[SpringBoot] 예외처리(Exception)

import lombok.Getter;
import lombok.RequiredArgsConstructor;
import org.springframework.http.HttpStatus;

@RequiredArgsConstructor
@Getter
public enum ErrorCode {

    INTERNAL_SERVER_ERROR(HttpStatus.INTERNAL_SERVER_ERROR, "S-001", "서버 에러가 발생했습니다."),
    VALIDATION_FAIL(HttpStatus.BAD_REQUEST, "S-002", "유효성 검사에 실패했습니다."),
    ;

    private final HttpStatus httpStatus;
    private final String code;
    private final String message;
}

import com.openmpy.ecommerce.global.exception.constants.ErrorCode;
import lombok.Getter;

@Getter
public class CustomException extends RuntimeException {

    private final ErrorCode errorCode;

    public CustomException(ErrorCode errorCode) {
        super(errorCode.getMessage());
        this.errorCode = errorCode;
    }
}

import com.openmpy.ecommerce.global.exception.constants.ErrorCode;
import org.springframework.http.ResponseEntity;
import org.springframework.validation.FieldError;
import org.springframework.web.bind.MethodArgumentNotValidException;
import org.springframework.web.bind.annotation.ExceptionHandler;
import org.springframework.web.bind.annotation.RestControllerAdvice;

import java.util.HashMap;
import java.util.Map;

@RestControllerAdvice
public class GlobalExceptionHandler {

    @ExceptionHandler(CustomException.class)
    public ResponseEntity<ErrorResponseDto> handleBusinessException(CustomException e) {
        ErrorResponseDto responseDto = new ErrorResponseDto(e.getErrorCode().getCode(), e.getMessage(), null);
        return new ResponseEntity<>(responseDto, e.getErrorCode().getHttpStatus());
    }

    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ErrorResponseDto> handleValidationException(MethodArgumentNotValidException e) {
        Map<String, String> errors = new HashMap<>();
        for (FieldError error : e.getBindingResult().getFieldErrors()) {
            errors.put(error.getField(), error.getDefaultMessage());
        }

        ErrorResponseDto responseDto =
                new ErrorResponseDto(ErrorCode.VALIDATION_FAIL.getCode(), ErrorCode.VALIDATION_FAIL.getMessage(), errors);
        return new ResponseEntity<>(responseDto, ErrorCode.VALIDATION_FAIL.getHttpStatus());
    }
}

import java.util.Map;

public record ErrorResponseDto(
        String code,
        String message,
        Map<String, String> errors) {
}

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클라이언트 측에 내려줄 만한 내용은 HTTP 상태 코드, 커스텀 에러 코드, 에러 메시지, 유효성 검사 결과 등이 있다.

유효성 검사에 실패한다면 errors 필드에 Map 구조로 예외 처리 결과 내용이 들어간다.

즉, 에러가 발생하면 아래와 같은 예시로 응답 값을 나타낸다.

HTTP/1.1 500 
Content-Type: application/json
Transfer-Encoding: chunked
Date: Tue, 11 Jun 2024 13:54:31 GMT
Connection: close

{
  "code": "S-001",
  "message": "서버 에러가 발생했습니다.",
  "errors": null
}