Unidirectional OneToMany with composite children key, not propagating parent id

Question

I have the following 2 entites:

@Entity
@Table(name = "PARENT")
public class ParentEntity{
    @Id
    @Column(name = "PARENT_ID")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "dtvSeq")
    @SequenceGenerator(name = "dtvSeq", sequenceName = "PARENT_ID_SEQ")
    private Long parentId;

    @OneToMany(mappedBy = "childEntityPk.parentId", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    Collection<ChildEntity> childrenEntities;

    //getters and setters ommited

}

And the children entity, with a composed primary key, partly referencing Parent_id (fk):

@Entity
@Table(name = "CHILDREN")
public class ChildEntity {
    @EmbeddedId
    private ChildEntityPk childEntityPk;

    //other fields
    //getter and setters ommited

    @Embeddable
    private class ChildEntityPk implements Serializable{
        long parentId;
        String name;
    }
}

It works perfectly to fetch data. However, if I want to persist a ParentEntity and its children entities in one go, I get an exception from Oracle.

This exception is thrown because hibernate did not update childEntity.childEntityPk.parentId and is trying to insert null.

I also played with @JoinColumn but without success.

I don't want to have a bi-directional mapping.

Answer 1

Do you have addChild() method or just update the collection? I suggest

public void addChild(ChildEntity child) {
     child.setChildEntityPk(this.parentId, "name");
     childrenEntities.add(child);
}