Say I have a unidirectional @ManyToOne
relationship like the following:
@Entity
public class Parent implements Serializable {
@Id
@GeneratedValue
private long id;
}
@Entity
public class Child implements Serializable {
@Id
@GeneratedValue
private long id;
@ManyToOne
@JoinColumn
private Parent parent;
}
If I have a parent P and children C1...Cn referencing back to P, is there a clean and pretty way in JPA to automatically remove the children C1...Cn when P is removed (i.e. entityManager.remove(P)
)?
What I'm looking for is a functionality similar to ON DELETE CASCADE
in SQL.
Relationships in JPA are always unidirectional, unless you associate the parent with the child in both directions. Cascading REMOVE operations from the parent to the child will require a relation from the parent to the child (not just the opposite).
You'll therefore need to do this:
@ManyToOne
relationship to a bi-directional @ManyToOne
, or a unidirectional @OneToMany
. You can then cascade REMOVE operations so that EntityManager.remove
will remove the parent and the children. You can also specify orphanRemoval
as true, to delete any orphaned children when the child entity in the parent collection is set to null, i.e. remove the child when it is not present in any parent's collection.ON DELETE CASCADE
. You'll need to invoke EntityManager.clear()
after calling EntityManager.remove(parent)
as the persistence context needs to be refreshed - the child entities are not supposed to exist in the persistence context after they've been deleted in the database.