CODEWITHSUNDEEP
hibernatejpapolymorphismpolymorphic-associationscriteria-api
user2389372
user2389372

Reputation: 61

JPA / Hibernate Query on polymorphic field

Given the following type hierachy:

@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
class A { }

@Entity
class B extends A {
  String b;
}

@Entity
class C extends A {
  String c;
}

@Entity
class D {
  @ManyToOne
  A a;
}

Now I would like to query all records of type D with 'a' of type C and field 'c' equals a given string parameter:

...
Root<D> root
CriteriaBuilder cb
cb.equal(root.get("a").get("c").as(String.class), "Test");
...

As foreseeable, I will get an exception telling me that attribute 'c' is unknown, as it is not defined at supertype A.

Any ideas, how to tell JPA Query that it should only join C for field 'a' at D AND add a condition to field 'c'?

Upvotes: 2

Views: 1059

Answers (1)

Nils Rommelfanger
Nils Rommelfanger

Reputation: 696

    CriteriaQuery<Tuple> q = criteriaBuilder.createTupleQuery();
    Root<D> from = q.from(D.class);
    Join<D, A> path = from.join(D_.a);
    q.multiselect(path.get(A_.id)).where(criteriaBuilder.equal(path.type(), C.class));

Upvotes: 1

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