Spring boot JPA many to many with extra column insert and update issue - spring

Question

Here is my initial question.
Spring Data JPA Many to Many with extra column User and Roles
Now I have the right tables created, but can't make it work for the update.
Here is the code:
User.java
#Entity
#Table(name = "users")
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String username;
#OneToMany(mappedBy="user", cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
private List<UserRole> roles;
// getters and setters
}
Role.java
#Entity
#Table(name = "roles")
public class Role {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
// getters and setters
}
UserRole.java
#Entity
#Table(name = "users_to_role")
public class UserRole implements Serializable {
#Id
#ManyToOne
#JoinColumn(name = "user_id")
private User user;
#Id
#ManyToOne
#JoinColumn(name = "role_id")
private Role role;
private Date createdAt;
public UserRole(){}
public UserRole(User user, Role role, Date date) {
this.user = user;
this.role = role;
this.createdAt = date;
}
// getters and setters
}
Controller
#RestController
public class APIController {
#Autowired
RoleRepository roleRepository;
#Autowired
UserRepository userRepository;
#ResponseBody
#RequestMapping(value = "create", method = RequestMethod.GET)
public String create(){
//Insert test - WORKING BUT NOT SURE IF ITS RIGHT WAY
List<UserRole> userRoles = new ArrayList<>();
Role role = roleRepository.getOne((long) 1);
//Create user
User user = new User();
user.setUsername("test");
//Create userRole
userRoles.add(new UserRole(user, role, new Date()));
user.setRoles(userRoles);
userRepository.save(user);
return "created";
}
#ResponseBody
#RequestMapping(value = "edit", method = RequestMethod.GET)
public String edit(){
//Edit test - NOT working
List<UserRole> userRoles = new ArrayList<>();
Role role = roleRepository.getOne((long) 2);
//get user from db
User user = userRepository.getOne((long) 1);
//Create userRole
userRoles.add(new UserRole(user, role, new Date()));
// WAS FIRST ATTEMPT using user.setRoles(userRoles); but got error and use
//https://stackoverflow.com/questions/9430640/a-collection-with-cascade-all-delete-orphan-was-no-longer-referenced-by-the-ow
//user.setRoles(userRoles);
user.getRoles().clear();
user.getRoles().addAll(userRoles);
userRepository.save(user);
return "done";
}
}
I am getting this error:
com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'user_id' cannot be null