See How do we get access to the session for ways to retrieve the session.
One way of invalidating a session; contributed by Ray Clough.
Session Invalidation
// Code fragment from class implementing SessionAware containing the
// session map in a instance variable "session". Attempting to invalidate
// an already-invalid session will result in an IllegalStateException.
if (session instanceof org.apache.struts2.dispatcher.SessionMap) {
try {
((org.apache.struts2.dispatcher.SessionMap) session).invalidate();
} catch (IllegalStateException e) {
logger.error(msg, e);
}
}