What do you mean by "same session"? A "session" is usually an instance of an interaction between one user and one web application.
Yes, I know that. Actually, I am developing a system for a client in which he emphasizes on saparate modules(as in saparate applications). So session handling in this becomes very difficult. Presently, I am handling it through cookies, but someone told me that there may be a way for a single session for all the war files within a web container. So if there is any such way to do this, it will save me from alot of other complexities.