在Spring Data JPA Repository中使用EntityGraph进行过滤

Question

我有一个Listing表至极有一与多的关系ListingAttachment 。 现在在整个应用程序中，每个表/实体都有deleteFlag ，每个存储库只能使用deleteFlag 0获取数据。所以基本上，我们不会删除任何仅将deleteFlag标记为1的数据。

以下是我的实体结构：

Listing.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。

对于例如，在我的情况，我应该取Listing与deleteFlag 0及其所有附件（ListingAttachments），这反过来也必须有deleteFlag 0。使用EntityGraph如上面的资料库，它提取不管所有附件deleteFlag 。 有什么办法可以根据deleteFlag过滤附件吗？

Answer 1

EntityGraph定义了实体的哪些属性或（子）图应该被提取（急切或懒惰），而不必在实体本身上定义它们。

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

使用EntityGraph，您可以为每个查询定义属性和（子）图。

EntityGraph不用于过滤元素。

如果您要查找的Listings为删除未标明（ delete flag = 0 ），并且至少有一个ListingAttachment没有被标记为删除，你可以通过使用一个做到这一点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);

}

你需要加入ListingAttachments ，因为你不能直接取消引用deleteFlag使用的JPA查询listingAttachments收藏。

上面的示例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。

如果要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")