The project I am working in is a web portal and there are several applications been hosted on it. Some of them are J2EE applications while some are still written in ASP and they are just hosted on our portal (request goes to some other URL when you try to access these ASP applications).
We have used this listener for enabling SSO ( single sign on ) as when user logs in to portal we make his credentials go into a database from where these ASP applications can read the credentials and they allow user to access them without doing a 'login' for second time.
When user logs out the listener takes care of deleting the credentials from the table.
First of all do you know what this listener does? Usually it's used for if you want to know the class/object that you created by yourself has been added, removed from a session. It's in page 183 of HFJS.