Save either a new or detached child object using Spring JPA and Hibernate

[Salil Surendran]

I have a class like this:

@Entity
@Table(name = "parent")
class Parent{

 @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "child")
    private Child child;
}

The child class and therefore the child table has no references to Parent. Now the problem is that I have code like:

//Brand new transient parent created
Parent parent = new Parent();
//Either find child in the DB using the attributes or create a brand new one
Child child = createOrFindChild(childAttributes)
//Set child in parent
parent.setChild();
parentRepository.save(parent)

The problem here is that if I don't find the child and try to save I get the error: "object references an unsaved transient instance - save the transient instance before flushing"

If I set CascadeType.PERSIST then it works when a brand new child but when I find the child in the DB and it is detached then I get the error: "detached entity passed to persist".

Anyway to make it work without explicitly saving child first?

[Frits Walraven]

What about:

@Entity
@Table(name = "parent")
class Parent{

   @ManyToOne(fetch = FetchType.LAZY, cascade = { CascadeType.PERSIST, CascadeType.MERGE })
   @JoinColumn(name = "child")
   private Child child;