Hi all, (Sorry for my goofy english)

I am developing a web application, configured with struts2, ibatis and mysql. Its a content management app, the user want to subscribe for the full view of the content and description.

If a user has logged in a system, then the same user should not be allowed to login in another system, if the session expires then the other one can log in. (I never want to save this feature in database)

How to do this? is there any need of using "OpenID for Java Web applications" ?

your help is highly appreciated