51 lines
1.5 KiB
Java
51 lines
1.5 KiB
Java
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Updating session items
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package com.ack.web.servlet;
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import java.io.IOException;
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import java.io.PrintWriter;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import javax.servlet.http.HttpSession;
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public class UpdatingSessionItems extends HttpServlet {
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public void doGet( HttpServletRequest req, HttpServletResponse res )
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throws ServletException, IOException {
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res.setContentType( "text/html" );
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PrintWriter pw = res.getWriter();
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pw.println( "<HTML><BODY>" );
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HttpSession theSession = req.getSession();
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// updated a named item in the session
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synchronized( theSession ) {
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/**
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* when updating items within a session object, you must
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* ensure that you have exclusive access to session object
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* by first synchronizing on the session
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*/
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Integer counter = (Integer) theSession.getAttribute( "counter" );
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if( counter == null ) {
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theSession.setAttribute( "counter", new Integer( 1 ) );
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}
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else {
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theSession.setAttribute( "counter", new Integer( counter.intValue() + 1 ) );
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}
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pw.println( "<BR>" + counter );
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/**
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* also note that items inside your session object should really
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* be serializable to ensure that your session can scale within
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* a clustered environment
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*/
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}
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pw.println( "</BODY></HTML>" );
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}
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}
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