Web Development with JavaEE Developing Custom Tag Libraries and XML Processing with JSP

Transcription

1 Applied Autonomous Sensor Systems Web Development with JavaEE Developing Custom Tag Libraries and XML Processing with JSP AASS Mobile Robotics Lab, Teknik Room T2222

2 Contents 1. Introduction to Custom Tags 2. Developing Custom Tag Libraries Tag, TagIteration, and BodyTag interface 3. XML Processing With JSP xml library (JSTL), XPath, JDOM 4. Session Tracking

3 Contents Introduction To Custom Tags

4 1 Introduction To Custom Tags Custom Action Elements (= Custom Tags) custom actions can manipulate JSP content (Beans can t) implemented by a tag handler class Advantages portability work in any JSP container simplicity can be used by unsophisticated users allows for a convenient division of the work Java programmers can implement custom tags and page authors can use them in a familiar way (XML syntax)

5 1 Introduction To Custom Tags Tag Library collection of custom actions class file tag library descriptor (TLD file) [action names class] mapping using the TLD, the container can verify that the attributes are correct can be packaged (JAR file) for simple deployment JSP containers must accept packaged tag libraries the package must include a TLD the prefix is used as an XML namespace

6 1 Introduction To Custom Tags Tag Handler run-time representation of a custom action implements a tag handler interface Tag Handler Interfaces Tag: basic methods needed in all tag handlers tag init, dostarttag(), doendtag() IterationTag: re-evaluation of the body doafterbody() BodyTag: tag body manipulation setbodycontent(), doinitbodytag()

7 1 Introduction To Custom Tags Custom Tags Development implement a tag handler class make the compiled class available for the container place the.class file in WEB-INF/classes write the TLD file place the.tld file in WEB-INF

8 1 Introduction To Custom Tags Using Custom Tags A Simple Example <p> <% for(int i = 1; i <= 5; ++i) { %> <font size="<%=i%>">different sizes...</font><br/> <% %> </p> <%@taglib uri="/mycustomtags" prefix="my" %>... <p> <my:repeattext rep="5" reptext="different sizes..." /> </p>

9 1 Introduction To Custom Tags Using Custom Tags taglib directive uri="/mycustomtags" prefix="my" %> import a set of compiled action classes into a JSP assign a prefix to the loaded tag library call the custom action as <prefix:actionname> <my:repeattext rep="5" reptext="different sizes..." />

10 1 Introduction To Custom Tags Custom Tag to Action Class Mapping TagHandler class implements the custom action tag library declaration wdwj2ee.mytag a tag library descriptor (TLD) in WEB-INF (required in JSP 2) the correct TLD is identified by the URI in the TLD URIs are mapped when the server starts globally unique URI required mytld.tld <%@taglib uri="se.oru.wdwj2ee.mycustomtags" prefix="my" %>... <my:repeattext rep="5" reptext="different sizes..." />

11 1 Introduction To Custom Tags Custom Tag to Action Class Mapping RepeatTextTag.class mytld.tld <taglib... > <uri>se.oru.wdwj2ee.mycustomtags</uri> <tag> <name>repeattext</name> <tag-class>wdwj2ee.repeattexttag</tag-class> </tag> </taglib> uri="se.oru.wdwj2ee.mycustomtags" prefix="my" %>... <my:repeattext rep="5" reptext="different sizes..." />

12 1 Introduction To Custom Tags Tag Library Descriptor (TLD) XML document that describes a tag library maps action names to tag handler classes defines the attributes web container can verify whether the provided attribute list is correct specifies which scripting variables are created by the action! intended to be used also by authoring tools! file extension = tld! TLD must be deployed in WEB-INF (META-INF for JARs)

13 3 Introduction To Custom Tags The TLD file URI <?xml version="1.0" encoding="utf-8"?> <taglib version="2.0"... > <tlib-version>1.0</tlib-version> <jsp-version>1.2</jsp-version> <short-name>mytags</short-name> <uri>se.oru.wdwj2ee.mycustomtags</uri> <tag> <name>checklogin</name> <tag-class>wdwj2ee.checklogintag</tag-class> <body-content>empty</body-content> <description>forwards to "loginurl" </description> <attribute> <name>loginurl</name> <required>true</required> <rtexprvalue>true</rtexprvalue> </attribute> </tag> </taglib> default prefix tag name tag class (incl. package) action body treatment attribute name obligatory or not? allow request time expressions?

14 3 Introduction To Custom Tags The TLD file [default] <body-content> empty action body must be empty JSP action body can contain JSP elements (actions, scriptlets,...) tagdependent disables processing of JSP elements in the body <rtexprvalue> true or yes request-time expressions are allowed: <... attr = '<%=request.getparameter("parname")%>'/>

15 3 Introduction To Custom Tags The checklogin Custom Tag checks whether the user is logged in and forwards to a central login page otherwise <% if(session.getattribute("loggedin") == null) { %> <% %> <html> <jsp:forward page="/login.jsp" /> <head><title>for authorised users only... </head></title> <body>...

16 3 Introduction To Custom Tags The checklogin Custom Tag checks whether the user is logged in and forwards to a central login page otherwise <%@taglib uri="/mycustomtags" prefix="my" %> <my:checklogin loginurl="/login.jsp" /> <html> <head><title>for authorised users only... </head></title> <body>...

17 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.jspwriter; import javax.servlet.jsp.jspexception; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { private String m_strloginurl; public String getloginurl() { return m_strloginurl; public void setloginurl(string strloginurl) { m_strloginurl = strloginurl; public int dostarttag() throws JspException {... WDWJ2EE/src/se/oru/wdwj2ee/CheckLoginTagHandler.java

18 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.jspwriter; import javax.servlet.jsp.jspexception; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { private String m_strloginurl; public String getloginurl() { return m_strloginurl; public void setloginurl(string strloginurl) { m_strloginurl = strloginurl; public int dostarttag() throws JspException {... WDWJ2EE/src/se/oru/wdwj2ee/CheckLoginTagHandler.java

19 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.jspwriter; import javax.servlet.jsp.jspexception; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { private String m_strloginurl; public String getloginurl() { return m_strloginurl; public void setloginurl(string strloginurl) { m_strloginurl = strloginurl; public int dostarttag() throws JspException {... WDWJ2EE/src/se/oru/wdwj2ee/CheckLoginTagHandler.java

20 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.jspwriter; import javax.servlet.jsp.jspexception; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { private String m_strloginurl; public String getloginurl() { return m_strloginurl; public void setloginurl(string strloginurl) { m_strloginurl = strloginurl; public int dostarttag() throws JspException {... WDWJ2EE/src/se/oru/wdwj2ee/CheckLoginTagHandler.java

21 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.jspwriter; import javax.servlet.jsp.jspexception; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { private String m_strloginurl; public String getloginurl() { return m_strloginurl; public void setloginurl(string strloginurl) { m_strloginurl = strloginurl; public int dostarttag() throws JspException {... WDWJ2EE/src/se/oru/wdwj2ee/CheckLoginTagHandler.java

22 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class public int dostarttag() throws JspException { try { HttpSession session = pagecontext.getsession(); if(session.getattribute("loggedin") == null) { pagecontext.forward(m_strloginurl); return SKIP_BODY; catch(java.io.ioexception ioe) { throw new JspException(ioe.toString()); catch(javax.servlet.servletexception se) { throw new JspException(se.toString()); return EVAL_BODY_INCLUDE;! custom tags can access predefined variables: pagecontext, request, response, session, application,...

23 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class public int dostarttag() throws JspException { try { HttpSession session = pagecontext.getsession(); if(session.getattribute("loggedin") == null) { pagecontext.forward(m_strloginurl); return SKIP_BODY; catch(java.io.ioexception ioe) { throw new JspException(ioe.toString()); catch(javax.servlet.servletexception se) { throw new JspException(se.toString()); return EVAL_BODY_INCLUDE;! custom tags can access predefined variables: pagecontext, request, response, session, application,...

24 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class public int dostarttag() throws JspException { try { HttpSession session = pagecontext.getsession(); if(session.getattribute("loggedin") == null) { pagecontext.forward(m_strloginurl); return SKIP_BODY; catch(java.io.ioexception ioe) { throw new JspException(ioe.toString()); catch(javax.servlet.servletexception se) { throw new JspException(se.toString()); return EVAL_BODY_INCLUDE;! custom tags can access predefined variables: pagecontext, request, response, session, application,...

25 3 Introduction To Custom Tags The checklogin Custom Tag Tag Handler Class public int dostarttag() throws JspException { try { HttpSession session = pagecontext.getsession(); if(session.getattribute("loggedin") == null) { pagecontext.forward(m_strloginurl); return SKIP_BODY; catch(java.io.ioexception ioe) { throw new JspException(ioe.toString()); catch(javax.servlet.servletexception se) { throw new JspException(se.toString()); return EVAL_BODY_INCLUDE;! custom tags can access predefined variables: pagecontext, request, response, session, application,...

26 Contents Developing Custom Tag Libraries

27 2 Developing Custom Tag Libraries Custom Actions Tag Interface <prefix:actionname attr1="value1" attr2="value2" > The body </prefix:actionname> Properties handled by get/set methods setattr1("value1") setattr2("value2") dostarttag() doendtag()! custom actions can be thought of as extended JavaBeans

28 2 Developing Custom Tag Libraries Tag Handler can add content to the response can set response headers can add or remove variables in the JSP scopes can initiate to include the action s body or not TagSupport Class sets PageContext provides a default implementation for dostarttag() and doendtag()

29 2 Developing Custom Tag Libraries dostarttag() called when the start tag is encountered used for initialisation to decide whether to ignore the body (SKIP_BODY) or to include the result of processing it (EVAL_BODY_INCLUDE) doendtag() called when the end tag is encountered must return EVAL_PAGE: continue processing the rest of the page SKIP_PAGE: aborts processing of the rest of the page <c:if> <c:redirect>

30 2 Developing Custom Tag Libraries Custom Actions Tag Interface <prefix:actionname attr1="value1" attr2="value2" > The body </prefix:actionname> SimpleTagSupport Class setattr1("value1") setattr2("value2") dostarttag() doendtag() default implementation for Tags own Tags can inherit basic functionality

31 2 Developing Custom Tag Libraries SimpleTagSupport (JSP 2.0) simpler invocation protocol single dotag() method no integer return values (like SKIP_BODY) called once and only once tag body can be accessed as a JSP Fragment tag body can be evaluated repeatedly (JspBody().invoke()) tag body cannot be modified SimpleTag interface has the same power as the Tag interface predefined variables are not defined by default convenient for writing very simple tags no return value in the SimpleTagSupport implementation

32 2 Developing Custom Tag Libraries Custom Actions Tag Interface package se.oru.wdwj2ee; import javax.servlet.jsp.tagext.*; import javax.servlet.jsp.*; import javax.servlet.http.httpsession; public class CheckLoginTagHandler extends TagSupport { public int dostarttag() throws JspException { // initialisation, return SKIP_BODY or EVAL_BODY_INCLUDE public int doendtag() throws JspException { // initialisation, return EVAL_PAGE or SKIP_PAGE public void release() { // set used variables to null super.release();... // get/set methods for the attribute values

33 2 Developing Custom Tag Libraries Custom Actions IterationTag interface inherits Tag can ask the container to evaluate the body multiple times TagSupport Class default implementation for IterationTags own IterationTags extend TagSupport

34 2 Developing Custom Tag Libraries Custom Actions IterationTag interface <prefix:actionname attr1="value1" attr2="value2" > The body </prefix:actionname> doafterbody() setattr1("value1" ) setattr2("value2" ) dostarttag() doafterbody() doendtag() called after the action element s body was processed <c:foreach>

35 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach> <%@taglib uri="my.mycompany.mytaglib" prefix="my"%> <%@taglib uri=" prefix="c"%>... <ul> <my:simpleloop items="mycollection" var="curritem"> <li> <c:out value="${curritem.name"/> (<c:out value="${curritem.gender"/>) </li> </my:simpleloop> </ul>...

36 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach>... public class SimpleLoopTag extends TagSupport { private Iterator ititems; private String stritems; public void setitems(string stritems) { this.stritems = stritems; private String strvar; public void setvar(string strvar) { this.strvar = strvar; public int dostarttag() throws JspException { public int doafterbody() {

37 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach>... public class SimpleLoopTag extends TagSupport { private Iterator ititems; private String stritems; public void setitems(string stritems) { this.stritems = stritems; private String strvar; public void setvar(string strvar) { this.strvar = strvar; public int dostarttag() throws JspException { public int doafterbody() {

38 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach>... public class SimpleLoopTag extends TagSupport { private Iterator ititems; private String stritems; public void setitems(string stritems) { this.stritems = stritems; private String strvar; public void setvar(string strvar) { this.strvar = strvar; public int dostarttag() throws JspException { public int doafterbody() {

39 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach> public class SimpleLoopTag extends TagSupport { public int dostarttag() throws JspException { Collection coll = (Collection) pagecontext.findattribute(stritems); if(coll == null) throw new JspException("No items found"); this.ititems = coll.iterator(); if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_INCLUDE; return SKIP_BODY; public int doafterbody() { if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_AGAIN; return SKIP_BODY;

40 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach> public class SimpleLoopTag extends TagSupport { public int dostarttag() throws JspException { Collection coll = (Collection) pagecontext.findattribute(stritems); if(coll == null) throw new JspException("No items found"); this.ititems = coll.iterator(); if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_INCLUDE; return SKIP_BODY; public int doafterbody() { if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_AGAIN; return SKIP_BODY;

41 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach> public class SimpleLoopTag extends TagSupport { public int dostarttag() throws JspException { Collection coll = (Collection) pagecontext.findattribute(stritems); if(coll == null) throw new JspException("No items found"); this.ititems = coll.iterator(); if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_INCLUDE; return SKIP_BODY; public int doafterbody() { if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_AGAIN; return SKIP_BODY;

42 2 Developing Custom Tag Libraries IterationTag Interface a simple <foreach> public class SimpleLoopTag extends TagSupport { public int dostarttag() throws JspException { Collection coll = (Collection) pagecontext.findattribute(stritems); if(coll == null) throw new JspException("No items found"); this.ititems = coll.iterator(); if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_INCLUDE; return SKIP_BODY; public int doafterbody() { if(ititems.hasnext()) { pagecontext.setattribute(strvar,ititems.next()); return EVAL_BODY_AGAIN; return SKIP_BODY;

43 2 Developing Custom Tag Libraries Custom Actions BodyTag Interface inherits IterationTag add methods that provide access to the body can read and process the element body! just using the body does not require a BodyTag BodyTagSupport Class default implementation for BodyTags own BodyTags extend BodyTagSupport

44 2 Developing Custom Tag Libraries Custom Actions BodyTag Interface <prefix:actionname attr1="value1" attr2="value2" > The body </prefix:actionname> setattr1("value1") setattr2("value2") dostarttag() setbodycontent() doinitbody() doafterbody() doendtag()

45 2 Developing Custom Tag Libraries BodyTagSupport Class dostarttag() returns EVAL_BODY_BUFFERED process the body and make the result available the body content is buffered in a BodyContent object! the JSP output is temporarily redirected to the BodyContent object! BodyContent is a subclass of JspWriter setbodycontent() sets bodycontent doinitbody() preparation before the first invocation of the action body can be here doafterbody() here the buffered body content can be accessed

46 2 Developing Custom Tag Libraries BodyTag Interface <menuitem> uri="my.mycompany.mytaglib" prefix="my"%>... <my:menuitem page="login.jsp"> Login first </my:menuitem> wraps the body with an HTML link element but only if page isn t the current page

47 2 Developing Custom Tag Libraries BodyTag Interface <menuitem>... public class MenuItemTag extends BodyTagSupport { private String strpage; public void setpage(string strpage) { this.strpage = strpage; public int doafterbody() { public int doendtag() throws JspException {

48 2 Developing Custom Tag Libraries BodyTag Interface <menuitem> public class MenuItemTag extends BodyTagSupport { public int doendtag() throws JspException { HttpServletRequest request = (HttpServletRequest) pagecontext.getrequest(); String requesturi = request.getcontextpath() + request.getservletpath(); String servletpath = pagecontext.getservletcontext().getrealpath(requesturi); String servletpathbase = servletpath; int lastpathseparator = servletpathbase.lastindexof(file.separatorchar); if(lastpathseparator > -1) servletpathbase = servletpathbase.substring(0,lastpathseparator); String pagepath = servletpathbase + File.separatorChar + this.strpage; StringBuffer text = null; String strbody = getbodycontent().getstring(); // not tostring()!!! if(servletpath.equals(pagepath)) { text = new StringBuffer(strBody);... getbodycontent() returns a reference to the BodyContent object

49 2 Developing Custom Tag Libraries BodyTag Interface <menuitem> public class MenuItemTag extends BodyTagSupport { public int doendtag() throws JspException {... if(servletpath.equals(pagepath)) { text = new StringBuffer(strBody); // if(servletpath.equals(pagepath)) else { String contextsenspath = requesturi; int lastsep = contextsenspath.lastindexof('/'); if(lastsep > -1) contextsenspath = contextsenspath.substring(0,lastsep); String uri = contextsenspath + '/' + this.strpage; HttpServletResponse response = (HttpServletResponse) pagecontext.getresponse(); text = new StringBuffer("<a href=\""); text.append(response.encodeurl(uri)); text.append("\">"); text.append(strbody); text.append("</a>"); // else[if(servletpath.equals(pagepath))]...

50 2 Developing Custom Tag Libraries BodyTag Interface <menuitem> public class MenuItemTag extends BodyTagSupport { public int doendtag() throws JspException {... if(servletpath.equals(pagepath)) { text = new StringBuffer(strBody); // if(servletpath.equals(pagepath)) else {... // else[if(servletpath.equals(pagepath))] try { JspWriter out = getpreviousout(); out.print(text); catch(ioexception ioe) { return EVAL_PAGE; returns the BodyContent object of the enclosing action (JspWriter at top level)

51 2 Developing Custom Tag Libraries Custom Actions BodyTag Interface <prefix:actionname attr1="value1" attr2="value2" > The body </prefix:actionname> setattr1("value1") setattr2("value2") dostarttag() setbodycontent() doinitbody() doafterbody() doendtag() not called in case of an empty body (keep in mind!)

52 Contents XML Processing With JSP

53 3 XML Processing With JSP Generating XML Response page contenttype="text/xml" %> JSTL Actions (xml library) XML HTML transformation digesting XML documents (parsing, accessing XML data) Java APIs JDOM SAX simple accessing, manipulating, and writing of XML documents particularly suited for large XML documents

54 3 XML Processing With JSP The XML Library uri=" prefix="x"%> x depends on Apache Xalan (XSLT processor) Xalan is included in JDK ! also included in JDK 1.5 but with different package name! new interfaces for XPath x might not find Xalan add xalan.jar to /WEB-INF/lib

55 3 XML Processing With JSP XML HTML with XSLT XSL: Extensible Stylesheet Language defines transformations to other types of documents (XSLT) defines formatting for display <? xml version="1.0" encoding="utf-8" /> uri=" prefix="c"%> uri=" prefix="x"%> <c:import url="htmltable.xsl" var="stylesheet" /> <x:transform xslt="${stylesheet" />... </x:transform>

56 3 XML Processing With JSP The XML Library transform XSLT transformation <x:transform xml="xmldoc.xml" xslt="xsltsheet.xsl" /> xml xslt var result scope xmlsystemid xsltsystemid XML file to transform (can also be specified in the body) XSLT stylesheet variable to hold the result as a Document object variable to hold the result as a Result object scope of var or result base URI for the XML source base URI for the XSLT stylesheet

57 3 XML Processing With JSP The XML Library param pass parameters to the XSLT stylesheet <? xml version="1.0" encoding="utf-8" /> <x:transform xml="xmldoc.xml" xslt="xsltsheet.xsl" > <x:param name="username" value="${param.name" />... some XML </x:transform> name value name of the dynamic parameter value to pass to the XSLT stylesheet

58 3 XML Processing With JSP Parsing XML Documents <c:import url="xmldoc.xml" varreader="xmlsource"> <x:parse var="xmldoc" xml="${xmlsource" scope="session" /> </c:import> <x:parse var="xmldoc" scope="application"> XML Document </x:parse> xml systemid var scope filter XML document to parse (String or Reader) base URI for the XML document name of the result variable (implementation specific) scope of var filter class that removes parts of the XML document

59 3 XML Processing With JSP Accessing XML Data XPath a syntax for defining parts of an XML document uses path expressions to navigate in XML documents contains a library of standard functions is a major element in XSLT is a W3C Standard XPath Expressions expressions to select nodes or node-sets in an XML document look very much like the expressions for file system access

60 3 XML Processing With JSP Accessing XML Data XPath Expressions XPath language (similar to EL) /news/march/d22 (first <d22> element in <march> in <news>) //news/march (all <march> elements in <news>) $variables can appear anywhere (must start with '$'!) relative to a specific context can be used in the 'select' attribute of JSTL xml actions <c:import url="xmldoc.xml" varreader="xmlsource"> <x:parse var="xmldoc" xml="${xmlsource" scope="session" /> </c:import> <x:out select="$xmldoc/news/march/d22" /> <x:out select="$param:username" />

61 3 XML Processing With JSP Accessing XML Data XPath Expressions <c:import url="xmldoc.xml" varreader="xmlsource"> <x:parse var="xmldoc" xml="${xmlsource" scope="session" /> </c:import> <c:usebean id="xmldoc.xml" varreader="xmlsource" /> <x:foreach select="$xmldoc/news/march/d22" /> <x:out select="$param:username" />

62 3 XML Processing With JSP XSLT and XPath provide tools for specialized tasks many applications are not covered Working with XML often requires parsing XML documents into XML trees navigating through XML trees constructing XML trees outputting XML trees as XML documents DOM and SAX: language independent APIs for working with XML JDOM: an API that is tailored to Java

63 3 XML Processing With JSP SAX Simple API for XML event based provides serial access to an XML document (stream) required to read large XML documents not designed for construction of XML documents not designed for manipulation of XML documents Using SAX write a SAX handler ( org.xml.sax.helpers.defaulthandler) implement methods for particular events startdocument(), enddocument(), startelement(), endelement() create a org.xml.sax.xmlreader and call its method parse()

64 3 XML Processing With JSP DOM Document Object Model standard API to access HTML and XML documents includes manipulation of HTML and XML documents programming language independent entire document must be parsed and stored in memory DOM if the document elements have to be randomly accessed... the document elements have to be manipulated SAX if the XML document is large... there are only a few elements of interest in the XML document

65 3 XML Processing With JSP JDOM (org.jdom) Java specific DOM representation only for XML documents not to confuse with standard DOM requires library (jdom.jar) from simpler than the org.w3c.dom DOM implementation

66 3 XML Processing With JSP JDOM (org.jdom) Creating XML Trees import org.jdom.*;... Document xmldoc = new Document(); Element root = new Element("root"); root.settext("some text"); xmldoc.setrootelement(root); or even shorter import org.jdom.*;... Document xmldoc = new Document(new Element("root").setText("Some text")); <root>some Text</root>

67 3 XML Processing With JSP JDOM (org.jdom) Creating XML Trees Document xmldoc = new Document(); Element root = new Element("numbers"); root.settext("some text"); root.setattribute(new Attribute("language","german"); xmldoc.setrootelement(root); Element node1 = new Element("one"); node1.settext("eins"); root.addcontent(node1); Element node2 = new Element("two"); node2.settext("zwei"); root.addcontent(node2);... <numbers language="german"> <one>eins</one> <two>zwei</two>... </numbers>

68 3 XML Processing With JSP JDOM (org.jdom) Structure DocType Document Namespace Element String/Text Attribute ProcessingInstruction Element

69 3 XML Processing With JSP JDOM Creating An XML Tree From a Source <%@page import="java.io.*,java.net.*,org.jdom.*,org.jdom.input.saxbuilder"%> <% %> URL fileurl = new URL(" + request.getservername() + ":" + request.getserverport() + request.getcontextpath() + "/xmldocs/testdocument.xml"); SAXBuilder docbuilder = new SAXBuilder(); docbuilder.setvalidation(false); try { Document xmldoc = docbuilder.build(fileurl); catch(ioexception ioe) { out.println(ioe.getmessage());! without XML validation catch(jdomexception jdome) { out.println(jdome.getmessage());! SAX to read in an XML document

70 3 XML Processing With JSP JDOM Creating An XML Tree From a Source <%@page import="java.io.*,java.net.*,org.jdom.*,org.jdom.input.saxbuilder"%> <% URL fileurl = new URL(" + request.getservername() + ":" + request.getserverport() + request.getcontextpath() + "/xmldocs/testdocument.xml"); SAXBuilder docbuilder = new SAXBuilder(); docbuilder.setvalidation(true); docbuilder.setignoringelementcontentwhitespace(true); try { Document xmldoc = docbuilder.build(fileurl);! with XML validation catch(ioexception ioe) { out.println(ioe.getmessage()); catch(jdomexception jdome) { out.println(jdome.getmessage()); %>

71 3 XML Processing With JSP JDOM Traversing XML Trees import="java.io.*,java.net.*,org.jdom.*,org.jdom.input.saxbuilder"%> <% %>... try { Document xmldoc = docbuilder.build(fileurl); Element root = xmldoc.getrootelement(); List children = root.getchildren(); Iterator iterator = children.iterator(); while(iterator.hasnext()) { Element child = (Element) iterator.next(); printnodecontent(child); catch(exception e) {! JDOM to manipulate the XML structure

72 3 XML Processing With JSP JDOM Traversing XML Trees // get root element Element node = xmldoc.getrootelement(); // get a sub element (child) of an Element Element children = node.getchild("name"); Element children = node.getchild("name","namespace"); // get sub elements (children) of an Element List children = node.getchildren(); List children = node.getchildren("name"); List children = node.getchildren("name","namespace"); // get the first Element in a List Element firstelement = (Element) children.get(0);

73 3 XML Processing With JSP JDOM Traversing XML Trees // check whether this Element is the root element if(node.isrootelement()) {... // get the parent Element Element parent = node.getparent();

74 3 XML Processing With JSP JDOM Accessing The Content Of XML Trees // get the content of an Element String text = node.gettext(); String text = node.gettexttrim(); String text = node.gettextnormalize(); // get attributes of an Element Attribute attr = node.getattribute("name"); Attribute attr = node.getattribute("name","namespc"); List attributes = node.getattributes(); // get the attribute values of an Element String attval = node.getattributevalue("name"); String attval = node.getattributevalue("name","namespc");

75 3 XML Processing With JSP JDOM Accessing The Content Of XML Trees // get the content of an Element String text = node.gettext(); String text = node.gettexttrim(); String text = node.gettextnormalize(); // get attributes of an Element Attribute attr = node.getattribute("name"); Attribute attr = node.getattribute("name","namespc"); List attributes = node.getattributes(); // get the attribute values of an Element String attval = node.getattributevalue("name"); String attval = sequences of whitespaces node.getattributevalue("name","namespc"); one whitespace ignores surrounding whitespaces

76 3 XML Processing With JSP JDOM Manipulating XML Trees // add a child Element to a parent Element parentnode.addcontent(childnode); // remove a child Element from a parent Element List children = parentnode.getchildren(); children.remove(0); // remove an attribute from an Element node.removeattribute(anattribute); node.removeattribute("name"); removes the first child element ( live List)

77 3 XML Processing With JSP JDOM Manipulating XML Trees, Example remove administrators Element root = xmldoc.getrootelement(); List users = root.getchildren("user"); Element curruser = null; Element username = null; for(int i = 0; i < users.size( ); i++) { curruser = (Element) users.get(i); username = curruser.getchild("name"); if(username.getattributevalue("admin").equals("true")) { root.removecontent(curruser); check for null pointers in real code <users> <user> <name admin="true">jpelle</name> <password>itsme</password> </user> <user> <name admin="false">par62</name> <password>god</password> </user> </users> <users> <user> <name admin="false">par62</name> <password>god</password> </user> </users>

78 3 XML Processing With JSP JDOM Storing XML Documents import="java.io.*,org.jdom.output.xmloutputter"%> <% Document xmldoc = new Document();... // create some content XMLOutputter xmlout = new XMLOutputter(); try { xmlout.output(xmldoc, out); // add response to the JSP page xmlout.output(xmldoc, System.out); // add response to the console File xmlfile = new File("C:\\my.xml"); xmlfile.createnewfile(); FileOutputStream xmlfileout = new FileOutputStream(xmlFile); xmlout.output(xmldoc, xmlfileout); // write response to a file catch(ioexception ioe) { %>

79 3 XML Processing With JSP JDOM Storing XML Documents, Formatting Output // using predefined formatting options xmlout.setformat(format.getcompactformat()); // default xmlout.setformat(format.getprettyformat()); xmlout.setformat(format.getrawformat()); // add self-defined settings xmlout.setformat( Format.getRawFormat().setIndent(" ")); xmlout.setformat( Format.getRawFormat().setOmitDeclaration(true)); xmlout.setformat( Format.getRawFormat().setOmitEncoding(true));

80 3 XML Processing With JSP JDOM An Example XML declaration must be in the first line! <?xml version="1.0" encoding="utf-8"?> contenttype="text/xml;charset=utf-8"%> import="org.jdom.*, org.jdom.input.*,org.jdom.output.*"%> <jsp:usebean id="person" class="mybeans.xmlperson" scope="page" /> <jsp:setproperty name="person" property="*" /> <% %> Document xmldoc = person.getasxml(); XMLOutputter xmlout = new XMLOutputter(); xmlout.setformat(format.getprettyformat() try {.setomitdeclaration(true).setomitencoding(true)); xmlout.output(xmldoc, out); // use the JspWriter out to write the XML stream catch(ioexception ioe) { do not repeat the XML declaration in the first line!

81 3 XML Processing With JSP JDOM Summary stream/file/url/string JDOM SAXBuilder SAXHandler DOMBuilder... org.jdom.input org.jdom Attribute Document Element NameSpace DocType... XMLOutputter SAXOutputter DOMOutputter... JDOMResult JDOMSource... JDOM stream/file org.jdom.output org.jdom.transform org.jdom.adapters org.jdom.filter org.jdom.xpath

82 Contents Session Tracking

83 4 Session Tracking Session Tracking required since HTTP is a stateless protocol Typical Session Tracking store the user state on the server send back an identifier (session ID) as a cookie or HTTP/ OK Set-cookie: JSESSIONID=AAA1A1D29C24264A08A6B31747B1F531 encoded into the URL (URL rewriting) <a href="nextpage.jsp; JSESSIONID=AAA1A1D29C24264A08A6B31747B1F531> GET /nextpage.jsp;jsessionid=aaa1a1d29c24264a08a6b31747b1f531 HTTP/1.0

84 4 Session Tracking URL Rewriting Support important if the user disables cookies, or if the client doesn t support cookies (PDA, cell phone, ) <c:url > Encode the URL When Needed <a href="<c:url value="next.jsp"/>">a Link</a> value context var scope path to encode (absolute, context-, or page-relative) context path (if resource is not part of this application) name of a variable that holds the encoded URL scope for var

85 4 Session Tracking <c:url > Encode the URL When Needed <c:url value="next.jsp"/> = /WDWJ2EE/next.jsp if the container received a cookie with the request = /WDWJ2EE/next.jsp;JSESSIONID=AAA1A1D29C2 if the container did not receive a cookie <c:url value="next.jsp"> <c:param name="user" value="hans Napf" /> </c:url> = /WDWJ2EE/next.jsp;JSESSIONID=AAA?name=Hans+Napf! path relative converted to a context relative path

86 4 Session Tracking Session Tracking and Multiple Browser Windows each different process is associated with a different session but usually one process controls multiple windows URL rewriting: each window is a separate session Cookies: all windows belong to one session cookies are shared by all windows in the same process

87 Contents Web Services

88 5 Web Services Web Services = a software for interoperable machine-to-machine interaction over a network... using XML based messages... that has an interface defined in an XML format (WSDL) WSDL = Web Services Description Language... that is identified by a unique URI! Web Services = Web Pages for Computers SOAP protocol for exchanging XML based messages used to make a call to a web service

89 5 Web Services SOAP Request (Google Web Services) <?xml version='1.0' encoding='utf-8'?> <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Body> <ns1:dospellingsuggestion xmlns:ns1="urn:googlesearch" SOAP-ENV:encodingStyle=" <key xsi:type="xsd:string"> </key> <phrase xsi:type="xsd:string">britney speers</phrase> </ns1:dospellingsuggestion> </SOAP-ENV:Body> </SOAP-ENV:Envelope> messages are contained in an envelope no header in this example (date, authentication,...)

90 5 Web Services SOAP Response (Google Web Services) <?xml version='1.0' encoding='utf-8'?> <SOAP-ENV:Envelope xmlns:soap-env=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Body> <ns1:dospellingsuggestionresponse xmlns:ns1="urn:googlesearch" SOAP-ENV:encodingStyle=" <return xsi:type="xsd:string">britney spears</phrase> </ns1:dospellingsuggestionresponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

91 5 Web Services JSP and Web Services Server (googlesearch) Web Client MySearch.jsp forward XML [request] XML [response] Web Service SearchResult.jsp

92 Contents 1. Introduction to Custom Tags 2. Developing Custom Tag Libraries Tag, TagIteration, and BodyTag interface 3. XML Processing With JSP xml library (JSTL), XPath, JDOM 4. Session Tracking

93 Applied Autonomous Sensor Systems Web Development with JavaEE Developing Custom Tag Libraries and XML Processing with JSP Thank you!