Hi,

I'm trying to implement object history tracking using the Event handlers, as suggested by Christian to be a replacement for the "old" interceptor way.

The idea is to implement a PreUpdateEventListener that creates a "backup" of the old object state before doing the actual update. The easiest approach is to use the "oldState" fields, supplied by the PreUpdateEvent to create this "historical" new entry and this actually works.

However, when you use detached objects, the oldState of the object isn't available! This is logical in a way, but breaks the approach above.

What would be the best approach to actually read the "old" values in the database, without coming into conflict with the cache or overwriting the updates that have been made to the object? I've tried several approaches, but a lot of it runs into "possible nonthreadsafe access to session" errors or similar. It just doesn't seem possible to get the old state of an object after it has been modified.

Please help!
(Hibernate 3.0 RC1)

Does anybody know the answer to this?

It seems strange that the oldState property has been provided in both PreUpdateEvent and PostUpdateEvent even though it's never assigned a value.

J

On my app server, and in my unit tests the old state is set, but in my tapestry (web) app, its not set.

The old state is set from the EntityEntry getLoadedState() (in whatever makes the EntityUpdateAction).

In the EntityEntry object, the loaded state is set after a postUpdate call.

So I have a theory, that maybe the loaded state is not available if the update is called from a flush event.


The more I look inside this stuff, I see glaring architecture issues :(
Not saying I could do better but if your gonna have a public method called getOldState(), you should either:

(A) Explain in javadocs that the method is not reliable (i.e. so don't use it)
(B) Or fix the architecture so it will always give you the value it says it will

that event package has no documentation.

-gabe

Try doing the update using session.merge(). This should give you the oldState of the detached objects. You are likely to have troubles with the oldState of the embedded collections, however, or at least I do - the collection members are the same in the state and the oldState although they have been modified.