How restrict users ? Please guid to me...

[changemylife]

Hi all!
I use

"jboss-4.0.5.GA", EJB 3.0.

I have a problem that need help: My application allows multi-client access at the same time. But now, I want set up:

If a client, called John, use his account (ex: called johnA). And at this time, Anna also want use johnA to access application >> she can't access !

>> How I can setup ? or show to me some documents !

Please help me! Thanks.

[changemylife]

I want add some informations:
I use DatabaseServerLoginModule to authenticate users. Jboss supports some options to me can solve my problem above ?