The easiest way is probably to have a single listener that implements both
the HttpSessionListener and HttpSessionActivationListener interfaces. This
has a single count of active sessions.
In the sessionCreated() method, increment the count
In the sessionDestroyed() method, decrement the count
In the sessionDidActivate() method, increment the count
In the sessionWillPassivate() method, decrement the count.
This should eliminate the need to store anything in the session.
Hope this helps
Andy
-----Original Message-----
From: Christian Hauser [mailto:[EMAIL PROTECTED]
Sent: 04 September 2003 10:01
To: Tomcat Users List
Subject: Re: Counting active sessions if server restarts very often
Shapira, Yoav wrote:
> Howdy,
>
>
>>Is there an other way to implement this? Maybe by saving the variable
>>activeSessions to a session (which is restored when the server has
>>restarted)?
>
>
> This is not a bad idea, and might be the easiest way. A DB write on
> shutdown/read on startup is also an option.
To recapitulate: I want to display all active sessions (~ active users).
I use HttpSessionListener and increment a static int field every time
sessionCreated is called. Unfortunately the server is restarted very
often so I'd like to remember the active sessions by putting them into
the session.
But how? Like this?
public class SessionCounter implements HttpSessionListener {
public synchronized void sessionCreated(HttpSessionEvent event) {
Integer i =
(Integer)event.getSession().getAttribute("session.counter");
if (i == null) {
i = new Integer(0);
}
int activeSessions = i.intValue() + 1;
event.getSession().setAttribute("session.counter", activeSessions);
}
public synchronized void sessionDestroyed(HttpSessionEvent event) {
Integer i =
(Integer)event.getSession().getAttribute("session.counter");
if (i == null) {
i = new Integer(0);
}
int activeSessions = i.intValue();
if (activeSessions > 0) {
activeSessions--;
}
event.getSession().setAttribute("session.counter", activeSessions);
}
public static int getActiveSessions() {
return activeSessions;
}
}
Jon Wingfield gave me the hint to put an object that implements
HttpSessionActivationListener as an attribute to the session.
But if I do that in the SessionListener#sessionCreated method I have 100
of those objects around when 100 concurrent users are using my web
application. Does that make any sense?
And what should I do when the object implementing
HttpSessionActivationListener enters sessionWillPassivate? How do I save
the count of active sessions?
Sorry for all those questions, but I'd like to count the sessions even
when the server restarts very often.
Thank you for your help,
Christian
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