You are not removing the attribute from the session.
You are invalidating the session, which deletes the session.
Go back and look at the example again.
> Date: Thu, 28 Aug 2008 04:25:35 -0700
> Subject: [java ee programming] Homework 5-Advanced Servlets
> From: [EMAIL PROTECTED]
> To: java-ee-j2ee-programming-with-passion@googlegroups.com
>
>
> Hi all,
>
> I am have a bit of trouble wid homework on Servlet Advanced. I have
> read posts related to this problem but i dont seem to find the answer.
> The program runs fine but i get this exception in my glassfish log:
>
> PWC1412: WebModule[/ServletAdvanced]
> ServletContext.log():requestInitialized() method is invoked
> PWC1412: WebModule[/ServletAdvanced]
> ServletContext.log():sessionCreated() method is invoked
> PWC2775: Session attribute event listener threw exception
> java.lang.NullPointerException
> at
> servlets.MyOwnEventListener.attributeAdded(MyOwnEventListener.java:20)
> at
> org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:
> 1706)
> at
> org.apache.catalina.session.StandardSessionFacade.setAttribute(StandardSessionFacade.java:
> 163)
> at servlets.GreetingServlet.doGet(GreetingServlet.java:52)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:
> 718)
> at javax.servlet.http.HttpServlet.service(HttpServlet.java:
> 831)
> at
> org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:
> 411)
> at
> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
> 317)
> at
> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:
> 198)
> at
> org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:
> 390)
> at
> org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:
> 230)
> at
> org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:
> 198)
> at
> org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:
> 288)
> at
> org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:
> 271)
> at
> org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:
> 202)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 632)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 577)
> at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:
> 94)
> at
> org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:
> 206)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 632)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 577)
> at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:
> 571)
> at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1080)
> at
> org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:
> 150)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 632)
> at
> org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:
> 577)
> at
> org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:
> 571)
> at
> org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1080)
> at
> org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:
> 272)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:
> 637)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:
> 568)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:
> 813)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:
> 341)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:
> 263)
> at
> com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:
> 214)
> at com.sun.enterprise.web.portunif.PortUnificationPipeline
> $PUTask.doTask(PortUnificationPipeline.java:380)
> at
> com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:
> 265)
> at
> com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:
> 106)
> PWC1412: WebModule[/ServletAdvanced]
> ServletContext.log():requestDestroyed() method is invoked
>
>
> **********************************************************************************************************************************
>
> Does anyone have any idea about this?
> This how i set the attribute: HttpSession session =
> request.getSession();
>
> session.setAttribute("name","Vithya");
>
> And this is how i removed it:HttpSession session =
> request.getSession();
> session.getAttribute("name");
>
> request.getSession().invalidate();
>
> This is my EventListenter.java
>
> package servlets;
> import javax.servlet.ServletContext;
> import javax.servlet.http.HttpSessionAttributeListener;
> import javax.servlet.http.HttpSessionBindingEvent;
> /**
> * Web application lifecycle listener.
> * @author vithya
> */
> public class MyOwnEventListener implements
> HttpSessionAttributeListener {
> ServletContext servletContext;
>
> public void attributeAdded(HttpSessionBindingEvent arg0) {
> servletContext.log("attributeAdded() method is invoked");
> }
> public void attributeRemoved(HttpSessionBindingEvent arg0) {
> servletContext.log("attributeRemoved() method is invoked");
> }
> public void attributeReplaced(HttpSessionBindingEvent arg0) {
> servletContext.log("attributeReplaced() method is invoked");
> }
> }
>
> ******************************************************************************************************
> Can anyone help me with the exception? PLZ
>
> Regards
> Vithya
>
>
> >
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