Cascading merge() leading to "Attempt to persist a reference to a non managed instance" error

Dear Support

Using Objectdb 2.3.4_02 I ran into an exception while performing some tests with a parent/child relationship and cascading merge() operations. The parent has an application defined id, while the child's id is generated, but I don't know if this is of concern.

The following "test case" reproduces the error:

public final class ObjectDbCascadingMergeTest {

  public void go() {
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("objectdb:test.tmp;drop");
    EntityManager em = emf.createEntityManager();

    EntityTransaction tx = em.getTransaction();
    tx.begin();

    em.merge(new Child(new Parent("Joe")));
    em.merge(new Child(new Parent("Tim")));

    tx.commit();

    emf.close();
  }

  public static void main(String[] args) {
    new ObjectDbCascadingMergeTest().go();
  }

  @Entity
  public static final class Parent {

    @Id
    @SuppressWarnings("unused")
    private String name;

    public Parent(String name) {
      this.name = name;
    }

  }

  @Entity
  public static final class Child {

    @Id
    @GeneratedValue
    @SuppressWarnings("unused")
    private int id;

    @ManyToOne(cascade = CascadeType.ALL)
    @SuppressWarnings("unused")
    private Parent owner;

    public Child(Parent owner) {
      this.owner = owner;
    }

  }

}

The root cause is:

com.objectdb.o.UserException: Attempt to persist a reference to a non managed ObjectDbCascadingMergeTest$Parent instance - field ObjectDbCascadingMergeTest$Child.owner
at com.objectdb.o.MSG.d(MSG.java:61)
at com.objectdb.o.TYW.writeElement(TYW.java:249)
at com.objectdb.o.UMR$Q.y(UMR.java:960)
at com.objectdb.o.UMR.x(UMR.java:549)
at com.objectdb.o.UML.u(UML.java:515)

Forum threads with similar problems: 591 or 333

Thanks for your assistance.

Thank you for reporting this problem. Cascading merge to new entity objects (the Parent instances in your code) is currently broken. This is also reported in issue #595 and hopefully will be fixed soon.

As a workaround - either use persist instead of merge:

    em.persist(new Child(new Parent("Joe")));
    em.persist(new Child(new Parent("Tim")));

or merge the parents explicitly with no cascading:

    Parent p1 = new Parent("Joe");
    em.merge(p1);
    em.merge(new Child(p1));
    Parent p2 = new Parent("Tim");
    em.merge(p2);
    em.merge(new Child(p2));