JPA not saving foreign key to @OneToMany relation

Question

I\'m using Spring with Hibernate as a JPA provider and are trying to get a @OneToMany (a contact having many phonenumbers) to save the foreign key in the phone numbers table

Answer 1

You have to manage the Java relationships yourself. For this kind of thing you need something like:

@Entity
public class Contact {
  @Id
  private Long id;

  @OneToMany(cascade = CascadeType.PERSIST, mappedBy = "contact")
  private List<Phone> phoneNumbers;

  public void addPhone(PhoneNumber phone) {
     if (phone != null) {
        if (phoneNumbers == null) {
            phoneNumbers = new ArrayList<Phone>();          
        }
        phoneNumbers.add(phone);
        phone.setContact(this);
     }
  }

  ...
}

@Entity
public class Phone {
  @Id
  private Long id;

  @ManyToOne
  private Contact contact;

  ...
}

Answer 2

If the Contact-Phone relationship is unidirectional, you can also replace mappedBy in @OneToMany annotation with @JoinColumn(name = "contact_id").

@Entity
public class Contact {
  @Id
  private Long id;

  @OneToMany(cascade = CascadeType.PERSIST)
  @JoinColumn(name = "contact_id")
  private List<Phone> phoneNumbers;

  // normal getter/setter
  ...
}

@Entity
public class PhoneNumber {
  @Id
  private Long id;

  ...
}

Similar in JPA @OneToMany -> Parent - Child Reference (Foreign Key)

Answer 3

I don't think the addPhone method is necessary, you only have to set the contact in the phone object:

phone.setContact(contact);

Answer 4

If you want your relationship unidirectional i.e. can navigate from Contact to Phone's only, you need to add

@JoinColumn(name = "contact_id", nullable = false)

Under your @OneToMany on your parent entity.

nullable = false IS VITAL if you want hibernate to populate the fk on the child table

Answer 5

In reply to Cletus' answer. I would say that it's important to have the @column annotation on the id fields, as well as all the sequence stuff. An alternative to using the mappedBy parameter of the @OneToMany annotation is to use the @JoinColumn annotation.

As a kinda aside your implementation of addPhone needs looking at. It should probably be something like.

public void addPhone(PhoneNumber phone) {
    if (phone == null) {
        return;
    } else {
        if (phoneNumbers == null) {
            phoneNumbers = new ArrayList<Phone>();
        }
        phoneNumbers.add(phone);
        phone.setContact(this);
    }
}

Answer 6

Try this sample:

@Entity
public class Contact {
    @Id
    private Long id;

    @JoinColumn(name = "contactId")
    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<Phone> phones;
}

@Entity
public class Phone {
    @Id
    private Long id;
    private Long contactId;
}