Question

How to check if a session is invalid or not? There is no method in the API.

Is it the same as isNew()? And what is the difference if not?

Answer 1

If you want to know whether it valid based on a request:

request.isRequestedSessionIdValid()    or  HttpSession sess = request.getSession(false); if (sess != null) {    // it's valid } 

If you have stored a reference to the session and need to validate I would

try {   long sd = session.getCreationTime(); } catch (IllegalStateException ise) {   // it's invalid }