📄 jsp-el.xtp

📁 RESIN 3.2 最新源码
💻 XTP
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<document>  <header>    <product>resin</product>    <title>JSP EL</title>    <version>Resin 3.0</version>    <description>      <p>JSP EL is a simple expression language for accessing      data.</p>    </description>  </header>  <body>    <summary/>    <s1 title="JSP EL variables">      <p>EL Variables come from one of two places:</p>      <ol>        <li>implicit variable          <deftable>          <tr><td>pageContext              </td><td>          </td></tr><tr><td>pageScope              </td><td>          </td></tr><tr><td>requestScope              </td><td>          </td></tr><tr><td>sessionScope              </td><td>          </td></tr><tr><td>applicationScope              </td><td>          </td></tr><tr><td>param              </td><td>          </td></tr><tr><td>paramValues              </td><td>          </td></tr><tr><td>header              </td><td>          </td></tr><tr><td>headerValues              </td><td>          </td></tr><tr><td>cookie              </td><td>          </td></tr><tr><td>initParam              </td><td>          </td></tr></deftable>        </li><li>pageContext.findAttribute(varname)<br/>          which is like getting the first of:          <ul>          <li>page.getAttribute(varname)          </li><li>request.getAttribute(varname)          </li><li>session.getAttribute(varname)          </li><li>application.getAttribute(varname)          </li></ul>      </li></ol>      <p>So if you have a variable like:</p>      <example>&lt;% boolean a = true; %&gt;      </example>      <p>you have to store it as an attribute to make it available as an EL        variable:</p>      <example>&lt;%   boolean b = true;   pageContext.setAttribute("b",new Boolean(b));%&gt;&lt;c:if test="${b}"&gt;b is TRUE&lt;/c:if&gt;      </example>      <p>Here is an example that shows this a bit more:</p>      <example title="Making values available as JSP EL variables">&lt;%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %&gt; &lt;%   boolean a = true;   boolean b = true;   pageContext.setAttribute("b",new Boolean(b));  boolean c = false;   pageContext.setAttribute("c",new Boolean(c));  boolean param = true;  pageContext.setAttribute("param",new Boolean(param));%&gt; &lt;%--   this is false because 'a' is not findable by  pageContext.findAttribute(varname)--%&gt;&lt;c:if test="${'${'}a}"&gt;a is TRUE&lt;/c:if&gt;&lt;c:if test="${'${'}b}"&gt;b is TRUE&lt;/c:if&gt;&lt;%-- this is false because 'c' was set to false --%&gt;&lt;c:if test="${'${'}c}"&gt;c is TRUE&lt;/c:if&gt;&lt;%--   This is false because 'param' is an implicit variable  which is used instead of pageContext.findAttribute("param")--%&gt;&lt;c:if test="${'${'}param}"&gt;param is TRUE&lt;/c:if&gt;      </example>      <results>b is TRUE      </results>    </s1>  </body></document>
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