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| <li>Summary: </li> |
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| <div class="subTitle">org.apache.taglibs.standard.lang.jstl</div> |
| <h2 title="Class ELEvaluator" class="title">Class ELEvaluator</h2> |
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| <ul class="inheritance"> |
| <li>java.lang.Object</li> |
| <li> |
| <ul class="inheritance"> |
| <li>org.apache.taglibs.standard.lang.jstl.ELEvaluator</li> |
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| <pre>public class <span class="typeNameLabel">ELEvaluator</span> |
| extends java.lang.Object</pre> |
| <div class="block"><p>This is the main class for evaluating expression Strings. An |
| expression String is a String that may contain expressions of the |
| form ${...}. Multiple expressions may appear in the same |
| expression String. In such a case, the expression String's value |
| is computed by concatenating the String values of those evaluated |
| expressions and any intervening non-expression text, then |
| converting the resulting String to the expected type using the |
| PropertyEditor mechanism. |
| |
| <p>In the special case where the expression String is a single |
| expression, the value of the expression String is determined by |
| evaluating the expression, without any intervening conversion to a |
| String. |
| |
| <p>The evaluator maintains a cache mapping expression Strings to |
| their parsed results. For expression Strings containing no |
| expression elements, it maintains a cache mapping |
| ExpectedType/ExpressionString to parsed value, so that static |
| expression Strings won't have to go through a conversion step every |
| time they are used. All instances of the evaluator share the same |
| cache. The cache may be bypassed by setting a flag on the |
| evaluator's constructor. |
| |
| <p>The evaluator must be passed a VariableResolver in its |
| constructor. The VariableResolver is used to resolve variable |
| names encountered in expressions, and can also be used to implement |
| "implicit objects" that are always present in the namespace. |
| Different applications will have different policies for variable |
| lookups and implicit objects - these differences can be |
| encapsulated in the VariableResolver passed to the evaluator's |
| constructor. |
| |
| <p>Most VariableResolvers will need to perform their resolution |
| against some context. For example, a JSP environment needs a |
| PageContext to resolve variables. The evaluate() method takes a |
| generic Object context which is eventually passed to the |
| VariableResolver - the VariableResolver is responsible for casting |
| the context to the proper type. |
| |
| <p>Once an evaluator instance has been constructed, it may be used |
| multiple times, and may be used by multiple simultaneous Threads. |
| In other words, an evaluator instance is well-suited for use as a |
| singleton.</div> |
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| <h3>Constructor Summary</h3> |
| <table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Constructor Summary table, listing constructors, and an explanation"> |
| <caption><span>Constructors</span><span class="tabEnd"> </span></caption> |
| <tr> |
| <th class="colOne" scope="col">Constructor and Description</th> |
| </tr> |
| <tr class="altColor"> |
| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELEvaluator.html#ELEvaluator-org.apache.taglibs.standard.lang.jstl.VariableResolver-">ELEvaluator</a></span>(<a href="../../../../../../org/apache/taglibs/standard/lang/jstl/VariableResolver.html" title="interface in org.apache.taglibs.standard.lang.jstl">VariableResolver</a> pResolver)</code> |
| <div class="block">Constructor</div> |
| </td> |
| </tr> |
| <tr class="rowColor"> |
| <td class="colOne"><code><span class="memberNameLink"><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELEvaluator.html#ELEvaluator-org.apache.taglibs.standard.lang.jstl.VariableResolver-boolean-">ELEvaluator</a></span>(<a href="../../../../../../org/apache/taglibs/standard/lang/jstl/VariableResolver.html" title="interface in org.apache.taglibs.standard.lang.jstl">VariableResolver</a> pResolver, |
| boolean pBypassCache)</code> |
| <div class="block">Constructor</div> |
| </td> |
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| <tr> |
| <th class="colFirst" scope="col">Modifier and Type</th> |
| <th class="colLast" scope="col">Method and Description</th> |
| </tr> |
| <tr id="i0" class="altColor"> |
| <td class="colFirst"><code>java.lang.Object</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELEvaluator.html#evaluate-java.lang.String-java.lang.Object-java.lang.Class-java.util.Map-java.lang.String-">evaluate</a></span>(java.lang.String pExpressionString, |
| java.lang.Object pContext, |
| java.lang.Class pExpectedType, |
| java.util.Map functions, |
| java.lang.String defaultPrefix)</code> |
| <div class="block">Evaluates the given expression String</div> |
| </td> |
| </tr> |
| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>java.lang.String</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELEvaluator.html#parseAndRender-java.lang.String-">parseAndRender</a></span>(java.lang.String pExpressionString)</code> |
| <div class="block">Parses the given expression string, then converts it back to a |
| String in its canonical form.</div> |
| </td> |
| </tr> |
| <tr id="i2" class="altColor"> |
| <td class="colFirst"><code>java.lang.Object</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELEvaluator.html#parseExpressionString-java.lang.String-">parseExpressionString</a></span>(java.lang.String pExpressionString)</code> |
| <div class="block">Gets the parsed form of the given expression string.</div> |
| </td> |
| </tr> |
| </table> |
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| <!-- --> |
| </a> |
| <h3>Methods inherited from class java.lang.Object</h3> |
| <code>clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait</code></li> |
| </ul> |
| </li> |
| </ul> |
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| <h3>Constructor Detail</h3> |
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| <h4>ELEvaluator</h4> |
| <pre>public ELEvaluator(<a href="../../../../../../org/apache/taglibs/standard/lang/jstl/VariableResolver.html" title="interface in org.apache.taglibs.standard.lang.jstl">VariableResolver</a> pResolver)</pre> |
| <div class="block">Constructor</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>pResolver</code> - the object that should be used to resolve |
| variable names encountered in expressions. If null, all variable |
| references will resolve to null.</dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="ELEvaluator-org.apache.taglibs.standard.lang.jstl.VariableResolver-boolean-"> |
| <!-- --> |
| </a> |
| <ul class="blockListLast"> |
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| <h4>ELEvaluator</h4> |
| <pre>public ELEvaluator(<a href="../../../../../../org/apache/taglibs/standard/lang/jstl/VariableResolver.html" title="interface in org.apache.taglibs.standard.lang.jstl">VariableResolver</a> pResolver, |
| boolean pBypassCache)</pre> |
| <div class="block">Constructor</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>pResolver</code> - the object that should be used to resolve |
| variable names encountered in expressions. If null, all variable |
| references will resolve to null.</dd> |
| <dd><code>pBypassCache</code> - flag indicating if the cache should be |
| bypassed</dd> |
| </dl> |
| </li> |
| </ul> |
| </li> |
| </ul> |
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| <a name="evaluate-java.lang.String-java.lang.Object-java.lang.Class-java.util.Map-java.lang.String-"> |
| <!-- --> |
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| <h4>evaluate</h4> |
| <pre>public java.lang.Object evaluate(java.lang.String pExpressionString, |
| java.lang.Object pContext, |
| java.lang.Class pExpectedType, |
| java.util.Map functions, |
| java.lang.String defaultPrefix) |
| throws <a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></pre> |
| <div class="block">Evaluates the given expression String</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>pExpressionString</code> - the expression String to be evaluated</dd> |
| <dd><code>pContext</code> - the context passed to the VariableResolver for |
| resolving variable names</dd> |
| <dd><code>pExpectedType</code> - the type to which the evaluated expression |
| should be coerced</dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>the expression String evaluated to the given expected |
| type</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></code></dd> |
| </dl> |
| </li> |
| </ul> |
| <a name="parseExpressionString-java.lang.String-"> |
| <!-- --> |
| </a> |
| <ul class="blockList"> |
| <li class="blockList"> |
| <h4>parseExpressionString</h4> |
| <pre>public java.lang.Object parseExpressionString(java.lang.String pExpressionString) |
| throws <a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></pre> |
| <div class="block">Gets the parsed form of the given expression string. If the |
| parsed form is cached (and caching is not bypassed), return the |
| cached form, otherwise parse and cache the value. Returns either |
| a String, Expression, or ExpressionString.</div> |
| <dl> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></code></dd> |
| </dl> |
| </li> |
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| <h4>parseAndRender</h4> |
| <pre>public java.lang.String parseAndRender(java.lang.String pExpressionString) |
| throws <a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></pre> |
| <div class="block">Parses the given expression string, then converts it back to a |
| String in its canonical form. This is used to test parsing.</div> |
| <dl> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../../../../org/apache/taglibs/standard/lang/jstl/ELException.html" title="class in org.apache.taglibs.standard.lang.jstl">ELException</a></code></dd> |
| </dl> |
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