Advice를 이용한 예외 처리

- IdAlreadyExistException

public class IdAlreadyExistingException extends RuntimeException {
    public IdAlreadyExistingException(String userId){
        super("user id \""+userId+"\" is already exist");
    }
}

- UserExceptionAdvice

@ControllerAdvice
public class UsersExceptionAdvice {
    @ResponseBody
    @ExceptionHandler(IdAlreadyExistingException.class)
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    String idAlreadyExistingHandler(IdAlreadyExistingException ex){
        return ex.getMessage();
    }
}