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<title>JSP 2.0 Expression Language - Implicit Objects</title>
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<h1>JSP 2.0 Expression Language - Implicit Objects</h1>
<hr>
This example illustrates some of the implicit objects available
in the Expression Lanaguage. The following implicit objects are
available (not all illustrated here):
<ul>
<li>pageContext - the PageContext object</li>
<li>pageScope - a Map that maps page-scoped attribute names to
their values</li>
<li>requestScope - a Map that maps request-scoped attribute names
to their values</li>
<li>sessionScope - a Map that maps session-scoped attribute names
to their values</li>
<li>applicationScope - a Map that maps application-scoped attribute
names to their values</li>
<li>param - a Map that maps parameter names to a single String
parameter value</li>
<li>paramValues - a Map that maps parameter names to a String[] of
all values for that parameter</li>
<li>header - a Map that maps header names to a single String
header value</li>
<li>headerValues - a Map that maps header names to a String[] of
all values for that header</li>
<li>initParam - a Map that maps context initialization parameter
names to their String parameter value</li>
<li>cookie - a Map that maps cookie names to a single Cookie object.</li>
</ul>
<blockquote>
<u><b>Change Parameter</b></u>
<form action="implicit-objects.jsp" method="GET">
foo = <input type="text" name="foo" value="${param["foo"]}">
<input type="submit">
</form>
<br>
<code>
<table border="1">
<thead>
<td><b>EL Expression</b></td>
<td><b>Result</b></td>
</thead>
<tr>
<td>\${param.foo}</td>
<td>${param.foo} </td>
</tr>
<tr>
<td>\${param["foo"]}</td>
<td>${param["foo"]} </td>
</tr>
<tr>
<td>\${header["host"]}</td>
<td>${header["host"]}</td>
</tr>
<tr>
<td>\${header["accept"]}</td>
<td>${header["accept"]}</td>
</tr>
<tr>
<td>\${header["user-agent"]}</td>
<td>${header["user-agent"]}</td>
</tr>
</table>
</code>
</blockquote>
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