@Data
@AllArgsConstructor
@NoArgsConstructor
public class ApiResponse<T> {
    private int code;
    private String message;
    private T data;

    // 成功響應(yīng)
    public static <T> ApiResponse<T> success(T data) {
        return new ApiResponse<>(200, "success", data);
    }

    // 失敗響應(yīng)
    public static <T> ApiResponse<T> error(int code, String message) {
        return new ApiResponse<>(code, message, null);
    }
}

// 業(yè)務(wù)異?；?
public class BusinessException extends RuntimeException {
    private int code;

    public BusinessException(int code, String message) {
        super(message);
        this.code = code;
    }

    public BusinessException(String message) {
        super(message);
        this.code = 500;
    }

    // getter
    public int getCode() {
        return code;
    }
}

@Service
public class OrderService {
    public void createOrder(Long productId, Integer quantity) {
        if (quantity <= 0) {
            throw new BusinessException(400, "購買數(shù)量必須大于0");
        }
        // ... 其他邏輯
    }
}

@RestControllerAdvice  // 等價于 @ControllerAdvice + @ResponseBody
@Slf4j
public class GlobalExceptionHandler {

    /**
     * 處理自定義業(yè)務(wù)異常
     */
    @ExceptionHandler(BusinessException.class)
    public ApiResponse<String> handleBusinessException(BusinessException e) {
        log.warn("業(yè)務(wù)異常: {}", e.getMessage());
        return ApiResponse.error(e.getCode(), e.getMessage());
    }

    /**
     * 處理參數(shù)校驗(yàn)異常（@Valid）
     */
    @ExceptionHandler(MethodArgumentNotValidException.class)
    public ApiResponse<String> handleValidationException(MethodArgumentNotValidException e) {
        // 獲取第一個錯誤信息
        String errorMessage = e.getBindingResult()
                .getFieldErrors()
                .stream()
                .map(FieldError::getDefaultMessage)
                .findFirst()
                .orElse("參數(shù)校驗(yàn)失敗");
        
        log.warn("參數(shù)校驗(yàn)異常: {}", errorMessage);
        return ApiResponse.error(400, errorMessage);
    }

    /**
     * 處理空指針異常
     */
    @ExceptionHandler(NullPointerException.class)
    public ApiResponse<String> handleNullPointerException(NullPointerException e) {
        log.error("空指針異常", e);
        return ApiResponse.error(500, "系統(tǒng)內(nèi)部錯誤，請聯(lián)系管理員");
    }

    /**
     * 處理所有未被捕獲的異常（兜底）
     */
    @ExceptionHandler(Exception.class)
    public ApiResponse<String> handleException(Exception e) {
        log.error("未處理異常", e);
        return ApiResponse.error(500, "系統(tǒng)繁忙，請稍后重試");
    }

    /**
     * 處理 404 Not Found
     */
    @ExceptionHandler(NoHandlerFoundException.class)
    @ResponseStatus(HttpStatus.NOT_FOUND)
    public ApiResponse<String> handle404(NoHandlerFoundException e) {
        log.warn("請求路徑不存在: {}", e.getRequestURL());
        return ApiResponse.error(404, "請求的資源不存在");
    }
}

@RestController
@RequestMapping("/api")
public class TestController {

    @GetMapping("/business")
    public ApiResponse<String> businessError() {
        throw new BusinessException(400, "用戶名已存在");
    }

    @PostMapping("/validate")
    public ApiResponse<String> validate(@Valid @RequestBody UserForm form) {
        return ApiResponse.success("驗(yàn)證通過");
    }

    @GetMapping("/null")
    public ApiResponse<String> nullPointer() {
        String str = null;
        str.length(); // 觸發(fā) NullPointerException
        return ApiResponse.success("success");
    }

    @GetMapping("/unknown")
    public ApiResponse<String> unknown() {
        throw new RuntimeException("未知錯誤");
    }
}

class UserForm {
    @NotBlank(message = "用戶名不能為空")
    private String username;

    @Min(value = 18, message = "年齡不能小于18歲")
    private Integer age;

    // getter & setter
}

// 用戶模塊異常處理器
@ControllerAdvice("com.example.controller.user")
public class UserExceptionHandler { ... }

// 訂單模塊異常處理器
@ControllerAdvice("com.example.controller.order")
public class OrderExceptionHandler { ... }

@Aspect
@Component
public class ExceptionLogAspect {

    @AfterThrowing(pointcut = "@within(org.springframework.web.bind.annotation.RestController)", 
                   throwing = "ex")
    public void logException(JoinPoint joinPoint, Exception ex) {
        String methodName = joinPoint.getSignature().getName();
        log.error("方法 {} 發(fā)生異常: {}", methodName, ex.getMessage());
    }
}

public enum ErrorCode {
    SUCCESS(200, "成功"),
    BAD_REQUEST(400, "請求參數(shù)錯誤"),
    UNAUTHORIZED(401, "未授權(quán)"),
    FORBIDDEN(403, "禁止訪問"),
    NOT_FOUND(404, "資源不存在"),
    SERVER_ERROR(500, "系統(tǒng)內(nèi)部錯誤");

    private final int code;
    private final String message;

    ErrorCode(int code, String message) {
        this.code = code;
        this.message = message;
    }

    // getter
}

throw new BusinessException(ErrorCode.BAD_REQUEST);