在Spring Data JPA Repository中使用EntityGraph進行過濾

Question

我有一個Listing表至極有一與多的關系ListingAttachment 。 現在在整個應用程序中，每個表/實體都有deleteFlag ，每個存儲庫只能使用deleteFlag 0獲取數據。所以基本上，我們不會刪除任何僅將deleteFlag標記為1的數據。

以下是我的實體結構：

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，我們可以輕松獲取OneToMany實體。 但問題是如何在Many相關實體上過濾或應用條件。

對於例如，在我的情況，我應該取Listing與deleteFlag 0及其所有附件（ListingAttachments），這反過來也必須有deleteFlag 0。使用EntityGraph如上面的資料庫，它提取不管所有附件deleteFlag 。 有什么辦法可以根據deleteFlag過濾附件嗎？

Answer 1

EntityGraph定義了實體的哪些屬性或（子）圖應該被提取（急切或懶惰），而不必在實體本身上定義它們。

在JPA 2.0（沒有EntityGraph）中，您必須在實體中定義是否要使用FetchType.LAZY （默認值）或FetchType.EAGER來加載關系，並始終使用此模式。

使用EntityGraph，您可以為每個查詢定義屬性和（子）圖。

EntityGraph不用於過濾元素。

如果您要查找的Listings為刪除未標明（ delete flag = 0 ），並且至少有一個ListingAttachment沒有被標記為刪除，你可以通過使用一個做到這一點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 ，因為你不能直接取消引用deleteFlag使用的JPA查詢listingAttachments收藏。

上面的示例返回所有未標記為已刪除的列表，並且至少有一個未標記為已刪除的ListingAttachment。

如果要返回未標記為已刪除但可能沒有ListingAttachments的列表，則必須將其更改為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")