SpringBoot接口如何統(tǒng)一異常處理

第SpringBoot接口如何統(tǒng)一異常處理目錄為什么要優(yōu)雅的處理異常實現案例@ControllerAdvice異常統(tǒng)一處理Controller接口運行測試進一步理解@ControllerAdvice還可以怎么用？@ControllerAdvice是如何起作用的（原理）？

為什么要優(yōu)雅的處理異常

如果我們不統(tǒng)一的處理異常，經常會在controller層有大量的異常處理的代碼，比如：

@Slf4j

@Api(value="UserInterfaces",tags="UserInterfaces")

@RestController

@RequestMapping("/user")

publicclassUserController{

*http://localhost:8080/user/add.

*@paramuserParamuserparam

*@returnuser

@ApiOperation("AddUser")

@ApiImplicitParam(name="userParam",type="body",dataTypeClass=UserParam.class,required=true)

@PostMapping("add")

publicResponseEntityStringadd(@Valid@RequestBodyUserParamuserParam){

//每個接口充斥著大量的異常處理

try{

//dosomething

}catch(Exceptione){

returnResponseEntity.fail("error");

returnResponseEntity.ok("success");

}

那怎么實現統(tǒng)一的異常處理，特別是結合參數校驗等封裝？

實現案例

簡單展示通過@ControllerAdvice進行統(tǒng)一異常處理。

@ControllerAdvice異常統(tǒng)一處理

對于400參數錯誤異常

/**

*Globalexceptionhandler.

@Slf4j

@RestControllerAdvice

publicclassGlobalExceptionHandler{

*exceptionhandlerforbadrequest.

*@parame

*exception

*@returnResponseResult

@ResponseBody

@ResponseStatus(code=HttpStatus.BAD_REQUEST)

@ExceptionHandler(value={BindException.class,ValidationException.class,MethodArgumentNotValidException.class})

publicResponseResultExceptionDatahandleParameterVerificationException(@NonNullExceptione){

ExceptionData.ExceptionDataBuilderexceptionDataBuilder=ExceptionData.builder();

log.warn("Exception:{}",e.getMessage());

if(einstanceofBindException){

BindingResultbindingResult=((MethodArgumentNotValidException)e).getBindingResult();

bindingResult.getAllErrors().stream().map(DefaultMessageSourceResolvable::getDefaultMessage)

.forEach(exceptionDataBuilder::error);

}elseif(einstanceofConstraintViolationException){

if(e.getMessage()!=null){

exceptionDataBuilder.error(e.getMessage());

}else{

exceptionDataBuilder.error("invalidparameter");

returnResponseResultEntity.fail(exceptionDataBuilder.build(),"invalidparameter");

對于自定義異常

/**

*handlebusinessexception.

*@parambusinessException

*businessexception

*@returnResponseResult

@ResponseBody

@ExceptionHandler(BusinessException.class)

publicResponseResultBusinessExceptionprocessBusinessException(BusinessExceptionbusinessException){

log.error(businessException.getLocalizedMessage(),businessException);

//這里可以屏蔽掉后臺的異常棧信息，直接返回"businesserror"

returnResponseResultEntity.fail(businessException,businessException.getLocalizedMessage());

}

對于其它異常

/**

*handleotherexception.

*@paramexception

*exception

*@returnResponseResult

@ResponseBody

@ExceptionHandler(Exception.class)

publicResponseResultExceptionprocessException(Exceptionexception){

log.error(exception.getLocalizedMessage(),exception);

//這里可以屏蔽掉后臺的異常棧信息，直接返回"servererror"

returnResponseResultEntity.fail(exception,exception.getLocalizedMessage());

}

Controller接口

（接口中無需處理異常）

@Slf4j

@Api(value="UserInterfaces",tags="UserInterfaces")

@RestController

@RequestMapping("/user")

publicclassUserController{

*http://localhost:8080/user/add.

*@paramuserParamuserparam

*@returnuser

@ApiOperation("AddUser")

@ApiImplicitParam(name="userParam",type="body",dataTypeClass=UserParam.class,required=true)

@PostMapping("add")

publicResponseEntityUserParamadd(@Valid@RequestBodyUserParamuserParam){

returnResponseEntity.ok(userParam);

}

運行測試

這里用postman測試下:

進一步理解

我們再通過一些問題來幫助你更深入理解

@ControllerAdvice還可以怎么用？

除了通過@ExceptionHandler注解用于全局異常的處理之外，@ControllerAdvice還有兩個用法：

@InitBinder注解

用于請求中注冊自定義參數的解析，從而達到自定義請求參數格式的目的；

比如，在@ControllerAdvice注解的類中添加如下方法，來統(tǒng)一處理日期格式的格式化

@InitBinder

publicvoidhandleInitBinder(WebDataBinderdataBinder){

dataBinder.registerCustomEditor(Date.class,

newCustomDateEditor(newSimpleDateFormat("yyyy-MM-dd"),false));

}

Controller中傳入參數（string類型）自動轉化為Date類型

@GetMapping("testDate")

publicDateprocessApi(Datedate){

returndate;

}

@ModelAttribute注解

用來預設全局參數，比如最典型的使用SpringSecurity時將添加當前登錄的用戶信息（UserDetails)作為參數。

@ModelAttribute("currentUser")

publicUserDetailsmodelAttribute(){

return(UserDetails)SecurityContextHolder.getContext().getAuthentication().getPrincipal();

}

所有controller類中requestMapping方法都可以直接獲取并使用currentUser

@PostMapping("saveSomething")

publicResponseEntityStringsaveSomeObj(@ModelAttribute("currentUser")UserDetailsoperator){

//保存操作，并設置當前操作人員的ID（從UserDetails中獲得）

returnResponseEntity.success("ok");

}

@ControllerAdvice是如何起作用的（原理）？

DispatcherServlet中onRefresh方法是初始化ApplicationContext后的回調方法，它會調用initStrategies方法，主要更新一些servlet需要使用的對象，包括國際化處理，requestMapping，視圖解析等等。

/**

*Thisimplementationcalls{@link#initStrategies}.

@Override

protectedvoidonRefresh(ApplicationContextcontext){

initStrategies(context);

*Initializethestrategyobjectsthatthisservletuses.

*pMaybeoverriddeninsubclassesinordertoinitializefurtherstrategyobjects.

protectedvoidinitStrategies(ApplicationContextcontext){

initMultipartResolver(context);//文件上傳

initLocaleResolver(context);//i18n國際化

initThemeResolver(context);//主題

initHandlerMappings(context);//requestMapping

initHandlerAdapters(context);//adapters

initHandlerExceptionResolvers(context);//異常處理

initRequestToViewNameTranslator(context);

initViewResolvers(context);

initFlashMapManager(context);

}

從上述代碼看，如果要提供@ControllerAdvice提供的三種注解功能，從設計和實現的角度肯定是實現的代碼需要放在initStrategies方法中。

@ModelAttribute和@InitBinder處理

具體來看，如果你是設計者，很顯然容易想到：對于@ModelAttribute提供的參數預置和@InitBinder注解提供的預處理方法應該是放在一個方法中的，因為它們都是在進入requestMapping方法前做的操作。

如下方法是獲取所有的HandlerAdapter，無非就是從BeanFactory中獲取

privatevoidinitHandlerAdapters(ApplicationContextcontext){

this.handlerAdapters=null;

if(this.detectAllHandlerAdapters){

//FindallHandlerAdaptersintheApplicationContext,includingancestorcontexts.

MapString,HandlerAdaptermatchingBeans=

BeanFactoryUtils.beansOfTypeIncludingAncestors(context,HandlerAdapter.class,true,false);

if(!matchingBeans.isEmpty()){

this.handlerAdapters=newArrayList(matchingBeans.values());

//WekeepHandlerAdaptersinsortedorder.

AnnotationAwareOrderComparator.sort(this.handlerAdapters);

else{

try{

HandlerAdapterha=context.getBean(HANDLER_ADAPTER_BEAN_NAME,HandlerAdapter.class);

this.handlerAdapters=Collections.singletonList(ha);

catch(NoSuchBeanDefinitionExceptionex){

//Ignore,we'lladdadefaultHandlerAdapterlater.

//EnsurewehaveatleastsomeHandlerAdapters,byregistering

//defaultHandlerAdaptersifnootheradaptersarefound.

if(this.handlerAdapters==null){

this.handlerAdapters=getDefaultStrategies(context,HandlerAdapter.class);

if(logger.isTraceEnabled()){

logger.trace("NoHandlerAdaptersdeclaredforservlet'"+getServletName()+

"':usingdefaultstrategiesfromDispatcherSperties");

}

我們要處理的是requestMapping的handlerResolver，作為設計者，就很容易出如下的結構

在RequestMappingHandlerAdapter中的afterPropertiesSet去處理advice

@Override

publicvoidafterPropertiesSet(){

//Dothisfirst,itmayaddResponseBodyadvicebeans

initControllerAdviceCache();

if(this.argumentResolvers==null){

ListHandlerMethodArgumentResolverresolvers=getDefaultArgumentResolvers();

this.argumentResolvers=newHandlerMethodArgumentResolverComposite().addResolvers(resolvers);

if(this.initBinderArgumentResolvers==null){

ListHandlerMethodArgumentResolverresolvers=getDefaultInitBinderArgumentResolvers();

this.initBinderArgumentResolvers=newHandlerMethodArgumentResolverComposite().addResolvers(resolvers);

if(this.returnValueHandlers==null){

ListHandlerMethodReturnValueHandlerhandlers=getDefaultReturnValueHandlers();

this.returnValueHandlers=newHandlerMethodReturnValueHandlerComposite().addHandlers(handlers);

privatevoidinitControllerAdviceCache(){

if(getApplicationContext()==null){

return;

ListControllerAdviceBeanadviceBeans=ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());

ListObjectrequestResponseBodyAdviceBeans=newArrayList();

for(ControllerAdviceBeanadviceBean:adviceBeans){

ClassbeanType=adviceBean.getBeanType();

if(beanType==null){

thrownewIllegalStateException("UnresolvabletypeforControllerAdviceBean:"+adviceBean);

//緩存所有modelAttribute注解方法

SetMethodattrMethods=MethodIntrospector.selectMethods(beanType,MODEL_ATTRIBUTE_METHODS);

if(!attrMethods.isEmpty()){

this.modelAttributeAdviceCache.put(adviceBean,attrMethods);

//緩存所有initBinder注解方法

SetMethodbinderMethods=MethodIntrospector.selectMethods(beanType,INIT_BINDER_METHODS);

if(!binderMethods.isEmpty()){

this.initBinderAdviceCache.put(adviceBean,binderMethods);

if(RequestBodyAdvice.class.isAssignableFrom(beanType)||ResponseBodyAdvice.class.isAssignableFrom(beanType)){

requestResponseBodyAdviceBeans.add(adviceBean);

if(!requestResponseBodyAdviceBeans.isEmpty()){

this.requestResponseBodyAdvice.addAll(0,requestResponseBodyAdviceBeans);

}

@ExceptionHandler處理

@ExceptionHandler顯然是在上述initHandlerExceptionResolvers(context)方法中。

同樣的，從BeanFactory中獲取HandlerExceptionResolver

/**

*InitializetheHandlerExceptionResolverusedbythisclass.

*pIfnobeanisdefinedwiththegivennameintheBeanFactoryforthisnamespace,

*wedefaulttonoexceptionresolver.

privatevoidinitHandlerExceptionResolvers(ApplicationContextcontext){

this.handlerExceptionResolvers=null;

if(this.detectAllHandlerExceptionResolvers){

//FindallHandlerExceptionResolversintheApplicationContext,includingancestorcontexts.

MapString,HandlerExceptionResolvermatchingBeans=BeanFactoryUtils

.beansOfTypeIncludingAncestors(context,HandlerExceptionResolver.class,true,false);

if(!matchingBeans.isEmpty()){

this.handlerExceptionResolvers=newArrayList(matchingBeans.values());

//WekeepHandlerExceptionResolversinsortedorder.

AnnotationAwareOrderComparator.sort(this.handlerExceptionResolvers);

else{

try{

HandlerExceptionResolverher=

context.getBean(HANDLER_EXCEPTION_RESOLVER_BEAN_NAME,HandlerExceptionResolver.class);

this.handlerExceptionResolvers=Collections.singletonList(her);

catch(NoSuchBeanDefinitionExceptionex){

//Ignore,noHandlerExceptionResolverisfinetoo.

//EnsurewehaveatleastsomeHandlerExceptionResolvers,byregistering

//defaultHandlerExceptionResolversifnootherresolversarefound.

if(this.handlerExceptionResolvers==null){

this.handlerExceptionResolvers=getDefaultStrategies(context,HandlerExceptionResolver.class);

if(logger.isTraceEnabled()){

logger.trace("NoHandlerExceptionResolversdeclaredinservlet'"+getServletName()+

"':usingdefaultstrategiesfromDispatcherSperties");

}

我們很容易找到ExceptionHandlerExceptionResolver

同樣的在afterPropertiesSet去處理advice

@Override

publicvoidafterPropertiesSet(){

//Dothisfirst,itmayaddRes