Whenever a specific change occurs to one of my domain objects I want to be able to make another change. As an example, I have an object that has a set of states that are a part of a relationship with other objects. However, I also need to maintain a state that takes into account all the states for the relationships.

Currently, I am just loading the object and generating the state on the fly. What I would like to do is update the state whenever one of the relationship states change. So far I can think of two places to do this:

1. When the state for the relationship is changed, also update consolidated state.

2. Use an interceptor. When save() is called, make the update.

Option 1 doesn't seem optimal, because this value will be set whenever I get the object back from Hibernate. For read only operations, I don't want to make a change to the database.

Option 2 seems like a better approach. However, my understanding is that this would only be called after a save(), so I might have a stale consolidated state for a period of time.

Is there yet a better approach? At worst, I can always call save in the DAO when it makes an update to the relationship state for the domain object. If there is a better solution I'd love to use it though :).

Did you look at Interceptor.onFlushDirty(...) ?

I created a test case to test out Interceptor.onFlushDirty(). It appeared to never get called, which surprised me. However, I do see onSave() getting called when I tell Hibernate to save my object.

I wasn't quite able to grasp exactly when .onFlushDirty() gets called, so it is quite possible I am not using this correctly. When should .onFlushDirty() get called?

Also, it does look I really want to be hooking on .onFlushDirty() because I can compare the current state against the previous state. I imagine this is what you were getting at. However, I am not sure how to get that method to be called.

I did some digging and discovered that it is expected behavior that .onFlushDirty() is not called when a collection is modified, which is exactly the case in my situation.

That said, I also read about an incident in sourceforge tracking this issue for Hibernate 2.1. However, it looks like the sourceforge bug tracking is no longer used, but JIRA is instead. I only found two issues regarding .onFlushDirty(), neither of which addresses the collections issue.

Did this fall off of the radar? Should I file an enhancement request?

I found a somewhat elegant alternative to using an interceptor. Basically, I made the set package private and only allow clients to manipulate it through another method (setStateOnSystem). This allows me to hook the way I wanted to.