Which version of JBoss AS? I think that 7.x bechaves somewhat differnetly that earlier versions. But if you mean 6.x or earlier, there are some thoughts:
* If you fail to close a connection when you app responds to a request, the app server will "close" the connection for you. (There should be a log message about this)
* Closing a connection really means "placing the connection back into the connection pool"
* Opening a connection really means "obtaining a connection from the connection pool"
* No physical connections are made to the database until a connection is requested. At that time min-pool-size physical connections are created and placed into the pool, one ofwhich is returned to the requester.
* If a connection remains unused for idle-timeout-minutes, it is physically closed and removed from the pool. (If that causes less than min-pool-size connections to be open, a new physical connection is opened and added to the pool.)