Converting Between Hibernate Collections and My Own Collections

Question

I have set up Hibernate to give me a Set<Integer> which I convert internally to and from a Set<MyObjectType> (MyObjectType can be represented by a single integer). That is to say, When Hibernate calls my void setMyObjectTypeCollection(Set<Integer> theSet) method I iterate through all the elements in theSet and convert them to MyObjectType. When Hibernate calls my Set<MyObjectType> getMyObjectTypeCollection() I allocate a new HashSet and convert MyObjectTypes to Integers.

The problem is that every time I call commit, Hibernate deletes everything in the collection and then re-inserts it regardless of whether any element of the collection has changed or even that the collection itself has changed.

While I don't technically consider this a bug, I am afraid that deleting and inserting many rows very often will cause the database to perform unnecessarily slowly.

Is there a way to get Hibernate to recognize that even though I have allocated and returned a different instance of the collection, that the collection actually contains all the items it used to and that there is no need to delete and reinsert them all?

Answer 1

I think the best way to achieve your goal would be to use a UserType. Basically it lets you handle the conversion from SQL to your own objects (back and forth).

You can see an example on how to use it here.