Spring MVC + HIbernate ManyToMany映射，删除级联自联接

Question

I have two tables

Users

Id | Name

1 | User 1

2 | User 2

User_Helper

user_id | helper_id

1 | 2

The user_id & helper_id are referenced id from users table.

Now, when I delete the user 1, the entry is deleted from Mapping table. But when I delete 2 , i get exception saying, it has been referenced in mapping table

This is my entity code

@ManyToMany(cascade = {CascadeType.ALL})
    @JoinTable(name = "user_helper", joinColumns = {
            @JoinColumn(name = "user_id", updatable = false)}, inverseJoinColumns = {
            @JoinColumn(name = "helper_id", updatable = false)})
    private Set<Users> helpers;

What am I missing

Answer 1

When deleting helper, you must first remove it from any Users that reference it. That will clear the references to it from join table.

user.getHelpers().remove(helper);
session.delete(helper);

Answer 2

I got it working by adding one more mapping line in Users entity as

@ManyToMany(cascade = {CascadeType.ALL})
@JoinTable(name = "user_helper", joinColumns = {
            @JoinColumn(name = "helper_id", updatable = false)}, inverseJoinColumns = {
            @JoinColumn(name = "user_id", updatable = false)})
private Set<Users> users;

and before deleting, i clear the users

userEntity.getUsers().clear(); // so, if there are any users associated with helpers, it will be cleared from mapping table
userEntityDAO.delete(userEntity);