Spring Data JPA从具有查询的实体获取投影

Question

In my application I have a Hero Entity. I also want to be able to return a list of each hero id and name. I got it working with this:

@Repository
public interface HeroEntityRepository extends JpaRepository<HeroEntity, Long> {
@Query("select s.id, s.name from HEROES s")
List<Object> getIdAndName();
}

// in controller:
@GetMapping
public List<Object> getHeroNames() {
    return heroEntityRepository.getIdAndName();
}

I tried the suggestion in another post to substitute the Object with a Interface, but then I receive a list of null values ( [{"name":null,"id":null},{"name":null,"id":null}, // etc ). The custom Interface:

public interface HeroNameAndId {

    Long getId();
    String getName();
}

When making a Entity with only id and name values I received a 'ConverterNotFoundException'. Im not sure what the right way to go is. I have it working with Object but this doesn't seem very clean.

My HeroEntity:

@Getter
@Builder
@Entity(name = "HEROES")
@AllArgsConstructor
public class HeroEntity extends HasId<Long> {

    private String name;
    private String shortName;
    private String attributeId;

    @ElementCollection private List<String> translations;

    @OneToOne(cascade = CascadeType.ALL) private HeroIconEntity icon;

    private String role;
    private String type;
    private String releaseDate;

    @OneToMany(cascade = CascadeType.ALL) private List<AbilityEntity> abilities;

    @OneToMany(cascade = CascadeType.ALL) private List<TalentEntity> talents;
}

@MappedSuperclass
public abstract class HasId<T> {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Setter
    @Getter
    private T id;
}

Answer 1

You must use field aliases to make @Query with projection work:

@Query("select s.id as id, s.name as name from HEROES s")

The aliases must match the names in your HeroNameAndId interface.