JPA級聯洗掉因自定義洗掉方法而失敗

我在 spring data jpa 中遇到了自定義洗掉方法的錯誤。基本上有一個包含物品的包，洗掉包時，應該洗掉其中的所有物品。

這是物體：

@Entity
@Table(name = "bag")
public class Bag {
    @Id private Long id;
    @Column("uid") private Long uid;
    @Column("name") private String name;

    @OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Item> items;
}

@Entity
@Table(name = "item")
public class Item {
    @Id private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "bid", referencedColumnName = "id")
    private Bag bag;
}

和存盤庫：

@Repository
public interface BagRepository extends JpaRepository<Bag, Long> {
    Bag findByUidAndName(Long uid, String name);

    @Transactional
    @Modifying
    @Query(value = "DELETE FROM `bag` WHERE `uid` = :uid AND `name` = :name", nativeQuery = true)
    void deleteByUidAndName(@Param("uid") Long uid, @Param("name") String name);
}

當我打電話時bagRepository.deleteByUidAndName(uid, name)，我從休眠中得到一個與外鍵約束有關的例外。設定spring.jpa.show-sql=true顯示它不會在洗掉包之前先嘗試洗掉專案。

但是，如果我打電話Bag bag = bagRepository.findByUidAndName(uid, name)，然后bagRepository.deleteById(bag.getId())一切都很好。

我想知道自定義此洗掉方法有什么問題以及如何修復它。

uj5u.com熱心網友回復：

如果通過 bagRepository.deleteById(bag.getId())Hibernate 洗掉物體將從父物體洗掉到子物體，因為您在關系上定義了cascade = CascadeType.ALL。當我們對目標物體執行某些操作時，相同的操作將應用于關聯物體。邏輯在 Hibernate 中，不使用資料庫級聯。

    @OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Item> items;

如果bagRepository.deleteByUidAndName(uid, name)您定義了本機查詢以進行洗掉。這意味著 Hibernate 邏輯將被忽略，查詢將按原樣執行。在這種情況下，您直接使用資料庫并通過本機 SQL 洗掉記錄，您需要ON DELETE CASCADE在資料庫級別定義以具有類似的邏輯。

    @Query(value = "DELETE FROM `bag` WHERE `uid` = :uid AND `name` = :name", nativeQuery = true)
    void deleteByUidAndName(@Param("uid") Long uid, @Param("name") String name);

解決方案一、@OnDelete(action = OnDeleteAction.CASCADE)

如果您有自動生成的表，您可以將特定于 Hibernate 的注釋添加@OnDelete到關系中。在表生成期間ON DELETE CASCADE將應用外鍵約束。
關系定義：

    @OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
    @OnDelete(action = OnDeleteAction.CASCADE)
    private List<Item> items;

自動生成的約束：

    alter table item 
       add constraint FK19sn210fxmx43i8r3icevbeup 
       foreign key (bid) 
       references bag 
       on delete cascade

實施：

import org.hibernate.annotations.OnDelete;
import org.hibernate.annotations.OnDeleteAction;

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "bag")
public class Bag {
    @Id
    private Long id;
    @Column(name = "uid")
    private Long uid;
    @Column(name = "name")
    private String name;

    @OneToMany(mappedBy = "bag", cascade = CascadeType.ALL, orphanRemoval = true)
    @OnDelete(action = OnDeleteAction.CASCADE)
    private List<Item> items;
}

方案二、@JoinColumn注解帶外鍵 ON DELETE CASCADE 用for entity
指定外鍵ON DELETE CASCADEItem

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "bid", referencedColumnName = "id",
            foreignKey = @ForeignKey(
                    name="FK_ITEMS_ID",
                    foreignKeyDefinition = "FOREIGN KEY (ID) REFERENCES ITEM(BID) ON DELETE CASCADE"))
    private Bag bag;

執行：

import javax.persistence.*;

@Entity
@Table(name = "item")
public class Item {
    @Id
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "bid", referencedColumnName = "id",
            foreignKey = @ForeignKey(
                    name="FK_ITEMS_ID",
                    foreignKeyDefinition = "FOREIGN KEY (ID) REFERENCES ITEM(BID) ON DELETE CASCADE"))
    private Bag bag;
}

解決方案 3，不要使用原生查詢
在這種情況下，將應用 Hibernate 邏輯。
定義存盤庫，如：

@Repository
public interface BagRepository extends JpaRepository<Bag, Long> {
    Bag findByUidAndName(Long uid, String name);

    @Transactional
    @Modifying   
    void deleteByUidAndName(@Param("uid") Long uid, @Param("name") String name);
}

解決方案 4，手動添加 ON DELETE CASCADE 到資料庫
如果您的表不是自動生成的，您可以手動添加ON DELETE CASCADE到資料庫中。

    alter table item 
       add constraint FK_BAG_BID
       foreign key (bid) 
       references bag 
       on delete cascade

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