Investigate improvement of Set handling [DATAJDBC-300]

Jens Schauder opened DATAJDBC-300 and commented

As described in this Stackoverflow question entities with a broken equals/hashcode contract trigger unexpected behavior when included in Sets since instances end up twice in the Set after saving.

What happens internally is the following: the Person entity gets saved. This might or might not create a new Person instance if Person is immutable.

Then the Address gets saved and thereby gets a new id which changes it's hashcode. Then the Address gets added to the Person since again it might be a new Address instance.

But it is the same instance yet now with a changed hashcode, which results in the single set containing the same Address twice.

Options to mitigate this are:

• setting the complete set instead of single elements (would also work better when the parent instance is immutable.
• removing the old instance before adding the new one

No further details from DATAJDBC-300