How can I Return a JSON Object without Nested Objects From Other Classes?

I want to return a JSON Object with information from two different Classes. Like I want the username from the class User and the rolename from the Class Role together in one JSON Object.

My current code:

@Entity
@DynamicUpdate
public class User {
    private String username;
    private String phone;
    private String email;
    private Set<Role> role;
}

@Entity
public class Role {
    private int idRole;
    private String name;
}

@Projection(name = "CustomUser", types = {User.class})
public interface CustomUser {
    String getUsername();
    RoleTest getRole();

    interface RoleTest {
        String getName();
    }
}

@Repository
public interface UserRepository extends JpaRepository<User, Integer> {
    List<CustomUser> findAllBy();
}

@Controller
@RequestMapping
public class UserController  {
    @Autowired
    private UserRepository userRepository;
    @GetMapping
    @ResponseStatus(HttpStatus.ACCEPTED)
    public @ResponseBody List<CustomUser> getAllUsers() {
        return userRepository.findAllBy();
    }
}

What I currently get:

{ 
   "role": {
       "name": "ADMIN"
   },
   "username": "test" 
}

However, my goal is it to get something like this:

{ 
  "role": "ADMIN",
  "username": "test"
}

If you are using the Jackson library, please check @JsonUnwrapped. The documentation is here

The problem here is that @JsonUnwrapped doesn't work with the Collections. As you indicated in one of your comments if the Role need not be a set, this will solve your problem. If you have questions on why the @JsonUnwrapped doesn't work with the Collcetions, this will help to understand further.