JpaRepository - 内部连接 - 后续选择

Question

当我尝试获取 ServiceCup 列表及其 ServiceLanguage 时遇到问题。当我尝试在我的服务层中操作 ServiceCup 列表时，hibernate 正在执行第二个查询并再次使用所有 ServiceLanguage 填充我的 ServiceCup。

ServiceCup x ServiceLanguage x LanguageCup

服务杯:

@Data
@Entity
@Table(name = "csm_service")
public class ServiceCup extends BaseEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    private String context;

    // bi-directional many-to-one association to CsmServiceLanguage
    @OneToMany(mappedBy = "service")
    private List<ServiceLanguage> serviceLanguages;

}

服务语言：

@Data
@Entity
@Table(name = "csm_service_language")
public class ServiceLanguage extends BaseEntity implements Serializable {
    private static final long serialVersionUID = 1L;

    @Column(name = "translated_name")
    private String translatedName;

    // bi-directional many-to-one association to CsmLanguage
    @ManyToOne
    @JoinColumn(name = "csm_language_id_fk")
    private LanguageCup language;

    // bi-directional many-to-one association to CsmService
    @ManyToOne
    @JoinColumn(name = "csm_service_id_fk")
    private ServiceCup service;

}

JpaRepository:

    @Query(value = "select s, sl from ServiceCup s \n" + "INNER JOIN FETCH ServiceLanguage sl on s.id = sl.service \n"
            + "where sl.language.id = :languageId")
    List<ServiceCup> findAllServicesByLanguageId(@Param("languageId") String languageId);

存储层查询：

select *all_fields* from csm_service servicecup0_ inner join csm_service_language servicelan1_ on (servicecup0_.id=servicelan1_.csm_service_id_fk) where servicelan1_.csm_language_id_fk=?

但是在服务层执行了很多查询，把ServiceCup的所有关系都带过来了。我想要填充 ServiceCup 对象，但只填充查询中的结果。

如何获取只有查询结果的ServiceCup对象？

PS：在我的服务层方法中，我有 @Transactional(readOnly = true) 但是如果我删除我无法获得与 ServiceCup 相关的对象.

Answer 1

我需要使用投影而不是实体来只执行一次查询。

ServiceCupProj

public interface ServiceCupProj {

    public Long getId();

    public String getDescription();

    public String getInternalname();
......

存储库

@Repository
public interface CupServiceRepository extends JpaRepository<ServiceCup, Long> {

@Query(value = "select servicecup0_.id as id, servicelan1_.translated_description as description, servicelan1_.translated_name as internalname \n"
            + "from csm_service servicecup0_ inner join csm_service_language servicelan1_ on (servicecup0_.id=servicelan1_.csm_service_id_fk) \n"
            + "where servicelan1_.csm_language_id_fk = :languageId ", nativeQuery = true)
    List<ServiceCupProj> findAllServicesByLanguageId(@Param("languageId") String languageId);
......

并且在服务层中，我将这个 ServiceCupProj 转换为我需要的实体。

JpaRepository - 内部连接 - 后续选择

JpaRepository - Inner Join - Subsequent selects

hibernate-mapping

spring-data-jpa

spring-boot

JpaRepository - 内部连接 ​​- 后续选择

JpaRepository - Inner Join - Subsequent selects

hibernate-mapping

spring-data-jpa

spring-boot

JpaRepository - 内部连接 - 后续选择