Question

@Entity
@Table(name = "parent")
public final class Parent extends Base {

@OneToOne(cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
private Person person;

and doing (amongst other things) this :

Parent parent = new Parent();
Person person = new Person();
parent.setPerson(person);
session.save(parent);

I get the mentioned exception ?

Do I manually need to call session.save(person) before ? do I have to add a cascade type annotation to the childs class definition(where it references the parent) ?

Or have I missed something else obvious ?

I don’t want to use CascadeType.ALL as when a parent is deleted I want to keep the person(child).

Both entities/tables extend a common Base table :

@MappedSuperclass()
public abstract class Base {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    public Integer getId() {
    return id;
    }

Will this effect which cascade type is required ?

Answer 1

You haven’t mentioned the Hibernate version, but this hasn’t changed since I ever started using it.

As you can read in the Hibernate reference, to get the Java standard SAVE_UPDATE you need {CascadeType.PERSIST, CascadeType.MERGE} in Hibernate.

EDIT: Seeing the updated info, what you’re doing now causes Hibernate to treat it as a bi-directional one-to-one mapping. This basically means that for each object in any of those two tables, there has got to be a counterpart in the other table with the same ID. Therefore, you cannot delete only one of them, you would lose FK integrity.

If you want it to be a unidirectional mapping, e.g., if you want to be able to delete the person but leave the parent — you have to specify a FK, usually via @JoinColumn, like
@JoinColumn(name="PERSON_ID", unique=false, nullable=true, insertable=true, updatable=true)