Question

My entities representing a one-to-many:

@Entity
@Table(name = "Users")
public class User {
    @Id
    @GeneratedValue
    private int id = -1;

    @OneToMany(mappedBy = "user", cascade = CascadeType.ALL)
    private List<SignIn> signIns;
}

@Entity
@Table(name = "SignIns")
public class SignIn {
    @Id
    @GeneratedValue
    private int id;
    @ManyToOne
    private User user;

    public SignIn(User user) {
        this.user = user;
    }
}

When I persist a User and then persist a SignIn with the created User, everything works fine (each table will have 1 row).
When I reuse the created User to persist another sign in, the first sign in row gets replaced by the new sign in.

The code that persists:

User user = new User();
persist(user);
SignIn signIn = new SignIn(user);
SignIn signIn2 = new SignIn(user);
persist(signIn);
persist(signIn2);

private void persist(Object entity) {
        EntityManager em = entityManagerFactory.createEntityManager();
        EntityTransaction tx = em.getTransaction();
        try {
            tx.begin();
            em.merge(entity);
            tx.commit();
        } finally {
            if (tx.isActive()) {
                tx.rollback();
            }
            em.close();
        }
    }

What did I overlook?

Answer 1

I had to set the SignIn on the inverse side too (User in my case).

So:
– create a sign in
– merge it
– add it the the User
– merge the User