Question

你可以帮助我删除继承记录。我正在使用实体管理器作为对象，当我调用em.remove（childInstance）时，仅删除子节点，并且父节点保持未删除状态。你能说出我做错了吗？

一般表格：

@MappedSuperclass
public abstract class General {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID", columnDefinition = "serial")
    private Long id;

    // some other columns, getters and setters
}

父表：

@Entity
@Table(name = "PARENT_TABLE")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Parent extends General {

    // some columns and getters and setters
}

儿童班：

@Entity
@Table(name = "CHILD_TABLE")
@OnDelete(action = OnDeleteAction.CASCADE)
public class Child extends Parent {

@ManyToOne(fetch = FetchType.LAZY)
@OnDelete(action = OnDeleteAction.CASCADE)
@JoinColumn(name = "main_child",
        nullable = true,
        columnDefinition = "integer default 0")
private Child mainChild;

@OnDelete(action = OnDeleteAction.CASCADE)
@OneToMany(fetch = FetchType.LAZY, mappedBy = "child")
private Set<MyObjectA> objects = new HashSet<>();

    @OnDelete(action = OnDeleteAction.CASCADE)
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "id")
    private Set<Child> subChildren = new HashSet<>();

    // some columns and getters and setters
}

MyObjectA类：

@Entity
@Table(name = "object_a")
public class MyObjectA extends General {

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "child_id", nullable = false)
    private Child child;
}

编辑：1 我忘了写其他实体引用子对象，而子对象引用它自己。

编辑：2 我尝试添加到One To Many：

cascade = CascadeType.ALL, orphanRemoval = true

并且它返回了我的错误

org.postgresql.util.PSQLException：错误：在表上更新或删除＆＃34;父＆＃34;违反外键约束＆＃34; xxxxxxxxxxxxxxxxxxxxxxx＆＃34;在桌子上＆＃34;孩子＆＃34;

我在数据库中查看该约束是什么，它引用该脚本：

ALTER TABLE public.child
  ADD CONSTRAINT xxxxxxxxxxxxxxxxxxxxxxx FOREIGN KEY (id)
      REFERENCES public.parent (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION; -- here should be ON DELETE CASCADE

Answer 1

删除父级可能会失败，因为该父级还有其他子级。一般来说，为了删除某个孩子的父母，你需要删除那个孩子的所有兄弟姐妹。

我对你的设计感到有点困惑 - 如果你真的打算将所有兄弟姐妹带给他们的孩子，你应该

在父/子双向
将父级删除也级联到子级

例如，在孩子的事情中：

@ManyToOne(cascade=CascadeType.REMOVE)
private Parent parent;

并在父母

中

@OneToMany(cascade=CascadeType.REMOVE, mappedBy="parent")
private Collection<Child> children;

在你的情况中的儿童

@OneToMany(fetch = FetchType.LAZY, mappedBy = "id")
private Set<Child> subChildren = new HashSet<>();

应改为

// maps Child to itself bi-dir, note mappedBy changed form "id"
@OneToMany(fetch = FetchType.LAZY, mappedBy = "mainChild", 
              cascade=CascadeType.REMOVE) 
private Set<Child> subChildren = new HashSet<>();

JPA继承 - 不会删除子级

1 个答案: