Allow sort on JPA discriminator column or entity type [DATAJPA-1224]

[spring-projects-issues]

Brice Roncace opened DATAJPA-1224 and commented

Using JPA 2's type operator, JPQL queries can filter or sort by entity type. However this is not possible using Spring Data JPA's Sort.

For example, given a simple class inheritance hierarchy:

@Entity
@Inheritance(strategy = InheritanceType.JOINED)
@DiscriminatorColumn(name = "type")
public abstract class Animal implements Serializable {...}

@Entity
public class Cat extends Animal {...}

@Entity
public class Bird extends Animal {...}

A full listing of animals sorted by type can be retrieved from the JpaRepository thusly:

public interface AnimalRepository extends JpaRepository<Animal,Long> {
  @Query("from Animal a order by type(a)")
  List<Animal> findAllSortedByType();
}

However this same type of query (where only an entity sort by type is desired) is not possible using a Sort parameter to findAll:

List<Animal> animals = animalRepository.findAll(new Sort("type"));

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Affects: 1.11.8 (Ingalls SR8)

Reference URL: https://stackoverflow.com/q/43974210/225217