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POaccessing constants in JSP (without scriptlet)
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  1. POaccessing constants in JSP (without scriptlet)
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    copied!<p>I have a class that defines the names of various session attributes, e.g.</p> <pre><code>class Constants { public static final String ATTR_CURRENT_USER = "current.user"; } </code></pre> <p>I would like to use these constants within a JSP to test for the presence of these attributes, something like:</p> <pre><code>&lt;%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %&gt; &lt;%@ page import="com.example.Constants" %&gt; &lt;c:if test="${sessionScope[Constants.ATTR_CURRENT_USER] eq null}"&gt; &lt;%-- Do somthing --%&gt; &lt;/c:if&gt; </code></pre> <p>But I can't seem to get the sytax correct. Also, to avoid repeating the rather lengthy tests above in multiple places, I'd like to assign the result to a local (page-scoped) variable, and refer to that instead. I believe I can do this with <code>&lt;c:set&gt;</code>, but again I'm struggling to find the correct syntax.</p> <p><strong>UPDATE:</strong> Further to the suggestion below, I tried:</p> <pre><code>&lt;c:set var="nullUser" scope="session" value="${sessionScope[Constants.ATTR_CURRENT_USER] eq null}" /&gt; </code></pre> <p>which didn't work. So instead, I tried substituting the literal value of the constant. I also added the constant to the content of the page, so I could verify the constant's value when the page is being rendered</p> <pre><code>&lt;c:set var="nullUser" scope="session" value="${sessionScope['current.user'] eq null}" /&gt; &lt;%= "Constant value: " + WebHelper.ATTR_CURRENT_PARTNER %&gt; </code></pre> <p>This worked fine and it printed the expected value "current.user" on the page. I'm at a loss to explain why using the String literal works, but a reference to the constant doesn't, when the two appear to have the same value. Help.....</p>
 

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