Strange JPA one-to-many behavior when trying to set the "many" on the "one" entity
- by errr
I've mapped two entities using JPA (specifically Hibernate). Those entities have a one-to-many relationship (I've simplified for presentation):
@Entity
public class A {
@ManyToOne
public B getB() { return b; }
}
@Entity
public Class B {
@OneToMany(mappedBy="b")
public Set<A> getAs() { return as; }
}
Now, I'm trying to create a relationship between two instances of these entities by using the setter of the one-side/not-owner-side of the relationship (i.e the table being referenced to):
em.getTransaction().begin();
A a = new A();
B b = new B();
Set<A> as = new HashSet<A>();
as.add(a);
b.setAs(as);
em.persist(a);
em.persist(b);
em.getTransaction().commit();
But then, the relationship isn't persisted to the DB (the row created for entity A isn't referencing the row created for entity B). Why is it so? I'd excpect it to work.
Also, if I remove the "mappedBy" property from the @OneToMany annotation it will work. Again - why is it so? and what are the possible effects for removing the "mappedBy" property?
