I want to check if a detached persistent instance has been changed since it was loaded from the database. Can Hibernate do this for me? or do I have to load another instance from the database and perform a manual field-by-field comparison in memory?

I tried using Session.lock with LockMode.NONE and LockMode.READ and passing it the modified transient instance.
I expected it to throw an HibernateException (since the instance I'm trying to lock has been modified) but it didn't.

Thanks in advance

You can use optimistic locking using a version field in your table. Read the hibernate reference manual about this. They have explained it in detail there.

That would work if wanted to check if someone else changed the database since I loaded my objects. However, what I want to do is check if the objects have changed in memory (the version number isn't increased until I perform an update and then it would be too late)