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;
}