本篇文章给大家分享的是有关使用@RestControllerAdvice怎么对异常进行处理,小编觉得挺实用的,因此分享给大家学习,希望大家阅读完这篇文章后可以有所收获,话不多说,跟着小编一起来看看吧。
从DispatcherServlet入口,如下:
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception { if (logger.isDebugEnabled()) { String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : ""; logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed + " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]"); } // Keep a snapshot of the request attributes in case of an include, // to be able to restore the original attributes after the include. Map<String, Object> attributesSnapshot = null; if (WebUtils.isIncludeRequest(request)) { attributesSnapshot = new HashMap<String, Object>(); Enumeration<?> attrNames = request.getAttributeNames(); while (attrNames.hasMoreElements()) { String attrName = (String) attrNames.nextElement(); if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) { attributesSnapshot.put(attrName, request.getAttribute(attrName)); } } } // Make framework objects available to handlers and view objects. request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext()); request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver); request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver); request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response); if (inputFlashMap != null) { request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap)); } request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap()); request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager); try { //直接看这个方法 doDispatch(request, response); } finally { if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Restore the original attribute snapshot, in case of an include. if (attributesSnapshot != null) { restoreAttributesAfterInclude(request, attributesSnapshot); } } } } protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // Determine handler for the current request. mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // Process last-modified header, if supported by the handler. String method = request.getMethod(); boolean isGet = "GET".equals(method); if (isGet || "HEAD".equals(method)) { long lastModified = ha.getLastModified(request, mappedHandler.getHandler()); if (logger.isDebugEnabled()) { logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified); } if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) { return; } } if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // Actually invoke the handler. mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } applyDefaultViewName(processedRequest, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } catch (Throwable err) { // As of 4.3, we're processing Errors thrown from handler methods as well, // making them available for @ExceptionHandler methods and other scenarios. dispatchException = new NestedServletException("Handler dispatch failed", err); } //处理结果(里面含异常处理) processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Throwable err) { triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", err)); } finally { if (asyncManager.isConcurrentHandlingStarted()) { // Instead of postHandle and afterCompletion if (mappedHandler != null) { mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response); } } else { // Clean up any resources used by a multipart request. if (multipartRequestParsed) { cleanupMultipart(processedRequest); } } } }
进入异常处理的地方
进入到resolveException方法,默认解析器有3个,ExceptionHandlerExceptionResolver,ResponseStatusExceptionResolver,DefaultHandlerExceptionResolver;具体实例化的地方在WebMvcConfigurationSupport#addDefaultHandlerExceptionResolvers方法
protected final void addDefaultHandlerExceptionResolvers(List<HandlerExceptionResolver> exceptionResolvers) { ExceptionHandlerExceptionResolver exceptionHandlerResolver = createExceptionHandlerExceptionResolver(); exceptionHandlerResolver.setContentNegotiationManager(mvcContentNegotiationManager()); exceptionHandlerResolver.setMessageConverters(getMessageConverters()); exceptionHandlerResolver.setCustomArgumentResolvers(getArgumentResolvers()); exceptionHandlerResolver.setCustomReturnValueHandlers(getReturnValueHandlers()); if (jackson2Present) { exceptionHandlerResolver.setResponseBodyAdvice( Collections.<ResponseBodyAdvice<?>>singletonList(new JsonViewResponseBodyAdvice())); } exceptionHandlerResolver.setApplicationContext(this.applicationContext); exceptionHandlerResolver.afterPropertiesSet(); exceptionResolvers.add(exceptionHandlerResolver); ResponseStatusExceptionResolver responseStatusResolver = new ResponseStatusExceptionResolver(); responseStatusResolver.setMessageSource(this.applicationContext); exceptionResolvers.add(responseStatusResolver); exceptionResolvers.add(new DefaultHandlerExceptionResolver()); }
先看ExceptionHandlerExceptionResolver的处理如下: ExceptionHandlerExceptionResolver初始化的时候,
@Override public void afterPropertiesSet() { // Do this first, it may add ResponseBodyAdvice beans initExceptionHandlerAdviceCache(); if (this.argumentResolvers == null) { List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers(); this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers); } if (this.returnValueHandlers == null) { List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers(); this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers); } }
find所有ControllerAdvice Annotion注解的bean(找@ControllerAdvice注解或者其作为meta annotation,可以看下AnnotationUtils#findAnnotation方法),并排序;如果该类实现了ResponseBodyAdvice(可自定义扩展统一response的返回)接口
public ExceptionHandlerMethodResolver(Class<?> handlerType) { for (Method method : MethodIntrospector.selectMethods(handlerType, EXCEPTION_HANDLER_METHODS)) { for (Class<? extends Throwable> exceptionType : detectExceptionMappings(method)) { addExceptionMapping(exceptionType, method); } } } public static final MethodFilter EXCEPTION_HANDLER_METHODS = new MethodFilter() { @Override public boolean matches(Method method) { return (AnnotationUtils.findAnnotation(method, ExceptionHandler.class) != null); } };
找到标有ExceptionHandler注解的方法,并缓存再exceptionHandlerCache上,然后判断该ControllerAdviceBean是否能应用到该controller上
protected ServletInvocableHandlerMethod getExceptionHandlerMethod(HandlerMethod handlerMethod, Exception exception) { Class<?> handlerType = null; if (handlerMethod != null) { // Local exception handler methods on the controller class itself. // To be invoked through the proxy, even in case of an interface-based proxy. handlerType = handlerMethod.getBeanType(); ExceptionHandlerMethodResolver resolver = this.exceptionHandlerCache.get(handlerType); if (resolver == null) { resolver = new ExceptionHandlerMethodResolver(handlerType); this.exceptionHandlerCache.put(handlerType, resolver); } Method method = resolver.resolveMethod(exception); if (method != null) { return new ServletInvocableHandlerMethod(handlerMethod.getBean(), method); } // For advice applicability check below (involving base packages, assignable types // and annotation presence), use target class instead of interface-based proxy. if (Proxy.isProxyClass(handlerType)) { handlerType = AopUtils.getTargetClass(handlerMethod.getBean()); } } for (Map.Entry<ControllerAdviceBean, ExceptionHandlerMethodResolver> entry : this.exceptionHandlerAdviceCache.entrySet()) { ControllerAdviceBean advice = entry.getKey(); //判断是否匹配 if (advice.isApplicableToBeanType(handlerType)) { ExceptionHandlerMethodResolver resolver = entry.getValue(); Method method = resolver.resolveMethod(exception); if (method != null) { return new ServletInvocableHandlerMethod(advice.resolveBean(), method); } } } return null; }
可以看一下ControllerAdvice注解
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Component public @interface ControllerAdvice { /** * Alias for the {@link #basePackages} attribute. * <p>Allows for more concise annotation declarations e.g.: * {@code @ControllerAdvice("org.my.pkg")} is equivalent to * {@code @ControllerAdvice(basePackages="org.my.pkg")}. * @since 4.0 * @see #basePackages() */ @AliasFor("basePackages") String[] value() default {}; /** * Array of base packages. * <p>Controllers that belong to those base packages or sub-packages thereof * will be included, e.g.: {@code @ControllerAdvice(basePackages="org.my.pkg")} * or {@code @ControllerAdvice(basePackages={"org.my.pkg", "org.my.other.pkg"})}. * <p>{@link #value} is an alias for this attribute, simply allowing for * more concise use of the annotation. * <p>Also consider using {@link #basePackageClasses()} as a type-safe * alternative to String-based package names. * @since 4.0 */ @AliasFor("value") String[] basePackages() default {}; /** * Type-safe alternative to {@link #value()} for specifying the packages * to select Controllers to be assisted by the {@code @ControllerAdvice} * annotated class. * <p>Consider creating a special no-op marker class or interface in each package * that serves no purpose other than being referenced by this attribute. * @since 4.0 */ Class<?>[] basePackageClasses() default {}; /** * Array of classes. * <p>Controllers that are assignable to at least one of the given types * will be assisted by the {@code @ControllerAdvice} annotated class. * @since 4.0 */ Class<?>[] assignableTypes() default {}; /** * Array of annotations. * <p>Controllers that are annotated with this/one of those annotation(s) * will be assisted by the {@code @ControllerAdvice} annotated class. * <p>Consider creating a special annotation or use a predefined one, * like {@link RestController @RestController}. * @since 4.0 */ Class<? extends Annotation>[] annotations() default {}; }
最后,定位到ServletInvocableHandlerMethod#invokeAndHandle异常方法处理 RequestResponseBodyMethodProcessor#handleReturnValue 通过消息解析器,把流写出去
protected <T> void writeWithMessageConverters(T value, MethodParameter returnType, ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage) throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException { Object outputValue; Class<?> valueType; Type declaredType; if (value instanceof CharSequence) { outputValue = value.toString(); valueType = String.class; declaredType = String.class; } else { outputValue = value; valueType = getReturnValueType(outputValue, returnType); declaredType = getGenericType(returnType); } HttpServletRequest request = inputMessage.getServletRequest(); List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(request); List<MediaType> producibleMediaTypes = getProducibleMediaTypes(request, valueType, declaredType); if (outputValue != null && producibleMediaTypes.isEmpty()) { throw new IllegalArgumentException("No converter found for return value of type: " + valueType); } Set<MediaType> compatibleMediaTypes = new LinkedHashSet<MediaType>(); for (MediaType requestedType : requestedMediaTypes) { for (MediaType producibleType : producibleMediaTypes) { if (requestedType.isCompatibleWith(producibleType)) { compatibleMediaTypes.add(getMostSpecificMediaType(requestedType, producibleType)); } } } if (compatibleMediaTypes.isEmpty()) { if (outputValue != null) { throw new HttpMediaTypeNotAcceptableException(producibleMediaTypes); } return; } List<MediaType> mediaTypes = new ArrayList<MediaType>(compatibleMediaTypes); MediaType.sortBySpecificityAndQuality(mediaTypes); MediaType selectedMediaType = null; for (MediaType mediaType : mediaTypes) { if (mediaType.isConcrete()) { selectedMediaType = mediaType; break; } else if (mediaType.equals(MediaType.ALL) || mediaType.equals(MEDIA_TYPE_APPLICATION)) { selectedMediaType = MediaType.APPLICATION_OCTET_STREAM; break; } } if (selectedMediaType != null) { selectedMediaType = selectedMediaType.removeQualityValue(); for (HttpMessageConverter<?> messageConverter : this.messageConverters) { if (messageConverter instanceof GenericHttpMessageConverter) { if (((GenericHttpMessageConverter) messageConverter).canWrite( declaredType, valueType, selectedMediaType)) { outputValue = (T) getAdvice().beforeBodyWrite(outputValue, returnType, selectedMediaType, (Class<? extends HttpMessageConverter<?>>) messageConverter.getClass(), inputMessage, outputMessage); if (outputValue != null) { addContentDispositionHeader(inputMessage, outputMessage); ((GenericHttpMessageConverter) messageConverter).write( outputValue, declaredType, selectedMediaType, outputMessage); if (logger.isDebugEnabled()) { logger.debug("Written [" + outputValue + "] as \"" + selectedMediaType + "\" using [" + messageConverter + "]"); } } return; } } else if (messageConverter.canWrite(valueType, selectedMediaType)) { outputValue = (T) getAdvice().beforeBodyWrite(outputValue, returnType, selectedMediaType, (Class<? extends HttpMessageConverter<?>>) messageConverter.getClass(), inputMessage, outputMessage); if (outputValue != null) { addContentDispositionHeader(inputMessage, outputMessage); ((HttpMessageConverter) messageConverter).write(outputValue, selectedMediaType, outputMessage); if (logger.isDebugEnabled()) { logger.debug("Written [" + outputValue + "] as \"" + selectedMediaType + "\" using [" + messageConverter + "]"); } } return; } } } if (outputValue != null) { throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes); } }
在body writer之前,会先调用ResponseBodyAdvice match做一层处理,也就是说,
@RestControllerAdvice public class GlobalExceptionHandler extends ResponseEntityExceptionHandler implements ResponseBodyAdvice {}
以上就是使用@RestControllerAdvice怎么对异常进行处理,小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注亿速云行业资讯频道。
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