Spring Data Repository does not delete ManyToOne Entity

Question

I'm am currently trying to use a Spring Data repository to delete some of my entities. The delete call works without any exceptions/error messages, but the entity is not deleted afterwards.

Those are my entities:

public class Board implements Serializable {

    @Id
    @GeneratedValue(generator = "uuid2")
    @GenericGenerator(name = "uuid2", strategy = "uuid2")
    @Column(columnDefinition = "BINARY(16)")
    private UUID uuid;

    @OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL, orphanRemoval = true, mappedBy = "board")
    private List<Post> posts = new ArrayList<Post>();
}

and

public class Post implements Serializable {

    @Id
    @GeneratedValue
    private long id;

    @ManyToOne(optional = false)
    @JoinColumn(name="board_uuid", updatable = false, nullable = false)
    @JsonBackReference
    private Board board;
}

The repository is as simple as it can be:

@Repository
public interface PostRepository extends CrudRepository<Post, Long> {
}

The delete call is something like

postRepository.delete(50);

Any ideas why this change doesn't reflect in the database?

Edit 1:

I found a workaround, but I still don't understand what the real problem is. It "works" if I delete the Post like this (there are a couple of exceptions because of constraint violations, but still the Post gets deleted):

post.setBoard(null);
postRepo.delete(post);

Edit 2:

When I have a look at the SQL statements executed I can see that hibernate is not even trying to delete. The only thing that happens are those two select statements:

Hibernate: select post0_.id as id1_1_0_, post0_.board_uuid as board_uu6_1_0_, post0_.content as content2_1_0_, post0_.x as x3_1_0_, post0_.y as y4_1_0_, post0_.z as z5_1_0_, board1_.uuid as uuid1_0_1_ from Post post0_ left outer join Board board1_ on post0_.board_uuid=board1_.uuid where post0_.id=?
Hibernate: select posts0_.board_uuid as board_uu6_0_0_, posts0_.id as id1_1_0_, posts0_.id as id1_1_1_, posts0_.board_uuid as board_uu6_1_1_, posts0_.content as content2_1_1_, posts0_.x as x3_1_1_, posts0_.y as y4_1_1_, posts0_.z as z5_1_1_ from Post posts0_ where posts0_.board_uuid=?

Edit 3

Turns out the cascade=CascadeType.ALL on posts seems to be the problem. Without it the delete works fine (but I am missing the cascade of changes to posts now)

Answer 1

The problem seems to be that you are using cascade=CascadeType.ALL , which also includes CascadeType.PERSIST . CascadeType.PERSIST means that the child entity is completely managed by the parent and you cannot delete it directly. In order to delete you just need to remove it from the parent.

You could just add the other CascadeTypes instead of all. eg CascadeType.REMOVE , if the only thing you would want is to remove the child if the parent is removed.

Answer 2

Building on the excellent answer from user2936091 above, I just wanted to mention a (related) workaround I stumbled upon today: if the parent entity is not fetched into the Hibernate context, you are able to delete it directly.

In my case this was achieved by setting fetch = FetchType.LAZY on the @ManyToOne relationship. I wanted this change for performance reasons anyway, and noticed that without the parent eagerly fetched Hibernate was free to delete it via the repository method call.

Answer 3

cascade=CascadeType.PERSIST is used for updating insert in both side but for delete it will restrict.

@ManyToOne(cascade=CascadeType.PERSIST, fetch = FetchType.LAZY)
//  @JoinColumn(name = "qid")
    @JoinColumn(name = "qid", referencedColumnName = "qid", foreignKey = @ForeignKey(name = "qid"), nullable = false)
    // @JsonIgnore
    @JsonBackReference
    private QueueGroup queueGroup;

Answer 4

这是因为你在 Post 类上设置了mappingBy = "board" ，这样做你就知道 Post 的主人是 Board。

Answer 5

A simple alternative:

@Repository
public interface PostRepository extends CrudRepository<Post, Long> {

@Modifying(clearAutomatically = true, flushAutomatically = true)
@Query(value = "DELETE FROM post WHERE id = ?1", nativeQuery = true)
void deleteById(long postId);

}

Answer 6

What @user2936091 said is true but it doesn't solve the problem. I also had the exact same problem like you.

The solution is to remove fetch=FetchType.EAGER from the parent class. Wen fetch type EAGER is used, the instance of board in the post object will have the

 private List<Post> posts = new ArrayList<Post>();

populated because it was eagerly loaded, which means it still has a reference to itself, like @user2936091 mentions.

My workaround to still load related properties eagerly was to create a DBService class and load the objects from there like this

@Service
public class DBService {

    BoardRepository boardRepo;

    @Transactional
    public Board getBoardProcess(Long id) {
       Board board = boardRepo.findById(id).get();
       board.getPosts().size(); // This will trigger the db query so that posts gets loaded
       // It needs to be done within a transactional so that the session is still the same to populate the fields. If it's done from outside of this method. It will not work
    }
}