code: public StandardSession getSessionByToken(String token) {
  		StandardSession session;
  		synchronized (sessions) {
  			session = (StandardSession) sessions.get(token);
  			if (session != null) {
  				session.updateLastAccessedTime();
  			}
  		}
  		return session;
  	}
docs: Returns a session if found
  and updates the last time it was accessed.
  
  @param token session identifier stored by the client
  @return a session stored by the given session ID or null if it can't be found