Handling collection updates with JPA

Question

I have a collection of custom objects and I'd like to persist it in the easiest way using JPA.

My CustomObject class is mapped to a table. Now I'm wondering if JPA provides some kind of utility to handle object collection.

In particular I'd like to add or remove objects to/from my collection and then pass to a save(Collection<CustomObject> cco) method without checking which objects have changed (which of them I need to add and which to remove...)

Is it possible?

Solution

If you are looking for something in EntityManager which will save or update a collection, the answer is no. You will have to loop and do a save or update.

If you use EntityManager.merge() API it will update if record is existing or else will insert a new record.

As far as delete is concerned, how will JPA or any other ORM determine that you want to delete that instance, if its a soft delete like updating a column like is_active to true/false, then yes by calling merge it can be done, but if you want a hard delete then JPA won't be able to determine by itself, you will have to do it manually.

Comments

[Fritz]

+1 The deleting part is the one that gets tricky, you should have some sort of metadata for your objects (or another list and maintain a relationship through the indexes) to know which ones should be updated and which ones should be deleted.

[mprabhat]

Yep, deletion cannot be done that easy, mapping has to be there somewhere :)