Can not persist Parent-Child mapping when child refers to parent via parent's
primary identity (and not parent's object reference) and parent uses database
sequence for its own identity
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Key: OPENJPA-693
URL: https://issues.apache.org/jira/browse/OPENJPA-693
Project: OpenJPA
Issue Type: Bug
Reporter: Pinaki Poddar
The following use case is reported in the users' group [1].
A typical Parent-Child (Address has many Phones) relationship. But Phone refers
to Address by its primary key. And database assigns the primary key of the
Address.
When and how to set the child's reference field to its parent?
Approach A:
1. Remove all children from Parent, but remember them
2. flush() the Parent.
3. Database will now assign identity to Parent
4. Add the children back and set each child's identifier to the newly assigned
identifier of the Parent
5. commit
The other approach B which is cleaner
1. Add a @PostPersist method to Parent.java as follows
@PostPersist
public void postPersist() {
if (children== null) return;
for (Child child : children)
parent.setParentId(this.getId());
}
2. commit()
Unfortunately Approach B does not work as expected with existing OpenJPA
because it prohibits Phone.addressId value to be reassigned during a flush
cycle as resulted from Address.postPersist() method.
I have added a fix to relax that prohibition under some circumstances but I am
concerned whether this relaxing of restriction will now allow other truly
invalid use cases those the original restriction was duly imposing.
The fix passes the OpenJPA test corpus -- but that is also not proof enough of
its robustness.
Comments/thoughts?
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