MultipleBagFetchException：不能同时获取多个包

Question

我有以下实体

注册程序

@Data
@NoArgsConstructor
@Entity
@EntityListeners(RegisteredProgramAuditListener.class)
public class RegisteredProgram extends Auditable<String> {

    @OneToMany(mappedBy = "registeredProgram", cascade = CascadeType.ALL)
    @JsonBackReference
    private List<Trainer> trainerList;

    @OneToMany(mappedBy = "registeredProgram", cascade = CascadeType.ALL)
    @JsonBackReference
    private List<Official> officialList;
}

培训师

@Data
@NoArgsConstructor
@EntityListeners(TrainerAuditListener.class)
@Entity
public class Trainer extends Auditable<String> {

    @ManyToOne
    @JoinColumn(name = "REGISTERED_PROGRAM_ID", nullable = false)
    @JsonManagedReference
    private RegisteredProgram registeredProgram;

    @Type(type = "yes_no")
    private Boolean isDeleted = false;
}

官方

@Data
@NoArgsConstructor
@EntityListeners(OfficialAuditListener.class)
@Entity
public class Official extends Auditable<String> {

    @ManyToOne
    @JoinColumn(name = "REGISTERED_PROGRAM_ID", nullable = false)
    @JsonManagedReference
    private RegisteredProgram registeredProgram;

    @Type(type = "yes_no")
    private Boolean isDeleted = false;
}

基本上，我与RegisteredProgram 有多对一关系的实体（培训师注册计划，官方注册计划）。现在我有一项服务已经达到了我的要求，通过 id 获取注册程序，我应该只包含所有 Trainer 和 Official 和 isDeleted false。请参阅以下服务：

服务

@Override
public RegisteredProgramRequestDto getRegisteredProgramDto(Long id) {
    RegisteredProgram registeredProgram = registeredProgramRepository.getOne(id);
    RegisteredProgramRequestDto registeredProgramRequestDto = programRegistrationMapper
            .registeredProgramToRequestDto(registeredProgram);
    registeredProgramRequestDto.setOfficialDtoList(
            registeredProgramRequestDto.getOfficialDtoList()
                    .stream()
                    .filter(officialDto -> !officialDto.getIsDeleted())
                    .collect(Collectors.toList())
    );
    registeredProgramRequestDto.setTrainerDtoList(
            registeredProgramRequestDto.getTrainerDtoList()
                    .stream()
                    .filter(trainerDto -> !trainerDto.getIsDeleted())
                    .collect(Collectors.toList())
    );
    return registeredProgramRequestDto;
}

现在，我尝试使用@Query 和@EntityGraph，这样我就可以只使用单个查询获得所需的输出。

存储库

@Repository
public interface RegisteredProgramRepository extends JpaRepository<RegisteredProgram, Long>, QuerydslPredicateExecutor<RegisteredProgram> {

    @Query("select rp from RegisteredProgram rp join rp.officialList rpos join rp.trainerList rpts where rp.id = :id and rpos.isDeleted = false and rpts.isDeleted = false")
    @EntityGraph(attributePaths = {"officialList", "trainerList"}, type = EntityGraph.EntityGraphType.LOAD)
    RegisteredProgram getByIdNotDeleted(@Param("id") Long id);
}

更新服务

@Override
public RegisteredProgramRequestDto getRegisteredProgramDto(Long id) {
    RegisteredProgram registeredProgram = registeredProgramRepository.getByIdNotDeleted(id);
    return programRegistrationMapper
            .registeredProgramToRequestDto(registeredProgram);
}

但是在实现之后，我遇到了以下错误：

org.hibernate.loader.MultipleBagFetchException：无法同时获取多个包：[com.tesda8.region8.program.registration.model.entities.RegisteredProgram.officialList, com.tesda8.region8.program.registration.model.entities。 RegisteredProgram.trainerList]

我已经通过 stackoverflow 搜索并遇到了this，但我仍然无法让我的查询正确执行。关于我应该如何处理这个问题的任何想法？

Answer 1

解决MultipleBagFetchException 的常规修复方法是在Set 类型上更改List 类型字段，如下所示：

...
public class RegisteredProgram extends Auditable<String> {

    @OneToMany(mappedBy = "registeredProgram", cascade = CascadeType.ALL)
    @JsonBackReference
    private Set<Trainer> trainerList = new HashSet<>();

    @OneToMany(mappedBy = "registeredProgram", cascade = CascadeType.ALL)
    @JsonBackReference
    private Set<Official> officialList = new HashSet<>();
    ...
}

更多详情见：https://thorben-janssen.com/hibernate-tips-how-to-avoid-hibernates-multiplebagfetchexception/

注意：记住equals 和hashcode 用于Set 数据结构并避免Lombok 和Hibernate 陷阱(https://thorben-janssen.com/lombok-hibernate-how-to-avoid-common-pitfalls/)。请注意“避免@Data”主题，因为我看到您正在使用该组合，该组合会产生意外行为！