I have a question about one-to-many collections. I have the following two classes.


Now for a Parent instance that had been saved in a previous session, I make some changes in a UI tier, like adding new Children, modifying some existing Children and removing some other exisiting Children from the Parent's children collection.

Now in order to saveOrUpdate() this Parent instance in a new Session, do I simply do session.saveOrUpdate( parent )? If so, will Hibernate know which Children are new, which ones modified and which ones to delete from the database?

Or would I have to manually iterate over the children collection in the dao tier to see which ones to saveOrUpdate and which ones to delete?

Thanks

Please read http://www.hibernate.org/hib_docs/reference/html/parent-child.html#parent-child-cascades. It is explained there pretty well

The explanation is pretty good for one-to-many "bidirectional" relationship. But what I am actually trying to do is a one-to-many "uni-directional" relationship with a "list" on many end. It is like this.



And in this, when I save a Parent instance the first time (using just session.saveOrUpdate( parent ); session.flush(); ), everything is fine.

But if I try to save the same Parent instance, with some modifications to the list of children using the same two above statements, then it gives me an exception saying "you may not dereference a collection with cascade="all-delete-orphan" option. If I change that option to just cascade="all", then it does save my Parent instance, but leaves behind any orphaned children in the childrens table.

If anyone can throw some light on the correct way of mapping this relation and also the steps (or method calls) to save or update such instances, I would appreciate. Just to note, all changes to my Parent instance (including adding/modifying/deleting children from the collection) are being done in a UI tier where I dont have the session instance.

Thanks

With all-delete-orphan you can not do something like this: object.setList(someOtherList).

With delete, you have to delete the orphaned childs manually.

In every case, saveOrUpdate(parent) is all you need to do.