為什么不建議用try catch處理異常？
什么是統(tǒng)一異常處理
目標
統(tǒng)一異常處理實戰(zhàn)
| 用 Assert（斷言）替換 throw exception
@Test
public void test1() {
...
User user = userDao.selectById(userId);
Assert.notNull(user, "用戶不存在.");
...
}
@Test
public void test2() {
// 另一種寫法
User user = userDao.selectById(userId);
if (user == null) {
throw new IllegalArgumentException("用戶不存在.");
}
}
public abstract class Assert {
public Assert() {
}
public static void notNull(@Nullable Object object, String message) {
if (object == null) {
throw new IllegalArgumentException(message);
}
}
}
Assert
public interface Assert {
/**
* 創(chuàng)建異常
* @param args
* @return
*/
BaseException newException(Object... args);
/**
* 創(chuàng)建異常
* @param t
* @param args
* @return
*/
BaseException newException(Throwable t, Object... args);
/**
* <p>斷言對象<code>obj</code>非空。如果對象<code>obj</code>為空，則拋出異常
*
* @param obj 待判斷對象
*/
default void assertNotNull(Object obj) {
if (obj == null) {
throw newException(obj);
}
}
/**
* <p>斷言對象<code>obj</code>非空。如果對象<code>obj</code>為空，則拋出異常
* <p>異常信息<code>message</code>支持傳遞參數(shù)方式，避免在判斷之前進行字符串拼接操作
*
* @param obj 待判斷對象
* @param args message占位符對應的參數(shù)列表
*/
default void assertNotNull(Object obj, Object... args) {
if (obj == null) {
throw newException(args);
}
}
}
| 善解人意的 Enum
public interface IResponseEnum {
int getCode();
String getMessage();
}
/**
* <p>業(yè)務異常</p>
* <p>業(yè)務處理時，出現(xiàn)異常，可以拋出該異常</p>
*/
public class BusinessException extends BaseException {
private static final long serialVersionUID = 1L;
public BusinessException(IResponseEnum responseEnum, Object[] args, String message) {
super(responseEnum, args, message);
}
public BusinessException(IResponseEnum responseEnum, Object[] args, String message, Throwable cause) {
super(responseEnum, args, message, cause);
}
}
public interface BusinessExceptionAssert extends IResponseEnum, Assert {
@Override
default BaseException newException(Object... args) {
String msg = MessageFormat.format(this.getMessage(), args);
return new BusinessException(this, args, msg);
}
@Override
default BaseException newException(Throwable t, Object... args) {
String msg = MessageFormat.format(this.getMessage(), args);
return new BusinessException(this, args, msg, t);
}
}
@Getter
@AllArgsConstructor
public enum ResponseEnum implements BusinessExceptionAssert {
/**
* Bad licence type
*/
BAD_LICENCE_TYPE(7001, "Bad licence type."),
/**
* Licence not found
*/
LICENCE_NOT_FOUND(7002, "Licence not found.")
;
/**
* 返回碼
*/
private int code;
/**
* 返回消息
*/
private String message;
}
BAD_LICENCE_TYPE
LICENCE_NOT_FOUND
/**
* 校驗{@link Licence}存在
* @param licence
*/
private void checkNotNull(Licence licence) {
ResponseEnum.LICENCE_NOT_FOUND.assertNotNull(licence);
}
private void checkNotNull(Licence licence) {
if (licence == null) {
throw new LicenceNotFoundException();
// 或者這樣
throw new BusinessException(7001, "Bad licence type.");
}
}
| 定義統(tǒng)一異常處理器類
@Slf4j
@Component
@ControllerAdvice
@ConditionalOnWebApplication
@ConditionalOnMissingBean(UnifiedExceptionHandler.class)
public class UnifiedExceptionHandler {
/**
* 生產(chǎn)環(huán)境
*/
private final static String ENV_PROD = "prod";
@Autowired
private UnifiedMessageSource unifiedMessageSource;
/**
* 當前環(huán)境
*/
@Value("${spring.profiles.active}")
private String profile;
/**
* 獲取國際化消息
*
* @param e 異常
* @return
*/
public String getMessage(BaseException e) {
String code = "response." + e.getResponseEnum().toString();
String message = unifiedMessageSource.getMessage(code, e.getArgs());
if (message == null || message.isEmpty()) {
return e.getMessage();
}
return message;
}
/**
* 業(yè)務異常
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler(value = BusinessException.class)
@ResponseBody
public ErrorResponse handleBusinessException(BaseException e) {
log.error(e.getMessage(), e);
return new ErrorResponse(e.getResponseEnum().getCode(), getMessage(e));
}
/**
* 自定義異常
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler(value = BaseException.class)
@ResponseBody
public ErrorResponse handleBaseException(BaseException e) {
log.error(e.getMessage(), e);
return new ErrorResponse(e.getResponseEnum().getCode(), getMessage(e));
}
/**
* Controller上一層相關異常
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler({
NoHandlerFoundException.class,
HttpRequestMethodNotSupportedException.class,
HttpMediaTypeNotSupportedException.class,
MissingPathVariableException.class,
MissingServletRequestParameterException.class,
TypeMismatchException.class,
HttpMessageNotReadableException.class,
HttpMessageNotWritableException.class,
// BindException.class,
// MethodArgumentNotValidException.class
HttpMediaTypeNotAcceptableException.class,
ServletRequestBindingException.class,
ConversionNotSupportedException.class,
MissingServletRequestPartException.class,
AsyncRequestTimeoutException.class
})
@ResponseBody
public ErrorResponse handleServletException(Exception e) {
log.error(e.getMessage(), e);
int code = CommonResponseEnum.SERVER_ERROR.getCode();
try {
ServletResponseEnum servletExceptionEnum = ServletResponseEnum.valueOf(e.getClass().getSimpleName());
code = servletExceptionEnum.getCode();
} catch (IllegalArgumentException e1) {
log.error("class [{}] not defined in enum {}", e.getClass().getName(), ServletResponseEnum.class.getName());
}
if (ENV_PROD.equals(profile)) {
// 當為生產(chǎn)環(huán)境, 不適合把具體的異常信息展示給用戶, 比如404.
code = CommonResponseEnum.SERVER_ERROR.getCode();
BaseException baseException = new BaseException(CommonResponseEnum.SERVER_ERROR);
String message = getMessage(baseException);
return new ErrorResponse(code, message);
}
return new ErrorResponse(code, e.getMessage());
}
/**
* 參數(shù)綁定異常
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler(value = BindException.class)
@ResponseBody
public ErrorResponse handleBindException(BindException e) {
log.error("參數(shù)綁定校驗異常", e);
return wrapperBindingResult(e.getBindingResult());
}
/**
* 參數(shù)校驗異常，將校驗失敗的所有異常組合成一條錯誤信息
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler(value = MethodArgumentNotValidException.class)
@ResponseBody
public ErrorResponse handleValidException(MethodArgumentNotValidException e) {
log.error("參數(shù)綁定校驗異常", e);
return wrapperBindingResult(e.getBindingResult());
}
/**
* 包裝綁定異常結果
*
* @param bindingResult 綁定結果
* @return 異常結果
*/
private ErrorResponse wrapperBindingResult(BindingResult bindingResult) {
StringBuilder msg = new StringBuilder();
for (ObjectError error : bindingResult.getAllErrors()) {
msg.append(", ");
if (error instanceof FieldError) {
msg.append(((FieldError) error).getField()).append(": ");
}
msg.append(error.getDefaultMessage() == null ? "" : error.getDefaultMessage());
}
return new ErrorResponse(ArgumentResponseEnum.VALID_ERROR.getCode(), msg.substring(2));
}
/**
* 未定義異常
*
* @param e 異常
* @return 異常結果
*/
@ExceptionHandler(value = Exception.class)
@ResponseBody
public ErrorResponse handleException(Exception e) {
log.error(e.getMessage(), e);
if (ENV_PROD.equals(profile)) {
// 當為生產(chǎn)環(huán)境, 不適合把具體的異常信息展示給用戶, 比如數(shù)據(jù)庫異常信息.
int code = CommonResponseEnum.SERVER_ERROR.getCode();
BaseException baseException = new BaseException(CommonResponseEnum.SERVER_ERROR);
String message = getMessage(baseException);
return new ErrorResponse(code, message);
}
return new ErrorResponse(CommonResponseEnum.SERVER_ERROR.getCode(), e.getMessage());
}
}
進入 Controller 前的異常：handleServletException、handleBindException、handleValidException
自定義異常：handleBusinessException、handleBaseException
未知異常：handleException
異常處理器說明
| handleServletException
| handleBindException
| handleValidException
| handleBusinessException、handleBaseException
| handleException
異于常人的404
spring.mvc.throw-exception-if-no-handler-found=true
spring.resources.add-mappings=false
捕獲404對應的異常
| 統(tǒng)一返回結果
| 驗證統(tǒng)一異常處理
@Service
public class LicenceService extends ServiceImpl<LicenceMapper, Licence> {
@Autowired
private OrganizationClient organizationClient;
/**
* 查詢{@link Licence} 詳情
* @param licenceId
* @return
*/
public LicenceDTO queryDetail(Long licenceId) {
Licence licence = this.getById(licenceId);
checkNotNull(licence);
OrganizationDTO org = ClientUtil.execute(() -> organizationClient.getOrganization(licence.getOrganizationId()));
return toLicenceDTO(licence, org);
}
/**
* 分頁獲取
* @param licenceParam 分頁查詢參數(shù)
* @return
*/
public QueryData<SimpleLicenceDTO> getLicences(LicenceParam licenceParam) {
String licenceType = licenceParam.getLicenceType();
LicenceTypeEnum licenceTypeEnum = LicenceTypeEnum.parseOfNullable(licenceType);
// 斷言, 非空
ResponseEnum.BAD_LICENCE_TYPE.assertNotNull(licenceTypeEnum);
LambdaQueryWrapper<Licence> wrapper = new LambdaQueryWrapper<>();
wrapper.eq(Licence::getLicenceType, licenceType);
IPage<Licence> page = this.page(new QueryPage<>(licenceParam), wrapper);
return new QueryData<>(page, this::toSimpleLicenceDTO);
}
/**
* 新增{@link Licence}
* @param request 請求體
* @return
*/
@Transactional(rollbackFor = Throwable.class)
public LicenceAddRespData addLicence(LicenceAddRequest request) {
Licence licence = new Licence();
licence.setOrganizationId(request.getOrganizationId());
licence.setLicenceType(request.getLicenceType());
licence.setProductName(request.getProductName());
licence.setLicenceMax(request.getLicenceMax());
licence.setLicenceAllocated(request.getLicenceAllocated());
licence.setComment(request.getComment());
this.save(licence);
return new LicenceAddRespData(licence.getLicenceId());
}
/**
* entity -> simple dto
* @param licence {@link Licence} entity
* @return {@link SimpleLicenceDTO}
*/
private SimpleLicenceDTO toSimpleLicenceDTO(Licence licence) {
// 省略
}
/**
* entity -> dto
* @param licence {@link Licence} entity
* @param org {@link OrganizationDTO}
* @return {@link LicenceDTO}
*/
private LicenceDTO toLicenceDTO(Licence licence, OrganizationDTO org) {
// 省略
}
/**
* 校驗{@link Licence}存在
* @param licence
*/
private void checkNotNull(Licence licence) {
ResponseEnum.LICENCE_NOT_FOUND.assertNotNull(licence);
}
}
-- licence
INSERT INTO licence (licence_id, organization_id, licence_type, product_name, licence_max, licence_allocated)
VALUES (1, 1, 'user','CustomerPro', 100,5);
INSERT INTO licence (licence_id, organization_id, licence_type, product_name, licence_max, licence_allocated)
VALUES (2, 1, 'user','suitability-plus', 200,189);
INSERT INTO licence (licence_id, organization_id, licence_type, product_name, licence_max, licence_allocated)
VALUES (3, 2, 'user','HR-PowerSuite', 100,4);
INSERT INTO licence (licence_id, organization_id, licence_type, product_name, licence_max, licence_allocated)
VALUES (4, 2, 'core-prod','WildCat Application Gateway', 16,16);
-- organizations
INSERT INTO organization (id, name, contact_name, contact_email, contact_phone)
VALUES (1, 'customer-crm-co', 'Mark Balster', '[email protected]', '823-555-1212');
INSERT INTO organization (id, name, contact_name, contact_email, contact_phone)
VALUES (2, 'HR-PowerSuite', 'Doug Drewry','[email protected]', '920-555-1212');
開始驗證
| 捕獲自定義異常
licenceId=1
| 捕獲進入 Controller 前的異常
| 捕獲未知異常
小結
擴展
總結
@Slf4j
@RestControllerAdvice
public class GlobalExceptionHandler {
/**
* 沒有登錄
* @param request
* @param response
* @param e
* @return
*/
@ExceptionHandler(NoLoginException.class)
public Object noLoginExceptionHandler(HttpServletRequest request,HttpServletResponse response,Exception e)
{
log.error("[GlobalExceptionHandler][noLoginExceptionHandler] exception",e);
JsonResult jsonResult = new JsonResult();
jsonResult.setCode(JsonResultCode.NO_LOGIN);
jsonResult.setMessage("用戶登錄失效或者登錄超時,請先登錄");
return jsonResult;
}
/**
* 業(yè)務異常
* @param request
* @param response
* @param e
* @return
*/
@ExceptionHandler(ServiceException.class)
public Object businessExceptionHandler(HttpServletRequest request,HttpServletResponse response,Exception e)
{
log.error("[GlobalExceptionHandler][businessExceptionHandler] exception",e);
JsonResult jsonResult = new JsonResult();
jsonResult.setCode(JsonResultCode.FAILURE);
jsonResult.setMessage("業(yè)務異常,請聯(lián)系管理員");
return jsonResult;
}
/**
* 全局異常處理
* @param request
* @param response
* @param e
* @return
*/
@ExceptionHandler(Exception.class)
public Object exceptionHandler(HttpServletRequest request,HttpServletResponse response,Exception e)
{
log.error("[GlobalExceptionHandler][exceptionHandler] exception",e);
JsonResult jsonResult = new JsonResult();
jsonResult.setCode(JsonResultCode.FAILURE);
jsonResult.setMessage("系統(tǒng)錯誤,請聯(lián)系管理員");
return jsonResult;
}
}
-End-
最近有一些小伙伴，讓我?guī)兔φ乙恍?nbsp;面試題 資料，于是我翻遍了收藏的 5T 資料后，匯總整理出來，可以說是程序員面試必備！所有資料都整理到網(wǎng)盤了，歡迎下載！
面試題】即可獲取
好文分享給更多人↓↓評論
圖片
表情