Hi,
suppose this parent/child relation:
@Entity
class Parent
{
@Id(generate = GeneratorType.AUTO)
private Long id;
@OneToMany(mappedBy = "parent", cascade = CascadeType.ALL)
private Set<Children> children = new HashSet<Childer>();
}
@Entity
class Child
{
@Id(generate = GeneratorType.AUTO)
private Long id;
@ManyToOne(optional=false)
private Parent parent;
}
This code fails to merge(parent). Error: not-null property references a null or transient value (on Child.parent):
Parent parent = new Parent();
Child child = new Child();
child.setParent(parent);
parent.getChildren().add(child);
manager.merge(parent);
However for optional=true it works fine. Why?
This works fine:
Parent parent = new Parent();
manager.merge(parent);
Child child = new Child();
child.setParent(parent);
parent.getChildren().add(child);
manager.merge(parent);
Thanks for explanation, Jan
