I guess I don't really understand bidirectional one-to-many relations.
I have a parent, a child-A and child-B class with bidirectional relations between Parent <-> Child-A <-> Child-B. I want to add a child-B to the child-B-list of the child-A, but on every try to merge the parent I get an dublicated key exception. So how do I add a new child-B.
class Parent {
long id;
@One-To-Many, MappedBy Parent, Cascade All, OrphanRemoval true
list <child-A> childsA;
...
setter + getter
}
and
class Child-A {
long id;
@Many-To-One, JoinColums parentId, Cascade PERSIT MERGE REFRESH
Parent parent;
@One-To-Many, MappedBy Child-A, Cascade All, OrphanRemoval true
list <child-B> childsB;
...
setter + getter
}
and
class Child-B {
long id;
@Many-To-One, JoinColums Child-A-id, Cascade PERSIT MERGE REFRESH
Child-A child-A;
...
setter + getter
}
How do I add a new child-B to child-A and merge the parent to save everything in the db? So far I've tried:
Parent p = entityManager.getParent();
Child-A ca = p.getChildsA.get(indexOfCa); // the index is known
Child-B cb = new Child-B ();
... // fill cb with information
ca.add(cb); // automatically fires cb.setChild-A(ca);
p.getChildsA.set(index, ca);
entityManager.merge(p);
But this causes a DublicatedKeyException. So what is the best practise to add a child-B object to an already persisted child-A-object from an parent-object?
I also have to say, only merge is possible (no save, saveOrUpdate or persist) and it is not possible to edit the entity-classes. The entities are generated by something like a factory and every change will be overwritten when building the project. And the pom-file is not editable. Also this is a Java EE web-application with many different frameworks like primefaces and omnifaces.
