/**
* Copyright (C) 2011 JTalks.org Team
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
package org.jtalks.jcommune.web.listeners;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;
import java.util.concurrent.atomic.AtomicLong;
/**
* Custom session listener implementation to track active user sessions
*
* @author Elena Lepaeva
*/
public class SessionStatisticListener implements HttpSessionListener {
/**
* It's static because 2 listeners are created - one by web server, one by Spring. We'll need to get rid
* of this hack.
*/
private static volatile AtomicLong totalActiveSessions = new AtomicLong(0);
/**
* @return active sessions count
*/
public long getTotalActiveSessions() {
return totalActiveSessions.get();
}
/**
* {@inheritDoc}
*/
@Override
public void sessionCreated(HttpSessionEvent se) {
totalActiveSessions.incrementAndGet();
}
/**
* {@inheritDoc}
*/
@Override
public synchronized void sessionDestroyed(HttpSessionEvent se) {
/**
* Tomcat may not invalidate HTTP session on server restart while counter variable
* will be set to 0 on class reload. So we can quickly get our session count negative when
* persisted sessions will expire. This check provides us with a self-correcting facility
* to overcome this problem
**/
if (totalActiveSessions.get() > 0) {
totalActiveSessions.decrementAndGet();
}
}
}