Define sort property for referenced field during order by in JPQL

问题

I have rest repository with 2 entities and projection:

@Entity
public class Person {
    @Id
    @GeneratedValue
    private Long id;

    String name;

    @ManyToOne
    Language language;
}

@Entity
public class Language {
    @Id
    @GeneratedValue
    private Long id;

    private String name;
}

public interface PersonRepository extends PagingAndSortingRepository<Person, Long> {
}

@Projection(name = "details", types = {Person.class})
interface PersonProjection {

    Long getId();

    String getName();

    @Value("#{target.language.name}")
    String getLanguage();
}

When I'm trying to sort it by language field

/api/persons/?projection=details&sort=language

it produce SQL that trying to sort it by language.id

select person0_.id as i... order by language1_.id asc limit ?

Is there a way to tell Spring Data, JPA to use different default property for sorting without explicitly specifying it in url?

回答1:

Spring data-rest as you configured it uses property traversal on your entity objects. In your case, for Person and Language you have a name clash on the property "name". In order to solve this issue your sort param should reference the correct property, i.e: For sorting by language name your url should be like /api/persons/?projection=details&sort=language_name For sorting by person's name your url parameter shoud look /api/persons/?projection=details&sort=person_name

回答2:

First override the findAll() method in your PersonRepository interface:

public interface PersonRepository extends PagingAndSortingRepository<Person, Long> {
    @Override
    @Query
    public Iterable<User> findAll();
}

Then add a named query to your User entity class:

@Entity
@NamedQuery(name = "User.findAll", query="select p from Person p order by p.language.name")
public class Person {
    @Id
    @GeneratedValue
    private Long id;

    String name;

    @ManyToOne
    Language language;
}

来源：https://stackoverflow.com/questions/40825366/define-sort-property-for-referenced-field-during-order-by-in-jpql