在所有嵌套实体中选择几个：spring JPA

Question

我有一个像下面这样的场景。

假设EntityA有三个嵌套实体EntityB、EntityC、EntityD。并且所有EntityB、EntityC、EntityD都有几个嵌套的实体。

但是在选择entitya时，它选择的是整个嵌套实体树。而我想取一个特定的分支。假设只提取实体A、EntityB和EntityB的所有子实体，留下EntityC和EntityD，那么我不确定如何做到这一点。随着spring，jpa将所有嵌套对象带回给我。

我正在使用下面的集合映射。

 @Entity
 @Table(name = "customer_party_mapping")
 @Data
 public class CustomerPartyMappingEntity {
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Integer id;
    
    @Column(name = "customer_id")
    private Integer custmerId;
    
    @Column(name = "orgtype_id")
    private Integer orgTypeId;
    
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL )
    @JoinColumn(name = "customer_party_mapping_id")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<CustomerPartyBookingLocationEntity> customerPartyBookingLocation=new ArrayList<CustomerPartyBookingLocationEntity>();
    
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL )
    @JoinColumn(name = "customer_party_mapping_id")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<CustomerPartyFieldMappingEntity> customerPartyFieldMappingEntity=new ArrayList<CustomerPartyFieldMappingEntity>();

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL )
    @JoinColumn(name = "customer_party_mapping_id",referencedColumnName="id")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<CustomerPartyOtherDocumentEntity> otherDocumentsList=new 
    ArrayList<>();
    
    @OneToOne( cascade={ CascadeType.PERSIST, CascadeType.MERGE })
    @JoinColumn(name = "customer_name_screening_id", referencedColumnName="id") 
    private CustomerNameScreeningEntity customerNameScreeningEntity;
        
    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL )
    @JoinColumn(name = "customer_party_mapping_id")
    @Fetch(value = FetchMode.SUBSELECT)
    private List<CustomerDocInfoTrackingEntity> customerDocInfoTrackingList=new 
    ArrayList<CustomerDocInfoTrackingEntity>();
}

我打电话给你

List<CustomerPartyMappingEntity> customerPartyMappingEntityList = customerPartyMappingRepository.findByCustmerId(customerid);

它获取所有嵌套映射的实体列表，而我只需要CustomerPartyMappingEntity和它的CustomerPartyFieldMappingEntity嵌套对象列表。

任何帮助都将不胜感激。

Answer 1

首先对嵌套实体使用fetchType.lazy。然后可以使用@entitygraph按名称提取嵌套实体，以及在存储库中使用它们的名称和.提取嵌套实体。用于在attributePaths中指定嵌套属性，如

@EntityGraph(attributePaths = {"customerPartyBookingLocation"})

和CustomerPartyBookingLocation的嵌套属性类似

@EntityGraph(attributePaths = {"customerPartyFieldMappingEntity.subField"})

示例：

@EntityGraph(attributePaths = {"customerPartyBookingLocation", "customerPartyFieldMappingEntity.subField"})
List<CustomerPartyMappingEntity> findByCustmerId(Integer customerid);

注意：不能将@EntityGraph与@Query批注一起使用