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<TITLE>Preventing Concurrent Requests to a Servlet
(Java Developers Almanac Example)
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<META CONTENT="Patrick Chan" NAME="AUTHOR">
<META CONTENT="Code Examples from The Java Developers Almanac 1.4" NAME="DESCRIPTION">
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<B><A HREF="../javax.servlet/pkg.html">javax.servlet</A></B><font color="#666666" SIZE="-2">
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<B><A HREF="../javax.servlet/pkg.html#Requests">Requests</A></B><font color="#666666" SIZE="-2">
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<h3>
e1040.
Preventing Concurrent Requests to a Servlet</h3>
By default, a servlet container will use a servlet instance to
concurrently process multiple requests. Although, this behavior
burdens the servlet developer to properly synchronize shared state,
this ability to handle multiple requests allows for a more scalable
architecture. However, if it is necessary to disable this ability,
the servlet should implement the <code>SingleThreadModel</code> interface:
<pre>
// This servlet can only handle a single request at a time.
public class <font color="#0066ff"><i>MyServlet</i></font> extends HttpServlet implements SingleThreadModel {
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
// Handle GET request...
}
}
</pre>
However, forcing the servlet container to route requests one at a time
through a servlet does not prevent the container from creating
multiple instances of the servlet. Hence, the servlet developer must
still properly synchronize shared state. Effectively, the main
<font color="#0066ff"><i>benefit</i></font> of implementing the <code>SingleThreadModel</code> is not having
to synchronize the servlet's instance variables.
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Related Examples
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e1039. <a class="eglink" href="GetReqParam.html?l=rel">
Getting a Request Parameter in a Servlet
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e1041. <a class="eglink" href="GetReqUrl.html?l=rel">
Getting the Requesting URL in a Servlet
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e1042. <a class="eglink" href="GetHeaders.html?l=rel">
Getting a Request Header in a Servlet
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e1043. <a class="eglink" href="DoHead.html?l=rel">
Processing a HEAD Request in a Servlet
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e1044. <a class="eglink" href="GetClientInfo.html?l=rel">
Getting the Client's Address in a Servlet
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