@PostMapping
public ResponseEntity<HttpStatus> saveStudent(@Valid @RequestBody StudentDto dto, BindingResult br){
    if (br.hasErrors()) {
        throw new InvalidRequestException("Wrong resource", br);
    }

    divisionService.saveStudent(dto);
    return new ResponseEntity<>(HttpStatus.CREATED);
}

if (br.hasErrors()) {
    throw new InvalidRequestException("Wrong resource", br);
}

@ControllerAdvice
public class ValidationErrorHandlingAdvice {

    /**
     * Handler for {@link MethodArgumentNotValidException}s. These are triggered by
     * Spring {@link Validator} implementations being invoked by the Spring MVC
     * controllers and returning validation errors.
     *
     *
     * @param ex The {@link MethodArgumentNotValidException} to be handled.
     *
     * @return {@link Map} keyed by field to which the error is bound and with the
     *         value of the field as a value.
     */
    @ResponseStatus(code = HttpStatus.BAD_REQUEST)
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public @ResponseBody ValidationErrors handleMethodArgumentNotValidException(MethodArgumentNotValidException ex) {
        Map<String, List<String>> errorMap = new TreeMap<>();

        BindingResult result = ex.getBindingResult();
        for (FieldError error : result.getFieldErrors()) {

            if (!errorMap.containsKey(error.getField())) {
                errorMap.put(error.getField(), new ArrayList<String>());
            }

            errorMap.get(error.getField()).add(error.getDefaultMessage());
        }

        return new ValidationErrors(errorMap);
    }


    private static class ValidationErrors {
        private Map<String, List<String>> errors;

        public ValidationErrors(Map<String, List<String>> errors) {
            this.errors = errors;
        }

        @SuppressWarnings("unused")
        public Map<String, List<String>> getErrors() {
            return errors;
        }
    }
}