Untitled

What does a relationship owner mean in Hibernate?

@Entity

public class Troop {

    @OneToMany(mappedBy="troop")

    public Set<Soldier> getSoldiers() {

    ...

}

 

@Entity

public class Soldier {

    @ManyToOne

    @JoinColumn(name="troop_fk")

    public Troop getTroop() {

    ...

}

       

Troop has a bidirectional one to many relationship with Soldier through the troop property. You don't have to (must not) define any physical mapping in the mappedBy side.

       

Troup t = new Troup();

t.getSoldiers().add(soldier);

       

Troup t = new Troup();

t.getSoldiers().add(soldier);

session.SaveOrUpdate(t);

session.Flush();

       

throws references transient instances

       

INSERT INTO troops (id, ...) VALUES (1, ...)

INSERT INTO soldiers (..., troop_fk) VALUES (..., NULL)

UPDATE soldiers SET troop_fk=1    <- troop sets its key

       

INSERT INTO troops (id, ...) VALUES (1, ...)

INSERT INTO soldiers (..., troop_fk) VALUES (..., 1) <- soldier saves the reference