java - 在 Spring Data JPA 存储库中使用 EntityGraph 进行过滤

Question

我有一个与 ListingAttachment 具有一对多关系的 Listing 表。现在在整个应用程序中，每个表/实体都有 deleteFlag 并且每个存储库应该仅使用 deleteFlag 0 来获取数据。所以基本上，我们不会删除任何数据，只是将 deleteFlag 标记为 1。

以下是我的实体结构:

列表.java

@Entity
public class Listing {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    String title;

    String description;

    @OneToMany(mappedBy = "listing", cascade={CascadeType.ALL})
    private Set<ListingAttachment> listingAttachments;

    private int deleteFlag; 

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public int getDeleteFlag() {
        return deleteFlag;
    }

    public void setDeleteFlag(int deleteFlag) {
        this.deleteFlag = deleteFlag;
    }

    public Set<ListingAttachment> getListingAttachments() {
        return listingAttachments;
    }

    public void setListingAttachments(Set<ListingAttachment> listingAttachments) {
        this.listingAttachments = listingAttachments;
    }

    public ListingAttachment addListingAttachment(ListingAttachment listingAttachment) {
        getListingAttachments().add(listingAttachment);
        listingAttachment.setListing(this);
        return listingAttachment;
    }

    public ListingAttachment removeListingAttachment(ListingAttachment listingAttachment) {
        getListingAttachments().remove(listingAttachment);
        listingAttachment.setListing(null);
        return listingAttachment;
    }
}

ListingAttachment.java

@Entity
public class ListingAttachment {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    String fileName;

    @ManyToOne
    @JoinColumn(name = "LISTING_ID")    
    private Listing listing;

    private int deleteFlag;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getFileName() {
        return fileName;
    }

    public void setFileName(String fileName) {
        this.fileName = fileName;
    }

    public Listing getListing() {
        return listing;
    }

    public void setListing(Listing listing) {
        this.listing = listing;
    }

    public int getDeleteFlag() {
        return deleteFlag;
    }

    public void setDeleteFlag(int deleteFlag) {
        this.deleteFlag = deleteFlag;
    }


}

ListingRepository.java

public interface ListingRepository extends JpaRepository<Listing, Long> {

        @EntityGraph(attributePaths = { "listingAttachments" }) 
        @Query("SELECT l FROM Listing l WHERE l.id = (:id) and deleteFlag = 0")
        public ListingfindOneWithImagesAndAttachments(@Param("id") Long id);

}

使用EntityGraph我们可以轻松获取 OneToMany 实体。但问题是如何在 Many 相关实体上过滤或应用条件。

例如，在我的例子中，我应该使用 deleteFlag 0 及其所有附件 (ListingAttachments) 获取 Listing，而 deleteFlag 也必须具有 deleteFlag 0。使用如上面存储库中所示的 EntityGraph，它会获取所有附件，而不管 deleteFlag。有什么方法可以根据 deleteFlag 过滤附件吗？

Answer 1

EntityGraph 定义应获取(急切或惰性)实体的哪些属性或(子)图，而不必在实体本身上定义它们。

在 JPA 2.0(没有 EntityGraph)中，您必须在实体处定义是否要使用 FetchType.LAZY(默认)或 FetchType.EAGER 来加载关系，并且始终使用此模式。

使用 EntityGraph，您可以定义每个查询的属性和(子)图。

EntityGraph不用于过滤元素。

如果您想要查找未标记为已删除 (delete flag = 0) 且至少有一个 ListingAttachment 未标记为已删除的 Listings，您可以使用 FETCH JOIN

public interface ListingRepository extends JpaRepository<Listing, Long> {

    @EntityGraph(attributePaths = { "listingAttachments" }) 
    @Query("SELECT l FROM Listing l JOIN l.listingAttachments a 
        WHERE l.id = (:id) and l.deleteFlag = 0 and a.deleteFlag = 0")
    public Listing findOneWithImagesAndAttachments(@Param("id") Long id);

}

您需要加入 ListingAttachments，因为您无法使用 listingAttachments 集合直接取消引用 JPA 查询中的 deleteFlag。

以上示例会返回所有未标记为已删除的列表，并且至少有一个未标记为已删除的 ListingAttachment。

如果您想返回未标记为已删除但可能没有 ListingAttachments 的列表，则必须将其更改为 LEFT OUTER JOIN

@Query("SELECT l FROM Listing l 
   LEFT OUTER JOIN  l.listingAttachments a 
   WHERE l.id = (:id) and l.deleteFlag = 0 and a.deleteFlag = 0")