Session ID


Is there a way to generate the session ID myself instead of servlet engin generating it?

I am developing a web site that users must login to access it.  I want to prevent users from openning 2 browsers and login them both.  In other words, I want to allow only 1 access to my site at a time for a same user.  The second login from the second browser should logoff the first login from the first browser.  

I can achieve this by generating the Session ID based on the username. But I just don't know if it is possible to generate Session ID myself.

Thanks in advance.


Who is Participating?
cheekycjConnect With a Mentor Commented:
You could accomplish the same thing by maintaining an apllication-scope list where you associate the servlet-engine generated sessionID's with a username as a user logs in. Then, each time a client accesses a page, do a lookup to see if the username and the sessionID of the current session match the sessionID in your list (ie the sessionID of the last session that logged in with the username in question). If they don't match, log the user out in teh current session. Make sense?

What servlet engine?

For example IPlanet.. you have to:

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if u want only one user to login with the same name, then instead to going for session u can set a flag in the database. u set the flag in the database as "1" as soon as the user signs in. so next time from another system if the user tries to login check for the Flag, if it is set to "1" then don't allow him to signin. actually this is how i've done. it actually help. if go for session its a real pain to the server.
samanthaAuthor Commented:
Thanks, guys.


I thought about your way. But if my site will serve thousands of users, would application-scope variables  degrade the performance? If it won't, I think I will use your way.

I am using Tomcat 4.0. Doesn it provide the Session Manager API like IPlanet? Could you point me to the right link?

Unfortunately, one of the requirment of my project is not to store this info on the server disk or database.

Thanks again,
The one downside I see to pellep's idea is that application scope variables won't die with the session. This means that, without a log off or similar action, or some sort of timer-driven event to clean up old records, your list will continue to grow until you bounce the server (or otherwise clear the relevant application attributes). Note that, even with a "log off" button, many users will simply close the browser, etc. Oh, another possibility is binding a user session bean object to the session with HttpSessionBindingListener. This would allow you to release any held resources when the session is about to die by way of the objects valueUnbound method. Pretty handy stuff really and I've had success with that in Tomcat 4.0.

In a similar vain to pallep's idea, if you were happy to only support users that accept session cookies, you could implement your control by setting a cookie of your own. This is of course exactly what your servlet engine is doing, unless it finds that the user does not accept cookies.

One more drawback all around: If a user logs on with one browser, and then spawns a new browser window *from* that first one (eg. File... New... Window), the two browsers actually share the same session. This may not be a problem some how, but definitely allows a user to make changes from more than one browser.

ah jeez,
sorry for the misspelling pellep.

samanthaAuthor Commented:
Thanks again, guys.

I give the point to cheekyci because his answer is more close to what I originally asked.

But all your answers are excellent and helpful.
Glad I could help.  Thanx for the "A"
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