예외 처리 전략

// 베이스
public abstract class BusinessException extends RuntimeException {
    public abstract HttpStatus getStatus();
    public abstract String getCode();

    public BusinessException(String message) {
        super(message);
    }
}


// 도메인별
public class UserNotFoundException extends BusinessException {
    public UserNotFoundException(Long id) {
        super("사용자 ID " + id + "를 찾을 수 없음");
    }

    @Override public HttpStatus getStatus() { return HttpStatus.NOT_FOUND; }
    @Override public String getCode() { return "USER_NOT_FOUND"; }
}


public class DuplicateEmailException extends BusinessException {
    public DuplicateEmailException(String email) {
        super("이메일이 이미 등록됨: " + email);
    }

    @Override public HttpStatus getStatus() { return HttpStatus.CONFLICT; }
    @Override public String getCode() { return "DUPLICATE_EMAIL"; }
}

@RestControllerAdvice
@Slf4j
public class GlobalExceptionHandler {

    // 비즈니스 예외
    @ExceptionHandler(BusinessException.class)
    public ResponseEntity<ProblemDetail> handleBusiness(BusinessException e) {
        ProblemDetail problem = ProblemDetail.forStatusAndDetail(
            e.getStatus(), e.getMessage()
        );
        problem.setProperty("code", e.getCode());
        return ResponseEntity.status(e.getStatus()).body(problem);
    }


    // Validation 실패
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ResponseEntity<ProblemDetail> handleValidation(MethodArgumentNotValidException e) {
        Map<String, String> errors = new HashMap<>();
        e.getBindingResult().getFieldErrors().forEach(err ->
            errors.put(err.getField(), err.getDefaultMessage())
        );

        ProblemDetail problem = ProblemDetail.forStatusAndDetail(
            HttpStatus.BAD_REQUEST, "유효성 검사 실패"
        );
        problem.setProperty("errors", errors);
        return ResponseEntity.badRequest().body(problem);
    }


    // 그 외 모든 예외 — 마지막 방어선
    @ExceptionHandler(Exception.class)
    public ResponseEntity<ProblemDetail> handleAll(Exception e) {
        log.error("Unexpected error", e);
        ProblemDetail problem = ProblemDetail.forStatusAndDetail(
            HttpStatus.INTERNAL_SERVER_ERROR,
            "서버 오류가 발생했습니다."
        );
        return ResponseEntity.internalServerError().body(problem);
    }
}

{
    "type": "about:blank",
    "title": "Not Found",
    "status": 404,
    "detail": "사용자 ID 123를 찾을 수 없음",
    "instance": "/api/users/123",
    "code": "USER_NOT_FOUND"
}

public record SignupRequest(
    @NotBlank(message = "이름 필수")
    @Size(min = 2, max = 50)
    String name,

    @Email(message = "이메일 형식 오류")
    @NotBlank
    String email,

    @NotBlank
    @Pattern(regexp = "^(?=.*[A-Z])(?=.*\d).{8,}$",
             message = "8자 이상, 대문자+숫자 포함")
    String password
) {}


@RestController
@RequiredArgsConstructor
public class UserController {
    private final UserService userService;

    @PostMapping("/users")
    public ResponseEntity<UserDto> signup(@Valid @RequestBody SignupRequest req) {
        // @Valid 실패 시 자동으로 MethodArgumentNotValidException
        // GlobalExceptionHandler에서 처리
        return ResponseEntity.ok(userService.signup(req));
    }
}

@RestControllerAdvice
@Slf4j
@RequiredArgsConstructor
public class GlobalExceptionHandler {
    // ... 위 핸들러들

    @ExceptionHandler(Exception.class)
    public ResponseEntity<ProblemDetail> handleAll(Exception e, HttpServletRequest req) {
        // MDC에 요청 컨텍스트 추가
        MDC.put("requestId", UUID.randomUUID().toString());
        MDC.put("path", req.getRequestURI());
        MDC.put("method", req.getMethod());

        log.error("Unexpected error: {}", e.getMessage(), e);

        // Sentry 통합
        Sentry.captureException(e);

        return ResponseEntity.internalServerError()
            .body(ProblemDetail.forStatusAndDetail(
                HttpStatus.INTERNAL_SERVER_ERROR, "서버 오류"
            ));
    }
}