If I retrieve an object from the database and immediately save it, then should hibernate save the object? I set up a test to see if hibernate would avoid doing the update if nothing changed in the POJO. I'm doing this with two different DAO calls, hence there are two sessions. One to retrieve the object and another to save the object.

Can anyone tell me if there is a way to prevent hibernate from saving the POJO if nothing changed?

If you're using a session that didn't load the object, how can it know if the object is different from the database version, or not? It has to save the object, because it doesn't know if it can take shortcuts.

You could use session.refresh or session.lock before saving the object. That will issue a select, and now hibernate knows whether or not the object is dirty, and can avoid saving it if possible.

Seems the way around this is to do a select-before-update="true". I've tried using session.lock and session.refresh but it doesn't work. Can I get anyone elses opinions or experiences on this?

thanks,
Mike

I would avoid the save step. If you retreive an object in a current Session, Hibernate is tracking that object as a managed object and tracks changes to it.

When your transaction commits, Hibernate will flush changes to the database. At this point if you have made modifications Hibernate will issue an update statement, if not then it will not issue an update.

He's using two sessions: the one that's saving is not the one that loaded the object. Your statement is correct but not applicable in this case.