====== @ControllerAdvice ======
  * [[https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/web/bind/annotation/ControllerAdvice.html|@ControllerAdvice]]
  * '' @ExceptionHandler'','' @InitBinder'', ''@ModelAttribute''를 여러 컨트롤러에 걸쳐 공통으로 설정할 수 있다.

===== @ExceptionHandler =====
  * [[springframework:mvc:handlerexceptionresolver|HandlerExceptionResolver]]
  * [[springframework:problem_spring_web|Problem Spring Web]]
  * [[https://dzone.com/articles/global-exception-handling-with-controlleradvice|Global Exception Handling With @ControllerAdvice - DZone Java]]
  * ''@ControllerAdvice''에 각종 예외 처리 핸들러(''@ExceptionHandler'')를 미리 등록해 두고 component-scan을 하면 자동 에러 처리가 된다.
  * [[http://www.javabeat.net/exception-controlleradvice-spring-3-2/|Exception Handling With @ControllerAdvice in Spring 3.2]]
<code java>
package javabeat.net;

import java.io.IOException;
import java.sql.SQLException;

import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@ControllerAdvice
public class ControllerAdviceTest {
    @ExceptionHandler(IOException.class)
    public ModelAndView handleIOException(IOException exception){
        ModelAndView andView = new ModelAndView();
        andView.setViewName("error");
        return andView;
    }
    @ExceptionHandler(SQLException.class)
    public ModelAndView handleSQLException(SQLException exception){
        ModelAndView andView = new ModelAndView();
        andView.setViewName("error");
        return andView;
    }
    // JSON 에러 내면서 Http Status Code 변경
    @ExceptionHandler(Exception.class)
    @ResponseBody
    public ResponseEntity<SomeErrorObject> exceptionHandler(Exception e) {
        // org.springframework.http.HttpStatus 를 참조할 것.
        HttpStatus httpStatus = HttpStatus.INTERNAL_SERVER_ERROR;
        SomeErrorObject errorObject = new SomeErrorObject();

        return new ResponseEntity<>(errorObject, httpStatus);
    }
}
</code>

==== Parameter Validation/Binding Exception 처리 ====
=== @Valid 에 의한 파라미터 Validation 오류 핸들러 ===
  * ''@Valid'' Validation 시에 오류가 발생했을 때의 처리 핸들러
  * [[https://www.petrikainulainen.net/programming/spring-framework/spring-from-the-trenches-adding-validation-to-a-rest-api/|Spring From the Trenches: Adding Validation to a REST API]] 참조.
<code java>
@ControllerAdvice
public class RestErrorHandler {
 
    private MessageSource messageSource;
 
    @Autowired
    public RestErrorHandler(MessageSource messageSource) {
        this.messageSource = messageSource;
    }
 
    @ExceptionHandler(MethodArgumentNotValidException.class)
    @ResponseStatus(HttpStatus.BAD_REQUEST)
    @ResponseBody
    public ValidationErrorDTO processValidationError(MethodArgumentNotValidException ex) {
        BindingResult result = ex.getBindingResult();
        List<FieldError> fieldErrors = result.getFieldErrors();
 
        return processFieldErrors(fieldErrors);
    }
 
    private ValidationErrorDTO processFieldErrors(List<FieldError> fieldErrors) {
        ValidationErrorDTO dto = new ValidationErrorDTO();
 
        for (FieldError fieldError: fieldErrors) {
            String localizedErrorMessage = resolveLocalizedErrorMessage(fieldError);
            dto.addFieldError(fieldError.getField(), localizedErrorMessage);
        }
 
        return dto;
    }
 
    private String resolveLocalizedErrorMessage(FieldError fieldError) {
        Locale currentLocale =  LocaleContextHolder.getLocale();
        String localizedErrorMessage = messageSource.getMessage(fieldError, currentLocale);
 
        //If the message was not found, return the most accurate field error code instead.
        //You can remove this check if you prefer to get the default error message.
        if (localizedErrorMessage.equals(fieldError.getDefaultMessage())) {
            String[] fieldErrorCodes = fieldError.getCodes();
            localizedErrorMessage = fieldErrorCodes[0];
        }
 
        return localizedErrorMessage;
    }
}
</code>
=== BindingException 처리 ===
  * [[https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/validation/BindException.html|BindException]] 은 Controller에서 쿼리 파라미터를 객체로 변환할 때 타입이 다르던가 날짜 포맷팅이 잘못됐던가 할 때 발생한다.
<code java>
@ExceptionHandler(BindException.class)
@ResponseStatus(HttpStatus.BAD_REQUEST)
public ExDto handleBindException(BindException e) {
  // BindException이 BindingResult, Errors를 상속하고 있으므로 해당 데이터를 꺼내서 사용하면 된다.
}
</code>

==== 주요 Spring MVC Exception에 대해 오버라이드 하지 말 것 ====
  * ''ControllerAdvice''나 ''ExceptionHandler''를 override 했을 경우 Spring이 기본으로 지정한 에러코드가 아닌 다른 에러코드로 응답 코드가 내려갈 수도 있다.
  * [[https://doanduyhai.wordpress.com/2012/05/06/spring-mvc-part-v-exception-handling/|Spring MVC part V: Exception handling | DuyHai's Java Blog]]
  * 주요 Exception들에 대해 올바른 응답 코드가 내려가도록 처리한다.
  * [[https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/servlet/mvc/support/DefaultHandlerExceptionResolver.html|DefaultHandlerExceptionResolver]]를 보면 각 예외별 응답 코드 기본값을 알 수 있다.

===== ResponseBodyAdvice, RequestBodyAdvice =====
  * [[https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyAdvice.html|ResponseBodyAdvice (Spring Framework 5.1.3.RELEASE API)]]
  * https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/servlet/mvc/method/annotation/RequestBodyAdvice.html
  * [[https://chung-develop.tistory.com/61|[Spring]스프링에서 공통 Response처리 하기(@ControllerAdvice 이용)]]

===== 참고 =====
  * [[http://wonwoo.ml/index.php/post/2208|Spring 의 @ControllerAdvice]]