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Document ID: 511
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Name: Advanced Control Flow - JXTemplate (previously Tags)
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Updated on: 6/7/07 6:07:36 PM
Updated by: Reinhard Pötz
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+++ <h1>JXTemplate Generator</h1>
+++
+++ <p>The JXTemplate Generator is a page template processor that allows you to
+++ inject data from Java and JavaScript objects passed by a Cocoon Flowscript
into
+++ a Cocoon pipeline. It provides a set of tags (similar to the
+++ <a href="http://java.sun.com/products/jsp/jstl/";>JSTL</a> core tags) that
allow
+++ you to iterate over Java collections (and Java or JavaScript arrays) and to
test
+++ for the presence of optional or alternate bean properties, as well as
embedded
+++ expressions to specify conditions and to access the properties of objects.
The
+++ <em>JX</em>Template Generator gets its name from the embedded expression
+++ languages it supports, namely
+++ <a href="http://jakarta.apache.org/commons/jxpath";>Apache
<em>JX</em>Path</a>
+++ and <a href="http://jakarta.apache.org/commons/jexl";>Apache
+++ <em>J</em>e<em>X</em>l</a>.</p>
+++
+++ <p>To use the JXTemplate Generator, add a generator entry to your
+++ <a href="daisy:580">sitemap</a> with the <tt>src</tt> attribute set to
+++ <tt>org.apache.cocoon.generation.JXTemplateGenerator</tt>, for example like
+++ this:</p>
+++
+++ <pre><map:generators>
+++ <map:generator label="content,data"
+++ logger="sitemap.generator.jx" name="jx"
+++ src="org.apache.cocoon.generation.JXTemplateGenerator"/>
+++ </map:generators>
+++ </pre>
+++
+++ <h1>Expression Languages</h1>
+++
+++ <p>The JXTemplate Generator supports two embedded expression languages:
+++ <a href="http://jakarta.apache.org/commons/jexl";>Jexl</a> and
+++ <a href="http://jakarta.apache.org/commons/jxpath";>JXPath</a>. Apache
+++ <a href="http://jakarta.apache.org/commons/jexl";>Jexl</a> provides an
extended
+++ version of the expression language of the
+++ <a
href="http://java.sun.com/webservices/docs/1.0/tutorial/doc/JSTL.html";>JSTL</a>.
+++ Apache <a href="http://jakarta.apache.org/commons/jxpath";>JXPath</a>
provides an
+++ interpreter of the <a href="http://www.w3.org/TR/xpath";>XPath</a> expression
+++ language that can apply XPath expressions to graphs of Java objects of all
+++ kinds: JavaBeans, Maps, Servlet contexts, DOM etc, including mixtures
thereof.
+++ </p>
+++
+++ <p>Having an embedded expression language allows a page author to access an
+++ object using a simple syntax such as</p>
+++
+++ <pre><site signOn="${accountForm.signOn}">
+++ </pre>
+++
+++ <p>Embedded Jexl expressions are contained in <tt>${}</tt>.</p>
+++
+++ <p>Embedded JXPath expressions are contained in <tt>#{}</tt>.</p>
+++
+++ <p>The referenced objects may be Java Beans, DOM, or JavaScript objects
from a
+++ Flowscript. In addition, a special <tt>cocoon</tt> object providing access
to
+++ the Cocoon <a href="daisy:518#FOM">FOM</a> is available as both a JXPath and
+++ Jexl variable in a template.</p>
+++
+++ <p>The <tt>cocoon</tt> object contains the following properties:</p>
+++
+++ <ul>
+++ <li><a href="daisy:518#request">request</a>: <br/>
+++ The current Cocoon request</li>
+++ <li><a href="daisy:518#session">session</a>: <br/>
+++ The user session associated with the current request</li>
+++ <li><a href="daisy:518#context">context</a>: <br/>
+++ The Cocoon context associated with the current request</li>
+++ <li><tt>parameters</tt>: <br/>
+++ A map containing the parameters passed to the generator in the pipeline</li>
+++ <li><a href="daisy:518#WebContinuation">continuation</a>: <br/>
+++ The current Web Continuation from your Flowscript</li>
+++ </ul>
+++
+++ <p>Jexl Example:</p>
+++
+++ <pre>The content type of the current request is
${cocoon.request.contentType}
+++ </pre>
+++
+++ <p>JXPath Example:</p>
+++
+++ <pre>The content type of the current request is
#{$cocoon/request/contentType}
+++ </pre>
+++
+++ <p>You would typically access the <tt>id</tt> of the Web Continuation:</p>
+++
+++ <pre><form action="${cocoon.continuation.id}">
+++ </pre>
+++
+++ <p>You can also reach previous continuations via its <tt>parent</tt>
property:
+++ </p>
+++
+++ <pre><form action="${cocoon.continuation.parent.id}" >
+++ </pre>
+++
+++ <p>or using an XPath expression:</p>
+++
+++ <pre><form action="#{$cocoon/continuation/parent/id}" >
+++ </pre>
+++
+++ <p>Deprecated Variables:</p>
+++
+++ <p>The following variables are deprecated but still supported:</p>
+++
+++ <ul>
+++ <li>
+++ <a
href="file:/home/daisy/tmpdocimport/documentation/apidocs/org/apache/cocoon/environment/Request.html">org.apache.cocoon.environment.Request</a>
+++ <tt>request</tt>: <br/>
+++ The current Cocoon request (deprecated: use <tt>cocoon.request</tt> instead)
+++ </li>
+++ <li>
+++ <a
href="file:/home/daisy/tmpdocimport/documentation/apidocs/org/apache/cocoon/environment/Session.html">org.apache.cocoon.environment.Session</a>
+++ <tt>session</tt>: <br/>
+++ The current user session (deprecated: use <tt>cocoon.session</tt>
instead)</li>
+++ <li>
+++ <a
href="file:/home/daisy/tmpdocimport/documentation/apidocs/org/apache/cocoon/environment/Context.html">org.apache.cocoon.environment.Context</a>
+++ <tt>context</tt>: <br/>
+++ The current context (deprecated: use <tt>cocoon.context</tt> instead)</li>
+++ <li>
+++ <a
href="file:/home/daisy/tmpdocimport/documentation/apidocs/org/apache/cocoon/components/flow/WebContinuation.html">org.apache.cocoon.components.flow.WebContinuation</a>
+++ <tt>continuation</tt>: <br/>
+++ The current Web Continuation (deprecated: use <tt>cocoon.continuation</tt>
+++ instead)</li>
+++ </ul>
+++
+++ <p class="note">When used inside flow, JXTemplate has access to Java and can
+++ therefore evaluate expressions like "java.util.Date()" or
"java.util.HashMap()".
+++ This does <strong>NOT</strong> work when JXTemplates are used without flow.
Some
+++ symptoms:<br/>
+++ [*<jx:out value="${java.util.Date()"/>*] results in [**]</p>
+++
+++ <p class="note"><jx:formatDate value="${java.util.Date()}"
+++ pattern="yyyyMMdd"/> results in 'Cannot format given Object as a
Date'</p>
+++
+++ <h1>Parameters</h1>
+++
+++ <h2>lenient-xpath</h2>
+++
+++ <p>By default XPath evaluation throws an exception if the supplied XPath
does
+++ not map to an existing property. This constraint can be relaxed by setting
the
+++ parameter <tt>lenient-xpath</tt> to <tt>true</tt>. In the lenient mode
+++ evaluation simply returns null if the path maps to nothing.</p>
+++
+++ <p>Example:</p>
+++
+++ <pre> <map:match pattern="*.jx">
+++ <map:generate type="jx" src="documents/{1}.jx">
+++ <map:parameter name="lenient-xpath" value="true"/>
+++ </map:generate>
+++ <map:serialize type="xhtml"/>
+++ </map:match>
+++ </pre>
+++
+++ <h1>Tags</h1>
+++
<p>The JXTemplate Generator tags are defined in the namespace</p>
<pre>http://apache.org/cocoon/templates/jx/1.0
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