What is the best way to return different types of ResponseEntity in Spring MVC or Spring-Boot

Question

I have written simple rest application using Spring MVC 4 (or Spring-Boot). Within the controller I have return ResponseEntity. But in some cases I want to give

Answer 1

Spring 2 introduced ResponseStatusException using this you can return String, different HTTP status code, DTO at the same time.

@PostMapping("/save")
public ResponseEntity saveUser(@RequestBody UserDto userDto) {
    if(userDto.getId() != null) {
        throw new ResponseStatusException(HttpStatus.NOT_ACCEPTABLE,"A new user cannot already have an ID");
    }
    return ResponseEntity.ok(userService.saveUser(userDto));
}