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| <title>Advanced Control Flow</title> |
| <link href="http://purl.org/DC/elements/1.0/" rel="schema.DC"> |
| <meta content="Christopher Oliver" name="DC.Creator"> |
| <meta content="Ovidiu Predescu" name="DC.Creator"> |
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| |
| <h1>JPath Logic Sheet</h1> |
| |
| <p> |
| The JPath Logic Sheet is an <a href="../xsp/index.html">XSP</a> logic sheet that allows |
| you to access data from a Cocoon Flowscript in an XSP page and inject it into a Cocoon |
| pipeline. It provides a set of tags (similar to the those defined by |
| <a class="external" href="http://www.w3.org/TR/xslt">XSLT</a>) 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. It is based on |
| <a class="external" href="http://jakarta.apache.org/commons/jxpath">Apache JXPath</a>. |
| </p> |
| |
| <p>Samples of this Logic Sheet are avaliable in the XSP implementation of the petstore block</p> |
| |
| |
| <h1>Tags</h1> |
| |
| <p>The JPath tags are defined in the namespace</p> |
| |
| <pre class="code">http://apache.org/xsp/jpath/1.0</pre> |
| |
| <h2>if</h2> |
| <p>The <span class="codefrag">if</span> tag allows the conditional execution of its body according to value of its <span class="codefrag">test</span> attribute:</p> |
| <pre class="code"> |
| <if test="XPathExpression"> |
| body |
| </if> |
| </pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <jpath:if test="cart/numberOfItems = 0"> |
| Your cart is empty |
| </jpath:if> |
| </pre> |
| |
| <h2>choose</h2> |
| <p>The <span class="codefrag">choose</span> tag performs conditional block execution by its embedded |
| <span class="codefrag">when</span> sub tags. It renders the body of the first <span class="codefrag">when</span> tag whose |
| <span class="codefrag">test</span> condition evaluates to true. If none of the <span class="codefrag">test</span> conditions |
| of its nested <span class="codefrag">when</span> tags evaluate to <span class="codefrag">true</span>, then the body of its |
| <span class="codefrag">otherwise</span> tag is evaluated, if present:</p> |
| <pre class="code"> |
| <choose> |
| <when test="XPathExpression"> |
| body |
| </when>+ |
| <otherwise> |
| body |
| </otherwise>? |
| </choose> |
| </pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <choose> |
| <when test="not(user/loggedIn)"> |
| You're not logged in |
| </when> |
| <otherwise> |
| You're already logged in |
| </otherwise> |
| </choose> |
| </pre> |
| |
| <h2>value-of</h2> |
| <p>The <span class="codefrag">value-of</span> tag evaluates an expression and outputs the result of the evaluation:</p> |
| <pre class="code"> |
| <value-of select="XPathExpression"/> |
| </pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <value-of select="cart/numberOfItems"> |
| </pre> |
| |
| <h2>for-each</h2> |
| <p>The <span class="codefrag">for-each</span> tag allows you to iterate over a collection of objects:</p> |
| <pre class="code"> |
| <for-each select="XPathExpression"> |
| body |
| </for-each> |
| </pre> |
| <p>When using XPath expressions within <span class="codefrag">for-each</span> the current element is the |
| context node and can be referenced with XPath dot operator:</p> |
| <pre class="code">.</pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <for-each select="cart/cartItems[position() <= $count]"> |
| <td><value-of select="./productId"></td> |
| </for-each> |
| </pre> |
| |
| <h2>continuation</h2> |
| <p>The <span class="codefrag">continuation</span> tag returns the id of the current web continuation of your |
| Flowscript. You can refer to previous continuations by supplying the optional |
| <span class="codefrag">level</span> attribute. Zero is the current level, <span class="codefrag">-1</span> refers to the |
| previous continuation, and so on.</p> |
| <pre class="code"> |
| <continuation [level="Number"]/> |
| </pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <xsp:attribute name="action"><xsp:expr><jpath:continuation/>+".form"</xsp:expr></xsp:attribute> |
| </pre> |
| |
| <h2>set-lenient</h2> |
| <div class="note">Since Cocoon 2.1.6</div> |
| <p> |
| The <span class="codefrag">set-lenient</span> tag switch the lenient setting of jxpath. |
| By default it is set to false. If set to true, xpaths that don't point to an |
| object or a set of them will return null (Instead of that annoying exception). |
| Saves all the checking if you can accept nulls and are sure there are no typos. |
| </p> |
| <p> |
| If the tag contains child elements it will scope the setting for the enclosed |
| elements, otherwise it is a global setting. You can't nest <jpath:set-lenient> |
| tags. |
| </p> |
| <pre class="code"> |
| <jpath:set-lenient lenient="true|false"> |
| </pre> |
| <p>Example:</p> |
| <pre class="code"> |
| <jpath:set-lenient lenient="true"> |
| </pre> |
| |
| |
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