Best way to count number of users in a Java EE web App

Question

What is the best way/pattern for counting the number of active users using a particular java EE JSF web app?

The two ways I know is HttpSessionListener and using JMX web beans, if there is a third better way I am open to suggestions. I am just trying to figure out the most elegant solution.

Help is much appreciated

Answer 1

If you want to track the number of active users at the same time in simple Java web app built without using any frameworks , then the standard way to do that is to implement HttpSessionListener . Code below is just a reference to the way you can implement it .

import java.util.concurrent.atomic.AtomicInteger;

import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class ActiveUserCounter implements HttpSessionListener {  

      private static AtomicInteger activeSessions = new AtomicInteger();    

      public void sessionCreated(HttpSessionEvent se) {  
              activeSessions.incrementAndGet();  
      }  

      public void sessionDestroyed(HttpSessionEvent se) {  
                if(activeSessions.get() > 0)  
                       activeSessions.decrementAndGet();  
      }  

     public static int getActiveSessions() {  
             return activeSessions.get();  
      }   
}  

Define the listener class in your web.xml .