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From Christian Hauser <c.hau...@active.ch>
Subject Re: HttpSessionListener: Negative session count
Date Tue, 12 Aug 2003 08:46:57 GMT
I have a further question:

Is it correct that I don't have to use
<jsp:useBean id="sessionCounter" class="SessionCounter" scope="session" />
and set the scope to "session"?

Because now I don't use "useBean". Should I?

Thank you in advance,
   Christian


Christian Hauser wrote:

> Hello J2EE programmers
> 
> I wrote a JSP some time ago that uses a class SessionCounter (which 
> implements HttpSessionListener) to count the active sessions of a web 
> application and to display them.
> 
> Unfortunately there seems to be a problem with my program, because the 
> web application says that there are currently -18 active sessions. 
> However, the lowest possible count should be 0.
> 
> Of course I could implement the sessionDestroyed the following way (to 
> prohibit a negative session count, but then the current session count 
> would not be correct, not?
>     public void sessionDestroyed(HttpSessionEvent event) {
>       if (activeSessions > 0)
>         activeSessions--;
>     }
> 
> Code of JSP file:
>   <tr>
>     <td>Concurrent sessions:</td>
>     <td><%= SessionCounter.getActiveSessions() %></td>
>   </tr>
>   <tr>
>     <td>Last refresh:</td>
>     <td><%= new Date() %></td>
>   </tr>
>   <tr>
>     <td>Last session change:</td>
>     <td><%= SessionCounter.getLastChange() %></td>
>   </tr>
> 
> Here's the class SessionCounter, which belongs to a utility JAR that is 
> situated in the lib directory of The web application.
> 
>   public class SessionCounter implements HttpSessionListener {
> 
>     /** Static variable to keep track of the current number of active 
> sessions. */
>     private static int activeSessions = 0;
> 
>     public void sessionCreated(HttpSessionEvent event) {
>       activeSessions++;
>     }
> 
>     public void sessionDestroyed(HttpSessionEvent event) {
>       activeSessions--;
>     }
> 
>     public static int getActiveSessions() {
>       return activeSessions;
>     }
>   }
> 
> 
> I'm using Tomcat 4.1.24 and hope that someone of you might give me a 
> hint on how I can get a reliable session counter.
> 
> Christian
> 
> 
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