CODEWITHSUNDEEP
hibernatejpajpa-2.0criteria-api
Jeroen
Jeroen

Reputation: 537

JPA criteria query, order on class

Is there a way with JPA criteria queries to order on class? Imagine the following domain objects:

abstract class Hobby { ... }
class Coding extends Hobby { ... }
class Gaming extends Hobby { ... }

Using regular QL I was able to do

from Hobby h order by h.class

But when I apply the same logic on a criteria query, the runtime exception "unknown attribute" occurs.

CriteriaQuery<Hobby> criteriaQuery = builder.createQuery(Hobby.class);
Root<Hobby> hobbyRoot = criteriaQuery.from(Hobby.class);
criteriaQuery.orderBy(builder.asc(hobbyRoot.get("class"));
List<Hobby> hobbies = entityManager.createQuery(criteriaQuery).getResultList();

JPA implementation used: Hibernate-EntityManager v3.5.5-Final

Upvotes: 8

Views: 10832

Answers (1)

Pascal Thivent
Pascal Thivent

Reputation: 570285

JPA 2.0 introduces a new TYPE expression that allow a query to restrict results based on class types.

You can use a type expression with the Criteria API using Path#type(). So you could try:

CriteriaQuery criteriaQuery = builder.createQuery(Hobby.class);
Root hobbyRoot = criteriaQuery.from(Hobby.class);
criteriaQuery.orderBy(builder.asc(hobbyRoot.type());
List hobbies = entityManager.createQuery(criteriaQuery).getResultList();

While this code compiles, I didn't test it (I'll give it a try tomorrow).

Actually, I wonder if this is legal or if the type() should be part of the select in order to order by it (maybe that's what the criteria query is supposed to generate). Need to check that.

References

  • JPA 2.0 specification
    • Section 4.6.17.4 "Entity Type Expressions"

More resources

Upvotes: 10

Related Questions