How to check which existing sessions are valid or invalid

Let me see if I understand correctly.  You created an object that implements the HttpSessionBindingListener interface and then added that object to the users session via something like
    session.setAttribute("listener", new HttpSessionBindingListenerImpl());
And the problem is that when the session becomes invalidated the valueUnbound() method on the HttpSessionBindingListenerImpl isn't firing.  Is that correct?

I would first try to debug the HttpSessionBindingListenerImpl object with logging code like:

public void valueUnbound(HttpSessionBindingEvent event){
      String sessionId=event.getSession().getId();
      logger.debug("The object was removed from the session with ID: "+sessionId);
}

public void valueBound(HttpSessionBindingEvent event) {
      String sessionId=event.getSession().getId();
      logger.debug("The object was added to the session with ID: "+sessionId);
}

This way you can see when the object is being bound and unbound to the session.  

Dave

public void valueUnbound(HttpSessionBindingEvent event){
      String sessionId=event.getSession().getId();
setDeletedSessionID(String sessionID)
      logger.debug("The object was removed from the session with ID: "+sessionId);
}

Hi Dave,

I am explaining through code what i am doing exactly and where i m strucking. As you have posted the code. i tried this as well but i did in the following way

line:1 public void valueUnbound(HttpSessionBindingEvent event){
line:2 String sessionId=event.getSession().getId();
line:3
line:4 // This line i am adding extra, to get the session ID which are going to invalidate
line:5       LoginCommand.setDeletedSessionID(String sessionID)  
line:6       logger.debug("The object was removed from the session with ID: "+sessionId);
line:7 }
line:8  // This method in LoginCommand.Java file, Where i am trying to catch session ID
line:9  public void setDeletedSessionID(String sessionID){
line:10  if(gc1.context.getAttribute("destroyedUserSessionTable") != null){
line:11  destroyedUserSessionTable = (ArrayList)gc1.context.getAttribute( "destroyedUserSessionTable");
line:12  }else
line:13  logger.debug(" No session id to delete " ) ;
line:14
line:15  destroyedUserSessionTable.add(sessionID) ;
line:16  logger.debug(" session ID deleted which is  =  " + sessionID) ;
line:17 }
line:18
            But Dave my control is not reaching to method setDeletedSessionID( ) and that session get invalidated.
            Even one more observation, if i am invoking that method from method valueUnbound( ) as in line no 5.
            The line 6 messag is not going to print in logger. If i am commenting out line no.5 then logger contains
            message which we are passing from line no. 6.

            One more thought for my problem :
                    My problem could be solved if i can get available active session ID's maintained by tomcat server. Since
               I am maintaining collection of session id as user makes log In.By comparing i can discard those
            session ID's from my collection which are not active.

Thanks
Ashish