this is what I was thinking of doing, in a web-enviroment

using threadlocal to hold the web request's session, one session per web request.

having a UserManager class, this does work with hibernate so ill have a
User UserManager.getUser(String userId) throws HibernateException
all it does is use session.load

and then in my action classes use it like:

executeAction() {
try {
// get session from threadlocal (session already created in a filter)
// start transaction
User user = UserManager.getUser(userId);
// do work with user and other "Manager" classes
// commit transaction
} catch(HibernateException e) {
// rollback the transaction
// a massive failure occured, we're screwed.. show user a "Fatal" error page if we get here..
}
}

theres a few problems here though, what if for some reason I need to use some other persistence mechanism, i wont be able to use this action anymore,
how would I go about generalizing the UserManager to be persistance store agnostic yet be able to use transactions?

im a little confused as to how to do this..
I could have UserManager throw a ManaberException that wraps HibernateExceptions but I would still need to use the hibernate sessions in the action class so I wont be able to use the actions without hibernate.. do not know, someone please advise!

Sounds like a job for JTA. Hibernate supports JTA transactions.

Definitely try to isolate persistence calls to a single layer rather than spanning multiple layers; this is true whatever your persistence mechanism happens to be. The DAO pattern is just what you are looking for, I think.

You might want to check out the Spring Framework which has really nice support for tying DAO and transactions usage together in a configurable way.

so JTA is what I need to look into, I just noticed that there was a new Spring released, M2, ill have to take a look at that too.