这次的议题是返回json和返回普通view经过的路线差异。
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org.springframework.web.servlet.DispatcherServlet#doDispatch
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(request, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Error err) { triggerAfterCompletionWithError(processedRequest, response, mappedHandler, 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); } } } }
1 view的设置
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#invokeHandleMethod
private ModelAndView invokeHandleMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ServletWebRequest webRequest = new ServletWebRequest(request, response); WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod); ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory); ServletInvocableHandlerMethod requestMappingMethod = createRequestMappingMethod(handlerMethod, binderFactory); ModelAndViewContainer mavContainer = new ModelAndViewContainer(); mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request)); modelFactory.initModel(webRequest, mavContainer, requestMappingMethod); mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect); AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response); asyncWebRequest.setTimeout(this.asyncRequestTimeout); final WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); asyncManager.setTaskExecutor(this.taskExecutor); asyncManager.setAsyncWebRequest(asyncWebRequest); asyncManager.registerCallableInterceptors(this.callableInterceptors); asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors); if (asyncManager.hasConcurrentResult()) { Object result = asyncManager.getConcurrentResult(); mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0]; asyncManager.clearConcurrentResult(); if (logger.isDebugEnabled()) { logger.debug("Found concurrent result value [" + result + "]"); } requestMappingMethod = requestMappingMethod.wrapConcurrentResult(result); } requestMappingMethod.invokeAndHandle(webRequest, mavContainer); // 请求并设置mavContainer if (asyncManager.isConcurrentHandlingStarted()) { return null; } return getModelAndView(mavContainer, modelFactory, webRequest); }
org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite#getReturnValueHandler
private HandlerMethodReturnValueHandler getReturnValueHandler(MethodParameter returnType) { for (HandlerMethodReturnValueHandler returnValueHandler : returnValueHandlers) { if (logger.isTraceEnabled()) { logger.trace("Testing if return value handler [" + returnValueHandler + "] supports [" + returnType.getGenericParameterType() + "]"); } if (returnValueHandler.supportsReturnType(returnType)) { // 遍历获取合适的returnValueHandler return returnValueHandler; } } return null; }
1.1 根据viewName来解析的Handler
org.springframework.web.servlet.mvc.method.annotation.ViewNameMethodReturnValueHandler#supportsReturnType
public boolean supportsReturnType(MethodParameter returnType) { Class<?> paramType = returnType.getParameterType(); return (void.class.equals(paramType) || String.class.equals(paramType)); }
org.springframework.web.servlet.mvc.method.annotation.ViewNameMethodReturnValueHandler#handleReturnValue
public void handleReturnValue( Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception { if (returnValue == null) { return; } else if (returnValue instanceof String) { String viewName = (String) returnValue; mavContainer.setViewName(viewName); if (isRedirectViewName(viewName)) { mavContainer.setRedirectModelScenario(true); } } else { // should not happen throw new UnsupportedOperationException("Unexpected return type: " + returnType.getParameterType().getName() + " in method: " + returnType.getMethod()); } }
1.2 支持ResponseBody的Handler
org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor#supportsReturnType
public boolean supportsReturnType(MethodParameter returnType) { return ((AnnotationUtils.findAnnotation(returnType.getContainingClass(), ResponseBody.class) != null) || (returnType.getMethodAnnotation(ResponseBody.class) != null)); }
org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor#handleReturnValue
public void handleReturnValue(Object returnValue, MethodParameter returnType, ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws IOException, HttpMediaTypeNotAcceptableException { mavContainer.setRequestHandled(true); if (returnValue != null) { writeWithMessageConverters(returnValue, returnType, webRequest); } }
org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor#writeWithMessageConverters(T, org.springframework.core.MethodParameter, org.springframework.http.server.ServletServerHttpRequest, org.springframework.http.server.ServletServerHttpResponse)
protected <T> void writeWithMessageConverters(T returnValue, MethodParameter returnType, ServletServerHttpRequest inputMessage, ServletServerHttpResponse outputMessage) throws IOException, HttpMediaTypeNotAcceptableException { Class<?> returnValueClass = returnValue.getClass(); HttpServletRequest servletRequest = inputMessage.getServletRequest(); List<MediaType> requestedMediaTypes = getAcceptableMediaTypes(servletRequest); List<MediaType> producibleMediaTypes = getProducibleMediaTypes(servletRequest, returnValueClass); 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()) { throw new HttpMediaTypeNotAcceptableException(producibleMediaTypes); } 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) { // 遍历获取合适的messageConverter(mediaType) if (messageConverter.canWrite(returnValueClass, selectedMediaType)) { returnValue = this.adviceChain.invoke(returnValue, returnType, selectedMediaType, (Class<HttpMessageConverter<?>>) messageConverter.getClass(), inputMessage, outputMessage); ((HttpMessageConverter<T>) messageConverter).write(returnValue, selectedMediaType, outputMessage); if (logger.isDebugEnabled()) { logger.debug("Written [" + returnValue + "] as "" + selectedMediaType + "" using [" + messageConverter + "]"); } return; } } } throw new HttpMediaTypeNotAcceptableException(this.allSupportedMediaTypes); }
2.设置了viewName的view解析
org.springframework.web.servlet.DispatcherServlet#processDispatchResult
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception { boolean errorView = false; if (exception != null) { if (exception instanceof ModelAndViewDefiningException) { logger.debug("ModelAndViewDefiningException encountered", exception); mv = ((ModelAndViewDefiningException) exception).getModelAndView(); } else { Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null); mv = processHandlerException(request, response, handler, exception); errorView = (mv != null); } } // Did the handler return a view to render? if (mv != null && !mv.wasCleared()) { // 如果没有设置view则不会进入viewResolver,返回json对象就不进入viewResolver render(mv, request, response); if (errorView) { WebUtils.clearErrorRequestAttributes(request); } } else { if (logger.isDebugEnabled()) { logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() + "': assuming HandlerAdapter completed request handling"); } } if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Concurrent handling started during a forward return; } if (mappedHandler != null) { mappedHandler.triggerAfterCompletion(request, response, null); } }
org.springframework.web.servlet.DispatcherServlet#resolveViewName
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception { for (ViewResolver viewResolver : this.viewResolvers) { // 遍历获取合适的viewResolver View view = viewResolver.resolveViewName(viewName, locale); if (view != null) { return view; } } return null; }