Using Entity entity = hibernateTemplate.get(Entity.class, id);
when I hit a entity.getChild()
which is a OneToOne relation, every other OneToOne relations are loaded as well. I use hibernate 5.4.1-Final.
I use bytecode enhancement as below :
<configuration>
<failOnError>true</failOnError>
<enableLazyInitialization>true</enableLazyInitialization>
<enableDirtyTracking>false</enableDirtyTracking>
<enableAssociationManagement>true</enableAssociationManagement>
</configuration>
A.java
@Entity
@Table(name = "A")
public class A {
@Id
@Column(name = "ID_A")
private String id;
@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "ID_A")
@LazyToOne(LazyToOneOption.NO_PROXY)
private B b;
@OneToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "ID_A")
@LazyToOne(LazyToOneOption.NO_PROXY)
private C c;
...
getters/setters
...
B.java
@Entity
@Table(name = "B")
public class B {
@Id
@Column(name = "ID_A")
private String id;
}
C.java
@Entity
@Table(name = "C")
public class C {
@Id
@Column(name = "ID_A")
private String id;
}
So when I do
A a = hibernateTemplate.get(A.class, "100");
// triggers an Hibernate query only on A entity. The B and C aren't fetched => OK
// Hibernate: select a0_.ID_A as ID_A_27_0_ from A a0_ where a0_.ID_A=?
a.getB(); // ERROR : triggers two queries : one on C and one on B
// Hibernate: select c0_.ID_A as ID_A _26_0_ from C c0_ where c0_.ID_A =?
// Hibernate: select b0_.ID_A as ID_A _13_0_ from B b0_ where b0_.ID_A =?
Even if I fetch the B
in an HQLQuery
, I still have a query to C
:
Query<A> queryA = hibernateTemplate.createHQLQuery("from A a join fetch a.b where a.id=:id", A.class);
queryA.setParameter("id", "100");
A a = queryA.uniqueResult(); // triggers an inner join
// Hibernate: select a0_.as ID_A1_27_0_, b1_.ID_A as ID_A1_13_1_ from A a0_ inner join B b1_ on a0_.ID_A=b1_.ID_A where a0_.ID_A=?
a.getB(); // KO -> triggers a query to select C !
// Hibernate: select c0_.ID_A as ID_A1_26_0_ from C c0_ where c0_.ID_A=?
I've tried to do a double mapping (OneToOne with mappedBy specified) without success. The PK of B and C are the same as A.
I expect the a.getB();
not to trigger the fetch of C. Is this a hibernate bug ? I can't find anything regarding this behaviour in their documentation.
Is my mapping correct ?
It seems that it works as designed :) b and c belong to the same default "LazyGroup". If any of b or c needs to be loaded, the whole group will.
Quote from the bytecode enhancer documentation :
Lazy attributes can be designated to be loaded together and this is called a "lazy group". By default, all singular attributes are part of a single group, meaning that when one lazy singular attribute is accessed all lazy singular attributes are loaded. Lazy plural attributes, by default, are each a lazy group by themselves. This behavior is explicitly controllable through the @org.hibernate.annotations.LazyGroup annotation.
Just add the @LazyGroup("b")
on the b field, and @LazyGroup("c")
on c and it should work as expected : b will be loaded only on getB()
, anc c on getC()
.