How to return http response in Spring - spring

Question

I want to replace the http exception with a response, that is, I use responseentity I want to return for example 409 if the user is not found by name, and 509 if not found by mail, can I determine the error number and its description in responseEntity? If so, can give an example?
#RequestMapping(value = "/change", method = RequestMethod.POST)
public void change(#RequestBody User user) throws Exception {
UserDetails userDetails = (UserDetails) SecurityContextHolder.getContext().getAuthentication().getPrincipal();
User userByUsername = userService.findUserByUsername(userDetails.getUsername());
if (userByUsername == null) {
throw new Exception("Пользователь не найден");
//TODO: return ResponseEntity code 409 if userByusername not found
}
user.setId(userByUsername.getId());
if (user.getPassword() == null) {
user.setPassword(userByUsername.getPassword());
}
user.setRoles(userByUsername.getRoles());
userService.save(user);
}

Answer 1

public ResponseEntity<Object> change(#RequestBody User user) throws Exception {
UserDetails userDetails = (UserDetails) SecurityContextHolder.getContext().getAuthentication().getPrincipal();
ErrorResponse errorResponse = new ErrorResponse(HttpStatus.CONFLICT, "not found user by username",409);
User userByUsername = userService.findUserByUsername(userDetails.getUsername());
if (userByUsername == null) {
return new ResponseEntity<>(errorResponse, new HttpHeaders(), errorResponse.getStatus());
}
user.setId(userByUsername.getId());
if (user.getPassword() == null) {
user.setPassword(userByUsername.getPassword());
}
user.setRoles(userByUsername.getRoles());
userService.save(user);
return null;
}
public class ErrorResponse {
private HttpStatus status;
private String message;
private Integer errors;
public ErrorResponse(HttpStatus status, String message, Integer errors) {
super();
this.status = status;
this.message = message;
this.errors = errors;
}
public HttpStatus getStatus() {
return status;
}
}