How to check which existing sessions are valid or invalid

Hello Experts,

In my application i am maintaining collection( In this collection i am maintaining user ID and session ID) of session which are active and deleting those session from the collection which user logs out. Till here it is working fine.
But when user is inactive for a timeslot which is set for invalidating a  session, In my collection these session id's still exists. My concern is how can i check in available collection which session's are valid and which are not.
To accomplish this, I worked with valueUnbound method of HttpSessionBindingListener interface. I tried to get session ID which are going to invalidate. To implement this i am invoking method setDeletedSessionID(String sessionID) from valueUnbound . But the control is not reaching to this method ( setDeletedSessionID() ) there and session get invalidated.

Will u please describe your views in sort of code flow,
Please help me to come out from this problem.
ThanksStart Free Trial