java JPA继承父级未随子级一起删除

Question

你能帮我删除继承记录吗。我正在为对象使用实体管理器，当我调用em.remove（childInstance）时，将只删除子对象，而父对象保持未删除状态。你能看出我做错了什么吗

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 我忘了写其他实体指的是子对象，子对象指的是它自己

编辑：2 我试着在一对多中添加以下内容：

cascade = CascadeType.ALL, orphanRemoval = true

它会给我这个错误

org.postgresql.util.PSQLException: ERROR: update or delete on table "parent" violates foreign key constraint "xxxxxxxxxxxxxxxxxxxxxxx" on table "child"

我在数据库中查看该约束是什么，它指的是该脚本：

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

删除父项可能会失败，因为该父项还有其他子项。通常，为了删除某个孩子的父母，在这种情况下，您还需要删除该孩子的所有兄弟姐妹

我对你的设计有点困惑，如果你真的想让一些父母和他们的孩子都失去兄弟姐妹，你应该这样做

• 使父母/子女之间的所有相关关系具有双向性
• 将父项删除也级联到子项

例如，在child中：

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

在父母身上

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

在你的案例中在儿童中

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

应该改成

// 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<>();