JPA 继承 - 父级不与子级一起删除

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，只删除了子项，而父项保持未删除。你能告诉我我做错了什么吗？

总表：

@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，子对象引用自己。

编辑：2 我尝试将这个添加到一对多：

cascade = CascadeType.ALL, orphanRemoval = true

它会返回那个错误

org.postgresql.util.PSQLException：错误：更新或删除表 “父”违反外键约束 “孩子”表上的“xxxxxxxxxxxxxxxxxxxxxxx”

我在数据库中查看该约束是什么，它引用了该脚本：

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。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 - 如果你真的打算让一些父母和他们的孩子一起移除所有兄弟姐妹 - 你应该

• 使父/子之间的所有相关关系都是双向的
• 使父级删除也级联到子级

例如，在孩子中是这样的：

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

在父母中

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

在您的情况中

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

应该改为

// 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<>();