Hibernate @OnDelete级联同一表

Question

我试图创建一个表，捕获父子关系，如树。我想只保留两列来捕获这个结构"id"one_answers"parent"。我希望数据库能够在删除一行时级联删除所有子行。下面是我创建的Hibernate实体，我添加了注释@OnDelete(action = OnDeleteAction.CASCADE)，但是，当Hibernate创建表时，ON DELETE CASCADE没有添加到表中。

这是一个bug吗?还是我错过了什么或者不理解什么?

@Entity
public class Tree {
    @Id
    @Column(name = "id", nullable = false)
    private Long id;
    @OneToMany(fetch = FetchType.EAGER)
    @JoinColumn(name = "parent", nullable = true)
    private List<Tree> children;
    @ManyToOne
    @OnDelete(action = OnDeleteAction.CASCADE)
    @JoinColumn(name = "parent", nullable = false)
    private Tree parent;
    public Tree(Long id) {
        this.id = id;
    }
    public Tree() {
    }
    public Long getId() {
        return id;
    }
    protected void setId(Long id) {
        this.id = id;
    }
    public List<Tree> getChildren() {
        return children;
    }
    public void setChildren(List<Tree> children) {
        this.children = children;
    }
    public Tree getParent() {
        return parent;
    }
    public void setParent(Tree parent) {
        this.parent = parent;
    }
}

Answer 1

@OnDelete应在@OneToMany侧使用:

@OneToMany(fetch = FetchType.EAGER, mappedBy = "parent")
@OnDelete(action = OnDeleteAction.CASCADE) 
private List<Tree> children; 

你还错过了mappedBy -它在双向关系中是必需的