code: public User login(Credentials credentials) throws AuthenticationException {
  		//if a user wants to log in, we assume he's not surprised if
  		//  his session was expired (hence the 'true')
  		User user = getSession(true).login(credentials);
  		entryPoint.onSessionUpdate(this, session);
  		return user;
  	}
docs: Tries to perform login on entry realm.
  Creates session if necessary.
  
  @param credentials
  @return
  @throws AuthenticationException if login fails for another reason than simply invalid credentials