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Java Programming Code Examples

Java > Servlets Code Examples

Handling invalid sessions

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Handling invalid sessions package com.ack.web.servlet; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class HandlingInvalidSessions extends HttpServlet { public void goGet( HttpServletRequest req, HttpServletResponse res ) throws ServletException, IOException { res.setContentType( "text/html" ); PrintWriter pw = res.getWriter(); pw.println( "<HTML><BODY>" ); HttpSession theSession = req.getSession(); try { Object obj = theSession.getAttribute( "counter" ); /** * the above call will throw an IllegalStateException * if theSession has been invalidated (e.g. by the * container or by another servlet) * * a defensive servlet programmer should wrap all accesses * to a servlet session (not just getAttribute()) in a * try/catch block so that they can take the appropriate * action to handle the case where a session is destroyed * at anytime */ } catch( IllegalStateException ise ) { // handle invalid session here } pw.println( "</BODY></HTML>" ); } }