Source Code

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    <%@page contentType="text/html; charset=UTF-8" %>
    <%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

    <html>
      <head>
        <title>JSP 2.0 Expression Language - Implicit Objects</title>
      </head>
      <body>
        <h1>JSP 2.0 Expression Language - Implicit Objects</h1>
        <hr>
        This example illustrates some of the implicit objects available
        in the Expression Language.  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="${fn:escapeXml(param["foo"])}">
              <input type="submit">
          </form>
          <br>
          <code>
            <table border="1">
              <thead>
                <td><b>EL Expression</b></td>
                <td><b>Result</b></td>
              </thead>
              <tr>
                <td>\${param.foo}</td>
                <td>${fn:escapeXml(param["foo"])}&nbsp;</td>
              </tr>
              <tr>
                <td>\${param["foo"]}</td>
                <td>${fn:escapeXml(param["foo"])}&nbsp;</td>
              </tr>
              <tr>
                <td>\${header["host"]}</td>
                <td>${fn:escapeXml(header["host"])}&nbsp;</td>
              </tr>
              <tr>
                <td>\${header["accept"]}</td>
                <td>${fn:escapeXml(header["accept"])}&nbsp;</td>
              </tr>
              <tr>
                <td>\${header["user-agent"]}</td>
                <td>${fn:escapeXml(header["user-agent"])}&nbsp;</td>
              </tr>
            </table>
          </code>
        </blockquote>
      </body>
    </html>