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<TITLE>Saving Data Using JSTL in a JSP Page (Java Developers Almanac Example)
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<h1>The Java Developers Almanac 1.4</h1>
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<h3>e1067. Saving Data Using JSTL in a JSP Page</h3>
When a JSP page needs to save data for its processing, it must
specify a location, called the <font color="#0066ff"><i>scope</i></font>. See
<a href="../javax.servlet.jsp/attr.html" class="eglink"><b>e1048</b> Saving Data in a JSP Page</a> for an explanation of the four
available scopes.
<P> Data is saved using a mechanism called scoped variables. A
scoped variable has a name, which is of type <code>String</code> and a value,
which is of type <code>Object</code>. For non-page scoped variables, it is
recommended that the name use the reverse domain name convention
(e.g., prefixed with com_mycompany) to minimize unexpected collisions
when integrating with third party modules.
<P> When using the JSTL's expression language (see
<a href="../javax.servlet.jsp.jstl.core/uselang.html" class="eglink"><b>e1065</b> Enabling the JSTL Expression Language in a JSP Page</a>), the variables in each
scope are made available in the implicit objects <code>pageScope</code>,
<code>requestScope</code>, <code>sessionScope</code>, and <code>applicationScope</code>.
<P> This example saves and retrieves values in scoped variables in
each of the four scopes:
<pre> <%-- Declare the core library --%>
<%@ taglib uri="/WEB-INF/tld/c.tld" prefix="c" %>
<%-- Save data in scoped variables --%>
<c:set var="name1" value="value1" scope="page" />
<c:set var="com_mycompany_name2" value="value2" scope="request" />
<c:set var="com_mycompany_name3" value="value3" scope="session" />
<c:set var="com_mycompany_name4" value="value4" scope="application" />
<%-- Show the saved values --%>
<c:out value='${pageScope.name1}' />
<c:out value='${requestScope.com_mycompany_name2}' />
<c:out value='${sessionScope.com_mycompany_name3}' />
<c:out value='${applicationScope.com_mycompany_name4}' />
</pre>
When retrieving a saved value, it is possible to omit the scope. If
the scope is omitted, the variable name is automatically searched for
in each of the scopes, in the order <code>pageScope</code>,
<code>requestScope</code>, <code>sessionScope</code>, and <code>applicationScope</code>.
<pre> <%-- Show the saved values without a specific scope --%>
<c:out value='${name1}' />
<c:out value='${com_mycompany_name2}' />
<c:out value='${com_mycompany_name3}' />
<c:out value='${com_mycompany_name4}' />
</pre>
It is also possible to specify the value to save using the contents
of the body, rather than through the <code>value</code> attribute:
<pre> <%-- Save data using body content --%>
<c:set var="name1" scope="page">
value 1 in body
</c:set>
<c:set var="com_mycompany_name2" scope="request" >
value 2 in body
</c:set>
<c:set var="com_mycompany_name3" scope="session" >
value 3 in body
</c:set>
<c:set var="com_mycompany_name4" scope="application">
value 4 in body
</c:set>
</pre>
When specifying the value using body contents, the body contents
is first trimmed of leading and trailing white space before it is
saved. For example,
<pre> <c:set var="name1" scope="page">
line 1
line 2
</c:set>
</pre>
would be saved as:
<pre> "line 1\n line 2"
</pre>
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<b>Related Examples</b></font></td>
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e1064. <a class="eglink" href="usejstl.html?l=rel">
Using the Java Standard Tag Library (JSTL) in a JSP Page
</a>
<br>
e1065. <a class="eglink" href="uselang.html?l=rel">
Enabling the JSTL Expression Language in a JSP Page
</a>
<br>
e1066. <a class="eglink" href="getparam.html?l=rel">
Getting a Request Parameter Using JSTL in a JSP Page
</a>
<br>
e1068. <a class="eglink" href="htmlfrag.html?l=rel">
Saving and Emitting HTML Fragments Using JSTL in a JSP Page
</a>
<br>
e1069. <a class="eglink" href="if.html?l=rel">
Conditionally Generating Output Using JSTL in a JSP Page
</a>
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