JPA递归一对一延迟加载引用未更新

Question

Using JPA 2.1 and Hibernate 4.3.6.Final, I have the following simple entity:

@Entity
@Table(name = "CONTACT")
public class Contact {
    @Id
    @Column(name = "ID")
    private String id = UUID.randomUUID().toString();

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "PARTNER_ID")
    private Contact partner;

    Contact() {
    }

    public void assignPartner(final Contact other) {
        this.partner = Objects.requireNonNull(other);
        other.partner = this;
    }

    public void unassignPartner() {
        if (partner != null) {
            partner.partner = null;
        }

        partner = null;
    }
}

Notice the lazy-loaded one-to-one recursive association to a partner Contact. Also notice how assignPartner() and unassignPartner() manage the bi-directional relationship.

And the following methods:

private static void assignPartner(final EntityManager entityManager) {
    entityManager.getTransaction().begin();

    final Contact contact1 = entityManager.find(Contact.class, CONTACT1_ID);
    final Contact contact2 = entityManager.find(Contact.class, CONTACT2_ID);

    contact1.assignPartner(contact2);

    entityManager.getTransaction().commit();
}

private static void unassignPartner(final EntityManager entityManager) {
    entityManager.getTransaction().begin();

    final Contact contact1 = entityManager.find(Contact.class, CONTACT1_ID);
    contact1.unassignPartner();

    entityManager.getTransaction().commit();
}

Assuming existing rows for CONTACT1_ID and CONTACT2_ID, after running assignPartner() then unassignPartner(), database state shows that contact1 has a null partner_id and contact2 still has a non-null partner_id.

However, if I change the Contact.partner fetch type to EAGER, after running assignPartner() then unassignPartner(), database state shows that both contact1 and contact2 have null partner_id.

Why is that? Why are changes to the partner entity not flushed to the database?

EDIT 1

Changes to the partner reference through direct field access, eg partner.firstName = "DUMPED", are not propagated either. Changes to the partner reference through method access, eg partner.setFirstName("DUMPED"), are propagated. Neither partner.partner = null or partner.setPartner(null) are propagated.

EDIT 2

As suggested by Rat2000, moving the unassignment logic outside the Contact.unassignPartner() method and inside the unassignPartner(EntityManager) method seems to work properly. So it's really something to do with how Hibernate deals with the contact1.partner proxy, and in particular the contact1.partner.partner proxy.

    final Contact contact1 = entityManager.find(Contact.class, CONTACT1_ID);
    contact1.getPartner().unassignPartner();
    contact1.unassignPartner();

Answer 1

Try this:

@OneToOne(fetch = FetchType.LAZY, cascade = CascadeType.UPDATE)
@JoinColumn(name = "PARTNER_ID")
private Contact partner;