Illegal state exception occurs when the session has been invalidated/expired, and you try to access it.
Throws IllegalStateException - if Object getAttribute(
String name) is called on an invalidated session
HttpSession-getAttribute()
ocjp 6 — Feeding a person with food is a great thing in this world. Feeding the same person by transferring the knowledge is far more better thing. The reason is the amount of satisfaction which we get through food is of only one minute or two. But the satisfaction which we can get through the knowledge is of life long.