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<TITLE>Saving Data 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>e1048. Saving Data 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>. There are four scopes
available - page, request, session, and application. Page - scoped data
is accessible only within the JSP page and is destroyed when the page
has finished generating its output for the request. Request-scoped
data is associated with the request and destroyed when the request is
completed. Session-scoped data is associated with a session and
destroyed when the session is destroyed. Application-scoped data is
associated with the web application and destroyed when the web
application is destroyed. Application-scoped data is not accessible
to other web applications.
<P> Data is saved using a mechanism called attributes. An
attribute is a key/value pair where the key is a string and the value
is any object. It is recommended that the key use the reverse domain
name convention (e.g., prefixed with com.mycompany) to minimize
unexpected collisions when integrating with third party modules.
<P> This example uses attributes to save and retrieve data in each
of the four scopes:
<pre> <%
// Check if attribute has been set
Object o = pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name1"</i></font>, PageContext.PAGE_SCOPE);
if (o == null) {
// The attribute com.mycompany.name1 may not have a value or may have the value null
}
// Save data
pageContext.setAttribute(<font color="#0066ff"><i>"com.mycompany.name1"</i></font>, <font color="#0066ff"><i>"value0"</i></font>); // PAGE_SCOPE is the default
pageContext.setAttribute(<font color="#0066ff"><i>"com.mycompany.name1"</i></font>, <font color="#0066ff"><i>"value1"</i></font>, PageContext.PAGE_SCOPE);
pageContext.setAttribute(<font color="#0066ff"><i>"com.mycompany.name2"</i></font>, <font color="#0066ff"><i>"value2"</i></font>, PageContext.REQUEST_SCOPE);
pageContext.setAttribute(<font color="#0066ff"><i>"com.mycompany.name3"</i></font>, <font color="#0066ff"><i>"value3"</i></font>, PageContext.SESSION_SCOPE);
pageContext.setAttribute(<font color="#0066ff"><i>"com.mycompany.name4"</i></font>, <font color="#0066ff"><i>"value4"</i></font>, PageContext.APPLICATION_SCOPE);
%>
<%-- Show the values --%>
<%= pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name1"</i></font>) %> <%-- PAGE_SCOPE --%>
<%= pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name1"</i></font>, PageContext.PAGE_SCOPE) %>
<%= pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name2"</i></font>, PageContext.REQUEST_SCOPE) %>
<%= pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name3"</i></font>, PageContext.SESSION_SCOPE) %>
<%= pageContext.getAttribute(<font color="#0066ff"><i>"com.mycompany.name4"</i></font>, PageContext.APPLICATION_SCOPE) %>
</pre>
See also <a href="../javax.servlet.jsp.jstl.core/attr.html" class="eglink"><b>e1067</b> Saving Data Using JSTL in a JSP Page</a>.
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<b>Related Examples</b></font></td>
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e1046. <a class="eglink" href="basic.html?l=rel">
The Quintessential JSP Page
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e1047. <a class="eglink" href="code.html?l=rel">
Running Java Code in a JSP Page
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e1049. <a class="eglink" href="myform.jsp.html?l=rel">
Implementing a Form in a JSP Page
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<br>
e1050. <a class="eglink" href="myformts.jsp.html?l=rel">
Implementing a Form That Prevents Duplicate Submissions in a JSP Page
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<br>
e1051. <a class="eglink" href="precompile.html?l=rel">
Precompiling a JSP Page
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e1052. <a class="eglink" href="nosession.html?l=rel">
Preventing the Creation of a Session in a JSP Page
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See also:
<a class="eglink" href="/egs/javax.servlet.jsp/pkg.html?l=rel#Java%20Server%20Pages%20Headers">
Java Server Pages Headers
</a>
<a class="eglink" href="/egs/javax.servlet.jsp/pkg.html?l=rel#Java%20Server%20Pages%20Input">
Java Server Pages Input
</a>
<a class="eglink" href="/egs/javax.servlet.jsp/pkg.html?l=rel#Java%20Server%20Pages%20Output">
Java Server Pages Output
</a>
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