code: @Override
  	public void sessionCreated(HttpSessionEvent event) {
  		if (!instanceEnabled) {
  			return;
  		}
  		// pour être notifié des passivations et activations, on enregistre un HttpSessionActivationListener (this)
  		final HttpSession session = event.getSession();
  		// Since tomcat 6.0.21, because of https://issues.apache.org/bugzilla/show_bug.cgi?id=45255
  		// when tomcat authentication is used, sessionCreated is called twice for 1 session
  		// and each time with different ids, then sessionDestroyed is called once.
  		// So we do not count the 2nd sessionCreated event and we remove the id of the first event.
  
  		// And (issue #795), in Tomcat's cluster after one instance restart
  		// sessions are synced with sessionDidActivate+sessionCreated
  		// so do not increment count for sessionCreated when session.getAttribute(SESSION_ACTIVATION_KEY) != null
  		// (but not == this because of deserialization)
  		if (session.getAttribute(SESSION_ACTIVATION_KEY) != null) {
  			// si la map des sessions selon leurs id contient une session dont la clé
  			// n'est plus égale à son id courant, alors on l'enlève de la map
  			// (et elle sera remise dans la map avec son nouvel id ci-dessous)
  			removeSessionsWithChangedId();
  		} else {
  			session.setAttribute(SESSION_ACTIVATION_KEY, this);
  
  			// pour getSessionCount
  			SESSION_COUNT.incrementAndGet();
  		}
  
  		// pour invalidateAllSession
  		addSession(session);
  	}
docs: {@inheritDoc}