt lt hour gt 06 lt hour gt lt minute gt 35 lt minute gt lt second gt 44 lt second gt A lt when gt lt where gt class com foobar servlet MainServlet class method init lt method gt where lt message gt lt more messages log As you can see from this example the file format is quite verbose Of particular concern is how the date and time are written Since log files can be quite large it would be a good idea to select a more concise format for this information Additionally the text is stored as an attribute on the message element and the type is stored as a child element It would make more sense to list the type as an attribute and the message as an element For example message type WARNING text This is the text of a message Multi line messages are easier when an element is used instead of an attribute text remainder omitted 3 5 2 The Identity Transformation Whenever writing a schema evolution stylesheet it is a good idea to start with an identity transformation This is a very simple template that simply takes the original XML document and transforms it into a new document with the same elements and attributes as the original document Example 3 11 shows a stylesheet that contains an identity transf
444. ng a St ring to a character array and passing that as a parameter to the characters method emit the lt value gt text lt value gt element ch startElement yalue EMPTY ATTR ch characters firstToken toCharArray 0 firstToken length ch endElement yalue 5 3 5 4 Using the parser To wrap things up let s look at how you will actually use this CSV parser with an XSLT stylesheet The code shown in Example 5 8 is a standalone Java application that allows you to perform XSLT transformations on CSV files As the comments indicate it requires the name of a CSV file as its first parameter and can optionally take the name of an XSLT stylesheet as its second parameter All output is sent to System out Example 5 8 SimpleCSVProcessor java package com oreilly javaxslt util import java io import javax xml transform import javax xml transform sax import javax xml transform stream import org xml sax Shows how to use the CSVXMLReader class This is a command line utility that takes a CSV file and optionally an XSLT file as command line parameters A transformation is applied and the output is sent to System out x public class SimpleCSVProcessor public static void main String args throws Exception if args length 0 System err println Usage java SimpleCSVProcessor class getName 9 csvFile xsltFile System err println csvFile is
445. ng questions about Java lt description gt lt board gt lt message id 1 day 1 gt lt subject gt First test message lt subject gt lt authorEmail gt burke_e yahoo com lt authorEmail gt message id 2 day 2 gt lt subject gt Re First test message lt subject gt lt authorEmail gt aidan nowhere com lt authorEmail gt lt message gt lt message gt message id 3 day 4 gt lt subject gt Another test message lt subject gt lt authorEmail gt burke_e yahoo com lt authorEmail gt lt message gt lt viewMonth gt Moving on to Example 7 5 we have the XML for the Post Reply Message page Example 7 5 postMsg xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xslt postMsg xslt lt postMsg gt lt board id 1 gt lt name gt Java Programming lt name gt lt description gt The board description lt description gt lt board gt lt inResponseTo id 4 gt lt subject gt Test Subject lt subject gt lt inResponseTo gt error code ALL FIELDS REQUIRED gt lt prefill gt lt subject gt Test Subject lt subject gt lt authorEmail gt lt authorEmail gt lt message gt My Message lt message gt lt prefill gt lt postMsg gt This XML is used for both posting new messages and replying to existing messages because the web pages are virtually identical and the data is the same in both cases The lt error gt and pr
446. ng the type of client is the most important role of the servlet There are two HTTP header values that are typically used for this purpose User Agent and Accept The text in Example 10 2 shows what an HTTP header looks like for the Ericsson R520m cell phone simulator Example 10 2 Example HTTP header GET HTTP 1 1 Host 25 12 44 22 Accept application vnd wap wmlc application vnd wap wbxml application vnd wap wmlscriptc text vnd wap wml application xml text xml text vnd wap wmlscript User Agent EricssonR520 R1A Accept Charset The HTTP header is text and each line after the first consists of a name value pair The Accept header indicates the MIME content types that this device knows how to display so searching for text vnd wap wml is a simple way to detect if the client device supports WML If the client accepts this MIME type it could be a wireless device Some browsers may also know how to display text vnd wap wml The Accept header is not a completely reliable way to determine the client type The User Agent header definitively identifies the device However vendors do not consistently follow standards Table 10 2 lists several user agents reported by various cell phone simulators Table 10 2 Sample user agents Simulator type User Agent Ericsson R320s EricssonR320 R1A Ericsson R380s R380 2 1 WAP1 1 Ericsson R520m EricssonR520 R1A Motorola Motorola VoxGateway 2 0 Nokia Nokia WAP Toolkit 2 1
447. ns setParameter image dir graphics You can set as many parameters as you like and these parameters will be saved and reused for every transformation you make with this Transformer instance If you wish to remove a parameter you must call clearParameters which clears all parameters for this Transformer instance Parameters work similarly to a java util Map if you set the same parameter twice the second value overwrites the first value Another use for the Transformer class is to get and set output properties through one of the following methods void setOutputProperties java util Properties props void setOutputProperty String name String value java util Properties getOutputProperties String getOutputProperty String name As you can see properties are specified as name value pairs of Strings and can be set and retrieved individually or as a group Unlike stylesheet parameters you can un set an individual property by simply passing in nu11 for the value The permitted property names are defined in the javax xml transform OutputKeys class and are explained in Table 5 1 Table 5 1 Constants defined in javax xml transform OutputKeys Constant Meaning Specifies a whitespace separated list of element names whose CDATA SECTION ELEMENTS content should be output as CDATA sections See the XSLT specification from the W3C for examples Only used if DOCTYPE_SYSTEM is also used this instructs the processor to ou
448. nsformations 9 1 2 2 A typical Ant build file The best way to learn about Ant is to download it read the first part of the user manual and then study several example build files Example 9 3 presents one such build file which can be used to compile some of the example code in this chapter as well as perform an XSLT transformation Example 9 3 build xml xml version 1 0 KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKAKKKKKK Example Ant build file as shown in Chapter 9 Assumes the following directory structure examples TU t chapters EE t chap9 Stud build xml this file S aidan xml example XML file E condensePerson xslt example XSLT file Xm common T StG com oreilly javaxslt swingtrans K aba build created by this build file k k KCKCKCKCK kk Ck CK Kk CK CK SKK CK KICK KK SKK KU S Kk S KU KC Ck kc ko KKK kk gt lt project name chap9 default help basedirz lt KKKKKKKKKK ck ck ck KKK AK KKK ck ok ck ck KKK kckck ck ck ck ck ck ck ck ck ck ck ck ck ck ck kck k k ck k kk KKK Global properties KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK KC KC KKK ck k kc k k kk lt property name builddir value build gt lt path id thirdparty class path gt lt pathelement path lib saxon 6 2 2 jar lt pathelement path lib jaxp 1 1 jar lt pathelement path lib servlet 2 3 jar lt pathelement path lib junit_3 5 jar gt
449. nt and even comments XSLT has the ability to select any of these items although you will probably want to select elements and attributes when transforming to HTML As mentioned earlier the pattern matches the document itself which is the root node of the entire tree A tree data structure is fundamentally recursive because it consists of leaf nodes and smaller trees Each of these smaller trees in turn also consist of leaf nodes and still smaller trees Algorithms that deal with tree structures can almost always be expressed recursively and XSLT is no exception The processing model adopted by XSLT is explicitly designed to take advantage of the recursive nature of every well formed XML document This means that most stylesheets can be broken down into highly modular easily understandable pieces each of which processes a subset of the overall tree i e a subtree Two important concepts in XSLT are the current node and current node list The current node is comparable to the current working directory on a file system The lt xsl value of select gt element is similar to printing the name of the current working directory The current node list is similar to the list of subdirectories The key difference is that in XSLT the current node appears in your source XML document The current node list is a collection of nodes As processing proceeds the current node and current node list are constantly changing as you traverse the sourc
450. ntWriter or OutputStream and perform the XSLT transformation For dynamically generated pages this is all that must be done If a web application also consists of static resources such as WMLScript files and WBMP images the web application deployment descriptor should also be updated Example 10 3 lists some additional content that should be added to the deployment descriptor Example 10 3 Deployment descriptor MIME mappings lt mime mapping gt lt extension gt wml lt extension gt lt mime type gt text vnd wap wml lt mime type gt lt mime mapping gt lt mime mapping gt lt extension gt wmls lt extension gt lt mime type gt text vnd wap wmlscript lt mime type gt lt mime mapping gt lt mime mapping gt lt extension gt wmlc lt extension gt lt mime type gt image vnd wap wbmp lt mime type gt lt mime mapping gt This effectively tells the web server to use the specified MIME type whenever the client requests files with the listed extensions 10 3 3 Movie Theater Example Admittedly this is a crash course introduction to WML hopefully a more complete example will clarify some of the concepts 10 3 3 1 Storyboard This example consists of three WML decks and several cards Through this interface users can select their city select a particular movie theater within that city and finally view showtimes for that theater The diagram in Figure 10 4 contains the storyboard for this application sho
451. ntifier and a Reader Source xmlSource new StreamSource xmlSystemId Source xsltSource new StreamSource new StringReader IDENTITY_XSLT send the result to a file File resultFile File createTempFile Streams xml Result result new StreamResult resultFile System out println Results will go to resultFile getAbsolutePath get the factory TransformerFactory transFact TransformerFactory newInstance get a transformer for this particular stylesheet Transformer trans transFact newTransformer xsltSource do the transformation trans transform xmlSource result The identity copy stylesheet simply matches which is the document itself It then uses lt xsl copy of select to select the document and copy it to the result tree In this case we coded our own stylesheet You can also omit the XSLT stylesheet altogether as follows construct a Transformer without any XSLT stylesheet Transformer trans transFact newTransformer js In this case the processor will provide its own stylesheet and do the same thing that our example does This is useful when you need to use JAXP to convert a DOM tree to XML text for debugging purposes because the default Transformer will simply copy the XML data without any transformation 5 3 4 JAXP DOM I O In many cases the fastest form of transformation available is to feed an instance of org w3c dom Document directly into JAXP Alt
452. ntioned previously XSLT stylesheets must be well formed XML documents Once again we use xs t as the filename extension but xs is also common This stylesheet is based on the skeleton document presented in Example 2 4 However it produces XHTML instead of HTML Example 2 6 schedule xslt lt xml version 1 0 encoding UTF 8 gt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform gt lt xsl output method xml doctype public z W3C DTD XHTML 1 0 Transitional EN doctype system http www w3 org TR xhtm11 DTD xhtmll transitional dtd KLAR RK KKK ck kck ck ck ck kckck ck ck k ck ck k kckck ck ck k KKK KKK KKK ck ck ck ck kck ck kck ck ck ck k ck ck k ck ck ck KKK KKK KK kk template OCC KK CC Ck C Ck CK Ck CK CIC KKK KKK Ck Ck Ck Ck C CIC CC CK Ck C Ck C Ck CK Ck kk E A A M M x x ko x M lt xsl template match gt lt html xmlns http www w3 0rg 1999 xhtml lt head gt lt title gt Schedule lt title gt lt head gt lt body gt lt h2 align center gt lt xsl value of select schedule owner name first gt lt xsl text disable output escaping yes gt amp amp nbsp lt xsl text gt lt xsl value of select schedule owner name last s Schedule lt h2 gt xsl apply templates select schedule appointment gt lt body gt lt html gt lt xsl template gt Ckckckck ck ck ck ck ckck kckck ck ck ck ck KK KKK ck ck ck ck k ck ck kc kck k ck ck k
453. nues the current node and current node list are constantly changing This is a good thing since you do not want to constantly search for patterns beginning from the document root element You are not limited to traversing down the tree however you can iterate over portions of the XML data many times or navigate back up through the document tree structure This gives XSLT a huge advantage over CSS because CSS is limited to displaying the XML in the order in which it appears in the document Comparing lt xsl template gt to xsl apply templates One way to understand the difference between xs1 template and xsl apply templates isto think about the difference between a Java method and the code that invokes the method For example a method in Java is declared as follows public void printMessageBoard MessageBoard board print information about the message board In XSLT the template plays a similar role lt xsl template match messageBoard gt print information about the message board lt xsl template gt In order to invoke the Java method use the following Java code someObject printMessageBoard currentBoard And in XSLT use xsl apply templates select gt to instantiate the template using the current lt messageBoard gt node While this is a good comparison to help illustrate the difference between xsl template and xsl apply templates itis important to remember
454. o learn Although the syntax is strange it can be argued that XSLT is easier to learn than a sophisticated programming language like Java There is resistance on this front however which is typical of a new technology that is unfamiliar The second potential weakness of the XSLT approach is runtime performance There is a performance penalty associated with XSLT transformation Fortunately there are numerous optimizations that can be applied The most common involves the caching of stylesheets so they do not have to be parsed with each request This and other techniques for optimization will be covered in later chapters Since XSLT stylesheets are actually XML documents any available XML editor will work for XSLT But eventually we should see more and more specialized XSLT editors that hide some of the implementation details for nonprogrammers As with first generation Java GUI builders these early tools may not generate stylesheets as cleanly as a handcoded effort 4 2 4 Development and Maintenance Benefits of XSLT As mentioned earlier testing JSPs can be difficult Since they can be executed only within a JSP container automated unit tests must start a web server and invoke the JSP via HTTP requests in order to test their output The XSLT based web approach does not suffer from this problem Referring back to Figure 4 6 you can see that the data model in an XSLT web application is represented as XML This XML is generated independently o
455. o not have to be repeatedly located using the ServietContext getRealPath method Example 7 29 XSLTRenderHelper java package com oreilly forum servlet import com oreilly javaxslt util StylesheetCache import java io import java net URL import java util import javax servlet import javax servlet http import javax xml transform import javax xml transform stream import org jdom import org jdom output A helper class that makes rendering of XSLT easier This eliminates the need to duplicate a lot of code for each of the web pages in this app public class XSLTRenderHelper private static Map filenameCache new HashMap Perform an XSLT transformation param servlet provides access to the ServletContext so the XSLT directory can be determined param xmlJDOMData JDOM data for the XML Document param xsltBaseName the name of the stylesheet without a directory param response the Servlet response to write output to gd public static void render HttpServlet servlet Document xmlJDOMData String xsltBaseName HttpServletResponse response throws ServletException IOException ox F ox String xsltFileName null try figure out the complete XSLT stylesheet file nam synchronized filenameCache xsltFileName String filenameCache get xsltBaseName if xsltFileName null S
456. o a web server The server processes the request and sends a response thus finishing the exchange This request response cycle is easy to understand but makes it tedious to develop an application that maintains state information as the user moves through a complex web application For example as a user adds items to a shopping cart a servlet must store that data somewhere while waiting for the client to make another request When that request arrives the servlet has to associate the cart with that particular client since the servlet could be dealing with hundreds or thousands of concurrent clients Other than establishing a timeout period the servlet has no idea when the client abandons the cart deciding to shop on a competitor s site instead The HTTP protocol makes it impossible for the server to initiate a conversation with the client so the servlet cannot periodically ping the client as it can with a normal client server application HTML itself can be another hindrance to web application development It was not designed to compete with feature rich GUI toolkits yet customers are increasingly demanding that applications of all sorts become web enabled This presents a significant challenge because HTML offers only a small set of primitive GUI components Sophisticated HTML generation is not the subject of this book but we will see how to use XSLT to separate complex HTML generation code from underlying programming logic and servlet code
457. o narrow down the list to the one lt met a gt tag that contains a navigationCategory attribute name navigationCategory If this is found the value of the content attribute is assigned to the global nav cate variable Otherwise the value is unknown 2 The XSLT stylesheet then contains a epi n e matches the ird This template defines the overall XHTML page layout by creating a lt table gt The document lt head gt however is simply copied from the input XHTML canner xsl copy of select html head gt Because the original lt head gt is merely copied to the result tree any styles or scripts that page authors include in their own documents are preserved The only drawback occurs when people define CSS styles that change the look and feel of the navigation areas such as changing the fonts and colors used in a page If this is a concern you might want to include logic in the XSLT stylesheet that ignores all lt style gt tags and style attributes in the original XHTML document Once the lt head gt is copied the XSLT stylesheet creates the lt body gt for the result tree An XHTML lt table gt controls the overall page layout and named XSLT templates are used to create the navicalioh areas lt xsl call template name createTopNavbar gt lt xsl call template name createLeftNavbar The createTopNavbar template is somewhat more complicated because it contains logic to display the current category differently
458. o the API specification represents a serious configuration error Generally this means that the factory cannot provide a parser with the requested features For instance a programmer may ask for a namespace aware parser but the only parser available does not support namespaces B XSLT processing requires namespace aware XML parsers public class ParserConfigurationException extends Exception public ParserConfigurationException String msg public ParserConfigurationException SAXParser This class defines a wrapper around an underlying SAX parser implementation It was part of JAXP 1 0 and supports both SAX 1 and SAX 2 features If possible programmers should avoid methods that use HandierBase because this is a deprecated SAX 1 interface Instead use the methods that deal with DefaultHandler public abstract class SAXParser protected SAXParser E public abstract Parser getParser throws SAXException public abstract Object getProperty String name publ publ publ throws SAXNotRecognizedException XMLReader getXMLReader throws SAXException ic abstract boolea ic abstract boolean isValidating ic abstract public void parse InputStream systemId publ publ publ publ publ publ publ publ publ publ c abstract cr pe ct pk cf Ep cr p cF p cb peoct peo oc o peo ope cb ope ctf SAXParserFactory hrows SAXExcep c void parse InputStream hrows SAXExcep c v
459. oardID message board id amp amp month message month amp amp year message year gt xsl call template name utils printLongMonthName gt xsl with param name monthNumber select message month gt lt xsl call template gt lt xsl value of select message year gt lt a gt messages for lt xsl value of select message board name gt lt li gt lt li gt Return to the lt a href home gt home page lt a gt lt li gt lt li gt lt a href postMsg mode replyToMsg amp amp origMsgID message id gt Reply lt a gt to this message lt li gt ul lt h3 gt Message lt h3 gt lt div class box2 gt lt xsl apply templates select message gt lt div gt lt body gt lt html gt lt xsl template gt 1 KK KK KKK KKK KKK KKK ck kk ck ckckck ckockock ckockock koc ck koc kk ck kk ck ckckckckck kc kckckckckock kk kk Show details for the message element ECKCKCKCkCkCkCkCk ck k kk k ck ck k kk k ck ck k ck kCkck ck Kk Ok k kCk ck k ck k ck k k ck ck ck ck ck ck KKK KKK KKK xsl template match message lt div gt div style font weight bold gt lt xsl value of select subject gt lt div gt lt xsl text gt posted by lt xsl text gt lt a href mailto authorEmail gt lt xsl value of select authorEmail gt lt a gt lt xsl text gt on lt xsl text gt xsl call template name utils printShortMonthName gt xsl with pa
460. ocated it is time to fix the problems 9 3 3 1 Stylesheet caching As mentioned several times in this book caching XSLT stylesheets is an essential performance technique JAXP includes the Templates interface for this purpose and we already saw the implementation of a stylesheet cache in Chapter 5 Table 9 4 illustrates the performance gains seen when using the Templates interface to transform a small XML file repeatedly For this test the same transformation is performed 100 times using various programming techniques Table 9 4 Benefits of caching Processor No templates Templates Templates and cached XML Xalan 2 0 SAXON 6 2 2 iu In the No templates column the Templates interface was not used for transformations As you can see this resulted in the slowest performance because the stylesheet had to be parsed from a file with each transformation In the next column a Templates instance was created once and reused for each transformation As you can see the performance increased substantially In the final column of the table the XML data was read into memory and cached as a DOM Document Instead of reparsing the XML file with each request the same DOM tree was cached and reused for each of the transformations This yielded a slight performance gain because the XML file did not have to be read from the file system with each transformation Although these results seem to imply that SAXON is faster than Xalan this may be a
461. ocument into a DOM Document org jdom output DOMOutputter domOut new org jdom output DOMOutputter org jdom adapters CrimsonDOMAdapter org w3c dom Document domDoc domOut output jdomDoc The second line is highlighted because it is likely to give you the most problems When JDOM converts its internal object tree into a DOM object tree it must use some underlying DOM implementation In many respects JDOM is similar to JAXP because it delegates many tasks to underlying implementation classes The DOMOut putter constructors are overloaded as follows use the default adapter class public DOMOutputter use the specified adapter class c DOMOutputter String adapterClass The first constructor shown here will use JDOM s default DOM parser which is not necessarily the same DOM parser that JAXP uses The second method allows you to specify the name of an adapter class which must implement the org jdom adapters DOMAdapter interface JDOM includes standard adapters for all of the widely used DOM implementations or you could write your own adapter class 5 3 6 3 JDOM to text approach In the final approach listed earlier you can utilize java io StringWriter and java io StringReader First create the JDOM data as usual then use org jdom output XMLOutputter to convert the data into a St ring of XML StringWriter sw new StringWriter org jdom output XMLOutputter xmlOut new org jdom output XMLOutputter false xmlOut
462. ode Although the list shown here approximates the order in which these steps will be performed in larger applications it is typical to implement a vertical slice of the system first This slice will implement one or two key screens and will require the development team to follow all of the previous steps As more screens are added to the system the process is followed again for each piece of functionality that is added This is very typical of most lightweight software development processes in which the system is developed in iterative steps rather than trying to implement the entire system in one pass The remainder of this chapter will present the implementation of the discussion forum The requirements design and code will be presented in roughly the same order as the list shown in this section 7 1 1 Requirements An online discussion forum will be developed using Java and XSLT For the reference implementation all features will be accessible via a web browser using XHTML and no client side Java or JavaScript will be required The target for deployment is a web hosting provider that supports Java 2 servlet 2 2 and access to a relational database such as MySQL It is assumed that any additional Java JAR files such as those required for JAXP and JDOM can be installed along with the web application The discussion forum will be divided into message boards each of which covers a different topic such as Dog Lovers or Cat Lovers Each
463. of select name first gt lt td gt lt tr gt lt xsl template gt lt i Display a president s name as a list item lt xsl template match president mode list gt lt li gt lt xsl value of select name last gt lt xsl text gt lt xsl text gt lt xsl value of select name first gt lt li gt lt xsl template gt lt xsl stylesheet gt 3 2 6 lt xsl template gt Syntax Summary Sorting through all of the possible variations of lt xs1 template gt is a seemingly difficult task but we have really only covered three attributes match Specifies the node in the XML data that a template applies to name Defines an arbitrary name for a template independent of specific XML data mode Similar to method overloading in Java allowing multiple versions of a template that match the same pattern The only attribute we have not discussed in detail is pri or ity which is used to resolve conflicts when more than one template matches The XSLT specification defines a very specific set of steps for processors to follow when more than one template rule matches From a code maintenance perspective it is a good idea to avoid conflicting template rules within a stylesheet When combining multiple stylesheets however you may find yourself with conflicting template rules In these cases specifying a higher numeric priority for one of the conflicting templates can resolve the problem Table 3 1 provides a few s
464. of the underlying XML elements This serialized form is good for storing XML data in files but may not be the most efficient format for exchanging data between systems or programmatically modifying the underlying data For particularly large documents a relational or object database offers far better scalability and performance than native XML text files 1 2 2 XML Syntax Example 1 1 shows a sample XML document that contains data about U S Presidents This document is said to be well formed because it adheres to several basic rules about proper XML formatting Example 1 1 presidents xml lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE presidents SYSTEM presidents dtd gt presidents dent em from 1789 to 1797 gt lt name gt lt first gt George lt first gt lt last gt Washington lt last gt lt name gt fi in first lt i ams lt last gt la O nt gt from 1797 to 1801 gt lt name gt lt first gt John lt first gt lt last gt Adams lt last gt XN In HTML a missing tag here and there or mismatched quotes are not disastrous Browsers make every effort to go ahead and display these poorly formatted documents anyway This makes the Web a much more enjoyable environment because users are not bombarded with constant syntax errors Since the primary role of XML is to represent structured data being well formed is very important When two banking systems exc
465. ofiling information to a log file as an application runs Example 9 13 shows the Help page reported by typing the command java Xrunhprof help Example 9 13 JVMPI command line options C gt java Xrunhprof help Hprof usage Xrunhprof help l option value Option Name and Value Description Default heap dump sites all heap profiling all cpu samples times old CPU usage off monitor y n monitor contention n format a b ascii or binary output a file lt file gt write data to file java hprof txt for ascii net lt host port send data over a socket write to file depth lt size gt stack trace depth d cutoff lt value gt output cutoff point 0 0001 lineno y n line number in traces y thread y n thread in traces n doe y n dump on exit y Example java Xrunhprof cpu samples file log txt depth 3 FooClass Although this is only an experimental feature of the JVM it is useful when other tools are not available To locate processor bottlenecks the cpu option should be set to samples which uses statistical estimates based on periodic samples of performance It defaults to of f because this feature can significantly decrease performance Example 9 14 lists a very small portion of the output from a single run of a Java application using the JVMPI feature This section ranks the methods according to which consume the most time For instance a method that takes 20 ms to execute but is called millions of t
466. oid parse InputStream hrows SAXExcep c void parse File hrows SAXExcep C void parse InputStream hrows SAXExcep C void parse S hrows SAXExcep c void parse InputSource hrows SAXExcep c void parse InputSource hrows SAXExcep c void parse S hrows SAXExcep c void parse File hrows SAXExcep tion Lion f tion Hand tion tring uri tion tion IOExc tion tion f tion IOExcept tion IOException tring systemId IOException DefaultHandler dh IOException void setProperty hrows SAXNotRecognizedException n isNamespaceAware is Defaul ion is Defaul is Handle IOException lerBase hb IOException is Handle IOException ndlerBase hb IOException HandlerBase hb Ha is eption is String name SAXNotSupportedException SAXNotSupportedException 3 tHandler dh String tHandler pl rBase hb String systemId rBase hb DefaultHandler dh IOException DefaultHandler dh Object value This class defines a factory for creating instances of SAX parsers Before creating these instances use the set Feature method to define which parsing features are required of the parser to be created See http www megginson com SAX ava features html for a list of core SAX 2 features public abstract class SAXParserFac protected SAXParserFactory s public abstract boolean getFea throws ParserConfiguratio
467. omcat the root directory can be found under TOMCAT HOME webapps ROOT where TOMCAT HOME points to the installation directory of Tomcat The getParameter method is also used for retrieving values from an HTML form When an HTML form is submitted each component on the form should have a name associated with it such as firstName lastName or ssn The servlet retrieves the form values simply by calling request getParameter foreach form element It is always a good idea to check for null and trim whitespace before accepting any of these parameters When the form element is missing the parameter value will be nu11 This could indicate an error in your HTML or perhaps an intentional attack on your web site The HttpServletResponse class provides access to either a PrintWriter oran OutputStream depending on whether you wish to send text or binary data to the client For HTML or XML data use the HttpServletResponse getWriter method For images or other types of binary data use the HttpServiet EN inse getOutputStream method You may also note that we set the content type of the response prior to getting the writer dip e NM GUN nd ext html PrintWriter pw response getWriter This is important because the HTTP response consists of a header followed by the actual content The content type is one of the header values so it must be sent prior to the actual data Without going into too many servlet details it is a good practice to
468. omcat release build for your operating system e Uncompress the distribution to a directory e Set the TOMCAT HOME environment variable to point to this directory e Set the JAVA HOME environment variable to point to your Java distribution Since web applications are required to read configuration information from their XML deployment descriptors web xml all current versions of Tomcat ship with an XML parser 9 1 3 1 Configuring Tomcat 3 2 x Tomcat 3 2 x includes several JAR files in its TOMCAT_HOME ib directory Among these are jaxp jar and parser jar which support JAXP Version 1 0 along with a SAX 1 0 and DOM 1 0 XML parser Any JAR file added to the ib directory becomes available to every web application Tomcat uses a simple script to locate jar in the ib directory adding each JAR file to the CLASSPATH as it is encountered The order of inclusion depends on how the operating system lists files which is generally alphabetically The complete CLASSPATH used by Tomcat 3 2 x includes the following e TOMCAT_HOME classes e TOMCAT_HOME ib jar e Anyexisting CLASSPATH e JAVA HOME jre lib tools jar Although the ib directory provides a convenient way to install utility code that all web applications must use conflicts arise when individual applications require different versions of SAX DOM or JAXP If Tomcat finds an older version of one of these tools before it finds a newer version exceptions typically occur For instance
469. one time initialization of the servlet A servlet container will invoke this method before this servlet is asked to handle any client requests The init method is further guaranteed to execute to completion before any other threads can access this servlet so concurrency is not an issue at this point If anything fails during initialization an instance of UnavailableBxception is thrown public void init throv ivailableException TransformerFactory t st TransformerFactory newInstance s String curName null This exception is provided in the avax serviet package and indicates that the servlet could not be loaded successfully In our case the most common cause of this error is a configuration problem For example your XSLT stylesheets may be installed in the wrong directory or some JAR file was not found The next thing the init method does is load the two stylesheets into memory The XSLT stylesheets are stored on the file system so St reamSource will be used to read them into JAXP But you definitely do not want to hardcode the absolute pathname of the stylesheets If you do this your code will probably work on your personal machine but will fail once it is deployed onto a production web server For example C7java tomcat webapps chap6 WEB INF is a Windows specific absolute pathname Using something so specific would cause the servlet to fail on all non Windows platforms as well as other Windows machines that have Tomcat
470. oop lt xsl for each select president gt li display every other row in bold xsl if test position mod 2 0 gt xsl attribute name style gt xsl text font weight bold lt xsl text gt xsl attribute xsl if In this example the lt xsl for each gt loop first selects all president elements that are immediate children of the presidents element As the loop iterates over this node set the position function returns an integer representing the current node position within the current node list beginning with index 1 The mod operator computes the remainder following a truncating division just as Java and ECMAScript do for their operator The XPath expression position mod 2 O will return true for even numbers therefore the style attribute will be added to the lt li gt tag for every other president making that list item bold This template continues as follows xsl apply templates select name gt 1 lt display some text after the last element gt xsl if test position last gt lt xsl text gt current president lt xsl text gt xsl if lt li gt xsl for each The last function returns an integer indicating the size of the current context in this case it returns the number of presidents When the position is equal to this count the additional text current president is appended to the result tree Java programmers shoul
471. oose xsl template xsl stylesheet Month numbers are indexed from position 0 to be consistent with the java util Calendar class which also uses 0 to represent January The templates convert the month number into an English month name viewMonth xslt is shown in Example 7 9 It generates an XHTML page that shows all messages in a month for a particular board Example 7 9 XSLT for the View Month page lt xml version 1 0 encoding UTF 8 gt 1 KEKE KKK ck ck Ck Ck ck kk Kk KC CC Ck Ck Ck CK CK CK C CC CK CK SCC Ck Ck Ck Ck Sk Ck Sk Sk Sk Sk kA kA Mk ko ko Sk ko ko A kx MA xx viewMonth xslt ck Shows a month view of messages in a given board CC CK CK CK Ck C Ck CK CI CK C CC CK CK Ck Ck CK CK Ck Ck C C CC CC Ck C CK CK Ck CK CI S A S Kx Sk Sk Pk Sk Kk kx Ax M xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl import href utils xslt xsl param name rootDir select docroot xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtmll DTD xhtmll strict dtd lsn Ssss Global Variables z2zzz2z2zz2z222z2z22z2z225 gt lt xsl variable name global boardName select viewMonth board name gt lt xsl variable name global boardID select viewMonth board id gt lt xsl variable name global monthNum select viewMonth month gt lt xs
472. or example Version 1 0 of your application may store all of its files in XML format but Version 2 0 might add new features that cannot be supported by the old 1 0 file format A perfect solution is to write a single stylesheet to transform all of the old 1 0 XML files to the new 2 0 file format 2 1 1 An XSLT Example You need three components to perform XSLT transformations an XML data source an XSLT stylesheet and an XSLT processor The XSLT stylesheet is actually a well formed XML document so the XSLT processor will also include or use an XML parser Apache s Xalan is used for most of the examples in this book the previous chapter listed several other processors that you may want to investigate You can download Xalan from http xml apache org It uses and includes Apache s Xerces parser but can be configured to use other parsers The ability to swap out parsers is important because this gives you the flexibility to use the latest innovations as competing and perhaps faster parsers are released Example 2 1 represents an early prototype of a discussion forum home page The complete discussion forum application will be developed in Chapter 7 This is the raw XML data without any formatting instructions or HTML As you can see the home page simply lists the message boards that the user can choose to view Example 2 1 discussionForumHome xml lt xml version 1 0 encoding UTF 8 gt lt d cussionForumHome gt ageBoard
473. ore than one client at a time Built in threading capability is one of the key reasons why Java is so well suited to server applications particularly when compared to a traditional CGI model As usual however tradeoffs are involved In particular writing code that can handle many concurrent tasks without corrupting data can be quite challenging at times Ideally this material can alert you to the most common causes of threading problems found in a servlet environment 6 5 1 Servlet Threading Model In the standard servlet model a client makes a request via the serviet s service method In the HttpServlet class the service method determines the type of HTTP request and delegates to methods such as doGet or doPost If several clients issue requests at the same time these methods will serve each client in a different thread Since most servlets are subclasses of HttpServiet your main concern is insuring that service doGet and doPost can handle many concurrent clients Before handling any requests a servlet s init method is invoked According to the servlet API specification this method must be invoked by only a single thread and must complete successfully before subsequent threads are allowed to enter the service method For this reason you do not have to worry about threading problems inside of the init method From there however all bets are off One simplistic approach to thread safety is to declare a
474. ormation template Example 3 11 identityTransformation xslt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method xml version 1 0 encoding UTF 8 indent yes gt lt xsl template match node lt xsl copy gt xsl apply templates select node gt lt xsl copy gt lt xsl template gt lt xsl stylesheet gt Amazingly it takes only a single template to perform the identity transformation regardless of the complexity of the XML data Our stylesheet encodes the result using UTF 8 and indents lines regardless of the original XML format In XPath node is a node test that matches all child nodes of the current context This is fine but it omits the attributes of the current context For this reason must be unioned with node as follows lt xsl template match 8 node Translated into English this means that the template will match any attribute or any child node of the current context Since node includes elements comments processing instructions and even text this template will match anything that can occur in the XML document Inside of our template we use xs1 copy As you can probably guess this instructs the XSLT processor to simply copy the current node to the result tree To continue processing xsl apply templates then selects all attributes or children of the current context using
475. ory public interface TransformerHandler extends ContentHandler LexicalHandler DTDHandler String getSystemId J3 Transformer getTransformer s void setResult Result result throws IllegalArgumentException void setSystemId String systemId Package javax xml transform stream This package defines how to perform transformations using Java I O streams StreamResult This allows transformation results to be sent to a File Writer of OutputStream public class StreamResult implements Result public static final String FEATURE http javax xml transform stream StreamResult feature public StreamResult OutputStream outputStream public StreamResult Writer writer public StreamResult String systemId public StreamResult File f public StreamResult public OutputStream getOutputStream public String getSystemId public Writer getWriter public void setOutputStream OutputStream outputStream public void setSystemId File f public void setSystemId String systemId public void setWriter Writer writer StreamSource This supports input from a URL File Reader or InputStream The system id is used to resolve relative URLs in the XML and XSLT public class StreamSource implements Source public static final String FEATURE http javax xml transform stream StreamSource feature public StreamSource InputStream inputStream public StreamSource InputStream inputStrea
476. ost O Reilly First of all WML is an XML based markup language This means that unlike HTML all WML documents must be well formed and valid For instance all tags must be lowercase and nested properly and attribute values must be quoted Example 10 1 lists a WML document 11 WML documents are XML documents that conform to one of the WML DTDs Example 10 1 A very simple WML page lt xml version 1 0 encoding UTF 8 lt DOCTYPE wml PUBLIC WAPFORUM DTD WML 1 1 EN http www wapforum org DTD wml 1 1 xml wml card id home title Name Entry gt lt p gt Enter your first name input name firstName lt p gt lt p gt Enter your age lt input name age format N gt lt p gt do type accept gt lt go href hello gt lt do gt lt card gt lt card id hello title Hello gt lt p gt Hello there firstName e lt p gt lt p gt You claim to be lt em gt S age e old can this possibly be t lt em gt years rue lt p gt lt p gt Click lt a href home gt here lt a gt to change your answer lt p gt lt card gt wml This particular WML document adheres to Version 1 1 of the WML specification as indicated by the document type declaration Unlike HTML the root element is v1 which is commonly known as a deck The WML deck contains one or more lt card gt elements each of which represents a single screen that is displayed on the
477. ovement on this design could be to add a Last Accessed timestamp to each MapEntry Object Another thread could then execute every couple of hours to flush map entries from memory if they have not been accessed for a period of time In most web applications this will not be an issue but if you have a large number of pages and some are seldom accessed this could be a way to reduce the memory usage of the cache Another potential modification is to allow 1javax xml transform Source objects to be passed as a parameter to the new ransformer method instead of as a filename However this would make the auto reload feature impossible to implement for all Source types Chapter 6 Servlet Basics and XSLT XSLT and servlets are a natural fit Java is a cross platform programming language XML provides portable data and XSLT provides a way to transform that data without cluttering up your servlet code with HTML Because your data can be transformed into many different formats you can also achieve portability across a variety of browsers and other devices Best of all a clean separation between data presentation and programming logic allow changes to be made to the look and feel of a web site without digging in to Java code This makes it possible for example to sell highly customizable web applications You can encourage your customers to modify the XSLT stylesheets to create custom page layouts and corporate logos while preventing access to your interna
478. overwrite an older version of a DLL file that existing applications depend on causing erratic behavior or outright system crashes 1 Commonly referred to as the blue screen of death More frequently than ever before Java developers must contend with incompatible JAR file versions For instance JAXP 1 0 and JAXP 1 1 both ship with a JAR file named jaxp jar Applications that require JAXP 1 1 functionality will fail if the 1 0 version of jaxp jaris listed on the CLASSPATH eatlier than the newer version This happens more often than developers expect because many commercial and open source development tools ship with XML parsers and XSLT processors The installation routines for these tools may install JAR files without informing developers or asking for their consent The simple fix is to locate and remove old versions of JAR files This is easier said than done because in many cases such as JAXP the version number is not part of the JAR filename Since many tools ignore or modify the CLASSPATH when they are executed simply removing older JAR files from the CLASSPATH will not eradicate all problems Instructions for fixing this problem in Ant Tomcat and JBuilder are coming up Some JAR files are beginning to include version information inside of the META INF MANIFEST MF file This is called the manifest and can be extracted with the following command where filename jar is the name of the JAR file jar xf filename jar META INF MANIFE
479. ow to Compile Deploy and Run In Java it often seems that half of the battle is devoted to figuring out CLASSPATH issues In order to compile this example the following JAR files must be listed on the CLASSPATH jaxp jar Java API for XML Processing JAXP 1 1 xalan jar Xalan XSLT processor use the one included with JAXP crimson jar Crimson XML parser use the one included with JAXP servlet jar Included with the Tomcat servlet container Of course the directory containing your own source code must also be listed on the CLASSPATH Once everything is set up you can compile PersonalData java PersonalDataXML java and PersonalDataServlet java by typing javac 5ava Whether you also wish to include SplashScreenServlet java is entirely up to you As mentioned earlier in this chapter use the jar command to create the WAR file To create chap6 war simply arrange your files into the directory structure shown in Figure 6 8 and issue the following command from the directory that contains index html jar cvfM chap6 war This command places chap6 war in the parent of your current working directory the forward slash works on Windows as well as Unix clients Once the WAR file has been created you can view its contents by changing to its directory and issuing the following command jar tvf chap6 war This shows the table of contents for the WAR file which must match the structure shown in Figure 6 8 Deployment to Tomcat is easy
480. owse movie theaters and showtimes 10 1 Wireless Technologies The family of technologies used by wireless devices is in its infancy just a few years old Because of this there are a few competing markup languages in use today In Japan the i mode protocol is the market leader i mode is defined by a company named NTT DoCoMo utilizing a subset of HTML known as Compact HTML cHTML This markup language shares much of the same syntax as HTML but is essentially proprietary and is not based on XML In Europe and the United States Wireless Access Protocol WAP is more popular WAP currently utilizes WML which is quite different from HTML and cHTML In coming years it is likely that most vendors will consolidate around XHTML Basic although existing markup languages will need to be supported for quite some time WML and cHTML will be seen as transitional technologies that allowed us to start experimenting with wireless services At any rate XSLT offers an excellent way to minimize risk as vendors work through their differences and technology progresses Phone Simulators A variety of cell phone simulators are illustrated throughout this chapter All of these tools run on a PC allowing developers to test various devices without purchasing actual phones and subscribing to wireless Internet access services Here are some products and URLs to start with e Ericsson WapIDE http www ericsson com e Motorola Mobile Application Development K
481. p www w3 org TR xslt variables xsl preserve space xsl preserve spac lements tokens gt See XSLT specification section 3 4 Whitespace Stripping http www w3 org TR xslt strip xsl processing instruction xsl processing instruction name ncname gt lt Content template gt lt xsl processing instruction gt See XSLT specification section 7 3 Creating Processing Instructions http www w3 org TR xslt section Creating Processing Instructions xsl sort xsl sort select string expression lang nmtoken data type text or number or qname but not ncname order ascending or descending aaca nrdar T unenar fivet Ar lawar first See XSLT specification section 10 Sorting http www w3 org TR xslt sorting xsl strip space xsl strip space lements tokens See XSLT specification section 3 4 Whitespace Stripping http www w3 org TR xslt strip xsl stylesheet xsl stylesheet version number id id extension element prefixes tokens exclude result prefixes tokens gt Content Any number of lt xsl import gt followed by top level elements gt lt xsl stylesheet gt See XSLT specification section 2 2 Stylesheet Element http www w3 org TR xsltZ stylesheet element xsl template xsl template mat
482. pects of a web application The important details of WAR files and deployment descriptors will be outlined in Chapter 6 Servlets are simple to implement portable can be deployed to any servlet container in a consistent way and offer high performance Because of these advantages servlets are the underlying technology for every other approach discussed in this chapter When used in isolation however servlets do have limitations These limitations manifest themselves as web applications grow increasingly complex and web pages become more sophisticated The screen shot shown in Figure 4 2 shows a simple web page that lists television shows for the current day In this first implementation a servlet is used It will be followed with a JavaServer Pages JSP implementation presented later in this chapter Figure 4 2 ScheduleServlet output BL DARE isi ile dit View Search Go Bookmarks Tasks Help Wf Haee My Netscape S NetzPhone Tod es Shows c hannel Fi oun To Tide l 2 i os 00 AM 08 00 AM Weather 3 106 00 AM 07 30 AM Soap Opera 4 os 00 AM 06 30 AM Olympic C Coverage Jos 00 AM 07 00 AM Paid Programming 06 30 AM 07 30 AM Advanced Computing 07 00 AM 09 00 AM Baseball ECE AM 0930 AM Standup Comedy Jor 30 AM 08 00 AM Game Show 108 00 AM 10 00 AM Intemational News 0800AM 0930 AM Stand up Comedy 09 00 AM 11 00 AM Auto Racing 09 30 AM 1 30 AM Entertamment News
483. pends prepare description Compile the SwingTransformer application gt lt javac srcdir z common src destdir builddir includes com oreilly javaxslt swingtrans lt classpath refid thirdparty class path javac target 1 C Ck OK Ck Ck C Ck Ck Ck Ck Sk Ck CC Ck Ck Ck CK Ck OK Ck Kk Ck Ck Sk Ck kk kk kk Ck kk Sk Sk ke kx x kx kx ko ko ko ko Run com oreilly javaxslt swingtrans SwingTransformer KCKCkCkCkCkCk ck ck kc kck kc kckckckck ck ck ck ck ck k ck ck k ck ck k ck ck ck ck ck ckck ck ck ck k ck ck kck ck kc KKK KKK target name run depends compile description Run the SwingTransformer application java fork yes classname com oreilly javaxslt swingtrans SwingTransformer lt classpath gt lt pathelement path builddir gt lt classpath gt lt classpath refid thirdparty class path gt lt java gt lt target gt T CK CK CK Ck C CK CC CK CK CK CK Ck Ck Ck CK CK CK C CCS CK Ck Ck Ck CK Ck S Sk S E E A x Kk Kk Sk ck Sk Sk A Ax M Performs an XSLT transformation If either the XML file or the XSLT stylesheet change the transformation is performed again XK basedir specifies the location of the XSLT destdir a required attribute however Ant 1 3 is pw ignoring this The messages on the console RE indicate that the destdir is being used however it was found that the out mE attribute also has to specify the output EE directory KCKCKCKCKkCk
484. ping tells the XSLT processor to pass amp nbsp to the result tree Web browsers then interpret and display the nonbreaking space properly In the final template shown in Example 2 6 you may notice the element xs1 vaiue of select date month gt The character represents an attribute so in this case the stylesheet is outputting the value of the month attribute on the date element For this element date month 03 day 15 year 2001 gt the value 03 is copied to the result tree 2 4 XPath Basics XPath is another recommendation from the W3C and is designed for use by XSLT and another technology called XPointer The primary goal of XPath is to define a mechanism for addressing portions of an XML document which means it is used for locating element nodes attribute nodes text nodes and anything else that can occur in an XML document XPath treats these nodes as part of a tree structure rather than dealing with XML as a text string XSLT also relies on the tree structure that XPath defines In addition to addressing XPath contains a set of functions to format text convert to and from numbers and deal with booleans Unlike XSLT XPath itself is not expressed using XML syntax A simplified syntax makes sense when you consider that XPath is most commonly used inside of attribute values within other XML documents XPath includes both a verbose syntax and a set of abbreviations which end up looking a lot like path names on a fi
485. plate instance represents a singled compiled stylesheet i gt Transformer s uu create gt gt into lt lt gt gt home xsit Templates gt Transformer i L om create into gt gt Templates 7 4 products xslt empates gt Transformer 4 Many users threadscan Share gt Transformer Templates instances Thread safety is an important issue in any Java application particularly in a web context where many users share the same stylesheet As Figure 5 6 illustrates an instance of Templates is thread safe and represents a single stylesheet During the transformation process however the XSLT processor must maintain state information and output properties specific to the current client For this reason a separate Transformer instance must be used for each concurrent transformation XSLT Stylesheets e Transformer is an abstract class in JAXP and implementations should be lightweight This is an important goal because you will typically create many copies of Transformer while the number of Templates is relatively small Transformer instances are not thread safe primarily because they hold state information about the current transformation Once the transformation is complete however these objects can be reused 5 4 2 A Stylesheet Cache XSLT transformations commonly occur on a shared web server with a large number of concurrent users so it makes sense to use Templates wh
486. ple the lt inResponseTo gt XML element occurs only when the user replies to an existing message Therefore the XSLT stylesheet can define a variable for the page title as follows lt xsl variable name global title gt lt xsl choose gt lt xsl when test postMsg inResponseTo gt lt xsl text gt Reply to Message lt xsl text gt lt xsl when gt lt xsl otherwise gt lt xsl text gt Post New Message lt x lt xsl otherwise gt l text YQ D xsl choose xsl variable xsl when test postMsg inResponseTo gt returns true when the lt inResponseTo gt element exists in the original XML data In this case the global titJle variable is set to Reply to Message Otherwise the title defaults to Post New Message This stylesheet optionally displays an error message when the user partially fills out the XHTML form and submits the data The servlet redisplays the page with an error message allowing the user to fix the problem It does this by inserting the following XML element into the data error code ALL FIELDS REQUIRED gt The XSLT stylesheet tests for the existence of this element as follows xsl if test postMsg error code ALL FIELDS REQUIRED lt p class error gt All fields are required lt p gt lt xslrit gt An additional trick used in this stylesheet involves its interaction with a servlet When the user submits the XHTML form data the servlet must deter
487. ple 3 5 Example 3 5 familyTree xslt lt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html processing begins here lt xsl template match gt lt html gt lt body gt lt select the top level person gt xsl apply templates select person gt xsl with param name level select 0 gt xsl apply templates body html xsl template 1 Output information for a person and recursively select all children gt xsl template match person xsl param name level gt indent according to the level div style text indent S 1leveljem lt xsl value of select name gt lt div gt lt recursively select children incrementing the level gt xsl apply templates select person gt xsl with param name level select Slevel 1 gt xsl apply templates lt xsl template gt lt xsl stylesheet gt As usual this stylesheet begins by matching the document root and outputting a basic HTML document It then selects the root lt person gt element passing 1eve1 0 as the parameter to the template that matches person xsl apply templates select person gt xsl with param name level select 0 xsl apply templates The person template uses an HTML lt div gt tag to display each person s name on a new line and specifi
488. priate instance of PersonalData If the object is not found in the session a new instance is created and stored The doGet method then calls the showPage method which does the actual work of sending the web page to the browser The parameters to showPage include e The HttpServletResponse Which provides access to the PrintWriter The result of the transformation will be sent to this writer e The instance of PersonalData so the showPage method knows what data to display e A false parameter indicating that error messages should not be shown That makes sense because doGet is called when the page is first displayed and users should not be warned about invalid data before they type something e Areference to the appropriate stylesheet In this case the stylesheet will show the HTML form so the user can fill out his or her information Once the user fills out the form and submits it to the servlet the doPost method is invoked The code for doPost is similar to doGet see Example 6 8 The only difference here is that all incoming data is validated via the PersonalData class If the request is valid the Thank You page is displayed Otherwise the current page is redisplayed with error messages enabled As you can see in the code the only distinction between these two pages is that they use different stylesheets The final piece to this puzzle resides in the showPage method This method begins by crea
489. project Regardless of what your XSLT will produce start by producing the XML For the schedule web application the XML is dynamic and must be programmatically generated JDOM code is shown in Example 4 4 which produces the XML necessary to create the schedule web page Example 4 4 ScheduleJDOM java package chap4 import java text SimpleDateFormat import org jdom import org jdom output Produces a JDOM Document for a tv schedule i public class ScheduleJDOM private SimpleDateFormat dateFmt new SimpleDateFormat hh mm a Simple main method for printing the XML document to System out useful for testing m public static void main String args throws Exception Document doc new ScheduleJDOM getTodaysShows 3 new XMLOutputter true UTF 8 output doc System out return a new JDOM Document for all TV shows scheduled for today ud public Document getTodaysShows Schedule sched Schedule getInstance ie Show shows sched getTodaysShows Element rootElem new Element schedule for int i20 i shows length i rootElem addContent createShowElement shows i return new Document rootElem A helper method to convert a Show object into a JDOM Element public Element createShowElement Show show Element new Element show e addContent
490. pt Language HTTP header which may contain a list of preferred languages en es ja From this list the application can attempt to select the appropriate language and character encoding without prompting the user Chapter 13 of Java Servlet Programming Second Edition by Jason Hunter O Reilly presents a detailed discussion of this technique along with a class called LocaleNegotiator that maps more than 30 language codes to their appropriate character encodings In Figure 8 10 the results of three different transformations are displayed In the first window a Chinese XSLT stylesheet is applied to a Chinese XML datafile In the second window the English version of the XSLT stylesheet is applied to the Spanish XML data Finally the Spanish XSLT stylesheet is applied to the Chinese XML data Figure 8 10 Several language combinations E REEE MEES aloz KI vr 92440 MN 231432021324 pw 2202322323 Athais e hietp Jlocsicet ra Ad ress f2 ben HiocsheersS o ehacat t gree Lks Custorere Links us g Custonze Urbs Pree Hitma Uks Customtre Links 2 Pree Mobnal TE thx XSLT XSLT in English XSLT en Espanol AE je eis a table of nun Aqui est un vect mer RY pW Chinese English Espariol Spanish Ingl s NM Chinese r r uno res 3 ius i h n Jen 3l T E z e CR Localiriranet D ie CH teal riranet 2 Ove CY Local intranet The character encoding is generally transparent to the user Swi
491. public boolean accept File f String name f getName return f isDirectory name endsWith xsl name endsWith xslt name endsWith XSL name endsWith XSLT public String getDescription return XSLT Files The next class shown in Example 9 11 creates the window shown in Figures 9 5 and 9 6 Much of this code is responsible for arranging the JTabbedPane component which contains the three folder tabs that make up the window This class also does the actual XSLT transformation these lines are emphasized Example 9 11 TransformerWindow java package com oreilly javaxslt swingtrans import java awt import java awt event import java io import javax swing import javax swing table import javax swing event XML related imports import javax xml transform SourceLocator import javax xml transform Transformer import javax xml transform TransformerConfigurationException import javax xml transform TransformerException import javax xml transform TransformerFactory import javax xml transform stream StreamResult import javax xml transform stream StreamSource A secondary JFrame that shows the result of a single XSLT showing transformation This frame has a JTabbedPane interface the transformation result error messages and the XML output kJ public class TransformerWindow extends JFrame the result of the XSLT trans
492. putter class The following code fragment demonstrates its usage TransformerFactory transFact TransformerFactory newInstance if transFact getFeature SAXTransformerFactory FEATURE SAXTransformerFactory stf SAXTransformerFactory transFact the stylesheet parameter is an instance of JAXP s javax xml transform Templates interface TransformerHandler transHand Nn ct Fh f newTransformerHandler stylesheet result is a Result instance transHand setResult result SAXOutputter saxOut new SAXOutputter transHand the jdomDoc parameter is an instance of JDOM s org jdom Document class In contains the XML data saxOut output jdomDoc else System err println SAXTransformerFactory is not supported 5 3 6 2 JDOM to DOM approach The DOM approach is generally a little slower and will not work if JDOM uses a different DOM implementation than JAXP JDOM like JAXP can utilize different DOM implementations behind the scenes If JDOM refers to a different version of DOM than JAXP you will encounter exceptions when you try to perform the transformation Since JAXP uses Apache s Crimson parser by default you can configure JDOM to use Crimson with the org jdom adapters CrimsonDOMAdapter class The following code shows how to convert a JDOM Document into a DOM Document org jdom Document jdomDoc createJDOMDocument add data to the JDOM Document convert the JDOM D
493. quals Birth date was not correct expectedBirthDate birthDateElem getText ch JDOMException jde fail XML was not valid jde getMessage return a TestSuite which is a composite of Test objects ur public static Test suite uses reflection to locate each method named test return new TestSuite SampleUnitTest class Allow the unit tests to be invoked from the command line in text only mode public static void main String args TestRunner run suite js First notice that SampleUnitTest extends from junit framework TestCase Each subclass of Test Case defines a fixture and can contain multiple individual unit tests Each method that begins with the word test is a unit test All of the private fields in SampleUnitTest are specific to our particular needs and are not part of the JUnit framework The constructor takes the name of a unit test as an argument i public SampleUnitTest String name super name The name argument is the test method name and JUnit uses the Java reflection API to locate and instantiate the correct method As we will see in a moment this constructor is rarely called directly The setUp method is called before each unit test is executed As expected this method is used to set up preconditions before a test is executed Its counterpart is the tearDown method which is called just after each test is executed If a fixture contains
494. r create an instance of TransformerFacto javax xml transform TransformerFactory transFact javax xml transform TransformerFactory newInstance javax xml transform Transformer trans transFact newTransformer xsltSource trans transform xmlSource result As in the earlier examples explicit package names are used in the code to point out which classes are parts of JAXP In future examples import statements will be favored because they result in less typing and more readable code Our new program begins by declaring that it may throw TransformerException public static void main String args throws javax xml transform TransformerException This is a general purpose exception representing anything that might go wrong during the transformation process In other processors SAX specific exceptions are typically propagated to the caller In JAXP TransformerException can be wrapped around any type of Exception object that various XSLT processors may throw Next the command line arguments are converted into File objects In the SAXON and Xalan examples we created a system ID for each of these files Since JAXP can read directly from a File object the extra conversion to a URI is not needed File xmlFile new File args 0 File xsltFile new File args 1 je E Source xmlSource new javax xml transform stream StreamSource xmlFile NR H Pe De Source xsltSource new javax xml transform stream
495. r The quality of error messages varies widely across different XSLT processors This class can wrap around other exceptions public class TransformerException extends Exception public TransformerException String msg Throwable e public TransformerException String msg SourceLocator locator public TransformerException Throwable e public TransformerException String msg public TransformerException String msg SourceLocator locator Throwable e public Throwable getCause public Throwable getException j public String getLocationAsString public SourceLocator getLocator public String getMessageAndLocation public synchronized Throwable initCause Throwable cause public void printStackTrace PrintStream ps public void printStackTrace PrintWriter pw public void printStackTrace s public void setLocator SourceLocator locator TransformerFactory This defines a portable way to access different Trans formerFactory instances and is the key abstraction that masks differences between XSLT processors from different vendors public abstract class TransformerFactory protected TransformerFactory ys public abstract Source getAssociatedStylesheet Source source String media String title String charset throws TransformerConfigurationException public abstract Object getAttribute String name throws IllegalArgumentException public abstract ErrorListener getErrorListen
496. r descending gt xsl apply templates Se C Ck KC Ck Kk Ck CK Ck CK Ck Ck Ck CK CK Ck Ck Ck Ck CC Ck Ck Ck kk Ck Ck Sk Ck Ck kk kk kk Ak A Mk x kx ko ko ko ko ko M lti field sorting KKEKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKEKKKKKKKKKKKKKKAKKKKKKK kx ko ko kk lt h2 gt Multi field sorting example lt h2 gt xsl apply templates select president name gt xsl sort select last xsl sort select first order descending xsl apply templates gl KKEAKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK Nested xsl for each loops Ck CK ck Ck Kk Ck kk Ck Kk C Ck Ck Ck CK CK Ck Ck Kk Ck Ck Kk Sk Kk Ck Ck Ck Ck kk Ck kk Ak Sk Kk v ko Kk KKK KK LH lt h2 gt All presidents and vice presidents using xsl for each lt h2 gt ul lt xsl for each select president gt lt xsl sort select name first order descending gt lt li gt lt xsl apply templates select name gt lt li gt lt ul gt lt xsl for each select vicePresident gt lt xsl sort select name first gt lt li gt xsl apply templates select name gt lt li gt xsl for each ul xsl for each ul ele KKAKKKKKKKKKKKKKKKKKKKKKKKKKKKK Kk UK Kk kk Sk UG KG Kk Kk ko k ok ck kk kc kok Same as previous only using xsl apply templates Ck CK ck Ck Ck Ck Sk Ck CK Ck C Ck Ck Ck CK CK CK Ck Ck Ck Kk CK Ck Sk Ck kk Sk Kk Ck Ck kk Ck kk Ck kk Ak E Kk v ko Kk ko ko ko kk RH
497. r by replacing null with an empty String and by trimming whitespace from non null Strings ind private static String cleanup String str return str null str trim a us Although the PersonalData Class is merely a data holder it can include simple validation logic For example the default constructor initializes all fields to non null values public PersonalData tns uu uu ui uy Additionally all of the set methods make use of the private cleanup method private static String cleanup String str return str null str trim J ws As a result instances of this class will avoid null references and whitespace eliminating the need to perform constant error checking in the servlet and XML generation classes Trimming whitespace is particularly helpful because a user may simply press the spacebar in one of the required fields potentially bypassing your validation rules The PersonalData class also contains an explicit validation method that checks for all required fields public boolean isValid return this firstName length 29 amp amp this lastName length gt 0 amp amp this daytimePhone length gt 0 amp amp this email length gt 0 1 J The only field that is not required is eveningPhone so it is not checked here By putting this method into this class we further reduce the work required of the servlet The next class PersonalDataXML is presented
498. r is probably the way to go because you only have to write the conditional logic around the section that changes The next column in the table contains the input field lt td gt lt input type text name name value gt td In the XHTML output this yields a cell containing lt input type text name firstName value Eric gt Finally the last column in the table contains an asterisk if the field has the required true attribute td xsl if test required true gt lt xsl if gt xsl template The next stylesheet confirmPersonalData xslt is listed in Example 6 5 This stylesheet is shorter because it shows only a summary of what the user entered on the previous page It does not have to display any error messages or show an HTML form The overall structure of the stylesheet is identical to editPersonalData xsit however so a line by line description is not necessary Example 6 5 confirmPersonalData xslt lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xmlns http www w3 org 1999 xhtml xsl output method xml indent yes encoding UTF 8 doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtml1 DTD xhtmll strict dtd CC CK CK Ck S CK Ck Ck Ck Ck Ck Ck CK CC CCS C Ck C Ck CK Ck CK Ck KC CC Ck Ck Ck Ck Sk S A Kx A Ax x M o oM Top level template Creates t
499. ram name monthNumber select month gt lt xsl call template gt lt xsl text gt lt xsl text gt lt xsl value of select day gt xsl text xsl text lt xsl value of select year gt xsl apply templates select inResponseTo gt lt div gt lt pre gt lt xsl value of select text gt lt pre gt lt xsl template gt Sie Ck ck Ck ck kkk ck kk ck ck ck ck ck ck ck ck KKK ck ck ck ck ck ck kk KKK ck ck ck kk ck ck ck ck ck ck ck ck ck Sk ck ko ck Sk ko kx ko Show a link to the message that this one is in response to KKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKKKKKKK KKK KK ck k KKK ko kk D gt lt xsl template match inResponseTo gt div style text indent 2em gt xsl text In response to lt xsl text gt a href viewMsg msgID id gt lt xsl value of select subject gt lt a gt lt div gt lt xsl template gt lt xsl stylesheet gt Appendix B JAXP API Reference This appendix summarizes Version 1 1 of the Java API for XML Processing JAXP 4 JAXP provides a standard way for Java programs to interact with XML parsers and XSLT processors and is freely available from http java sun com xml JAXP also includes classes and interfaces for DOM and SAX these are not listed here Al Before transformation support was added JAXP stood for Java API for XML Parsing The biggest changes from JAXP 1 0 to JAXP 1 1 are support for level 2 of DOM and
500. ram xsltFileName the file name of the stylesheet to remove public static synchronized void flush String xsltFileName cache remove xsltFileName Obtain a new Transformer instance for the specified XSLT file name A new entry will be added to the cache if this is the first request for the specified file nam Qparam xsltFileName the file name of an XSLT stylesheet return a transformation context for the given stylesheet public static synchronized Transformer newTransformer String xsltFileName throws TransformerConfigurationException File xsltFile new File xsltFileName determine when the file was last modified on disk long xslLastModified xsltFile lastModified MapEntry entry MapEntry cache get xsltFileName if entry null if the file has been modified more recently than the cached stylesheet remove the entry reference if xslLastModified gt entry lastModified entry null create a new entry in the cache if necessary if entry null Source xslSource new StreamSource xsltFile TransformerFactory transFact TransformerFactory newInstance Templates templates transFact newTemplates xslSource entry new MapEntry xslLastModified templates cache put xsltFileName entry return entry templates newTransformer prevent instantiation of this class private
501. ransFact newTransformerHandler new StreamSource new File xsltFileName When the XSLT stylesheet is not specified the transformer performs an identity transformation This is useful when you just want to see the raw XML output without applying a stylesheet You will probably want to do this first to see how your XSLT will need to be written If a stylesheet is provided however it is used for the transformation The custom parser is then constructed as follows CSVXMLReader csvReader new CSVXMLReader i The location of the CSV file is then converted into a SAX Input Source InputSource csvInputSrc new InputSource new FileReader csvFileName And finally the XSLT processor is attached to our custom parser This is accomplished by registering the TransformerHandler as the ContentHandler On csvReader A single call to the parse method causes the parsing and transformation to occur attach the XSLT processor to the CSVXMLReader csvReader setContentHandler transHand csvReader parse csvinputSrc For a simple test assume that a list of presidents is available in CSV format Washington George Adams John Jefferson Thomas Madison James etc Bush George Herbert Walker Clinton William Jefferson Bush George W To see what the XML looks like invoke the program as follows java com oreilly javaxslt util SimpleCSVProcessor presidents csv This will parse the CSV file and apply the iden
502. ransformation Process Now that we have seen an example let s back up and talk about some basics In particular it is important to understand the relationship between xs1 template match gt and xsl apply templates select This should help to solidify your understanding of the previous example and lay the groundwork for more sophisticated processing Although XSLT is a language it is not intended to be a general purpose programming language Because of its specialized mission as a transformation language the design of XSLT works in the way that XML is structured which is fundamentally a tree data structure 12 XSLT is declarative in nature while mainstream programming languages tend to be more procedural 2 2 1 XML Tree Data Structure Every well formed XML document forms a tree data structure The document itself is always the root of the tree and every element within the document has exactly one parent Since the document itself is the root it has no parent As you learn XSLT it can be helpful to draw pictures of your XML data that show its tree structure Figure 2 2 illustrates the tree structure for discussionForumHome xml Figure 2 2 Tree structure for discussionForumHome xml matched by the pattem discussionForumHomexml discussionForumHome gel ON messageBoard messageBoard messageBoard The document itself is the root of the tree and may contain processing instructions the document root eleme
503. rarely a good idea to try sending DOM trees directly from an EJB to a client Producing XML on the EJB tier has significant drawbacks however First the size of XML text is typically quite large Compression of the text is essential particularly as the size of the XML gets larger While compression reduces bandwidth requirements it increases the processor workload on both client and server for compression and decompression This is supported by java util zip GZIPInputStream and java util zip GZIPOutputStream The second drawback is that 100 percent of an application s business logic can rarely be placed inside of EJB components Although this is an admirable goal it means that the client must make a remote network call to the server for every operation By simply returning XML to the client it is much harder for some of the business logic to be offloaded to the client machine 9 3 5 2 Sending objects from EJBs The second option is to leave XML out of the EJB components altogether Instead each bean method returns instances of helper classes such as Employee and Project Info With this approach the client can perform some business logic by invoking methods locally on the returned objects Figure 9 10 illustrates where XML production occurs in this model Figure 9 10 Generating XML on the client tier EJB Container Glient CI serialization EJB tern gt momen 2 Employee DOM XSLT Component Object 00110101000111 Object API
504. rate XML via different XSLT stylesheets Once more browsers support XSLT transformation the server load will be greatly reduced Chapter 5 XSLT Processingwith Java Since many of the XSLT processors are written in Java they can be directly invoked from a Java application or servlet Embedding the processor into a Java application is generally a matter of including one or two JAR files on the CLASSPATH and then invoking the appropriate methods This chapter shows how to do this along with a whole host of other programming techniques When invoked from the command line an XSLT processor such as Xalan expects the location of an XML file and an XSLT stylesheet to be passed as parameters The two files are then parsed into memory using an XML parser such as Xerces or Crimson and the transformation is performed But when the XSLT processor is invoked programmatically you are not limited to using static files Instead you can send a precompiled stylesheet and a dynamically generated DOM tree directly to the processor or even fire SAX events as processor input A major goal is to eliminate the overhead of parsing which can dramatically improve performance This chapter is devoted to Java and XSLT programming techniques that work for both standalone applications as well as servlets with a particular emphasis on Sun s Java API for XML Processing JAXP API In Chapter 6 we will apply these techniques to servlets taking into account issu
505. re convert the InputSource into a BufferedReader BufferedReader br null if input getCharacterStream null br new BufferedReader input getCharacterStream 3 else if input getByteStream null br new BufferedReader new InputStreamReader input getByteStream else if input getSystemId null java net URL url new URL input getSystemId br new BufferedReader new InputStreamReader url openStream 963 52 else throw new SAXException Invalid InputSource object Assuming that our 1nput Source Was valid we can now begin parsing the CSV file and emitting SAX events The first step is to notify the Content Handler that a new document has begun ch startDocument s emit csvFile Ele ch startl nt csyFile EMPTY ATTR The XSLT processor interprets this to mean the following lt xml version 1 0 encoding UTF 8 gt lt csvFile gt Our parser simply ignores many SAX 2 features particularly XML namespaces This is why many values passed as parameters to the various Cont entHandler methods simply contain empty strings The EMPTY ATTR constant indicates that this XML element does not have any attributes The CSV file itself is very straightforward so we merely loop over every line in the file emitting SAX events as we read each line The parseLine method is a private helper method that does th
506. report detailed information about where transformation errors occur and why In Example 9 9 a custom Swing table model is presented This class implements the javax xml transform Errorlistener interface and is used by a JTable to display errors graphically Later in Example 9 11 we show how to register this error listener with a TransformerFactory and Transformer Example 9 9 ErrorListenerModel package com oreilly javaxslt swingtrans import java io import java util import javax swing table XML related imports import javax xml transform ErrorListener import javax xml transform SourceLocator import javax xml transform TransformerException A JTable data model that provides detail information about a list of javax xml transform TransformerException objects Af public class ErrorListenerModel extends AbstractTableModel implements ErrorListener column positions in the table private static final in INE COL 0 private static final int COLUMN COL private static final int PUBLIC ID COL 23 private static final int SYSTEM ID COL 3 private static final int MESSAGE AND LOC COL 4 private static final int LOCATION COL 5 private static final int EXCEPTION COL 6 private static final int CAUSE COL 7 1 Ce Ct TE EE Orr DE XT er E private static final String COLUMN_NAMES Line 7 Column Public XD System ID Message
507. request are passed to the CGI script via the QUERY_STRING environment variable HTTP POST data on the other hand is piped to the standard input stream of the CGI script CGI always sends results back to the web server via its standard output Ordinary CGI programs are invoked from the web server as external programs which is the most notable difference when compared with servlets With each request from the browser the web server spawns a new process to run the CGI program Aside from the obvious performance penalty this also makes it difficult to maintain state information between requests A web based shopping cart is a perfect example of state information that must be preserved between requests Figure 4 1 illustrates the CGI process Figure 4 1 CGI process Browser Web Server amp ORELY FastCGI is an alternative to CGI with two notable differences First FastCGl processes do not exit with each request response cycle Second the environment variable and pipe I O mechanism of CGI has been eschewed in favor of TCP connections allowing FastCGI programs to be distributed to different servers The net result is that FastCGI eliminates the most vexing problems of CGI while making it easy to salvage existing CGI programs Although technically possible using Java for CGI programming is not generally a good idea In fact it is an awful idea The Java Virtual Machine JVM would have to be launched with each and every request
508. request has been processed a subclass of Renderer selects the XML and XSLT stylesheet XSLTRenderHelper does the actual XSLT transformation sending the resulting XHTML back to the browser This is not designed to be a heavyweight web application framework Instead it is just a simple set of coding conventions and patterns that help keep the application highly modular It is easy to eliminate the ReqHandler classes and use several servlets instead The main advantage of explicit request handlers and renderers is that the design is clearly modularized which may promote more consistency across a team of developers The overall flow of control may be the hardest part to understand Once this flow is clear the implementation is a matter of creating additional request handlers and renderers Figure 7 10 is a UML sequence diagram that shows how a single web browser request is intercepted and processed Figure 7 10 Sequence diagram JDOM producer I request browser servlet iior renderer I I request createData or getData TIE ew ew ew ele ew we produceElementi When a browser issues a request it is always directed to the single servlet This servlet then locates the appropriate request handler based on information found in the requested URL The request handler is responsible for interacting with the data adapter layer to create and update domain objects and for creating the appropriate re
509. required System err println xsltFile is optional System exit 1 String csvFileName args 0 String xsltFileName args length gt 1 args 1 null TransformerFactory transFact TransformerFactory newInstance if transFact getFeature SAXTransformerFactory FEATURE SAXTransformerFactory saxTransFact SAXTransformerFactory transFact TransformerHandler transHand null if xsltFileName null transHand saxTransFact newTransformerHandler else transHand saxTransFact newTransformerHandler new StreamSource new File xsltFileName set the destination for the XSLT transformation transHand setResult new StreamResult System out hook the CSVXMLReader to the CSV file CSVXMLReader csvReader new CSVXMLReader InputSource csvinputSrc new InputSource new FileReader csvFileName attach the XSLT processor to the CSVXMLReader csvReader setContentHandler transHand csvReader parse csvInputSrc else System err printin SAXTransformerFactory is not supported System exit 1 As mentioned earlier in this chapter the TransformerHandler is provided by JAXP and is an implementation of the org xml sax ContentHandler interface It is constructed by the SAXTransformerFactory as follows TransformerHandler transHand null if xsltFileName null transHand saxTransFact newTransformerHandler s else transHand saxT
510. return WML CLIENT TYPE otherwise default to XHTML return XHTML CLIENT TYPE This servlet determines the client type by looking at the HTTP User Agent and Accept headers This logic is encapsulated in the determineClientType method which first checks the User Agent for Mozilla compatible browsers such as Microsoft Internet Explorer and Netscape Navigator If the client is not one of these browsers it then checks the Accept header for cext vnd wap wml1 If both tests fail the servlet defaults to XHTML because the device did not claim to accept the WML content type Once the client browser type is identified the HTTP Content Type response header is set to the appropriate MIME type switch clientType case XHTML CLIENT TYPE res setContentType text html break case WML CLIENT TYPE res setContentType text vnd wap wml break default res sendError HttpServletResponse SC INTERNAL SERVER ERROR return The default case will occur only if the servlet has a bug Therefore it simply causes the code to fail with an internal server error A helper method called 16catestyiesheet is then used to locate the appropriate XSLT stylesheet File xsltFile locateStylesheet req clientType pageToShow In this application there are two sets of XSLT stylesheets One resides in a directory named wml and another resides in a directory named xhtml Just lik
511. return the message with the specified id throws DataException if msgID does not exist or a database error occurs xj public Message getMessage long msgID throws DataException Connection con null Statement stmt null try con DBUtil getConnection dbURL stmt con createStatement ResultSet rs stmt executeQuery SELECT inReplyToID createDay createMonth createYear boardID subject authorEmail msgText FROM Message WHERE id msgID if rs next 9 d long inReplyToID rs getLong 1 int createDay rs getInt 2 int createMonth rs getInt 3 int createYear rs getInt 4 long boardID rs getLong 5 String subject rs getString 6 String authorEmail rs getString 7 String msgText DBUtil getLongString rs 8 BoardSummary boardSummary this getBoardSummary boardID stmt createYear return new MessageImpl msgID new DayMonthYear createDay createMonth boardSummary subject authorEmail msgText inReplyTOoID else throw new DataException Illegal msgID catch SQLException sqe finally Sqe printStackTrace throw new DataException sqe getMessage DBUtil close stmt con Add a reply to an existing message Qthrows DataException if a database error occurs or if any parameter is illegal af public Message replyToMessage long origMsgID
512. rform validation A really ambitious programmer might want to create a simple GUI front end that allows graphical editing of the lt dependent Ob ject gt structure An XSLT stylesheet performs the actual code generation The output method should be set to text and particular attention must be given to whitespace With HTML or XHTML output whitespace is largely irrelevant Since browsers collapse multiple spaces and linefeeds into a single space the XSLT stylesheet can be indented and spaced however you like But with a code generator formatting is a much higher priority This can lead to stylesheets that are much harder to read which is the main drawback of using XSLT as a code generator Example 8 15 shows the dependent object code generator stylesheet Example 8 15 dependentObject xslt lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method text gt lt xsl variable name className select dependentObject class gt 1 OK c Ok c Ck ck kk Ck ok Ck Ck Ck Ck Ck ck ck ck kk kk Ck ck Ck Ck kk ck Sk Ck ck ck Ck Ck ck ok ck kk kk Sk ck kk kk kk ck ck Sk Sk Sk Sk Sk Sk Mk Sk Mk Kk ko ko ko oko Generate the class skeleton Other templates will generate portions of the class CKCkCKkCkCk ckck ck ck ck kCckck ck KKK ck k ck kck KKK ck ck ck ck k ck ck ck ckckck ck ck ck ck k ck ck k ck ck k ck kck ck ck ckck ck KKK KKK KKK gt lt xsl
513. ring void DOMResult SAXResult StreamResult java io InputStream SAXSource DOMSource lt lt interface gt gt org w3c dom Node lt lt interface gt gt org xml sax XML Reader org xml sax InputSource java io InputStream java io Reader lt lt interface gt gt org w3c dom Node java io Reader lt lt interface gt gt org xml sax ContentHandler As you can see JAXP is not particular about where it gets its data or sends its results Remember that two instances of Source are always specified one for the XML data and another for the XSLT stylesheet 5 3 3 JAXP Stream I O As shown in Figure 5 3 St reamSource is one of the implementations of the Source interface In addition to the system identifiers that Source provides St reamSource allows input to be obtained from a File an InputStream ora Reader The SimpleJaxp class in Example 5 3 showed how to use St reamSource to read from a File object There are also four constructors that allow you to construct a St reamSource from either an InputStream or Reader The complete list of constructors is shown here public StreamSource public StreamSource File f public StreamSource String systemId public StreamSource InputStream byteStream public StreamSource InputStream byteStream String systemId public StreamSource Reader characterStream public StreamSource Reader characterStream String systemId
514. rning TransformerException ex The TranstormerException has the ability to wrap around another Exception or Throwable object and may return an instance of the SourceLocator class If the underlying XSLT implementation does not provide a SourceLocator null is returned The SourceLocator interface defines methods to locate where a TransformerException originated In the case of error and warning the XSLT processor is required to continue processing the document until the end For fatalError onthe other hand the XSLT processor is not required to continue If you do not register an ErrorListener object then all errors fatal errors and warnings are normally written to System err sformerFactoryConfigurationError and iformerConfigurationException round out the error handling APIs for JAXP indicating problems configuring the underlying XSLT processor implementation The TransformerFactoryConfigurationError class is generally used when the implementation class cannot be found on the CLASSPATH or cannot be instantiated at all TransformerConfigurationException simply indicates a serious configuration error according to its documentation 5 3 Input and Output XSLT processors like other XML tools can read their input data from many different sources In the most basic scenario you will load a static stylesheet and XML document using the java io File class More commonly the XSLT stylesheet will come from a file but the XML dat
515. rocess the text and XML output panels are blank Instead the user is presented with the display shown in Figure 9 7 Figure 9 7 Transformation problems XSLT Transformation f Text Output Transformation Problems XML Output Line Column Public 1D System ID Message amp Location Location Exception Cause 1 1 seelect attribute is not allowed Line 1 1 xsl value of requires attribute s Line amp N A N A N A N A java lang NullPointerE xce ption java lang java lang javax xml transform TransformerException Line Number 1 Column Number 1 Public ID mull System ID mull Message amp Location xsl value of requires attribute select Line 1 Column Location Do Line 1 Column 1 Exception gt mull Cause mull This display shows how the ErrorListenerModel presented in Example 9 9 is used The JTable atthe top of the screen shows a tabular view of all errors and the text area at the bottom of the screen shows the output from ErrorListenerModel s getDetailReport method In the error shown a select attribute was intentionally misspelled in an XSLT stylesheet as seelect 9 2 3 2 Source code The source code for the main window is shown in Example 9 10 This is a subclass of JF rame that allows the user to select XML and XSLT filenames This class is almost entirely GUI related code and is not discussed further Example 9 10 SwingTransformer java
516. rom the underlying XML data Once fully tested the XSLT can be deployed to the web server without recompiling the Java code or restarting the servlet The XML data produced by JDOM is shown in Example 4 5 Example 4 5 XML for schedule web page lt xml version 1 0 encoding UTF 8 lt xml stylesheet type text xsl href schedule xslt schedule show lt channel gt 2 lt channel gt lt from gt 06 00 AM lt from gt lt to gt 06 30 AM lt to gt lt title gt Baseball lt title gt lt show gt lt show gt lt channel gt 3 lt channel gt lt from gt 06 00 AM lt from gt lt to gt 08 00 AM lt to gt lt title gt Stand up Comedy lt title gt show remaining XML omitted lt schedule gt The stylesheet that produces the exact same output as the JSP and servlet is listed in Example 4 6 Example 4 6 schedule xslt lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html Produce the HTML Document gt lt xsl template match gt lt html gt lt head gt lt title gt Today s Shows lt title gt lt head gt lt body gt lt hl gt Today s Shows lt h1 gt lt table cellpadding 3 border 1 cellspacing 0 gt tr lt th gt Channel lt th gt lt th gt From lt th gt lt th gt To lt th gt lt th gt Title lt th gt ftr lt select the shows
517. roperties and stylesheet parameters In XSLT a stylesheet parameter is declared and used as follows lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html xsl param name z image dir select images gt lt xsl template match gt html lt body gt lt hl gt Stylesheet Parameter Example lt h1 gt img src image_dir sample gif gt lt body gt lt html gt lt xsl template gt lt xsl stylesheet gt The xs1 param element declares the parameter name and an optional select attribute This attribute specifies the default value if the stylesheet parameter is not provided In this case the string images is the default value and is enclosed in apostrophes so it is treated as a string instead of an XPath expression Later the image_dir variable is referred to with the attribute value template syntax image dir Passing a variable for the location of your images is a common technique because your development environment might use a different directory name than your production web server Another common use for a stylesheet parameter is to pass in data that a servlet generates dynamically such as a unique ID for session tracking From JAXP pass this parameter via the Transformer instance The code is simple enough javax xml transform Transformer trans transFact newTransformer xsltSource tra
518. roving all the time 9 1 Development Environment Specialized lightweight development tools have never been more important to Java developers Commercial integrated development environments IDEs are now only one small piece of a larger suite of essential tools used by a majority of Java development projects These build tools such as Ant testing tools such as JUnit and various XML parsers and XSLT processors Figure 9 1 illustrates some of the tools found in a typical Java and XSLT development environment Figure 9 1 Common Java XML and XSLT tools Servlet Container XSLT Processor Development Environment EJB Container Although this is a typical development environment it can be a large number of tools to keep track of Table 9 1 summarizes how each of these tools is used Tool Java 2 SDK Apache s JMeter EJB Container XML Parser XSLT Processor Servlet Container JAXP Apache s Ant IDE JUnit Table 9 1 Tool overview Description The Java 2 software development kit i e the JDK A stress testing tool primarily used to test scalability and performance of servlets and web sites Enterprise JavaBeans server such as JBoss Enhydra WebLogic or WebSphere Xerces Crimson or another SAX and or DOM parser Xalan SAXON or any other XSLT processor Apache s Tomcat or any other servlet host Many application servers include both servlet containers and EJB containers Provides a co
519. rrorDialog Unable to read XSLT file return show the results of the transformation in a new window new TransformerWindow transform xmlFile xsltFile The entry point into the application shows the main window Xy public static void main String args new SwingTransformer setVisible true Construct the main window and layout the GUI public SwingTransformer super Swing XSLT Transformer note this line requires Java 2 v1 3 setDefaultCloseOperation JFrame EXIT ON CLOSE Container cp getContentPane cp setLayout new GridBagLayout GridBagConstraints gbc new GridBagConstraints gbc anchor GridBagConstraints WEST gbc fill GridBagConstraints HORIZONTAL gbc gridx GridBagConstraints RELATIVE gbc gridy 0 gbc insets top 2 gbc insets left 2 gbc insets right 2 cp add new JLabel XML File gbc gbc weightx 1 0 cp add this xmlFileFld gbc gbc weightx 0 0 cp add new JButton this loadXMLAction gbc gbc gridy t cp add new JLabel XSLT File gbc gbc weightx 1 0 cp add this xsltFileFld gbe gbc weightx 0 0 cp add new JButton this loadXSLTAction gbc gbc gridyt gbc gridx 0 gbc gridwidth GridBagConstraints REMAINDER gbc anchor GridBagConstraints CENTER gbc fill GridBagConstraints NONE cp add new JButton this transformAction gbc
520. rs5 gt lt times gt 1 30 4 00 6 00 lt times gt lt movie gt lt movie ref back2future2 gt lt times gt 4 00 6 00 8 00 10 00 lt times gt lt movie gt lt theater gt A A A additional theater elements lt city gt additional city elements lt movies gt As you can see in the XML nothing in the data indicates that the output must be WML In fact this application can support both XHTML and WML output via different XSLT stylesheets Of course WML support is the primary goal of this application Therefore lt shortName gt is included to support wireless devices If this were targeted towards only web browsers this element would not be required 10 3 3 3 WML prototypes and screen shots When using XSLT to produce XHTML or WML it is a good idea to start with prototypes This is because XSLT adds a level of indirection that makes it hard to visualize the result It is much easier to simply create static WML first test it using a simulator and then develop the XSLT stylesheets once everything is working Example 10 6 lists the first WML deck used in this example As mentioned earlier this deck contains two cards the first of which is a splash screen that displays for 1 5 seconds Example 10 6 Home page WML lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE wml PUBLIC WAPFORUM DTD WML 1 1 EN http www wapforum org DTD wml_1 1 xml gt lt wml gt card ontimer home
521. rts by setting the output method to text and creating a variable for the class name The variable allows us to avoid typing lt xsl value of select dependentObject class gt whenever the class name is needed The xs1 text element is used frequently in code generator stylesheets because it allows for more control over whitespace In several places this element is used to introduce linefeeds in the output For instance xsl text implements java io Serializable xsl text Because the closing tag is on the next line the linefeed character will be preserved faithfully lt xsl text gt is also used to introduce individual spaces private lt xsl value of select type gt lt xsl text gt lt xsl text gt lt xsl value of select name gt lt xsl template gt By default XSLT processors ignore whitespace between two XSLT elements unless some nonwhitespace characters are also present The private text shown just before xs1 value of select type gt for example contains nonwhitespace text followed by a space In this case the space after the word private will be preserved But the space between the two xsl value oft elements will be ignored unless it is explicitly preserved with lt xs1 text gt lt xsl text gt Getting everything to indent and line up is challenging but is not an insurmountable problem It usually boils down to a lot of XSLT tweaking until everything looks just right Using a
522. rue ttribute cust IDR In this code the current Cust field is obtained from the Ht tpSession whenever a client enters the doGet method Unfortunately if another thread invokes this method an instant later the currentCust field will be overwritten before the first thread is complete In fact dozens of threads could enter the doGet method at roughly the same time repeatedly replacing the currentCust reference This would lead to complete failure of this servlet The easy fix is to make currentCust a local variable as follows public class HomeServlet extends HttpServlet protected void doGet HttpServletRequest request HttpServletResponse response throws IOException ServletException HttpSession session request getSession true Customer currentCust Customer session getAttribute cust currentCust setLastAccessedTime new Date ys This fixes our problem because each thread gets its own copy of local variables in Java By simply removing the object field and replacing it with a local variable this particular threading problem is resolved 6 5 2 2 Tip 2 Immutable objects are thread safe Whenever two or more threads make changes to the same object at the same time a race condition can occur Consider the following code public class Person private String firstName private String lastName public void setName String firstName String lastName this firstName firstN
523. rvlet import javax servlet http Handle a request to view a message F public class ViewMsgReqHandler extends ReqHandler protected String getPathInfo return viewMsg protected Renderer doGet HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException try DataAdapter adapter DataAdapter getInstance msgID is a required parameter and must be valid String msgIDStr request getParameter msgID if msgIDStr null servlet log Required parameter msgID was missing return new ErrorRenderer Invalid request Message msg adapter getMessage Long parseLong msgIDStr MessageSummary inResponseTo null if msg getInReplyTo gt 1 inResponseTo adapter getMessage msg getInReplyTo return new ViewMsgRenderer msg inResponseTo catch NumberFormatException nfe servlet log msgID parameter was not a number return new ErrorRenderer Invalid request catch DataException de return new ErrorRenderer de The corresponding renderer viewMsgRenderer is shown in Example 7 36 This class follows the same basic approach as other renderers it produces a JDOM Document and uses XSLTRenderHelper to perform the XSLT transformation Example 7 36 ViewMsgRenderer java package com oreilly forum servlet impor impor impor impor impor impor
524. s implementing the org xml sax XMLReader interface which provides numerous methods you can safely ignore for most applications For example when parsing a CSV file it is probably not necessary to deal with namespaces or validation The code for Abst ract XMLReader java is shown in Example 5 5 This is an abstract class that provides basic implementations of every method in the XMLReader interface except for the parse method This means that all you need to do to write a parser is create a subclass and override this single method Example 5 5 AbstractXMLReader java package com oreilly javaxslt util import java io IOException import java util import org xml sax An abstract class that implements the SAX2 XMLReader interface Th intent of this class is to make it easy for subclasses to act as SAX2 XMLReader implementations This makes it possible for example for them to emit SAX2 events that can be fed into an XSLT processor for transformation r public abstract class AbstractXMLReader implements org xml sax XMLReader private Map featureMap new HashMap private Map propertyMap new HashMap private EntityResolver entityResolver private DTDHandler dtdHandler private ContentHandler contentHandler private ErrorHandler errorHandler The only abstract method in this class Derived classes can parse any Source of data and emit SAX2 events to the ContentHandler
525. s IllegalArgumentException public abstract void setOutputProperty String name String value throws IllegalArgumentException public abstract void setParameter String name Object value public abs tURIResolver URIResolver resolver ract void se ract void transform Source xmlSource Result ct ct public abs outputTarget throws TransformerException TransformerConfigurationException This exception indicates a serious problem and may occur when an XSLT stylesheet has syntax errors that prevent instantiation of a Transformer instance This class can wrap around other exceptions For example an underlying parser exception may be wrapped by an instance of this class public class TransformerConfigurationExcept ion extends TransformerException public TransformerConfigurationException String msg public TransformerConfigurationException Throwable e public TransformerConfigurationException String msg Throwable e public TransformerConfigurationException String msg SourceLocator locator public locator ransformerConfigurationException String msg SourceLocator Throwable e public TransformerConfigurationException s TransformerException This is a general purpose exception that occurs during transformation If an ErrorListener is registered the processor should try to report exceptions there first Otherwise exceptions are written to System er
526. s a summary for an individual message Example 7 12 MessageSummary java package com oreilly forum domain import java util Basic information about a message not including the m public interface MessageSummary extends Comparable D n n w Q 0 Cr D x ct return iA long getInReplyTo Js ct 1e ID of the message that this one is a reply to or 1 if none jhk return NU long getID ct he unique ID of this message rA DayMonthYear getCreateDate return when this message was created return the board that this message belongs to BoardSummary getBoard return the subject of this messa te e it String getSubject kxk The author Email can be 80 characte String getAuthorEmail D 6 n The only thing missing from the MessageSummary interface is the actual message text The Message interface which extends from MessageSummary adds the get Text method This interface is shown in Example 7 13 Example 7 13 Message java package com oreilly forum domain Represent a message including the text k public interface Message extends MessageSummary The decision to keep the message text in a separate interface was driven by a prediction that performance could be dramatically improved Consider a web page that shows a hierarchical view of all messages for a
527. s are extremely fast because the same VM instance is used for most steps in the build process Ant can be acquired form http jakarta apache org ant The original author of Ant is working on a new Java build tool called Amber available at http www xiyo org Amber 9 1 2 1 Installing Ant To install Ant simply download the binary distribution and uncompress to a convenient directory Then set the ANT HOME environment variable to point to this directory and JAVA HOME to point to the Java installation directory To test type ant version This should display something similar to the following 2 Ant version 1 3 compiled on March 2 2001 Since Ant is written in Java care must be taken to avoid conflicts with Ant s JAR files and JAR files found in the system CLASSPATH This is a particular concern when using Ant to drive the XSLT transformation process because Ant ships with JAXP 1 0 JAR files that are not compatible with newer JAXP 1 1 implementations Once Ant is installed update ANT HOME lib jaxp jar and ANT HOME lib parser jar which are part of the older JAXP 1 0 reference implementation Any JAR files added to the ANT HOME Iib directory are automatically added to Ant s CLASSPATH and will be seen by the various Ant tasks during the build process Simply adding JAXP 1 1 compatible JAR files to the ANT HOME Iib directory will prevent most conflicts with newer applications that require DOM 2 SAX 2 or support for XSLT tra
528. s can be executed with a single command 9 2 1 2 Running the test To run the test from the command line type the following command java chap9 SampleUnitTest This works because the fixture contains the following main method oublic static void main String args I J J estRunner run suite yee The TestRunner Class is a command line tool that reports the following output when all tests succeed Time 1 081 OK 2 tests The two dots in the first line of output represent each of the test methods As each unit test executes a new dot appears If a test fails JUnit reports a stack trace a sometimes descriptive message and the line number of the failure At the end the number of tests failures and errors are reported JUnit also has a Swing GUI client that can be executed with the following command java junit swingui TestRunner chap9 SampleUnitTest Figure 9 4 shows the graphical output when errors occur Figure 9 4 JUnit output with errors name chap9 Sampleunit Test gt Run Reload classes every run turns rors Failures 2 2 ltestTransformVWimTemplates chapg SampieUnifTest Name was not correct expected Aidan Garrett Burke b Run testTranstormer chao9 SampleUnitT est Name was not correct expected Aldan Garet Burke but was Alde 4 d Failures Test Hierarchy junit framewark AssertlonF alledError Name was not correct expected Aldan Garrett Burke but was Alde
529. s chapter is to demonstrate how to design and implement a nontrivial web application using XSLT and Java The second goal is to produce a decent application that can actually be used in the real world Hopefully this has been achieved Although making an example of this size fit into a single chapter involves a few tradeoffs the design is flexible enough to allow new features such as user authentication to be implemented without too much additional effort The discussion forum requires the following Java packages e Java 2 Standard Edition v1 2 or later e JDOM beta 6 e Any JAXP 1 1 compatible XML parser and XSLT processor e Any servlet container that supports Version 2 2 or later of the servlet specification e Either MySQL or Microsoft Access 7 1 Overall Process Developing a web application using Java and XSLT can be broken down into several key steps As in any software development project a modular approach that can be dispatched to several developers simultaneously is highly desirable This speeds the overall process and allows developers of different skill levels to participate Our process consists of the following high level steps e Define the requirements e Create prototype XHTML web pages e Create prototype XML datafiles e Create XSLT stylesheets e Design and implement the Java domain classes e Design and implement the database and related code e Create XML producer objects e Implement the servlets and related c
530. s in the generated servlet code The only major performance hit occurs for the first person to visit the JSP because it will have to be translated and compiled Most JSP containers provide options to precompile the JSP so even this hit can be avoided Debugging in JSP can be somewhat challenging Since JSP pages are machine translated into Java classes method signatures and class names are not always intuitive When a programming error occurs you are often faced with ugly stack traces that show up directly in the browser You do have the option of specifying an error page to be displayed whenever an unexpected condition occurs This gives the end user a more friendly error message but does little to help you diagnose the problem Here is a portion of what Apache s Tomcat shows in the web browser when the closing curly brace is accidentally omitted from the loop shown in the JSP example A Servlet Exception Has Occurred org apache jasper JasperException Unable to compile class for JSP NworkNlocalhostNchap4N 0002fschedule 0002ejspschedule jsp 2 java 10 catch without try catch Throwable t O NworkNMlocalhostNchap4N 0002fschedule 0002ejspschedule jsp 2 java 112 try without catch or finally NworkNlocalhostNchap4N 0002fschedule 0002ejspschedule jsp 2 java 112 expected at org apache jasper compiler Compiler compile Compiler java 294 at org apache jasper servlet JspServlet doLoadJSP JspServlet ja
531. s is essentially the approach that java lang String takes Immutable objects are not always an option but can be a useful technique for many smaller data helper classes that seem to pop up in every application 6 5 2 3 Tip 3 Provide a single point of entry When dealing with a single instance of a shared resource such as a file that needs to be modified you should consider creating a facade around that resource This is a single class that provides controlled access to that resource thus providing a single point in your code for proper synchronization The following code snippet illustrates how you can essentially create a facade around a data source that holds Customer objects It is assumed that the Cust omer class is immutable making it impossible to change a Customer instance without going through this well defined API public class CustomerSource public static synchronized Customer getCustomer String id read the customer from a file or perhaps f from a database oe public static synchronized Customer createCustomer create a new customer in the file or database and return it public static synchronized void deleteCustomer String id i This is just one simple approach that works best on smaller applications A servlet s doGet or doPost method should utilize the Cust omerSource class without any data corruption If the methods in CustomerSource are slow however they wil
532. s moviedef id curId longName gt lt em gt lt p gt lt p gt lt xsl value of select times gt lt p gt lt card gt lt xsl template gt lt xsl stylesheet gt As described earlier in this chapter this deck creates a template that defines a Back button visible on all but the first card The template is produced just before the first card which also happens to be the one card that shadows the template with a lt noop gt element The following xs1 apply templates element selects the correct city and theater based on the stylesheet parameters city_id and theater_id C raa eg elect city id Scity_id theater id Stheater_id gt Although this syntax was covered in detail back in Chapter 2 here is a quick review of how it works 1 Select all lt city gt children of the lt movies gt element 2 Use the predicate 6 d city id to narrow this list down to the correct city 3 Select all neater children of the ci cy 4 Use the predicate id Stheater_id to narrow this list down to a single lt theater gt After the home card is created xs1 apbply templates is used to create one card per movie sess D pply templates t ec nity id Scity_id theater id Stheater_id movie se mode Cassata Q This uses template modes a technique covered in Chapter 3 It causes the following template to be instantiated since it has a matching mode lt xsl template match
533. s of lt name gt includes the lt first gt and lt last gt elements Another axis is parent which represents the immediate parent of the context node In many cases the axis is empty For example the document root node has no parent axis Figure 2 4 illustrates some of the other axes Figure 2 4 XPath axes parent axis ancestor axis context node self axis child axis a descendant axis department As you can see the second lt department gt element is the context node The diagram illustrates how some of the more common axes relate to this node Although the names are singular in most cases the axes represent node sets rather than individual nodes The code lt xsl apply templates select child team gt selects all lt team gt children not just the first one Table 2 1 lists the available axes in alphabetical order along with a brief description of each Table 2 1 Axes summary Axis name Description The parent of the context node its parent and so on until the root node is SRGEGSET reached The ancestor of the root is an empty node set ancestor or The same as ancestor with the addition of the context node The root node self is always included attribute All attributes of the context node All immediate children of the context node Attributes and namespace nodes niig E are not included a All children grandchildren and so forth Attribute and namespace nodes are descendan
534. s you can see required fields are marked with an asterisk This screen is rendered using editPersonalData xslt Figure 6 5 Blank personal information form http localhost 8080 chap6 personalData Microsoft Intern Ele Edt wew Favorites Tools Help Ka 42 Back A A Search LijFavorites BHistory or Address e http localhost 8080 chac6 personalata eGo wks Personal Information Fields marked with are required First Name Last Name Daytune Phone Evening Phone Email Submit CE Local intranet Figure 6 6 shows how this same screen looks after the user clicks on the Submit button If data is missing an error message is displayed in red and required fields are marked in bold Any other error messages are also displayed in red This view is also rendered using editPersonalData xslt Figure 6 6 Personal information form with errors T http localhost 8080 chap6 personalData Microsoft Intern si x Ble ER wew Favores Toos Heb e Adress ES http jlocalhost 8080 chap6 personalbata T Cw Moa Personal Information Fields marked with are required First Name Enc Last Name Burke Evening Phone Once all of the data has been entered properly the screen shown in Figure 6 7 is displayed Unlike the previous examples this screen is rendered using confirmPersonalData xsit To make changes to any of these screens one needs to edit only t
535. sagetTree is constructed it is given an Iterator of all messages in a month From this terator the idToMsgMap data structure is built All messages are stored in idToMsgMap Which is used for rapid retrieval based on message ids While building the idToMsgMap the constructor also builds the reply IDToMsghistMap The keys in this map are reply to ids and the values are lists of message ids In other words each key maps to a list of replies After the first two data structures are built the list of top level messages is built This is accomplished by looping over all keys in the idToMsgMap and then looking for messages that have a reply to id of 1 In addition messages whose reply to id could not be located are also considered to be top level messages This occurs when a message is in reply to a previous month s message All of this code can be seen in the MessageTree constructor 7 3 2 Data Adapter Layer Bridging the gap between an object oriented class library and a physical database is often quite difficult Enterprise JavaBeans EJB can be used for this purpose However this makes it extremely hard to deploy the discussion forum at a typical web hosting service By limiting the application to servlets and a relational database it is possible to choose from several ISPs that support both servlets and JDBC access to databases such as MySQL In addition to the software constraints found at most web hosting providers design flexibility is
536. se select a message board to view lt h3 gt lt ul gt lt xsl apply templates select discussionForumHome messageBoard gt lt ul gt lt body gt lt html gt lt xsl template gt When the XSLT processor begins its transformation process it looks in your stylesheet for a template that matches the pattern This pattern matches the source XML document that is being transformed You may recall from Chapter 1 that DOM uses the Document interface to represent the document which is what we are matching here This is always the starting point for processing so nearly every stylesheet you write will contain a template similar to this one Since this is the first template to be instantiated it is also where we create the framework for the resulting HTML document The second template which matches the messageBoard pattern is currently ignored This is because the processor is only looking at the root of the XML document and the messageBoard element is nested beneath the discussionForumHome element Most of the tags in this template do not start with lt xsl so they are simply copied to the result tree In fact the only dynamic content in this particular template is the following line which tells the processor to continue the transformation process xsl apply templates select discussionForumHome messageBoard Without this line the transformation process would be complete because the pattern was already located an
537. select all lt recipient gt elements from the previous example then filter reduce the list down to the first one burke_e ociweb com Positions start at 1 rather than 0 As Example 2 8 will show predicates can contain any XPath expression and can become quite sophisticated 2 4 4 Location Paths Location paths consist of one or more location steps separated by slash characters An absolute location path begins with the slash character and is relative to the document root All other types of location paths are relative to the context node Paths are evaluated from left to right just like a path in a file system or a web site The XML shown in Example 2 7 is a portion of a larger file containing basic information about U S presidents This is used to demonstrate a few more XSLT and XPath examples Example 2 7 presidents xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xpathExamples xslt presidents president term from 1789 to 1797 gt lt name gt lt first gt George lt first gt lt last gt Washington lt last gt lt name gt lt party gt Federalist lt party gt lt vicePresident gt lt name gt lt first gt John lt first gt lt last gt Adams lt last gt lt name gt lt vicePresident gt lt president gt lt president gt lt term from 1797 to 1801 gt lt name gt lt first gt John lt first gt lt last gt Adams lt last gt
538. sents the XML document itself using the org w3c dom Document interface The document root element on the other hand is represented using the org w3c dom Element interface In the presidents example the lt presidents gt element is the document root element In DOM almost every interface extends from the org w3c dom Node interface Document and Element are no exception The Node interface provides numerous methods to navigate and modify the DOM tree consistently Strangely enough the DOM Level 2 Recommendation does not provide standard mechanisms for reading or writing XML data Instead each vendor implementation does this a little bit differently This is generally not a big problem because every DOM implementation out there provides some mechanism for both parsing and serializing or writing out XML files The unfortunate result however is that reading and writing XML will cause vendor specific code to creep into any application you write At the time of this writing a new W3C document called Document Object Model DOM Level 3 Content Models and Load and Save Specification was in the working draft status Once this specification reaches the recommendation status DOM will provide a standard mechanism for reading and writing XML Since DOM does not specify a standard way to read XML data into memory most DOM if not all implementations delegate this task to a dedicated parser In the case of Java SAX is the preferred parsing te
539. ser Agent for Opera browsers always contains Opera version where version is something like 2 0 or 3 0 With these rules in mind the algorithm for detecting a browser might look something like this if begins with Lynx browser is only capable of displaying text else if contains MSIE browser is Internet Explorer else if contains Opera browser is Opera else if begins with Mozilla orowser is Netscape compatible else orowser is unknown In a servlet the following code is used to obtain the value of User Agent protected void doGet HttpServletRequest req HttpServletResponse res throws IOException ServletException String userAgent req getHeader User Agent String xslt null if userAgent startsWith Lynx xslt textHomePage xslt else xslt htmlHomePage xslt For more sophisticated applications it is desirable to use a utility class that can identify the browser its version number and possibly even its platform Although you can certainly write your own class using basic java lang String operations a better option is to use an existing API that someone else has written The screen capture shown in Figure 8 4 illustrates the output from a simple servlet that identifies various pieces of information about the browser Figure 8 4 Browser detection fi Netscape amp joj xj a Eile Edt View Search Go Bookmarks Tasks Help SN md n
540. sers and an XSLT processor its key benefit is the choice of tools afforded to Java developers Vendor lock in should be much less of an issue thanks to JAXP Since JAXP is primarily a Java based API we will cover its programmatic interfaces in depth as we talk about XSLT programming techniques in Chapter 5 JAXP currently includes Apache s Xalan as its default XSLT processor so the Xalan instructions presented in Chapter 2 will also apply to JAXP 1 5 Web Browser Support for XSLT In a web application environment performing XSLT transformations on the client instead of the server is valuable for a number of reasons Most importantly it reduces the workload on the server machine allowing a greater number of clients to be served Once a stylesheet is downloaded to the client subsequent requests will presumably use a cached copy therefore only the raw XML data will need to be transmitted with each request This has the potential to greatly reduce bandwidth requirements Even more interesting tricks are possible when JavaScript is introduced into the equation You can programmatically modify either the XML data or the XSLT stylesheet on the client side reapply the stylesheet and see the results immediately without requesting a new document from the server Microsoft introduced XSLT support into Version 5 0 of Internet Explorer but the XSLT specification was not finalized at the time Unfortunately significant changes were made to XSLT befor
541. session getAttribute shoppingCart if cart null cart new Cart s session setAttribute shoppingCart cart The first line of the doGet method locates the Ht tpSession instance associated with the current user The true parameter indicates that a new session should be created if one does not already exist Once the session is created a Cart object can be retrieved using HttpSession s getAttribute method Browser cookies provide the standard method of implementing HttpSession A cookie is a small piece of information stored on the client machine and generally contains a randomly generated sequence of characters that uniquely identifies a user When the browser issues a request to the servlet the servlet looks for a cookie named jsessionid and uses its value to locate an instance of Ht tpSession Figure 8 3 illustrates the normal session tracking model Figure 8 3 Session tracking Fred WEB TIER Instance Other users 2039858 Session data 3 E HttpSession Instance 3949576 eJ 7993622 e Client jsessionid is used to locate an instance HitpSession Fred s session of HttpSession Instance data jsessionid 7993622 jsessionid is stored in a cookie on Fred s machine Cookies are a mixed blessing Although they make session tracking very easy to implement this leads to security concerns because people do not want their browsing habits monitored Therefore quite a few people set
542. si attribute can be quite complex for a simple attribute value Fortunately XSLT provides a much simpler syntax called attribute value templates AVT The next example uses an AVT to achieve the identical result lt xsl template match book gt g Ali lt a href http www amazon com exec obidos ASIN isbn gt lt xsl value of select title gt a p lt a gt lt la gt lt xsl template gt The curly braces inside of the attribute value cause the magic to happen Normally when the stylesheet encounters attribute values for HTML elements it treats them as static text The braces tell the processor to treat a portion of the attribute dynamically In the case of isbn the contents of the curly braces is treated exactly as lt xsl value of select isbn gt in the previous approach This is obviously much simpler The text inside of the characters can be any location path so you are not limited to selecting attributes For example to select the title of the book simply change the value to title So where do you use AVTs and where don t you Well whenever you need to treat an attribute value as an XPath expression rather than static text you may need to use an AVT But for standard XSLT elements such as lt xsl template match pattern you don t need to use the AVT syntax For nonXSLT elements such as any HTML tag AVT syntax is required 2 6 3 lt xsl attribute set gt There are times when
543. sions of SAX 1 0 and 2 0 Many changes were made in version 2 0 and the SAX examples in this book use this version Most SAX parsers should support the older 1 0 classes and interfaces however you will receive deprecation warnings from the Java compiler if you use these older features Java SAX parsers are implemented using a series of interfaces The most important interface is org xml sax ContentHandler which has methods such as startDocument startElement characters endElement and endDocument During the parsing process startDocument is called once then startElement and endElement are called once for each tag in the XML data For the following XML lt first gt George lt first gt the startElement method will be called followed by characters followed by endElement The characters method provides the text George in this example This basic process continues until the end of the document at which time endDocument Is called Depending on the SAX implementation the characters method may break up contiguous character data into several chunks of data In this case the chaxacters method will be called several times until the character data is entirely parsed Since ContentHandler is an interface it is up to your application code to somehow implement this interface and subsequently do something when the parser invokes its methods SAX does provide a class called Defaul
544. sitors can either return to the month view or click on a link to reply to this message The final page allows users to either post a new message or reply to an existing message Since posting and replying are quite similar much of the Java and XSLT stylesheet code is reused Although using the same code for multiple web pages reduces the size of the application it can add complexity because the code must be capable of two modes of operation 7 2 Prototyping the XML Once the requirements and screen flow are well understood it is possible to move on to a more rigorous design process Web sites based on XSLT are highly modular facilitating a design and implementation process that can be farmed out to several members of a development team Each piece can be developed and tested independently before finally bringing everything together into the completed web application 7 2 1 XHTML Prototypes Creating user interface prototypes is an early task that can be handed off to less experienced programmers or perhaps to a dedicated web page designer At this stage in the game an overly complex and graphical web interface is not required The bells and whistles can be added later by merely updating XSLT stylesheets In fact too much effort at this early stage can make it more difficult to figure out what the XML and XSLT should look like Since the front end will be created using XHTML Strict a separate cascading style sheet CSS will be required to m
545. sl apply templates select project gt lt body gt lt html gt lt xsl template gt lt l kckckckckckckckckckckckckckckckck ck ck ck ockokokokokokckckckckckckckckckckckckckokokokokckckockckckckckckckckckckckckck k ko ko kk project templat KCKCKCKCkCk ck ck kckck kc kckck ck ck ck ck ck ck ck ck kckckckckckck ck ck ck k ck KKK KK ck ck k ck ck ck KKK KKK ck kc KKK KKK M lt xsl template match project gt show the project summary table listing basic info such as name default target and base directory gt table border 1 cellpadding 4 cellspacing 0 gt lt tr gt lt th colspan 2 gt Project Summary lt th gt lt tr gt lt tr gt lt td gt Project Name lt td gt lt td gt lt xsl value of select projectName td lt tr gt lt tr gt lt td gt Default Target lt td gt td xsl value of select default gt lt td gt lt tr gt lt tr gt lt td gt Base Directory lt td gt td xsl value of select basedir gt lt td gt tr table show all target dependencies as a tree lt h3 gt Target Dependency Tree lt h3 gt xsl apply templates select target not depends mode tree gt xsl sort select iname xsl apply templates lt p gt Show a table of all targets gt table border 1 cellpadding 4 cellspacing 0 gt lt tr gt lt th colspan 3 gt List of Targets lt th gt lt tr gt lt
546. someone else can be working on sample XML data for each web page Although different people may work on these tasks a certain degree of coordination is critical at this point The prototype XHTML pages may look great but the XML must provide the data to enable those pages to be created The XML designer will also have to work with the people who are designing the back end data sources to determine if the desired data is even available When designing XML the focus should be on data rather than presentation All of the fonts and colors that are part of the CSS should have absolutely zero impact on the design of the XML The XML will contain additional data that is not displayed however For example creating hyperlinks requires some sort of identifier for each object This allows the servlet to figure out which message the user clicked on The XML data contains the identifier for the message but the actual XHTML markup for the hyperlink comes from an XSLT stylesheet The XML data for the home page is shown in Example 7 3 Because the XML does not contain presentation information it is smaller than the XHTML markup Example 7 3 home xml lt xml version 1 0 encoding UTF 8 gt lt xml stylesheet type text xsl href xslt home xslt home board id 0 gt lt name gt Java Programming lt name gt lt description gt General programming questions about Java lt description gt lt messages month 1 year 2001 gt l
547. son to choose LotusXSL unless you are already using it 1 4 1 3 SAXON The SAXON XSLT processor from Michael Kay is available at http saxon sourceforge net SAXON is open source software in accordance with the Mozilla Public License and is a very popular alternative to Xalan SAXON provides full support for the current XSLT specification and is very well documented It also provides several value added features such as the ability to output multiple result trees from the same transformation and update the values of variables within stylesheets To transform a document using SAXON first include saxon jar in your CLASSPATH Then type java com icl saxon StyleSheet to list all available options The basic syntax for transforming a stylesheet is as follows D com icl saxon StyleSheet options source doc style doc To transform the presidents xml file and send the results to standard output type the following java com icl saxon StyleSheet presidents xml presidents xslt 1 4 1 4 JAXP Version 1 1 of Sun s Java API for XML Processing JAXP contains support for XSLT transformations a notable omission from earlier versions of JAXP It can be downloaded from http java sun com xml Parsing XML and transforming XSLT are not the primary focus of JAXP Instead the key goal is to provide a standard Java interface to a wide variety of XML parsers and XSLT processors Although JAXP does include reference implementations of XML par
548. specific time window may be different for each client using the application In order to display this XML data on most browsers it must first be converted to HTML As Figure 1 1 shows the XML data is fed into the processor as one input and an XSLT stylesheet is provided as a second input The output is then sent directly to the web browser as a stream of HTML The XSLT stylesheet produces HTML formatting instructions while the XML provides raw data 1 1 1 What s Wrong with HTML One of the fundamental problems with HTML is its haphazard implementation Although the specification for HTML is available from the World Wide Web Consortium W3C its evolution was driven mostly by competition between Netscape and Microsoft rather than a thoughtful design process and open standards This resulted in a bloated language littered with browser specific tags and varying support for standards Since no two browsers support the exact same set of HTML features web authors often limit themselves to a subset of HTML Another approach is to create and maintain separate copies of each web page which take advantage of the unique features found in a particular browser The limitations of HTML are compounded for dynamic sites in which Java programs are often responsible for accessing enterprise data sources and presenting that information through the browser Extracting information from back end data sources is much more difficult than simple web page authoring
549. sses are specific to each servlet container Furthermore the interfaces do not allow values to be modified To facilitate this capability Version 2 3 of the serviet API also adds wrapper classes that allow the request and response to be modified The following new classes are now available e javax servlet ServletRequestWrapper javax servlet ServletResponseWrapper e javax servlet http HttpServletRequestWrapper javax servlet http HttpServletResponseWrapper Each of these classes merely wraps around another request or response and all methods merely delegate to the wrapped object To modify behavior programmers must extend from one of these classes and override one or more methods Here is how a custom filter might look public class MyFilter implements Filter public void doFilter ServletRequest req ServletResponse res FilterChain chain throws IOException ServletException wrap around the original request and response MyRequestWrapper reqWrap new MyRequestWrapper req MyResponseWrapper resWrap new MyResponseWrapper res pass the wrappers on to the next entry chain doFilter reqWrap resWrap In this case MyRequestWrapper and MyResponseWrapper are doing the actual work of modifying the request and response This works fine for many types of simple filters but is more complex when modifying the response content To illustrate this point consider the getOutputStr
550. ssing In the previous chapter we saw a template that output the name of a president or vice president Its basic job was to display the first name middle name and last name A nonbreaking space was printed between each piece of data so the fields did not run into each other What we did not see was that many presidents do not have middle names so our template ended up printing the first name followed by two spaces followed by the last name To fix this we need to check for the existence of a middle name before simply outputting its content and a space This requires conditional logic a feature found in just about every programming language in existence XSLT provides two mechanisms that support conditional logic lt xs1 if gt and xsi choose These allow a stylesheet to produce different output depending on the results of a boolean expression which must yield t rue or false as defined by the XPath specification 3 1 1 lt xsl if gt The behavior of the lt xs1 if gt element is comparable to the following Java code if boolean expression do something In XSLT the syntax is as follows xsl if test boolean expression gt Content template gt xsl if The test attribute is required and must contain a boolean expression If the result is t rue the content of this element is instantiated otherwise it is skipped The code in Example 3 1 illustrates several uses of lt xsi if gt and related XPath express
551. st category programmer gt lt xsl value of select lang programmer gt lt xsl when gt lt xsl otherwise gt lt xsl value of select lang other gt lt xsl otherwise gt xsl choose td td lt xsl value of select phone gt lt td gt lt tr gt lt xsl for each gt lt table gt lt body gt lt html gt lt xsl template gt lt xsl stylesheet gt The XSLT stylesheet is now much more amenable to i18n All locale specific content is declared as a series of variables Therefore importing stylesheets can override them The lang naming convention makes the stylesheet more maintainable it is not a requirement or part of the XSLT specification Other than isolating this content the remainder of the stylesheet is exactly the same as it was before The Spanish version of the stylesheet is shown in Example 8 19 Example 8 19 directory_es xslt lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl import href directory en xslt xsl output method html encoding UTF 8 gt 1 Isolate locale specific content lt xsl variable name lang pageTitle select Empleado gu a telef nica lt xsl variable name lang nameHeading select Nombre lt xsl variable name lang categoryHeading select Categoria gt lt xsl variable name lang phoneHeading select Tel fono gt
552. string contains fullName Smith sering s bstring befote substring before fullName string string string substring after 1 m Y string string substring after fullName string substring string number number number string Vengthistring string length fullName string normalize space string substring SmiddleName 1 1 normalize space testing string translate string string string translate test aeiou AEIOU All string comparisons such as starts with and contains are case sensitive There is no concept of case insensitive comparison in XSLT One potential workaround is to convert both strings to upper or lowercase and then perform the comparison Converting a string to upper or lowercase is not directly supported by a function in the current implementation of XSLT but the translate function can be used to perform the task The following XSLT snippet converts a string from lower to uppercase translate text abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPORSTUVWXYZ In the substring before and substring after functions the second argument contains a delimiter string This delimiter does not have to be a single character and an empty string is returned if the delimiter is not found These functions could be used to parse formatted data such as dates lt date gt 06 25 1999 lt date gt The XSLT used to extract
553. structures Keeping XML production outside of domain objects is useful for several reasons e JDOM producer classes can be replaced with DOM producers or some other technology e Additional producers can be written to generate new forms of XML without modifying the domain objects or existing XML producers e Domain objects may be represented as Java interfaces with several different implementation classes By keeping XML production separate the same producer works with all implementations of the domain interfaces The HomeJDOM class shown in Example 7 20 is quite simple It merely produces a nome element containing a list of lt ooard gt elements Since a separate JDOM producer class creates the lt board gt elements the HomeJDOM class merely assembles those XML fragments into a larger structure Example 7 20 HomeJDOM java package com oreilly forum xml import com oreilly forum domain import java util import org jdom Produce JDOM data for the home page amp public class HomeJDOM param boards an iterator of lt code gt BoardSummary lt code gt objects public static Element produceElement Iterator boards Element homeElem new Element home while boards hasNext BoardSummary curBoard BoardSummary boards next homeElem addContent BoardSummaryJDOM produceElement curBoard j return homeElem private HomeJDOM l J As shown in t
554. t xsl param name rootDir select docroot gt xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtmll DTD xhtmll strict dtd 1 Global Variables lt xsl variable name global subject select postMsg prefill subject gt lt xsl variable name global email select postMsg prefill authorEmail gt lt xsl variable name global message select postMsg prefill message gt lt xsl variable name global title gt xsl choose xsl when test postMsg inResponseTo gt lt xsl text gt Reply to Message lt xsl text gt xsl when xsl otherwise lt xsl text gt Post New Message lt xsl text gt xsl otherwise xsl choose xsl variable Rs Ak Ck KC Ck C Ck SC Ck KC Ck KC Ck C CC Ck Sk Ck C Ck Ck Ck Ck Ck Sk kk Sk Ck kk Kk Sk A x Sk kx Kk ko ko ko ko ko Create the XHTML web page KCKCkCk Ck kCkCkckck ck ckckck kckckckck ck ck k ck ck k ck k ck ck k ck ck ck ck ck ck ck ck k ck ck ck ck ck ck ck k k ck ck KKK kk M lt xsl template match gt html xmlns http www w3 0rg 1999 xhtml head title xsl value of select global title title lt link href SrootDir forum css rel stylesheet type text css gt lt head gt lt body gt show the page title and board name di
555. t lt hl gt Shopping Example lt h1 gt remainder of page omitted lt form gt lt body gt lt html gt lt xsl template gt lt xsl template match cart gt Click on the link to move next a href shopping moveNext global sessionID param value Move Next lt a gt lt xsl template gt lt xsl stylesheet gt This stylesheet fully illustrates the three key components that make session tracking with XSLT possible First the session identifier is passed to the stylesheet as a parameter xsl param name global sessionID Next this session identifier is used for the form action lt form method post action chap8 shopping global sessionID gt And finally it is used for all hyperlinks lt a href shopping moveNext global sessionID param value Move Next lt a gt The param value string was added here to illustrate that request parameters are appended after the session identifier Therefore the full URL will look similar to the following when the user clicks on the hyperlink http localhost 8080 shopping moveNext jsessionid 298u1kj2348734jkj43 p aram value Tracking sessions is essential and the technique shown in this section works when browser cookies are disabled You should always test your web applications by disabling all browser cookies to see if every URL is properly encoded with the session identifier 8 3 Identifying the Browser A strength of XSLT is its ability to h
556. t not considered descendants of element nodes descendant 7 Same as descendant with the addition of the context node or self All elements in the document that occur after the context node Descendants followinc aibi of the context node are not included following All following nodes in the document that have the same parent as the context sibling node namespace The namespace nodes of the context node parent The immediate parent of the context node if a parent exists i All nodes in the document that occur before the context node except for preceding ancestors attribute nodes and namespace nodes All nodes in the document that occur before the context node and have the same parent This axis is empty if the context node is an attribute node or a namespace node preceding sibling self The context node itself 2 4 3 Location Steps As you may have guessed an axis alone is only a piece of the puzzle A location step is a more complex construct used by XPath and XSLT to select a node set from the XML data Location steps have the following syntax axis node test predicate 1 predicate n The axis and node test are separated by double colons and are followed by zero or more predicates As mentioned the job of the axis is to specify the relationship between the context node and the node test The node test allows you to specify the type of node that will be selected and the predicates filter th
557. t before the first comma then recursively process everything after the comma The following code assigns everything before the first comma to the first Token variable tt lt xsl variable name firstToken gt xsl choose xsl when test contains Sdepends xsl value of select normalize space substring before depends xsl when lt xsl otherwise gt lt xsl value of select normalize space Sdepends gt lt xsl otherwise gt lt xsl choose gt lt xsl variable gt If the depends parameter contains a comma the substring before function locates the text before the comma and noxmalize space trims whitespace If no commas are found there must be only one dependency Next any text after the first comma is assigned to the remainingTokens variable If there are no commas the remainingTokens variable will contain an empty string lt xsl variable name remainingTokens select normalize space substring after depends gt The template then outputs a pipe character followed by the value of the first token xsl text xsl text lt xsl value of select SfirstToken gt Next if the emainingTokens variable is nonempty the fixDependency template is instantiated recursively Otherwise another pipe character is output at the end lt xsl choose gt xsl when test S remainingTokens gt xsl call template name fixDependency xsl with param name depends select Sr
558. t cannot be changed This is comparable to a final field in Java In some circumstances however recursion combined with template parameters can achieve similar results The XML shown in Example 3 4 will be used to illustrate one such approach Example 3 4 familyTree xml lt xml version 1 0 encoding UTF 8 gt xml stylesheet type text xsl href familyTree xslt gt person name O0tto gt person name Sandra gt lt person name Jeremy gt lt person name Eliana gt lt person gt erson name Er T L A c gt lt person name Aidan gt lt person gt lt person name Philip gt lt person name Alex gt lt person name Andy gt lt person gt As you can see the XML is structured recursively Each lt person gt element can contain any number of lt person gt children which in turn can contain additional lt person gt children This is certainly a simplified family tree but this recursive pattern does occur in many XML documents When displaying this family tree it is desirable to indent the text according to the ancestry Otto would be at the root Sandra would be indented by one space and her children would be indented by an additional space This gives a visual indication of the relationships between the people For example Otto Sandra Jeremy Eliana Eric Aidan Philip Alex Andy The XSLT stylesheet that produces this output is shown in Exam
559. t confirmPersonalData xslt XSltURL getServletContext getResource curName xsltSystemID xsltURL toExternalForm this thanksTemplates transFact newTemplates new StreamSource xsltSystemID catch TransformerConfigurationException tce log Unable to compile stylesheet tce throw new UnavailableException Unable to compile catch MalformedURLException mue log Unable to locate XSLT file curName throw new UnavailableException Unable to locate XSLT file curName Handles HTTP GET requests such as when the user types in a URL into his or her browser or clicks on a hyperlink A protected void doGet HttpServletRequest request HttpServletResponse response throws IOException ServletException PersonalData personalData getPersonalData request the third parameter false indicates that error messages should not be displayed when showing the page showPage response personalData false this editTemplates Handles HTTP POST requests such as when the user clicks on a Submit button to update his or her personal data protected void doPost HttpServletRequest request HttpServletResponse response throws IOException ServletException locate the personal data object and update it with the information the user just submitted PersonalData pd getPersonalData request pd setFirstName request ge
560. t employee gt In addition to lt employee gt elements you may want to use this same code to output information for a lt programmer gt Or manager element In these circumstances xsl call template can be used to explicitly invoke a template by name rather than matching a pattern in the XML data The template will have the following form lt xsl template name formatSSN gt Content lt xsl template gt This template will be used to support the following XML data in which both lt manager gt and lt programmer gt elements have ssn attributes Using a single named template avoids the necessity to write one template for lt manager gt and another for lt programmer gt We will see an example XSLT stylesheet when we discuss parameters lt xml version 1 0 encoding UTF 8 gt team manager ssn 230568737 gt lt name gt Aidan Burke lt name gt lt manager gt lt programmer ssn 393776766 gt lt name gt Jennifer Burke lt name gt lt programmer gt lt programmer ssn 993885777 gt lt name gt Bill Tellam lt name gt lt programmer gt lt team gt 3 2 3 lt xsl param gt and lt xsl with param gt It is difficult to use named templates without parameters and parameters can also be used for regular templates Parameters allow the same template to take on different behavior depending on data the caller provides resulting in more reusable code fragments In the case of a named template parameters a
561. t gt are said to contain PCDATA which stands for parsed character data This is ordinary text that can contain markup such as nested tags The CDATA type which is used for attribute values cannot contain markup This means that lt characters appearing in attribute values will have to be encoded in your XML documents as amp 1t The term element is EMPTY meaning that it cannot have content This is not to say that it cannot contain attributes however This DTD specifies that t erm gt must have from and to attributes term from 1869 to 1877 gt We will not cover the remaining syntax rules for DTDs in this book primarily because they do not have much impact on our code as we apply XSLT stylesheets DTDs are primarily used during the parsing process when XML data is read from a file into memory When generating XML for a web site you generally produce new XML rather than parse existing XML so there is much less need to validate One area where we will use DTDs however is when we examine how to write unit tests for our Java and XSLT code This will be covered in Chapter 9 1 2 4 Java and XML Java APIs for XML such as SAX DOM and JDOM will be used throughout this book Although we will not go into a great deal of detail on specific parsing APIs the Java based XSLT tools do build on these technologies so it is important to have a basic understanding of what each API does and where it fits into the XML landscape For in dep
562. t messages month 2 year 2001 gt lt messages month 3 year 2001 gt lt board gt lt board id 1 gt lt name gt XSLT Basics lt name gt lt description gt Writing effective XSLT stylesheets lt description gt lt messages month 1 year 2001 gt lt messages month 2 year 2001 gt lt messages month 3 year 2001 gt lt board gt lt board id 3 gt lt name gt Sample empty board lt name gt lt description gt This board has no messages lt description gt lt board gt lt home gt Do not forget that this is still just a prototype XML file The actual XML data will be dynamically generated by JDOM once the application is finished this XML prototype code is used only for testing and development purposes In this XML data each message board is represented by a lt board gt element that has an id attribute When the user clicks on the Post Message web page hyperlink this id is used to figure out which message board he or she wants to post to The list of lt messages gt elements indicates months that have messages in them These do not need id attributes because the month and year are used in the hyperlink The second line of the XML links to the XSLT stylesheet lt xml stylesheet type text xsl href xslt home xslt gt This is not used in the final application but is very useful during the prototyping and development process By linking to the stylesheet the transformation can be
563. t name template c servlet name url pattern template url pattern servlet mapping web app Since all files are protected under the WEB INF directory the emp1ate URL pattern specified in the deployment descriptor is the only way for clients to access this application The URL users type into their browser is htto localhost 8080 chap8 template home xml This displays the page shown earlier in Figure 8 2 In this URL the word template maps to the servlet and home xm1 is the path information This is retrieved by the servlet using the getPathInfo method of HttpServletRequest The source code for TemplateServlet is shown in Example 8 4 Example 8 4 TemplateServlet java package chap8 import com oreilly javaxslt util StylesheetCache import java io import java net import javax servlet import javax servlet http import javax xml transform import javax xml transform stream Applies a standard stylesheet to every XML page on a site A public class TemplateServlet extends HttpServlet private String xsltFileName Locate the template stylesheet during servlet initialization ii public void init throws UnavailableException ServletContext ctx getServletContext this xsltFileName ctx getRealPath WEB INF xslt templatePage xslt File f new File this xsltFileName if f exists throw new Unava
564. tHandier that implements the ContentHandler interface To use DefaultHandler create a subclass and override the methods that interest you The other methods can safely be ignored since they are just empty methods If you are familiar with AWT programming you may recognize that this idiom is identical to event adapter classes such as java awt event WindowAdapter Getting back to XSLT you may be wondering where SAX fits into the picture It turns out that XSLT processors typically have the ability to gather input from a series of SAX events as an alternative to static XML files Somewhat nonintuitively it also turns out that you can generate your own series of SAX events rather easily without using a SAX parser Since a SAX parser just calls a series of methods on the Cont entcHandler interface you can write your own pseudo parser that does the same thing We will explore this in Chapter 5 when we talk about using SAX and an XSLT processor to apply transformations to non XML data such as results from a database query or content of a comma separated values CSV file 1 2 4 2 DOM The Document Object Model DOM is an API that allows computer programs to manipulate the underlying data structure of an XML document DOM is a W3C Recommendation and implementations are available for many programming languages The in memory representation of XML is typically referred to as a DOM tree because DOM is a tree data structure The root of the tree repre
565. tParameter firstName pd setLastName request getParameter lastName pd setDaytimePhone request getParameter daytimePhone pd setEveningPhone request getParameter eveningPhone pd setEmail request getParameter email if pd isValid show the Edit page with an error message showPage response pd true this editTemplates else show a confirmation page showPage response pd false this thanksTemplates A helper method that sends the personal data to the client browser as HTML It does this by applying an XSLT stylesheet to the DOM tree private void showPage HttpServletResponse response PersonalData personalData boolean includeErrors Templates stylesheet throws IOException ServletException try org w3c dom Document domDoc this personalDataXML produceDOMD ocument personalData includeErrors Transformer trans stylesheet newTransformer js response setContentType text html PrintWriter writer response getWriter trans transform new DOMSource domDoc new StreamResult writer catch Exception ex showErrorPage response ex If any exceptions occur this method can be called to display the stack trace in the browser window private void showErrorPage HttpServletResponse response Throwable throwable throws IOException PrintWriter pw response getWriter pw println html body
566. ta use xs1 value ot to directly output the current node This approach may result in duplicate code however a key reason to use templates is to modularize a stylesheet into reusable pieces of functionality This is a good example of the tradeoff between code maintenance and raw performance that developers are often faced with Sorting within the XSLT may introduce performance problems primarily because the entire node set must be sorted before any content can be output to the result tree If it is easy to pre sort the XML content using Java code the XSLT processor may be able to transform the document using less memory by outputting some of the result tree before the entire document is processed Finally writing smaller XSLT stylesheets is a great way to improve performance Cascading style sheets CSS should be used whenever possible because the CSS style instructions can be stored in a separate file thus keeping the XSLT and result tree much smaller JavaScript functions can also be placed in a separate file eliminating the need to embed the JavaScript code within the stylesheet CSS was used in this manner back in Chapter 7 for the discussion forum example It is worth mentioning again that CSS is used only for defining styles such as font colors indentation alignment and colors Many of these styles can also be defined directly in HTML for instance hl align center gt Some Heading lt h1 gt By defining the alignment in a
567. tainers regardless of the vendor The good news is that WAR files are very easy to create and require only that you carefully follow the guidelines for file and directory names If you are careful to avoid spelling errors and misplaced files you should not have any problem with WAR files 6 2 1 WAR Files Figure 6 2 shows the standard structure of a WAR file Since a WAR file is really just a JAR file with a war extension you can utilize the jar command to create your WAR files Figure 6 2 WAR file structure WEB INF and all sub directories Dj applame war are not directly visible to clients i e web browsers but can be index html accessed from your code The document root directory is s publicly accessible and may contain WEB INF directories just like a normal web site index html is the home page for this web xml The deployment descriptor WAR file m ql classes classes directory is added fo the CLASSPATH for this Le com particular web app This is a good place to put your XSLT stylesheets if you want to E lib prevent direct access by clients L foobar jar Lo other directories All JAR files in the lib directory are added to the CLASSPATH To create a WAR file simply arrange your files into the directory structure shown in Figure 6 2 and issue the following command from the directory that contains index html 1 index html is the home page for a web application jar cvfM appname w
568. tandalone processor as XSLT can The CSS processing model operates on the underlying data in a top down fashion in a single pass while XSLT can iterate and perform conditional logic on the XML data Although XSLT can produce style instructions its true role is that of a transformation language rather than a style language XSL Formatting Objects on the other hand is a style language that is much more comparable to CSS For wireless applications HTML is not typically generated Instead Wireless Markup Language WML is the current standard for cell phones and other wireless devices In the future new standards such as XHTML Basic may be used When using an XSLT approach the same XML data can be transformed into many forms all via different stylesheets Regardless of how many stylesheets are used the XML data will remain unchanged A typical web site might have the following stylesheets for a single XML home page homeBasic xslt For older web browsers homelE5 xslt Takes advantage of newer Internet Explorer features homeMozilla xslt Takes advantage of newer Netscape features homeWML xslt Transforms into Wireless Markup Language homeB2B xslt Transforms the XML into another XML format suitable for B2B style XML data feeds to customers Schema evolution implies an upgrade to an existing data source where the structure of the data must be modified When the data is stored in XML format XSLT can be used to support schema evolution F
569. tching to a different encoding makes no difference to the output displayed in Figure 8 10 However it does make a difference when the page source is viewed For example when the output is UTF 8 the actual Chinese or Spanish characters are displayed in the source of the HTML page When using ISO 8859 A however the source code looks something like this lt html gt lt head gt lt META http equiv Content Type content text html charset ISO 8859 1 gt lt title gt amp 20013 amp 25991 xXSLT lt title gt lt head gt lt body gt lt h1 gt amp 20013 amp 25991 XSLT lt h1 gt remainder of page omitted As you can see the Chinese characters are replaced by their corresponding character entities such as amp 20013 The XSLT processor creates these entities automatically when the output encoding type cannot display the characters directly Browser Fonts Recent versions of any major web browser can display UTF 8 and UTF 16 encoded characters without problems Font configuration is the primary concern If you are using Internet Explorer be sure to select the View Encoding Auto Select menu option Under Netscape 6 the View Character Coding Auto Detect menu option is comparable If you run the examples and see question marks and garbled text this is a good indication that the proper fonts are not installed on your system For the Chinese examples shown in this chapter the Windows 2000 SimHei and SimSun fonts wer
570. te 1 Ck ck ck ck ck ck ck ck ck ck CK ck CK Ck Ck ck ck ck ck ck Ck ck ck ck ck ck ck kk ck Ck ck ck ck ck ck ck kk kk ck ck ck ck ko Sk ko ko ko ko kv ko kx X Show the author s email address KCKCKCKCkCk ck ckckckck ck ckckckckckck ck kckck ck ckck ck ckckckck ck ck ck k ck ck k kck ck ck ck k KKK KKK KKK KKK lt xsl template match authorEmail gt lt a href mailto gt lt xsl value of select gt lt a gt lt xsl template gt lt xsl stylesheet gt Because viewMonth xslt shows a summary view of a large number of messages the actual text content for each message is not included in the output Instead the message subject author and create date are displayed These lines are grouped and indented according to replies making threads of discussion immediately visible This stylesheet declares a series of global variables These can be referenced throughout the stylesheet and are designed to make the code more maintainable Since each variable is prefixed with global the code is easy to understand when using the variables lt xsl value of select global boardName The global naming convention is not a standard part of XSLT It is just a convention used here to make the XSLT more self documenting The interesting part of this stylesheet involves construction of the tree of messages Since messages in the XML are hierarchical the XSLT must recursively process the data to properly show t
571. teElement publisher set id oreilly attribute pubElem setAttribute id pub getId Element name doc createElement name name appendChild doc createTextNode pub getName pubElem appendChild name Element street doc createElement street street appendChild doc createTextNode pub getStreet pubElem appendChild street Element city doc createElement city city appendChild doc createTextNode pub getCity pubElem appendChild city Element state doc createElement state state appendChild doc createTextNode pub getState pubElem appendChild state Element postal doc createElement postal postal appendChild doc createTextNode pub getPostal pubElem appendChild postal return pubElem private Element createBookElement Document doc Book book Element bookElem doc createElement book bookElem setAttribute publisher book getPublisher getId bookElem setAttribute isbn book getISBN Element edition doc createElement edition edition appendChild doc createTextNode Integer toString book getEdition bookElem appendChild edition Element publicationDate doc createElement publicationDate publicationDate setAttribute mm Integer toString book getPublicationMonth publicationDate setAttribute yy Integer toString book getP
572. tedDependency gt xsl call template name fixDependency gt xsl with param name depends select depends gt xsl call template xsl variable Now the dependency list is pipe delimited making it easier to reliably search for substrings Recursively instantiate this template for all targets that depend on the current target gt xsl if test contains correctedDependency concat curName xsl apply templates select mode tree gt xsl with param name indentLevel select nextLevel xsl apply templates xsl if xsl for each xsl template oem KAEKKKKK KK KKK kk kk ck Ck kk Ck kk Sk kk kk kk Ck Ck kk ko ck Sk ko ck Sk Ck ck Sk Ck ck Ck ck ck Sk Ck ko Sk Sk ko Sk Sk ko ko ko ko This template takes a comma separated list of dependencies and converts all commas to pipe characters It also removes all spaces For instance K Input depends a b c Ouput lalblicl K The resulting text is much easier to parse with XSLT KCKCK CK Kk CK CK Ck CK Kk CK CK SK Ck CK Ck Kk SKK Kk Sk SKK S KC SK Ck KC Sk KC kk k ck ck kc ko KKK kk lt xsl template name fixDependency gt lt xsl param name depends gt grab everything before the first comma or the entire string if there are no commas lt xsl variable name firstToken gt xsl choose xsl when test contains depends gt lt xsl value of select norma
573. ter lt i gt Fields marked with are required lt i gt lt form action chap6 personalData method post gt The template finally produces a table so that all of the headings and text fields are properly aligned As in earlier stylesheet examples this template creates the table while another template creates each row in the table lt table border 0 cellpadding 2 cellspacing 0 gt lt Select all immediate children such as firstName lastName daytimePhone etc xsl apply templates lt table gt lt div align center gt lt hr gt lt input type submit name submitBtn value Submit gt lt div gt lt form gt lt xsl template gt Since this particular instance of xs1 apply templates does not utilize the select attribute all child elements will be selected The next template is designed to match each of the possible types of elements that can appear and will be instantiated once for each occurrence of lt firstName gt lt lastName gt etc lt xsl template match firstName lastName daytimePhone eveningPhone email This template first produces a t r gt element If this particular element has a required true attribute the XML data contains lt requiredFieldsMissing gt The value of this element is an empty string the font is changed to bold and red This indicates to the user that a required field was missing The font weight and color are inserted as the st ye at
574. th information on any of these topics you might want to pick up a copy of Java amp XML by Brett McLaughlin O Reilly A parser is a tool that reads XML data into memory The most common pattern is to parse the XML data from a text file although Java XML parsers can also read XML from any Java InputStream or even a URL If a DTD or Schema is used then validating parsers will ensure that the XML is valid during the parsing process This means that once your XML files have been successfully parsed into memory a lot less custom Java validation code has to be written 1 2 4 1 SAX In the Java community Simple API for XML SAX is the most commonly used XML parsing method today SAX is a free API available from David Megginson and members of the XML DEV mailing list http www xml org xml dev It can be downloaded from http www megginson com SAX Although SAX has been ported to several other languages we will focus on the Java features SAX is only responsible for scanning through XML data top to bottom and sending event notifications as elements text and other items are encountered it is up to the recipient of these events to process the data SAX parsers do not store the entire document in memory therefore they have the potential to be very fast for even huge files I One does not generally need to download SAX directly because it is supported by and included with all of the popular XML parsers Currently there are two ver
575. that XSLT offers Table 4 1 summarizes the strengths and weaknesses of different approaches to Web application development Table 4 1 Different web technologies Technology Strengths Weaknesses Changes to HTML require Java code changes Hard to maintain Pure servlet Fastest runtime performance complex pages No separation of data logic and presentation Does not enforce separation of Best for pages that are mostly display only Java code and HTML Not good for Pure JSP static HTML with small amounts of dynamic _ validation of incoming requests content Fast runtime performance Requires deployment to web server for development and testing Still requires deployment to web Allows greater separation between Java code server for testing and development and HTML than pure servlet or JSP Hybrid ds Does not force programmers to approaches More modular design is easier to servlet JSP dn keep code out of JSPs Cannot maintain for large projects Fast runtime Itiple client device t arformance target mu tiple client device types P as effectively as XSLT Maximum separation between data programming logic and presentation XML Slowest runtime performance For and XSLT can be developed and tested pages that are mostly static HTML XSLT outside of the web server Maximum XSLT might be harder to write than modularity improves maintainability Easy to JSP Requires an extra step to target multiple client devices and languages gene
576. that these output properties are the same as the properties you can set on the xs1 output element in your stylesheets For example xsl output method xml indent yes encoding UTF 8 gt Using JAXP you can either specify additional output properties or override those set in the stylesheet To change the encoding write this code this will take precedence over any encoding specified in the stylesheet trans setOutputProperty OutputKeys ENCODING UTF 16 Keep in mind that this will in addition to adding encoding UTF 16 to the XML declaration actually cause the processor to use that encoding in the result tree For a value of UTF 16 this means that 16 bit Unicode characters will be generated so you may have trouble viewing the result tree in many ASCII only text editors 5 2 4 JAXP XSLT Design Now that we have seen some example code and have begun our exploration of the Transformer class let s step back and look at the overall design of the XSLT plugability layer JAXP support for XSLT is broken down into the packages listed in Table 5 2 Table 5 2 JAXP transformation packages Package Description Defines a general purpose API for XML transformations without any dependencies on SAX or DOM The javax xml transform Transformer class is obtained from the TransformerFactory class The Transformer transforms from a Source to a Result javax xml transform dom Defines how transformations can be performe
577. the appropriate request handler instance ask the handler to perform a GET or POST and then use the renderer to send a response to the client The code for ReqHandler java is shown in Example 7 26 This is an abstract class that provides doGet and doPost methods By default each method returns an error message back to the client so a derived class must override one or both methods to enable HTTP GET and or POST Once the method is complete the derived class must return an instance of Renderer which produces the next page to display Example 7 26 ReqHandler java package com oreilly forum servlet import java io import javax servlet import javax servlet http All request handlers must extend from this class f public abstract class ReqHandler protected abstract String getPathInfo protected Renderer doGet HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException return new ErrorRenderer Gl not allowed Es protected Renderer doPost HttpServlet servlet HttpServletRequest request HttpServletResponse response throws IOException ServletException return new ErrorRenderer POST not allowed The Renderer Class is shown in Example 7 27 This class like ReqHandler is abstract Derived classes are responsible for nothing more than producing content to the HttpServletResponse Basically
578. the cache will check its timestamp on the file system If the file has been modified a new Templates instance is instantiated without bringing down the servlet Fortunately integration with the cache actually makes the PersonalDataServlet simpler to implement Example 6 10 contains the modified listing and all modified lines are emphasized Example 6 10 Modified PersonalDataServlet java with stylesheet cache package chap import com oreilly javaxslt util StylesheetCache import java io import java net import javax servlet import javax servlet http import javax xml transform import javax xml transform dom import javax xml transform stream A modification of PersonalDataServlet that uses the com oreilly javaxslt util StylesheetCache class x public class PersonalDataServlet extends HttpServlet private PersonalDataXML personalDataXML new PersonalDataXML private String editXSLTFileName private String thanksXSLTFileName One time initialization of this Servlet public void init throws UnavailableException this editXSLTFileName getServletContext getRealPath WEB INF xslt editPersonalData xslt this thanksXSLTFileName getServletContext getRealPath WEB INF xslt confirmPersonalData xslt Handles HTTP GET requests such as when the user types in a URL into his or her browser or clicks on a hyperlink protected void doGet HttpSer
579. the current stylesheet The key reason to use lt xs1 import gt instead of xs1 inciude is to avoid conflicts If your stylesheet already has a template that matches pageHeader you will not be able to include pageElements xsit if it also has that template On the other hand you can use xs1 import In this case your own pageHeader template will take priority over the imported pageHeader Aa Changing all xs1 import elements to xs1 include was will help identify any naming conflicts you did not know about 3 4 Formatting Text and Numbers XSLT and XPath define a small set of functions to manipulate text and numbers These allow you to concatenate strings extract substrings determine the length of a string and perform other similar tasks While these features do not approach the capabilities offered by a programming language like Java they do allow for some of the most common string manipulation tasks 3 4 1 Number Formatting The ormat number function is provided by XSLT to convert numbers such as 123 into formatted numbers such as 123 00 The function takes the following form string format number number string string The first parameter is the number to format the second is a format string and the third optional is the name of an xsi1 decimal format element We will cover only the first two parameters in this book Interestingly enough the behavior of the oxmat number function is defined by
580. the month day and year looks like this lt xsl variable name dateStr select date gt lt xsl variable name dayYear select substring after dateStr gt Month lt xsl value of select substring before SdateStr gt lt br gt Day lt xsl value of select substring before dayYear gt lt br gt Year lt xsl value of select substring after dayYear In the first line of code the dat eSt r variable is initialized to contain the full date The next line then creates the dayYear variable which contains everything after the first character at this point dateStr 06 25 1999 and dayYear 25 1999 In Java this is slightly easier because you simply create an instance of the St ringTokenizer class and iterate through the tokens or use the last 1TndexOf method of java lang String to locate the second With XSLT the options are somewhat more limited The remaining lines continue chopping up the variables into substrings again delimiting on the character The output is as follows Month 06 Day 25 Year 1999 Another form of the substring function takes one or two number arguments indicating the starting index and the optional length of the subst ring If the second number is omitted the substring continues until the end of the input string The starting index always begins at position 1 so substring abcde 2 3 returns bcd and substring abcde 2 returns bcde 3 5 Schema Evol
581. the same testing code can be shared among a group of individual unit tests The validateCondensedFile method performs two levels of testing First the result of the transformation is validated against its DTD If an exception is thrown the test fails fail XML was not valid jde getMessage ee JUnit will intercept this failure and display the error message to the programmer running the test If the validation succeeds the unit test then uses the assertEquals method to test some of the actual XML content assertEquals Name was not correct expectedName nameElem getText ys In this method if the second two arguments are not equal the provided error message is displayed and the test fails One key additional method is suite gt Test suite ME ic public stat use reflection to locate each method named test return new TestSuite SampleUnitTest class This is useful because it automatically locates all methods whose names begin with test and adds them to a test suite Both Test Case and Test Suite implement the Test interface TestSuite Is acomposite of many individual Test objects By organizing tests into suites entire families of tests can be executed by running the suite As expected with a composite pattern test suites can also consist of other test suites At some point one top level test suite can directly or indirectly include every other test in the application Therefore all test
582. their browsers to disable all cookies When users disable cookies servlets must use another technique to enable session tracking The standard servlet API has a fallback mechanism when cookies are disabled It reverts to a technique called URL rewriting If cookies are disabled the session identifier is appended to the URL This way whenever a user clicks on a hyperlink or submits an XHTML form the session identifier is transmitted along with the request This cannot happen without some level of programmer intervention however Imagine a scenario where a servlet is requested and it returns an XHTML page with the following content Click on the link to move next lt a href shopping moveNext Move Next lt a gt This causes session tracking to fail because the session identifier is lost whenever the user clicks on the hyperlink We really want the HTML to look like this Click on the link to move next lt a href shopping moveNext jsessionid 0e394s8a576f67b38s7 gt Move Next lt a gt Now when the user clicks on the hyperlink the session identifier 5 s the servlet as part of the requested URL sionid is transmitted to The value for j sessionid cannot be hardcoded It must be dynamically generated for each instance of Ht tpSession making it much harder for hackers to obtain session identifiers to impersonate users This means that the XHTML cannot be entirely static the session identifier must be dynamicall
583. thout consulting this method The ciose method is useful because nearly everything done with JDBC requires the programmer to close a Statement and Connection This method should always be called from a finally block which is guaranteed to be called regardless of whether or not an exception was thrown For example Connection con null Statement stmt null try code to create the Connection and Statement code to access the database finally DBUtil close stmt con If JDBC resources are not released inside of a finally block it is possible to accidentally leave Connections open for long periods of time This is problematic because database performance can suffer and some databases limit the number of concurrent connections Although connection pooling is not supported in this version of the application DBUtil does include the following method public static Connection getConnection String dbURL In a future version of the class it will be very easy to have this method return a Connection instance from pool rather than creating a new instance with each call Additionally the DBUtil close method could return the Connection back to the pool instead of actually closing it These are left as future considerations to keep things reasonably sized for the book The setLongString and getLongString methods are used for setting and retrieving text for messages Since this text may be extremely long it cannot
584. thout making any changes to the Java code Although an XML approach makes the code more complex for a small example program such as this the benefits quickly outweigh the costs as web applications get more sophisticated The same is true for an Enterprise JavaBeans approach For a trivial program the configuration requirements seem very complex but as the application complexity increases the benefits of a sophisticated architecture become obvious Our program will consist of two web pages allowing visitors to enter personal information The first page will prompt for their name phone and email and the second page will display a summary of the data that was entered The first page does validation forcing the user to enter all of the required fields 6 3 1 Design The primary goal of this small application is to demonstrate how to use XSLT from a servlet Specifically JAXP will be used with DOM to create some dynamic XML data then XSLT stylesheets will be used to transform that data into HTML The design is presented in Figure 6 4 Figure 6 4 Personal data design PersonalData same gt lastName daytimePhone eveningPhone email PersonalDataServlet econvert i s a850445000050402554005020 PersonalDataXML i produceDOMDocument f Malaele Gli editPersonalData xsit LN transform confirmPersonalData xsit A As Figure 6 4 shows PersonalDataServlet is a subclass of HttpServiet This servlet overrides
585. throws DataException If no messages exist for the specified board and month return an empty iterator return an iterator of lt code gt MessageSummary lt code gt objects throws DataException if the boardID is illegal or a database error occurs public abstract Iterator getAllMessages long boardID MonthYear month throws DataException return an iterator of all lt code gt BoardSummary lt code gt objects wy public abstract Iterator getAllBoards throws DataException return a board summary for the given id Qthrows DataException if boardID is illegal or a database 5 error occurs KA public abstract BoardSummary getBoardSummary long boardID throws DataException DataAdapter consists of abstract methods and one static method called get Instance This implements a singleton design pattern returning an instance of a DataAdapter subclass The actual return type is specified in the ForumConfig class and Java reflection APIs are used to instantiate the object VI See Gamma et al Design Patterns Elements of Reusable Object Oriented Software Addison Wesley 1994 String adapterClassName ForumConfig getAdapterClassName try Class adapterClass Class forName adapterClassName instance DataAdapter adapterClass newInstance s catch Exception ex throw new DataException Unable to instantiate adapterClassName All remaining methods
586. ting a DOM Document instance by delegating to the PersonalDataxML helper class As you can see in the following code the servlet stays quite small because the DOM generation is factored out into the helper class private void showPage HttpServletResponse response nalData boolea throws IOException ServletExcep n includeErrors PersonalData perso Templates styles try org w3c dom Document domDoc this personalDataXML produceDOMDocument personalData includeErrors This method then proceeds to create a new instance of Transformer You may recall from Chapter 5 that Transformer instances are very lightweight and merely hold state information for the current transformation Since Transformer instances are not thread safe the instance is a local variable in this method With local variables each thread gets its own copy Transformer trans stylesheet newTransformer y Next the content type is configured for the HttpServletResponse aPrintWriter Is obtained and the transformation is performed The result tree is sent directly to the response s PrintWriter onse setContentType text html PrintWriter writer response getWriter ee trans transform new DOMSource domDoc new StreamResult writer catch Exception ex showErrorPage response ex If any exception occurs the showErrorPage method is invoked Since an exception can indicate that some XML library is unavailable the sho
587. tion exception throws TransformerException void warning TransformerException exception throws TransformerException OutputKeys These are constant definitions for legal output property settings on the Transformer interface They map directly to the legal attributes for the lt xs1 output gt element Programmatically specified output properties take priority over output properties specified in the XSLT stylesheet public class OutputKeys public static final String CDATA SECTION ELEMENTS cdata section elements public static final String DOCTYPE PUBLIC doctype public public static final String DOCTYPE SYSTEM doctype system public static final String ENCODING encoding public static final String INDENT indent public static final String MEDIA TYPE media type public static final String METHOD method public static final String OMIT XML DECLARATION omit xml declaration public static final String STANDALONE standalone public static final String VERSION version Result This is a common interface for classes that produce a transformation result DOMResult SAXResult and StreamResult are implementing classes The two constants in this interface are used when specifying whether output escaping is performed as discussed in section 16 4 of the XSLT specification at http www w3 org T
588. tional tests can be performed to determine if the semantic content of the result is correct For instance a DTD can report that a lt firstName gt element is present but it takes additional testing to determine if the content of lt firstName gt is actually the correct name 9 2 1 1 An example unit test Example 9 8 shows how to write a simple test fixture using the JUnit framework JUnit describes fixtures as a group of unit tests Example 9 8 Sample test fixture package chap9 import java io import java net import java util JAXP used for XSLT transformations import javax xml transform import javax xml transform stream JDOM used for XML parsing and validation t org jdom org jdom input JUnit classes junit framework Test junit framework TestCase junit framework T junit textui T An example JUnit This class performs an XSLT transformation and validates the result public class SampleUnitTest extends TestCase Fi le separator private String workingDir input XML files private File aidanXMLFile private File johnXMLFile a stylesheet that condenses the XML data private File condenseXSLTFile the transformation results private File aidanCondensedXMLFile private File johnCondensedXMLFile private TransformerFactory transFact All JUnit tests have a constructor that takes the test name public
589. title ABC Theaters id splash gt lt timer value 15 gt lt p align center gt lt big gt Welcome to ABC Theaters lt big gt lt p gt p Mmmm Popcorn p do type accept gt go href home gt do card card newcontext true title Home id home gt lt p align center gt Please select your city lt select multiple false name city gt lt option value chi gt Chicago lt option gt option value stl gt St Louis lt option gt lt option value seb gt Sebastopol lt option gt lt select gt lt p gt lt p gt lt em gt lt a href movieguide action theaters amp amp city city gt Show Theaters lt a gt lt em gt lt p gt lt card gt lt wml gt The ont imer attribute of the first card indicates the URL to load when the c imer gt element expires The timer value is 15 meaning 15 tenths of a second or 1 5 seconds This first card also contains a lt do gt element allowing the user to click on a button to jump to the home page if she does not want to wait for the timer to expire Like XHTML the lt p gt element indicates a paragraph of text causing text to appear on the next line of the display The next card contains a lt select gt element allowing the user to select from a list of cities The value of the selection is assigned to the city variable making it easy to submit the information to the server with the lt a gt tag lt a
590. tity transformation stylesheet sending the following output to the console lt xml version 1 0 encoding UTF 8 gt lt csvFile gt lt line gt lt value gt Washington lt value gt lt value gt George lt value gt lt value gt lt value gt lt line gt lt line gt ets csvFile Actually the output is crammed onto a single long line but it is broken up here to make it more readable Any good XML editor application should provide a feature to pretty print the XML as shown In order to transform this into something useful a stylesheet is required The XSLT stylesheet shown in Example 5 9 takes any output from this program and converts it into an HTML table Example 5 9 csvToHTMLTable xslt lt xml version 1 0 encoding UTF 8 lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method html lt xsl template match gt lt table border 1 gt xsl apply templates select csvFile line gt lt table gt lt xsl template gt lt xsl template match line gt tr xsl apply templates select value template gt template match value gt f a value is empty print a non breaking space o the HTML table looks OK gt f test e yes amp amp nbsp c xsl text lt xsl value of select gt lt td gt lt xsl template gt lt xsl stylesheet gt In order to apply this stylesheet type the following comma
591. to its actual directory structure When you look in the webapps directory you should see chap6 war as well as the chap6 directory If all else fails check the documentation for Tomcat double check your deployment descriptor and try the example servlets that come with Tomcat To see the Tomcat home page start Tomcat and visit http ocalhost 8080 If this does not work then something more fundamental is wrong with your Tomcat installation 6 2 4 Servlet API Highlights We will see more complex servlets throughout this book but a recurring theme is to minimize dependence on obscure servlet tricks and focus instead on using XML and XSLT to generate a majority of the content in your web application To make this happen it is necessary to look at a few of the commonly used classes that are part of the servlet package The javax servlet ServletConfig class provides initialization parameters to a servlet at startup time Each servlet has the following method which is called once when the servlet is first initialized public void init ServletConfig config throws ServletException The ServletConfig object provides name value St ring pairs used to configure servlets without hardcoding values into the application code For example you might write code that looks like this String xmlLocation config getInitParameter xmlLocation Since xml Location is an initialization parameter that is part of the XML deployment descriptor its valu
592. tput a PUBLIC document type declaration For example lt DOCTYPE rootElem PUBLIC public id system id DOCTYPE PUBLIC Instructs the processor to output a document type declaration For example DOCTYPE rootElem SYSTEM system id DOCTYPE SYSTEM ENCODING Specifies the character encoding of the result tree such as UTF 8 or UTF 16 INDENT Specifies whether or not whitespace may be added to the result tree making the output more readable Acceptable values are yes and no Although indentation makes the output more readable it does make the file size larger thus harming performance MEDIA TYPE The MIME type of the result tree The output method either xml html or text Although other METHOD values are possible such as xhtm1 these are implementation defined and may be rejected by your processor Acceptable values are yes and no specifying whether or not to B XM ECLAR O i bes prend include the XML declaration on the first line of the result tree Acceptable values are yes and no specifying whether or not the XML declaration indicates that the document is standalone For example lt xml version 1 0 encoding UTF 8 standalone yes gt STANDALONE Specifies the version of the output method typically 1 0 for XML VERSION output This shows up in the XML declaration as follows lt xm1 version 1 0 encoding UTF 8 gt It is no coincidence
593. trates another weakness of the current filtering API if res instanceof HttpServletResponse throw new ServletException This filter only supports HTTP Since there is no HTTP specific filter interface custom filters must use instanceof and downcasts to ensure that only HTTP requests are filtered Next the filter creates the buffered response wrapper and delegates to the next entry in the chain BufferedHttpResponseWrapper responseWrapper new BufferedHttpResponseWrapper HttpServletResponse res chain doFilter req responseWrapper This effectively captures the XML output from the chain making the XSLT transformation possible Before doing the transformation however one hack is required to work with Tomcat 4 0 byte origXML responseWrapper getBuffer if origXML null origXML length 0 just let Tomcat deliver its cached data back to the client chain doFilter req res N eturn The complete explanation is captured in the source code comments in Example 8 11 Basically Tomcat seems to cache its response when the user tries to reload the same static file consecutive times Without this check the code fails because the or igxML byte array is empty 6 This was quite difficult to figure out Because the servlet specification is not specific on this topic different servlet containers may behave slightly differently Finally the filter uses JAXP to perform the XSLT transformat
594. tribute on the lt t r gt element as follows tr xsl if test required true and requiredFieldsMissing zo L4 ana amp gt xsl attribute name style gt lt xsl text gt color red font weight bold xsl text lt xsl attribute gt lt xsl if gt The template then produces its first lt t d gt tag which contains the caption for the current field It would be nice if XSLT offered a lookup table mechanism for situations such as this but xsl choose does get the job done xsl when test name firstName gt First Name lt xsl when gt test name LastName gt Last Name lt xsl when gt est name gt L lt xsl when daytimePhone t Daytime Phone lt xsl when gt lt xsl when test name eveningPhone gt ening Phone lt xsl when gt xsl when test name email gt Email lt xsl when gt lt xsl choose gt This is still better than hardcoding the captions into the XML or servlet because we can make changes to the stylesheet without recompiling anything You can even change the captions to a foreign language without affecting any of the Java code offering remarkable flexibility to web page designers Design Choices The two stylesheets editPersonalData xslt and confirmPersonalData xslt had a lot in common To keep things simple they were written as two independent stylesheets This is not the only way to implement this
595. tripped down format that wireless devices will require 2 1 XSLT Introduction Why is transformation so important XML provides a simple syntax for defining markup but it is up to individuals and organizations to define specific markup languages There is no guarantee that two organizations will use the exact same markup in fact you may struggle to agree on consistent formats within the same group or company One group may use employee while others may use worker Or associate In order to share data the XML data has to be transformed into a common format This is where XSLT shines it eliminates the need to write custom computer programs to transform data Instead you simply create one or more XSLT stylesheets An XSLT processor is an application that applies an XSLT stylesheet to an XML data source Instead of modifying the original XML data the result of the transformation is copied into something called a result tree which can be directed to a static file sent directly to an output stream or even piped into another XSLT processor for further transformations Figure 2 1 illustrates the transformation process showing how the XML input XSLT stylesheet XSLT processor and result tree relate to one another Figure 2 1 XSLT transformation Result Tree L XSLT Stylesheet M Pratt HTML XML Text SSor XML Input 4 ee wansformedinto The XML input and XSLT stylesheet are normally two separate entities For the
596. ts in huge complex browsers that require far too many resources to execute on a handheld device Until all web pages are written using well formed HTML or XHTML browsers must support poorly written HTML Until browsers are more stringent however web authors will continue writing sloppy code 10 1 1 2 Limitations of current devices Another blow against HTML is the simple fact that current wireless devices have tiny displays small amounts of memory and very slow network connections Devices with five line displays simply cannot display HTML tables framesets and large fonts Instead these devices demand entirely new markup languages that are far smaller and make more efficient use of available resources 10 2 The Wireless Architecture Although wireless users want to access the internet they cannot simply dial a phone number and expect to browse web sites This is because wireless devices use protocols based on WAP rather than traditional web based protocols such as HTTP Figure 10 1 shows how a typical Web server fits into the wireless architecture Figure 10 1 WAP gateways WAP gateway WAP Web server e w WAP browser WML A eet et 9 1 O REILLY j Web browser XHTML As shown a new type of server called a WAP gateway is introduced into the equation This is a server that converts HTTP traffic into WAP traffic using protocols appropriate to the given wireless service The details of this are well be
597. ublicationYear bookElem appendChild publicationDate Element title doc createElement title title appendChild doc createTextNode book getTitle bookElem appendChild title Element author doc createElement author author appendChild doc createTextNode book getAuthor bookElem appendChild author return bookElem public static void main String args throws IOException javax xml parsers ParserConfigurationException Library lib new Library LibraryDOMCreator ldc new LibraryDOMCreator Document doc ldc createDocument lib write the Document using Apache Xerces output the Document with UTF 8 encoding indent each line eee ee co OU AH ae a fmt new org apa rialize OutputFormat doc UTF 8 true MLSerializer serial B ialize XMLSerializer System out fmt serial serialize doc getDocumentElement This example starts with the usual series of import statements Notice that org w3c dom is imported but packages such as org apache xml serialize are not The code is written this way in order to make it obvious that many of the classes you will use are not part of the standard DOM API These nonstandard classes all use fully qualified class and package names in the code Although DOM itself is a W3C recommendation many common tasks are not covered by the spec and can only be acco
598. ue xsl text xsl when xsl when test party Republican gt lt xsl text gt green lt xsl text gt xsl when xsl when test party Democratic Republican gt lt xsl text gt purple lt xsl text gt xsl when xsl when test party Federalist gt xsl text brown xsl text xsl when xsl when test party Whig xsl text black xsl text xsl when never executed in this example gt xsl otherwise xsl text red xsl text xsl otherwise xsl choose xsl variable li font color color gt show the party name gt xsl apply templates select name xsl text xsl text lt xsl value of select party gt lt font gt lt li gt xsl for each lt ul gt lt xsl template gt In this example the list of presidents is displayed in order along with the political party of each president The lt xs1 when gt elements test for each possible party setting the value of a variable This variable color is then used in a font tag to set the current color to something different for each party The xs1 otherwise element is never executed because all of the political parties are listed in the lt xs1 when gt elements If a new president affiliated with some other political party is ever elected then none of the xs1 when conditions would be t rue and the font color would be red One difference between the X
599. ue gt Aidan lt value gt lt value gt G lt value gt lt line gt lt csvFile gt One enhancement would be to design the CSV parser so it could accept a list of meaningful column names as parameters and these could be used in the XML that is generated Another option would be to write an XSLT stylesheet that transformed this initial output into another form of XML that used meaningful column names To keep the code example relatively manageable these features were omitted from this implementation But there are some complexities to the CSV file format that have to be considered For example fields that contain commas must be surrounded with quotes Consultant Author Teacher Burke Eric M Teacher Burke Jennifer L None Burke Aidan G To further complicate matters fields may also contain quotes In this case they are doubled up much in the same way you use double backslash characters in Java to represent a single backslash In the following example the first column contains a single quote so the entire field is quoted and the single quote is doubled up test quote Teacher Burke Jennifer L This would be interpreted as test quote Teacher Burke Jennifer L The code in Example 5 7 shows the complete implementation of the CSV parser Example 5 7 CSVXMLReader java package com oreilly javaxslt util import java io import java net URL import org xml sax import org xml sax helpers
600. ugh lt span gt is not used in this particular example lt div gt is used frequently to introduce line breaks and to apply styles using CSS The next prototype shown in Figure 7 3 shows what a message board looks like XHTML source code for the remaining screens is not listed here Figure 7 3 View Month prototype T XSLT Basics Microsoft Internet Explorer n x Ele Edt Yew Favorites Too Help EJ wExk gt QU i b search ajravortes jHexy 2 w 5 Address ei htto flocalhost 080 forum mainiviesionth board IDs OBmonthe Seyeare2001 J en links 2 Customve Links 2 FreeHotmal Z Windows 2 Windows Media XSLT Basics Messages for March 2001 Quick Actions t anew message e Return to the home page First message poste d dre by burke e ociweb com on 11 Mar 2001 je First mess ge Ai by burke yahoo com on 11 Mar 2001 Re Re First message posted j posted by anon whatever on 13 Mar 2001 Second message posted by burke e amp ociweb com on 11 Mar 2001 How do I select processing instructions posted by anont whatever com on 13 Mar 2001 a CE Local intranet Messages that are replies to other messages are indented a few spaces Later a simple change to the XSLT stylesheet can be employed to show graphical folders or other icons in front of each message The next screen shown in Figure 7 4 shows how users can post new messages to the discussion forum Figure 7
601. ully designed Part of the servlet design process involves figuring out what parameters are required and what the legal values are Until this work has been completed however an educated guess or TODO comment is fine Another key piece of this stylesheet shows how to call a utility template xsl call template name utils printShortMonthName gt xsl with param name monthNumber select month gt xsl call template The utils printShortMonthName template is part of utils xslt and is invoked just like a local template The only difference is that the current stylesheet must import utils xslt or the code will fail Prefixing the template name with utils has nothing to do with the actual filename it is a convention adopted only for this application that makes the code a little easier to read reducing the chances for naming conflicts The reusable XSLT stylesheet utils xslt is shown next in Example 7 8 Example 7 8 Reusable XSLT code lt xml version 1 0 encoding UTF 8 gt lt xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform lt xsl template name utils printShortMonthName gt xsl param name monthNumber gt lt xsl choose gt xsl when t xsl when t xsl when t xsl when tes oO Nn ct oll Ur Ur Ut N monthNumber 0 gt Jan lt xsl when gt monthNumber 1 gt Feb lt xsl when gt monthNumber 2 gt Mar lt xsl when gt ionthNumber 3 gt Apr lt xsl when
602. umber xsl apply templates select numberFormatting numberSamples number gt xsl with param name fmt select gt xsl apply templates table xsl for each lt body gt lt html gt lt xsl template gt output the number followed by the result of the format number function lt xsl template match number gt lt xsl param name fmt gt tr td align right gt lt xsl value of select gt ftd td align right gt the first param is a dot representing the text content of the number element gt lt xsl value of select format number fmt lt td gt lt tr gt lt xsl template gt lt xsl stylesheet gt This stylesheet first loops over the list of lt format gt elements lt xsl for each select numberFormatting formatSamples format gt Within the loop all of the lt number gt elements are selected This means that every format is applied to every number xsl apply templates select numberFormatting numberSamples number gt 3 4 2 Text Formatting Several text formatting functions are defined by the XPath specification allowing code in an XSLT stylesheet to perform such operations as concatenating two or more strings extracting a substring and computing the length of a string Unlike strings in Java all strings in XSLT and XPath are indexed from position 1 instead of position 0 Let s suppose that a stylesheet defines
603. ummarized examples of the various forms of lt xsl template gt 3 See section 5 5 of the XSLT specification at http www w3 org TR xslt Table 3 1 Summary of common template syntax Template example Notes lt xsl template match president gt Matches president nodes in the source XML document lt xsl template gt lt xsl template name formatName gt xsl param Defines a named template used in conjunction with name style gt xsl call template and xsl with param lt xsl template gt lt xsl template match customer Matches customer nodes when lt xsi apply templates gt mode myModeName gt n PP y p also uses mode myModeName cia debesbsE5b 3 3 Combining Multiple Stylesheets Through template parameters named templates and template modes we have seen how to create more reusable fragments of code that begin to resemble function calls By combining multiple stylesheets one can begin to develop libraries of reusable XSLT templates that can dramatically increase productivity Productivity gains occur because programmers are not writing the same code over and over for each stylesheet Reusable code is placed into a single stylesheet and imported or included into other stylesheets Another advantage of this technique is maintainability XSLT syntax can get ugly and modularizing code into small fragments can greatly enhance readability For example we have seen several examples relat
604. unds must be implemented to function reliably Finally this approach is slower than others The XML must be converted into text and buffered in memory before the XSLT transformation can be performed which is generally slower than sending SAX events or a DOM tree directly to the XSLT processor Generating XML and performing the XSLT transformation in a servlet can avoid the extra conversions to and from text that filters require 8 5 XSLT as a Code Generator For performance reasons EJB components typically return dependent objects rather than many individual fields These are implemented as read only classes that encapsulate a group of related fields Borrowing an example from Enterprise JavaBeans by Richard Monson Haefel O Reilly Example 8 13 shows a typical dependent object Example 8 13 Address java public class Address implements java io Serializable private String street private String city private String state private String zip x Construct a new dependent object instance public Address String street String city String state String zip this street street this city city this state state this zip zip public String ge 5 ctf Q ct ct o H Ow D ct J public String getCity return this city i J public String getState 1 return this state J public String getZip return this zip Now rather than containing numerous fine grain
605. ur list of presidents Example 1 2 presidents dtd presidents president gt l lt I ELEMEN president term name party vicePresident gt ELE T name first middle last nickname ELEMEN vicePresident name lt ELEMED first PCDATA gt lt ELEMED last PCDATA gt ELEMENT middle PCDATA gt ELEMENT nickname PCDATA gt ELEMENT party PCDATA gt ELEMENT term EMPTY gt lt ATTLIST term from CDATA REQUIRED to CDATA REQUIRED The first line in the DTD says that the lt presidents gt element can contain one or more president elements as children The lt president gt in turn contains one each of lt term gt lt name gt and party in that order It then may contain zero or more lt vicePresident gt elements If the XML data did not adhere to these rules the XML parser would have rejected it as invalid The name element can contain the following content exactly one lt first gt followed by zero or more middle followed by exactly one 13st followed by zero or one nickname If you are wondering why middle can occur many times consider this former president name lt first gt George lt first gt lt middle gt Herbert lt middle gt lt middle gt Walker lt middle gt lt last gt Bush lt last gt lt name gt Elements such as lt first gt George lt firs
606. use a DOM parser from one vendor a SAX parser from another vendor and yet another XSLT processor from someone else In reality you will probably need to use a DOM parser compatible with your XSLT processor if you try to transform the DOM tree directly Figure 5 1 illustrates the high level architecture of JAXP 1 1 Figure 5 1 JAXP 1 1 architecture Application Code DocumentBuilder SAXParser Transformer DOM API SAX Parser XSLT Processor Implementation Implementation Implementation As shown application code does not deal directly with specific parser or processor implementations such as SAXON or Xalan Instead you write code against abstract classes that JAXP provides This level of indirection allows you to pick and choose among different implementations without even recompiling your application The main drawback to an API such as JAXP is the least common denominator effect which is all too familiar to AWT programmers In order to maximize portability JAXP mostly provides functionality that all XSLT processors support This means for instance that Xalan s custom XPath APIs are not included in JAXP In order to use value added features of a particular processor you must revert to nonportable code negating the benefits of a plugability layer Fortunately most common tasks are supported by JAXP so reverting to implementation specific code is the exception not the rule Although the JAXP specification does not defi
607. ute gt xsl if xsl apply templates select name gt 1 display some text after the last element xsl if test position last gt xsl text current president lt xsl text gt xsl if lt li gt lt xsl for each gt ful lt xsl template gt KCkCKCKCk kCk ck Ck k k kc k Ck k kCk ck ck k kc kc kck k kc kck ck KKK KKK KKK KKK KKK KKK KKK KK KK name template CKCkCk ckck ck ck ck ck ckckckckckck Ck k ck ck ck KKK ck ck kckck ck ck k ck ck ck ck ck ck KKK kck ck ck ck KKK KK xsl template match name xsl value of select last xsl text xsl text lt xsl value of select first gt xsl if test middle gt xsl text disable output escaping yes gt amp nbsp lt xsl text gt lt xsl value of select middle gt xsl if lt xsl template gt lt xsl stylesheet gt The first thing the mat ch presidents template outputs is a heading that displays the number of presidents List of lt xsl value of select count president gt Presidents The count function is an XPath node set function and returns the number of elements in a node set In this case the node set is the list of lt president gt elements that are direct children ofthe lt presidents gt element so the number of presidents in the XML file is displayed The next block of code does the bulk of the work in this stylesheet outputting each president as a list item using a l
608. ution Looking beyond HTML generation a key use for XSLT is transforming one form of XML into another form In many cases these are not radical transformations but minor enhancements such as adding new attributes changing the order of elements or removing unused data If you have only a handful of XML files to transform it is a lot easier to simply edit the XML directly rather than going through the trouble of writing a stylesheet But in cases where a large collection of XML documents exist a single XSLT stylesheet can perform transformations on an entire library of XML files in a single pass For B2B applications schema evolution is useful when different customers require the same data but in different formats 3 5 1 An Example XML File Let s suppose that you wrote a logging API for your Java programs Log files are written in XML and are formatted as shown in Example 3 10 Example 3 10 Log file before transformation xml version 1 0 encoding UTF 8 log message text input parameter was null lt type gt ERROR lt type gt lt when gt lt year gt 2000 lt year gt lt month gt 01 lt month gt lt day gt 15 lt day gt lt hour gt 03 lt hour gt lt minute gt 12 lt minute gt lt second gt 18 lt second gt lt when gt lt where gt lt class gt com foobar util StringUtil lt class gt lt method gt reverse String lt method gt lt where gt lt message gt lt message text cannot read co
609. v class box1 gt hl xsl value of select S global title gt lt h1 gt div lt xsl value of select postMsg board name gt lt div gt lt div gt xsl apply templates select postMsg inResponseTo gt lt div class box2 gt optionally display error message xsl if test postMsg error code ALL FIELDS REQUIRED lt p class error gt All fields are required lt p gt lt xsl if gt lt Create an XHTML form The user will provide the subject and Email address and the message text lt form method post action postMsg gt div lt input type hidden name boardID value postMsg board id gt Determine the mode of operation gt xsl choose xsl when test postMsg inResponseTo gt lt input type hidden name origMsgID value postMsg inResponseTo id gt lt input type hidden name mode value replyToMsg gt xsl when xsl otherwise lt input type hidden name mode value postNewMsg gt lt xsl otherwise gt xsl choose div Show the input fields in a table to keep things aligned properly table lt tr gt td Subject td td lt input type text name msgSubject value Sglobal subject size 60 maxlength 70 gt lt td gt lt tr gt lt tr gt lt td nowrap nowrap gt Your Email lt td gt lt td gt lt input type text name authorEmail value
610. va 478 remainder of stack trace omitted The remainder of the stack trace is not very helpful because it simply lists methods that are internal to Tomcat 0002 schedule 0002ejspschedule jsp 2 is the name of the Java servlet class that was generated The line numbers refer to positions in this generated code rather than in the JSP itself Embedding HTML directly into servlets is not appealing because it requires a programmer to maintain With JSP you often embed Java code into HTML Although the embedding is reversed you still have not cleanly separated HTML generation and programming logic Think about the problems you encounter when the validation logic in a JSP goes beyond a simple one page example Do you really want hundreds of lines of Java code sprinkled throughout your HTML surrounded by those pretty lt gt gt tags Unfortunately far too many JSP pages have a substantial amount of Java code embedded directly in the HTML The first few iterations of JSP did not offer bulletproof approaches for separating Java code from the HTML Although JavaBeans tags were offered in an attempt to remove some Java code the level of sophistication was quite limited These tags allow JSPs to interact with helper classes written according to Sun s JavaBeans API http java sun com products javabeans Recent trends in the JSP specification have made substantial improvements The big push right now is for custom tags which finally allow you to remove
611. vailableException xslt directory is a required context param remainder of code omitted Now that the actual location of the stylesheets has been moved into the deployment descriptor changes can be made without any edits to the servlet 6 4 Stylesheet Caching Revisited We have seen two approaches that eliminate the need to hardcode the absolute pathname of XSLT stylesheets in your servlet code In the first approach the Servlet Context was used to load resources from the web application using a relative pathname In the second approach the location was specified as a context initialization parameter This takes care of compilation changes but now we have the issue of dynamic loading In the PersonalDataServlet class the two XSLT stylesheets are located and compiled into instances of the javax xml transform Templates interface Although this offers high performance for transformations the two stylesheets are never flushed from memory If changes are made to the XSLT stylesheets on disk the servlet must be stopped and started again 6 4 1 Integration with the Stylesheet Cache In Chapter 5 a stylesheet cache was implemented In this next example PersonalDataServlet is modified to use the cache instead of Templates directly This will offer virtually the same runtime performance However you will be able to modify the stylesheets and immediately see those changes in your web browser Each time a stylesheet is requested
612. ved from the Map If the entry is found its timestamp is compared against the current file s timestamp thus allowing auto reload MapEntry entry MapEntry cache get xsltFileName if entry null if the file has been modified more recently than the cached stylesheet remove the entry reference if xslLastModified gt entry lastModified entry null Next we create a new entry in the cache if the entry object reference is still u1 1 This is accomplished by wrapping a St reamSource around the File object instantiating a TransformerFactory instance and using that factory to create our Templates object The Templates object is then stored in the cache so it can be reused by the next client of the cache create a new entry in the cache if if entry null Source xslSource new StreamSource xsltFile t E Q Me TransformerFactory transFact TransformerFactory newInstance es Templates templates Bota eee ee DERE entry new MapEntry xslLastModified templates cache put xsltFileName entry Finally a brand new Transformer is created and returned to the caller return entry templates newTransformer Jes Returning a new Transformer is critical because although the Templates object is thread safe the Transformer implementation is not Each caller gets its own copy of Transformer so multiple clients do not collide with one another One potential impr
613. view of changes to the model Figure 4 5 illustrates the interaction between these three components Figure 4 5 Model view controller Controller ConcreteView ConcreteController ConcreteModel As shown the Model View and Controller are either abstract classes or interfaces The concrete classes are application specific and the open arrows indicate the direction of association between the various classes For example the abstract Mode1 sends notifications sense when you consider how hard it would be to create a specific view such as a customer editor panel without knowledge of a specific data model like Cust omer Since the Mode1 only knows about View instances in an abstract way however it can send generic notifications when it changes allowing new views to be attached later It is important to remember that this is just a pattern specific implementations may vary somewhat and use different class names One variation is to eliminate the explicit references from ConcreteViewto ConcreteModel and from Model to View In this approach the Controller would take a more prevalent role A common theme in Java is to remove the explicit controller using data models and view components that send notifications to event listeners Although typically thought of in terms of GUI applications the MVC architecture is not limited to this domain For web applications it is commonly used in e The hybrid servlet JSP approach e Most s
614. viewMsg xslt lt xml version 1 0 encoding UTF 8 gt e KKEKKKKKKK KK kk kk Ck kk Ck kk Sk Ck Ck kk kk kk kk kk kk Sk ko ck Sk ko ck Sk Ck ko Sk ck ko Sk kx ko ko ko ko viewMsg xslt K Shows details for a specific message CK CC CK CK Ck C Ck CK CI CK CK C CU CC Ck Ck CK CK Ck Ck CK CC C Ck Ck Ck C Ck CK Ck Sk CI S A S Kk Kk Kk x Mk Ax AK M xsl stylesheet version 1 0 xmlns xsl http www w3 0rg 1999 XSL Transform xsl import href utils xslt xsl param name rootDir select docroot xsl output method xml version 1 0 encoding UTF 8 indent yes doctype public W3C DTD XHTML 1 0 Strict EN doctype system http www w3 org TR xhtmll DTD xhtmll strict dtd spes CKkCkckCKkCk kk Ck Ck ok kk Ck Kk kk kk Kk Kk KK kk KU KA KG KK Kok ko ko kok kc ko Create the XHTML web page KKKKKKKKKKKKKKKKKKKKKAKKKKKKKKKKKKKKKAKKKKKKKKKK KK k kck kc k ko kk lt xsl template match gt html xmlns http www w3 0rg 1999 xhtml head title View Message lt title gt link href SrootDir forum css rel stylesheet type text css head body div class boxl hl View Message lt hl1 gt div lt xsl value of select message board name gt lt div gt lt div gt lt Quick Actions gt lt h3 gt Quick Actions lt h3 gt lt ul gt lt li gt Return to long line wrapped a href viewMonth b
615. vletRequest request HttpServletResponse response throws IOException ServletException PersonalData personalData getPersonalData request the third parameter false indicates that error messages should not be displayed when showing the page showPage response personalData false this editXSLTFileName Handles HTTP POST requests such as when the user clicks on a Submit button to update his or her personal data g protected void doPost HttpServletRequest request HttpServletResponse response throws IOException ServletException locate the personal data object and update it with the information the user just submitted PersonalData pd getPersonalData request pd setFirstName request getParameter firstName pd setLastName request getParameter lastName pd setDaytimePhone request getParameter daytimePhone pd setEveningPhone request getParameter eveningPhone pd setEmail request getParameter email if pd isValid show the Edit page with an error message showPage response pd true this editXSLTFileName else show a confirmation page showPage response pd false this thanksXSLTFileName A helper method that sends the personal data to the client browser as HTML It does this by applying an XSLT stylesheet to the DOM tree private void showPage HttpServletResponse response Person
616. w hundred visitors per day then eliminating EJB could be much faster because there is no additional application tier to hop through P BI Keep in mind that other benefits of EJB such as security will be lost 4 4 Summary of Key Approaches If separation of HTML from Java code is a goal then neither a pure servlet nor a pure JSP approach is desirable Although a hybrid approach does allow a clean separation you may have to create custom JSP tags to take full advantage of this capability This approach does not support WML output unless you duplicate all of the HTML generation code Even though the custom JSP tags hide the Java code from the page author you still end up with Java code somewhere producing HTML programmatically Web frameworks typically build on the hybrid approach including proprietary value added features and conveniences Frameworks have the advantage of defining a consistent way to structure the overall application which is probably more important in terms of software maintenance than any value added features The primary disadvantage of frameworks is that you could be locked into a particular approach and vendor The XSLT approach achieves the maximum attainable separation of presentation from underlying data It also supports multiple browsers and even WML targets XSLT transformation does incur additional processing load on the web tier This must be carefully weighed against benefits gained from the modular clean design
617. wed consistency is the most important goal If every class follows the same basic pattern then the development team only has to understand one example to be familiar with the entire system The code for ViewMont hJDOM is shown in Example 7 21 This class creates XML data for an entire month s worth of messages Example 7 21 ViewMonthJDOM java package com oreilly forum xml import java util import com oreilly forum import com oreilly forum adapter import com oreilly forum domain import org jdom Creates the JDOM for the month view of a board public class ViewMonthJDOM param board the message board to generate JDOM for iparam month the month and year to view x public static Element produceElement BoardSummary board MonthYear month throws DataException Element viewMonthElem new Element viewMonth viewMonthElem addAttribute month Integer toString month getMonth viewMonthElem addAttribute year Integer toString month getYear create the board element Element boardElem BoardSummaryJDOM produceNameIDElement board viewMonthElem addContent boardElem DataAdapter adapter DataAdapter getInstance MessageTree msgTree new MessageTree adapter getAllMessages board getID month get an iterator of MessageSummary objects Iterator msgs msgTree getTopLevelMessages while
618. which are themselves written in XML but often produce HTML What this basically means is that the stylesheet must contain well formed XML so it is difficult to produce HTML that is not well formed XHTML is certainly a more natural fit because it is also XML just like the XSLT stylesheet 1 2 3 Validation A well formed XML document adheres to the basic syntax guidelines just outlined A valid XML document goes one step further by adhering to either a Document Type Definition DTD or an XML Schema In order to be considered valid an XML document must first be well formed Stated simply DTDs are the traditional approach to validation and XML Schemas are the logical successor XML Schema is another specification from the W3C and offers much more sophisticated validation capabilities than DTDs Since XML Schema is very new DTDs will continue to be used for quite some time You can learn more about XML Schema at http www w3 org XML Schema The second line of Example 1 1 contains the following document type declaration lt DOCTYPE presidents SYSTEM presidents dtd gt This refers to the DTD that exists in the same directory as the presidents xml file In many cases the DTD will be referenced by a URI instead lt DOCTYPE presidents SYSTEM http www javaxslt com dtds presidents dtd gt Regardless of where the DTD is located it contains rules that define the allowable structure of the XML data Example 1 2 shows the DTD for o
619. wing how each screen links to the next Figure 10 4 Storyboard Deck 1 Deck 3 Splash Screen _seect ove Movie 1 5 Pie rm Movie 1 EH lt gt Select Theater Select Theater Theater Ea 2 Ea Movie n P Showtimes As the illustration indicates the first deck contains a splash screen that displays for 1 5 seconds This takes advantage of a WML timer automatically displaying the city selection page after the timer expires From this page the user can select from a list of cities The second deck consists of a single card which shows a list of theaters for the current city Once the user clicks on a particular city the third deck is displayed This deck may have many cards depending on how many movies are showing in that particular theater The user can browse from movie to movie without requesting additional data from the server For the servlet to dynamically build the appropriate decks and cards each page requires certain parameters These parameters are passed along to the XSLT stylesheet so it can select the appropriate data from the XML file Table 10 4 lists the required parameters for each deck These will appear in each of the WML files as well as in the servlet and XSLT stylesheets If any parameter is invalid or missing the application merely returns the user to the home page Table 10 4 Required parameters Deck Parameters 1 none Shows all cities Shows theaters for a single city action s
620. wkrrorPage does not attempt to use XML or XSLT for its output If it does another similar exception would almost certainly occur Instead it uses hardcoded printin statements to generate its HTML see Example 6 8 6 3 4 Deployment Figure 6 8 shows the complete contents of the WAR file used in this example You may notice that SplashScreenServlet class is still listed in this WAR file This example is merely an extension of the example created earlier in this chapter As in the earlier example placing the c13ss files under the classes directory made them available to the ClassLoader used by this web application Figure 6 8 WAR file for PersonalDataServlet D chap6 war e WEB INF web xml E classes L ex chap6 PersonalData class PersonalDataXML class PersonalDataServiet class SplashScreenServiet class e xsit F confirmPersonalData xsll editPersonalData xslt The XSLT stylesheets are placed under the WEB INF xsIt directory Since anything under the WEB INF directory is hidden from clients the XSLT stylesheets are not directly visible to anyone visiting your web site If you want to make these stylesheets publicly visible move them out of the WEB INF directory The index html file for example is the publicly visible home page for this web application It merely contains a link that the user can click on to view the servlet Although the stylesheets are hidden from clients they are accessible from your Java cod
621. wr Wn LELDE public PersonalData String firstName String lastName String daytimePhone String eveningPhone String email this firstName cleanup firstName this lastName cleanup lastName this daytimePhone cleanup daytimePhone this eveningPhone cleanup eveningPhone this email cleanup email lt code gt eveningPhone lt code gt is the only optional field return true if all required fields are present public boolean isValid return this firstName length gt 0 amp amp this lastName length gt 0 amp amp this daytimePhone length gt 0 amp amp this email length gt 0 public void setFirstName String firstName this firstName cleanup firstName public void setLastName String lastName this lastName cleanup lastName public void setDaytimePhone String daytimePhone this daytimePhone cleanup daytimePhone f public void setEveningPhone String eveningPhone this eveningPhone cleanup eveningPhone public void setEmail String email this email cleanup email public String getFirstName return this firstName public String getLastName return this lastName public String getDaytimePhone return this daytimePhone public String getEveningPhone return this eveningPhone public String getEmail return this email Cleanup the String paramete
622. xalan xslt XSLTInputSource xsltInputSource new org apache xalan xslt XSLTInputSource xsltSystemId XSLTInputSource is a subclass of org xml sax InputSource adding the ability to read directly from a DOM Node XSLTInput Source has the ability to read XML or XSLT data from a system ID java io InputStream java io Reader org w3c dom Node Or an existing InputSource As shown in the code the source of the data is specified in the constructor XSLTInputSource also has a no arg constructor along with get set methods for each of the supported data source types An instance of xSLTResult Target is created next sending the result of the transformation to System out org apache xalan xslt XSLTResultTarget resultTree new org apache xalan xslt XSLTResultTarget System out In a manner similar to xs T inputSource the XSLTResultTarget can also be wrapped around an instance of org w3c dom Node an OutputStream or Writer afilename not a system ID or an instance of org xml sax DocumentHandler The final line of code simply instructs the processor to perform the transformation processor process xmlInputSource xsltInputSource resultTree 5 1 3 SAXON Implementation For comparison a SAXON 5 5 1 implementation is presented in Example 5 2 As you scan through the code you will notice the word trax appearing in the Java packages This is an indication that Version 5 5 1 of SAXON was moving towards something called Transformat
623. xample 4 2 schedule jsp 0 page import chap4 java text SimpleDateFormat dateFmt new SimpleDateFormat hh mm a gt html head lt title gt Today s Shows lt title gt lt head gt lt body gt lt hl gt Today s Shows lt h1 gt Show shows Schedule getInstance getTodaysShows gt lt table border 1 cellpadding 3 cellspacing 0 gt lt tr gt lt th gt Channel lt th gt lt th gt From lt th gt lt th gt To lt th gt lt th gt Title lt th gt lt tr gt lt for int i 0 i lt shows length i 5 gt tr lt td gt lt shows i getChannel gt lt td gt dateFmt format shows i getStartTime 2 dateFmt format shows i getEndTime gt shows i getTitle gt lt td gt A Gh wh set aaga V A AA lt body gt lt html gt As schedule jsp shows most of the JSP is static HTML with dynamic content sprinkled in here and there using special JSP tags When a client first requests a JSP the entire page is translated into source code for a servlet This generated servlet code is then compiled and loaded into memory for use by subsequent requests During the translation process JSP tags are replaced with dynamic content so the end user only sees the HTML output as if the entire page was static Runtime performance of JSP is comparable to hand coded servlets because the static content in the JSP is generally replaced with a series of oxintin statement
624. xample 9 6 Expected output lt xml version 1 0 encoding UTF 8 gt lt DOCTYPE person SYSTEM condensed dtd gt lt person gt lt name gt Aidan Garrett Burke lt name gt lt birthDate gt 6 25 1999 lt birthDate gt lt person gt Finally the DTD for the condensed XML file is shown in Example 9 7 Example 9 7 condense dtd ELEMENT person name birthDate gt lt ELEMENT birthDate PCDATA gt lt ELEMENT name PCDATA gt By providing a DTD for the expected XML output a unit test can easily validate the result tree after performing one or more transformations Such a test simply writes the transformation results to a file and then attempts to parse them using a validating XML parser 9 2 1 JUnit JUnit is an open source testing framework available from http www junit org It is a lightweight tool designed to be used by programmers specifically for unit tests Other tools are generally better for integration testing and functional testing but these are not discussed here Since XSLT transformations can be performed independently of the remainder of an application they are a perfect candidate for automated unit testing A technology such as JSP however is quite difficult to test in an automated fashion because JSPs must be executed within the context of a JSP container and web browser An automated test is one that reports success or failure after execution
625. y Unfortunately you will have to do some detective work to figure out where the JAR files came from Although Java 2 Version 1 3 introduced enhanced JAR features that included versioning information most of the JAR files you encounter probably will not utilize this capability 5 1 1 The Design The design of this application is pretty simple A single class contains amain method that performs the transformation The application requires two arguments the XML file name followed by the XSLT file name The results of the transformation are simply written to System out We will use the following XML data for our example lt xml version 1 0 encoding UTF 8 lt message gt Yep it worked lt message gt The following XSLT stylesheet will be used It s output method is text and it simply prints out the contents of the lt message gt element In this case the text willbe Yep it worked lt xml version 1 0 encoding UTF 8 xsl stylesheet version 1 0 xmlns xsl http www w3 org 1999 XSL Transform xsl output method text encoding UTF 8 simply copy the message to the result tree gt lt xsl template match gt lt xsl value of select message gt lt xsl template gt lt xsl stylesheet gt Since the filenames are passed as command line parameters the application can be used with other XML and XSLT files You might want to try this out with one of the president examples
626. y difficult to write as your pages get more complex and it becomes very difficult to make changes to the HTML when new requirements arrive Web content authors and graphic designers are all but locked out of the process since it takes a programmer to create and modify the code Each minor change requires your programming staff to recompile test and deploy to the servlet container Beyond the tedious nature of HTML generation first generation servlets tend to do too much It is not clear where error handling form processing business logic and HTML generation are supposed to reside Although we are able to leverage two helper classes to generate the list of shows a more rigorous approach will be required for complex web applications All of the remaining technologies presented in this chapter are designed to address one or more of these issues which become increasingly important as web applications get more sophisticated 4 1 3 JSP You have no doubt heard about JSP This is a hot area in web development right now with some pretty hefty claims about productivity improvements The argument is simple instead of embedding HTML code into Java servlets which requires a Java programmer why not start out with static HTML Then add special tags to this HTML that are dynamically expanded by the JSP engine thus producing a dynamic web page Example 4 2 contains a very simple example of JSP that produces exactly the same output as 5cheduleServlet E
627. y inserted into the XHTML whenever a link or form action is required HttpServletResponse has a method called encodeURL that makes this possible BI Sessions and their associated identifiers typically expire after 30 minutes of inactivity and must be regenerated String originalURL shopping moveNext String encodedURL response encodeURL originalURL Now encodedURL will be encoded with the session id if the jsessionid cookie was not found For session tracking to work this technique must be used consistently for every hyperlink and form action on a web site 8 2 2 Session Tracking with Java and XSLT With XSLT session tracking is a little harder because the stylesheet generates the URL rather than the servlet For instance a stylesheet might contain the following code lt xsl template match cart gt Click on the link to move next lt a href shopping moveNext gt Move Next lt a gt lt xsl template gt Like before the j sessionid needs to be concatenated to the URL To make this happen the following steps must be performed 1 Inthe servlet determine if cookies are enabled or disabled 2 If cookies are disabled get the value of jsessionid xx is the 3 Pass jsessionid XXXX as a parameter to the XSLT stylesheet where x session identifier 4 Inthe stylesheet append the session id parameter to all URLs in hyperlinks and form actions If cookies are enabled there is no reason to manually impl
628. ying to parse 29 110 Encoding supported by Apache s Xerces parser are documented at http xml apache org xerces j faq general html If these tests do not uncover the problem try the following e Stick with UTF 8 encoding until problems are resolved This is the most compatible encoding e Verify that the servlet sets the Content Type header to Content Type text html charset UTF 8 e Verify that the XSLT stylesheet sets the appropriate encoding on the xs1 output element or override the encoding programmatically transformer setOutputProperty OutputKeys ENCODING UTF 8 e Insert some code into the servlet that performs the transformation but sends the result to a file instead of the HttpServletResponse s Writer Inspect this file with a Unicode compatible text editor e Use java io File or java io InputStream instead of java io Reader when reading XML and XSLT files Chapter 9 Development Environment Testing and Performance This chapter provides an overview of many different technologies that comprise a typical Java and XSLT software development environment Once the most commonly used tools are introduced strategies for testing XSLT and tuning performance are presented Instead of presenting specific performance benchmarks for various XSLT processors this chapter s focus is on effective programming techniques that should be applicable to a wide range of tools XSLT is a very young technology and tools are imp
629. yond the scope of this chapter and are generally unimportant to most developers This is because cell phone companies and other wireless portals provide these gateways allowing their customers to access the entire Internet via their wireless devices Typical web application developers can deploy servlets and WML content onto normal web servers and the content will be available to wireless users automatically 10 3 Java XSLT and WML Unless a web application is limited to a corporate intranet it must be designed to support a wide variety of device types As the upcoming examples will demonstrate wireless devices are far less consistent than web browsers This amplifies the need for the clean separation between data and presentation that XML and XSLT offer because many different presentation styles may be needed to take advantage of specific devices Java servlets are used to tie everything together detecting the type of client device and driving the XSLT transformation process 10 3 1 A WML Example WML is a relatively new XML based markup language specifically designed for wireless devices As such it is compact easy to parse and optimized for small displays WML is the product of the WAP Forum an association consisting of over 500 member companies that defines specifications for wireless devices You can learn more about WML by downloading the specification from http www wapforum org or by reading Learning WML and WMLScript by Martin Fr
630. you may want to define a group of attributes that can be reused For this task XSLT provides the xs1 attribute set element Using this element allows you to define a named group of attributes that can be referenced from other points in a stylesheet The following stylesheet fragment shows how to define an attribute set attribute set name body style gt l attribute name bgcolor gt yellow lt xsl attribute gt sl attribute name text gt green lt xsl attribute gt sl attribute name link gt navy lt xsl attribute gt sl attribute name vlink gt red lt xsl attribute gt l attribute set This is a top level element which means that it can occur as a direct child of the xsl stylesheet element The definition of an attribute set does not have to come before templates that use it The attribute set can be referenced from another lt xsi attribute set gt from xsi element orfrom xs1 copy elements We will talk about xs1 copy in the next chapter but here is how xs1 el1ement is used lt xsl template match gt lt html gt lt head gt lt title gt Demo of attribute set lt title gt lt head gt xsl element name body use attribute sets body style lt hl gt Books in my library hl ul xsl apply templates select library book ul xsl element lt html gt xsl template As you can probably guess the code shown here will output an HTML body tag that looks li
631. you specify and can write out XML to any Java output stream or file It even features a class called SAxOut putter that allows the JDOM data to be integrated with any tool that expects a series of SAX events I3 Sun has accepted JDOM as Java Specification Request JSR 000102 see http java sun com about ava communityprocess The code in Example 1 5 shows how much easier JDOM is than DOM it does the same thing as the DOM example but is about fifty lines shorter This difference would be greater for more complex applications Example 1 5 XML generation using JDOM package com oreilly javaxslt chapl import java io import java util import org jdom DocType import org jdom Document import org jdom Element import org jdom output XMLOutputter An example from Chapter l Creates the library XML file 7 public class LibraryJDOMCreator public Document createDocument Library library Element root new Element library JDOM supports the lt DOCTYPE gt DocType dt new DocType library library dtd Document doc new Document root dt add publisher children to the library element Iterator publisherIter library getPublishers iterator js while publisherIter hasNext Publisher pub Publisher publisherIter next Element pubElem createPublisherElement pub root addContent pubElem now add book children

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