Hibernate: Clean collection's 2nd level cache

问题:

I have a problem Hibernate does not update 2nd level cache for a collection of items which are subject of cascade removal.

Details

Assume we have an object Parent which has Parent.myChildren collection of Child objects. Now we have also object Humans with Humans.myAllHumans collection and all Parent and Child objects are in that collection.
Now we session.delete(parent) and all the children are cascade removed from the database, but Humans.myAllHumans collection's cache is not updated! It still assumes that cascade deleted objects are in database and we hit following exception while trying to iterrate the collection later:
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [foo.Child#751]

Approaches tried

1) I've tried SessionFactory.evictCollection() approach, but as I understand it is not transaction safe and hard removes data from 2nd level cache, I do not want that.

2) I can also manually (programatically) remove each object from the myAllHumans collection. In this case hibernate does update 2nd level cache. This approach I'll like to avoid since it just makes cascade delete feature useless.

Expected

I'd like hibernate to be smart enough to update the collection's cache automatically. Is it possible?
I'm using EhCache now, do you think using another cache implementation or configuring EhCache may help?

回答1:

The problem is that Hibernate doesn't actually do the delete. The database does that as part of a foreign key relationship, so Hibernate never sees all the objects that may get deleted and therefore, there is no way to update the cache that works in every case.

I think your best bet is to flush the cache (or part of it) when you delete.

回答2:

I've been struggling with other problem requiring remove collection from cache and I've worked out some solution. I don't know if it is possible to update the collection's cache automatically on cascade delete, but if you've tried SessionFactory.evictCollection() and it worked, I think that this solution can be transactional safe and it works also:

if (MYCOLLECTION instanceof AbstractPersistentCollection) ((AbstractPersistentCollection) MYCOLLECTION).dirty();

回答3:

Usually Hibernate need a politically incorrect refresh of the object to reload the cahe.

An important thing is how that EhCache handles the lazy properties. I found that the lazy attribute of the collection is not set, the cahe doesn't refresh the objects.

In your case, If the Humans set of the humanity attribute is set to lazy = true (default option), ehcache doesn't refresh it if the object. Try to set the lazy attribute of the humans and children collections to false.