@RestController
public class UserRestController {

    @Autowired
    UserService userService;
    @PostMapping(value = "/users")
    public List<UserEntity> users() {
        return userService.getAll();
    }

    @PostMapping(value = "/user/add", consumes = "application/json", produces = "application/json")
    public Result userAdd(Result result, @RequestBody UserEntity user) {
        userService.save(user);
        return result.set(true, "User successfully added!").add("user", user);
    }

}

public class Result {

    private boolean status = false;
    private String message = "";

    private Map<String, Object> data = new HashMap<>();

    public Result() { }

    public Result(boolean status, String message) {
        this.status = status;
        this.message = message;
    }

    public void init() { }

    public boolean isStatus() {
        return status;
    }

    public String getMessage() {
        return message;
    }

    public Result set(boolean status, String message) {
        this.status = status;
        this.message = message;

        return this;

    }

    public Result add(String key, Object object) {
        data.put(key, object);
        return this;
    }

}