带有CascadeType.ALL的ManyToMany导致传递的Detched实体持久化

Question

I have a many to many relationship with Users and Roles. The user is the owner of the relationship and has CascadeType.ALL. When i'm seeding the database, I first create users, create roles and assign the roles to the users. Afterwards I save all users with the repository.

I would imagine since I'm saving users, the roles also get saved in the database because of the cascadetype but the error I'm getting is the one mentioned in the title.

User:

@Entity
public class User {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private Long id;

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(
        name = "users_roles",
        joinColumns = @JoinColumn(
                name = "user_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(
                name = "role_id", referencedColumnName = "id"))
private List<Role> roles;   

Role:

@Entity
public class Role {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;

@JsonIgnore
@ManyToMany
private List<User> users;

The code used for seeding the database:

        User user1= new User();
        User user2= new User();

        Role role1 = new Role();
        Role role2 = new Role();

        user1.addRole(role1);
        user2.addRole(role1);
        user2.addRole(role2);

        role1.addUser(user1);
        role1.addUser(user2);
        role2.addUser(user2);

        userRepository.save(user1);
        userRepository.save(user2);

Any help is appreciated!

EDIT: I found that the problem only occurs when I add multiple roles to the same user and have updated the code.

Answer 1

This example works for me, no exception there. Please share more info: hibernate version, database and the actual code that you're running.

Answer 2

Your Cascading here is wrong. Having Cascade.ALL on a many to many collection does not make sense exactly because you can have Roles that are shared across users.

What hibernate is trying to tell you is that you already have a role that has associated ID and the you are trying to invoke persist on the same role.

You need to figure out how to manage your roles. You have two options:

1. Remove the cascading.
2. Reasign the managed roles to your user2, so that you are not using the detached one.

Personaly I would remove the Cascade.ALL. IMO it is wrong.