how to add @onetoone mapping for self entity in hibernate

Question

how to add one-to-one mapping for the self entity. Like in this example. I want to have parent-child relationship for the Person itself.

@Entity
@Table(name="PERSON")
public class Person {

@Id
@Column(name="personId")
private int id;

@OneToOne
@JoinColumn()
private Person parentPerson;
}

Answer 1

Here is example of bidirectional self mapping @OneToOne (I change column names to SQL notation):

@Entity
@Table(name="PERSON")
public class Person {

    @Id
    @Column(name="person_id")
    private int id;

    @OneToOne
    @JoinColumn(name = "parent_person_id")
    private Person parentPerson;

    @OneToOne(mappedBy = "parentPerson")
    private Person childPerson;
}

But, I don't understand why you want to use @OneToOne in this case.

Answer 2

I am using it like this:

@OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumn(name = "PARENT_ID", nullable = true)
private Person parent;

In order to add parent from your service layer, you need to already have at least one Person in the database.

Lets presume you do. Then create a new person. For e.g.:

@Transactional
public void createPerson() {
   Person parent = //get your parent
   Person child = new Person();
   if (parent != null) {
       child.setParent(parent);
   }
}

If this is what you mean..