JPA: Try to remove an entity from a bidirectional ManyToMany relation

Question

I try to remove an entity from a ManyToMany-Relation, but after saving the parent-Entity by my repository nothing is happen.

UserRepository:

public interface UserRepository extends EntityGraphJpaRepository<User, Long> {

    User findByEmailIgnoreCase(String email);

    Page<User> findBy(Pageable pageable);

    User findByEmail(String name, com.cosium.spring.data.jpa.entity.graph.domain.EntityGraph entityGraph);
}

AbstractEntity

@MappedSuperclass
public abstract class AbstractEntity implements Serializable {

    private static final long serialVersionUID = -2523912452050488728L;

    @Id
    @GeneratedValue
    private Long id;

    @Version
    private int version;

    public Long getId() {
        return id;
    }

    public int getVersion() {
        return version;
    }

    @Override
    public int hashCode() {
        if (id == null) {
            return super.hashCode();
        }

        return 31 + id.hashCode();
    }

    @Override
    public boolean equals(Object other) {
        if (id == null) {
            // New entities are only equal if the instance if the same
            return super.equals(other);
        }

        if (this == other) {
            return true;
        }
        if (!(other instanceof AbstractEntity)) {
            return false;
        }

        boolean test = id.equals(((AbstractEntity) other).id);
        return id.equals(((AbstractEntity) other).id);
    }

}

User-Entity

@NamedEntityGraphs(value = {
        @NamedEntityGraph(name = "User.roles.groups", attributeNodes = {
            @NamedAttributeNode("roles"),
            @NamedAttributeNode("groups")
        })
    })
@Entity(name="userInfo")
public class User extends AbstractEntity {

    @ManyToMany(mappedBy = "users", fetch = FetchType.LAZY, cascade= {CascadeType.PERSIST, CascadeType.MERGE}) //inverse side
    private Set<Role> roles = new HashSet<Role>();

    public void addRole(Role role) {
        this.roles.add(role);
        role.getUsers().add(this);
    }

    public void removeRole(Role role) { 
        this.roles.remove(role);
        role.getUsers().remove(this);
    }
//...
}

RoleEntity:

public class Role extends AbstractEntity {
    @ManyToMany(fetch = FetchType.LAZY, cascade= {CascadeType.PERSIST,CascadeType.MERGE}) //owning side
    @JoinTable(
      name = "role_user", 
      joinColumns = @JoinColumn(name = "role_id", referencedColumnName = "id"), 
      inverseJoinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"))
    private Set<User> users = new HashSet<User>(); 

UserService:

@Service
public class UserService implements CrudEntityServiceInterface{

    private UserRepository userRepository;

    @Autowired
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

public void save(User user) {
        this.userRepository.saveAndFlush(user);
    }


    public User updateRolesForUser(User user,Set<Role> roleItems,RoleService roleService) {

        Set<Role> rolesToRemove = new HashSet<Role>();

        for(Role oldRole: user.getRoles()) {
            //remove roles which are deselected
            if(!roleItems.contains(oldRole)) {
                Optional<Role> oldRoleLoaded = (roleService.getRepository()).findById(oldRole.getId(),EntityGraphs.named("Role.users.groups"));
                rolesToRemove.add(oldRoleLoaded.get()); 
            }
        }

        rolesToRemove.forEach(x -> user.removeRole(x));

        //added selected roles
        roleItems.forEach(x ->  {
            Optional<Role> xLoaded = (roleService.getRepository()).findById(x.getId(),EntityGraphs.named("Role.users.groups"));
            user.addRole(xLoaded.get());
        } );

        return user;


    }
//...
}

And in my Controller I call something like

user = userService.updateRolesForUser(user,roles,roleService);
userService.save(user);

I have to use the entityGraph since I don't want to use Fetch.Eager.

Have you any clue why I can't remove an role from the user? I also tried Cascade.Remove - but this does not fix the problem and is bad practice, I guess.

EDIT: When I call

rolesToRemove.forEach(x -> {user.removeRole(x); roleService.save(x);}); 

the entity I want to remove from the relation is removed. But I thought everything on the user is updated by calling save on the userRepository by CascadeType.Persist? Why I have additionaly call the save for role?

Answer 1

Old question, but Role controls the ManyToMany relationship. If you want changes persisted to the relationship, it is the role object that must be updated, not the user side.