Hibernate/JPA, save a new entity while only setting id on @OneToOne association

Question

I have two entities,

  class A { @OneToOne B b; } 

  class B { ... lots of properties and associations ... }

When I create new A() and then save, i'd like to only set the id of b.

So new A().setB(new B().setId(123)).

Then save that and have the database persist it.

I do not really need to or want to fetch the entire B first from the database, to populate an instance of A.

I remember this used to work, but when I am testing it is not.

I have tried Cascade All as well.

I don't think it will work if you don't fetch B entity first and set it to A at least while using JPQL — Harish Barma, Aug 04 '17 at 21:37
@zerocool You mean on B's assoications? Or \@OneToOne in A on b ? — mmm, Aug 04 '17 at 21:45

mmm · Accepted Answer · 2017-08-05T15:40:27.907

2

B b = (B) hibernateSession.byId(B.class).getReference(b.getId());
a.setB(b);

hibernateSession.load(...) // can also be used as it does the same.

The JPA equivalent is :

 entitymanager.getReference(B.class, id)

edited Aug 05 '17 at 15:40

answered Aug 04 '17 at 22:42

mmm

1

https://stackoverflow.com/questions/1607532/when-to-use-entitymanager-find-vs-entitymanager-getreference – aschoerk Aug 05 '17 at 10:01

score -2 · Answer 2 · answered Aug 04 '17 at 21:49

-2

Below code should help.It will fetch B only when its accessed.

class A { @OneToOne(fetch = FetchType.LAZY) B b; }

answered Aug 04 '17 at 21:49

zerocool

2 Answers2