JPA：删除时的外键约束

Question

我有以下关系

Class UserAccount{
//Other fields
@OneToMany(mappedBy = "userAccount", cascade = CascadeType.REMOVE)
private Set<Images> imagesShared;

@ManyToMany
@JoinTable(name = "USER_LIKES", joinColumns = @JoinColumn(name = "USER_NAME"),   inverseJoinColumns = @JoinColumn(name = "ID"))
private Set<Images> imagesLiked;
}

Class Images{
//other fields
@ManyToMany(mappedBy = "imagesLiked")
private Set<UserAccount> likes;
}

这些行之后我出现异常

Hibernate: delete from IMAGES where ID=?
Hibernate: delete from COMMENTS where COMMENT_ID=?
Hibernate: delete from COMMENTS where COMMENT_ID=?
Hibernate: delete from COMMENTS where COMMENT_ID=?
Hibernate: delete from COMMENTS where COMMENT_ID=?
Hibernate: delete from COMMENTS where COMMENT_ID=?
Hibernate: delete from IMAGES where ID=?

例外：

Cannot delete or update a parent row: a foreign key constraint fails (`testdb`.`USER_LIKES`, CONSTRAINT `FKC6704E28B4E3D8B` FOREIGN KEY (`ID`) REFERENCES `IMAGES` (`ID`))

据我了解，这是在JPA尝试删除imagesShared时发生的。 我尝试这样做：

for (Images image : userAccount.getImagesShared()){
            image.setLikes(null);
        }
em.remove(account);

但是同样的错误。 任何人？

更新

当我添加此行时，它工作正常。

 for (Images image : userAccount.getImagesShared()){
            image.setLikes(null);
        }
userAccount.getImagesShared().clear();
em.remove(account);

但是，JPA与我执行的删除操作之间有什么区别？

Answer 1

您的private Set<Images> imagesShared或private Set<Images> imagesLiked必须具有对您要删除的Image的引用。

您将必须遍历所有内容并删除图像参考，然后再将其删除。

编辑：

回答第二个问题。

 for (Images image : userAccount.getImagesShared()){
            image.setLikes(null);
        }
userAccount.getImagesShared().clear();
em.remove(account);

之所以有效，是因为您通过调用userAccount.getImagesShared().clear()清除了userAccount存储的图像引用userAccount.getImagesShared().clear()

以前，您只是在删除存储在该Image中的userAccount ，而不是从userAccount对象本身删除这些图像。

Answer 2

private Set<Images> imagesLiked具有对IMAGES （ ID ）的外键引用，因此，如果您要删除private Set<Images> imagesShared; 而不删除private Set<Images> imagesLiked; 。

因此，请尝试删除链接的图像

image.setImagesLinked(null);