In general is it considered bad form to use a Session without explicit transaction boundaries when using session per thread via getCurrentSession() ?

ie. it's very easy to end up with closed sessions coming back from getCurrentSession
if you use Session without explicit transaction boundaries because underneath the Session gets closed for you?

Is that true?

I have some code that currently wraps hibernate or attempts to and in order to do so uses session per operation. In order to avoid performance issues with select-before-update I need to convert the code to session per thread so that the session is longer lived. Right now the existing code does a lot of fetches without explicit transaction boundaries and I'm thinking that's the cause of the "Already closed" type messages.

I had assumed that I could be in charge of how the Session is used and used my own ThreadLocal to house my Session and it's removed from the ThreadLocal when the session is closed via the wrapper however it appears that somehow elsewhere the Session is closed and left inside the ThreadLocal and if it's expected that Hibernate can close a Session like this then it means that I'm forced to use ThreadLocalSessionContext and not my own ThreadLocal and that means that I'm required to have called beginTransaction on the Session before it can be used thus I'm actually forced into using explicit transaction boundaries whenever I want the Session bound to a Thread.