Spring3.2请求处理大致过程
处理过程
-
初始化:
- DispatcherServlet.onRefresh()
- DispatcherServlet.initStrategies()
- DispatcherServlet.initHandlerMappings()
-
处理请求:
- DispatcherServlet.doDispatch()
- RequestMappingHandlerAdapter.handle()
- RequestMappingHandlerAdapter.handleInternal()
- RequestMappingHandlerAdapter.invokeHandleMethod()
- WebAsyncManager.setTaskExecutor()
- WebAsyncManager.setAsyncWebRequest()
- WebAsyncManager.registerCallableInterceptors()
- WebAsyncManager.registerDeferredResultInterceptors()
- ServletInvocableHandlerMethod.invokeAndHandle()
- CallableMethodReturnValueHandler/DeferredResultMethodReturnValueHandler.handleReturnValue()
- WebAsyncManager.startCallableProcessing()/WebAsyncManager.startDeferredResultProcessing()
代码详述
DispatcherServlet.java
在onRefresh时，初始化
/**
* This implementation calls {@link #initStrategies}.
*/
@Override
protected void onRefresh(ApplicationContext context) {
initStrategies(context);
}
/**
* Initialize the strategy objects that this servlet uses.
* <p>May be overridden in subclasses in order to initialize further strategy objects.
*/
protected void initStrategies(ApplicationContext context) {
initMultipartResolver(context);
initLocaleResolver(context);
initThemeResolver(context);
initHandlerMappings(context);//初始化Handler映射,例如@RequestMapping(value = "/something", method = RequestMethod.PUT)
initHandlerAdapters(context);
initHandlerExceptionResolvers(context);
initRequestToViewNameTranslator(context);
initViewResolvers(context);
initFlashMapManager(context);
}
/**
* Initialize the HandlerMappings used by this class.
* <p>If no HandlerMapping beans are defined in the BeanFactory for this namespace,
* we default to BeanNameUrlHandlerMapping.
*/
private void initHandlerMappings(ApplicationContext context) {
this.handlerMappings = null;
if (this.detectAllHandlerMappings) {
// Find all HandlerMappings in the ApplicationContext, including ancestor contexts.
Map<String, HandlerMapping> matchingBeans =
BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);//从Context中，找@RequestMapping，构建映射关系
if (!matchingBeans.isEmpty()) {
this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values());
// We keep HandlerMappings in sorted order.
OrderComparator.sort(this.handlerMappings);
}
}
else {
try {
HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);//缺省
this.handlerMappings = Collections.singletonList(hm);
}
catch (NoSuchBeanDefinitionException ex) {
// Ignore, we'll add a default HandlerMapping later.
}
}
// Ensure we have at least one HandlerMapping, by registering
// a default HandlerMapping if no other mappings are found.
if (this.handlerMappings == null) {
this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
if (logger.isDebugEnabled()) {
logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default");
}
}
}
处理请求时，找handlerAdapter处理请求
/**
* Process the actual dispatching to the handler.
* <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
* The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
* to find the first that supports the handler class.
* <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
* themselves to decide which methods are acceptable.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception in case of any kind of processing failure
*/
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);//获取WebAsyncManager
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = processedRequest != request;
// Determine handler for the current request.
mappedHandler = getHandler(processedRequest, false);//获取HandlerExecutionChain
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());//获取映射处理封装类
// 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()) {
String requestUri = urlPathHelper.getRequestUri(request);
logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
try {
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());//调用handler处理
}
finally {
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
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
return;
}
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
/**
* Return the HandlerExecutionChain for this request.
* <p>Tries all handler mappings in order.
* @param request current HTTP request
* @return the HandlerExecutionChain, or <code>null</code> if no handler could be found
*/
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
return null;
}
RequestMappingHandlerAdapter.java
调用handle方法处理，handle调用handleInternal方法
protected final ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
// Always prevent caching in case of session attribute management.
checkAndPrepare(request, response, this.cacheSecondsForSessionAttributeHandlers, true);
}
else {
// Uses configured default cacheSeconds setting.
checkAndPrepare(request, response, true);
}
// Execute invokeHandlerMethod in synchronized block if required.
if (this.synchronizeOnSession) {
HttpSession session = request.getSession(false);
if (session != null) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
return invokeHandleMethod(request, response, handlerMethod);
}
}
}
return invokeHandleMethod(request, response, handlerMethod);
}
调用invokeHandleMethod
/**
* Invoke the {@link RequestMapping} handler method preparing a {@link ModelAndView} if view resolution is required.
*/
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);//创建请求映射方法,注意这里会设置
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
modelFactory.initModel(webRequest, mavContainer, requestMappingMethod);
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
//异步初始化
AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout);
final WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.setTaskExecutor(this.taskExecutor);//设置执行类AsyncManager会用到
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);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
}
return getModelAndView(mavContainer, modelFactory, webRequest);
}
private ServletInvocableHandlerMethod createRequestMappingMethod(
HandlerMethod handlerMethod, WebDataBinderFactory binderFactory) {
ServletInvocableHandlerMethod requestMethod;
requestMethod = new ServletInvocableHandlerMethod(handlerMethod);
requestMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
requestMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);//注入ReturnValueHandlers
requestMethod.setDataBinderFactory(binderFactory);
requestMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
return requestMethod;
}
/**
* Configure the complete list of supported return value types thus
* overriding handlers that would otherwise be configured by default.
*/
//如果需要异步处理，需要注入例如DeferredResultMethodReturnValueHandler等
public void setReturnValueHandlers(List<HandlerMethodReturnValueHandler> returnValueHandlers) {
if (returnValueHandlers == null) {
this.returnValueHandlers = null;
}
else {
this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite();
this.returnValueHandlers.addHandlers(returnValueHandlers);
}
}
/**
* Default constructor.
*/
public RequestMappingHandlerAdapter() {
StringHttpMessageConverter stringHttpMessageConverter = new StringHttpMessageConverter();
stringHttpMessageConverter.setWriteAcceptCharset(false); // See SPR-7316
this.messageConverters = new ArrayList<HttpMessageConverter<?>>();//converter均集成HttpMessageConverter来拦截http请求
this.messageConverters.add(new ByteArrayHttpMessageConverter());
this.messageConverters.add(stringHttpMessageConverter);
this.messageConverters.add(new SourceHttpMessageConverter<Source>());
this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
}
/**
* Provide the converters to use in argument resolvers and return value
* handlers that support reading and/or writing to the body of the
* request and response.
*/
public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters) {
this.messageConverters = messageConverters;
}
/**
* Set the default {@link AsyncTaskExecutor} to use when a controller method
* return a {@link Callable}. Controller methods can override this default on
* a per-request basis by returning an {@link WebAsyncTask}.
* <p>By default a {@link SimpleAsyncTaskExecutor} instance is used.
* It's recommended to change that default in production as the simple executor
* does not re-use threads.
*/
//设置异步执行类,给AsyncManager调用
public void setTaskExecutor(AsyncTaskExecutor taskExecutor) {
this.taskExecutor = taskExecutor;
}
ServletInvocableHandlerMethod.java
调用invokeAndHandle
/**
* Invokes the method and handles the return value through a registered
* {@link HandlerMethodReturnValueHandler}.
*
* @param webRequest the current request
* @param mavContainer the ModelAndViewContainer for this request
* @param providedArgs "given" arguments matched by type, not resolved
*/
public final void invokeAndHandle(ServletWebRequest webRequest,
ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception {
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
setResponseStatus(webRequest);
if (returnValue == null) {
if (isRequestNotModified(webRequest) || hasResponseStatus() || mavContainer.isRequestHandled()) {
mavContainer.setRequestHandled(true);
return;
}
}
else if (StringUtils.hasText(this.responseReason)) {
mavContainer.setRequestHandled(true);
return;
}
mavContainer.setRequestHandled(false);//异步处理，表示没有处理完毕
try {//调用HandlerMethodReturnValueHandler做异步处理，returnValue为DeferredResult or Callable or
this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(getReturnValueHandlingErrorMessage("Error handling return value", returnValue), ex);
}
throw ex;
}
}
CallableMethodReturnValueHandler.java
调用handleReturnValue方法
public void handleReturnValue(Object returnValue,
MethodParameter returnType, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest) throws Exception {
if (returnValue == null) {
mavContainer.setRequestHandled(true);
return;
}
Callable<?> callable = (Callable<?>) returnValue;
WebAsyncUtils.getAsyncManager(webRequest).startCallableProcessing(callable, mavContainer);
}
DeferredResultMethodReturnValueHandler.java
调用handleReturnValue方法
public void handleReturnValue(Object returnValue,
MethodParameter returnType, ModelAndViewContainer mavContainer,
NativeWebRequest webRequest) throws Exception {
if (returnValue == null) {
mavContainer.setRequestHandled(true);
return;
}
DeferredResult<?> deferredResult = (DeferredResult<?>) returnValue;
WebAsyncUtils.getAsyncManager(webRequest).startDeferredResultProcessing(deferredResult, mavContainer);
}
WebAsyncManager.java 参考Spring Servlet3 扩展模块笔记
调用startCallableProcessing方法
/**
* Start concurrent request processing and execute the given task with an
* {@link #setTaskExecutor(AsyncTaskExecutor) AsyncTaskExecutor}. The result
* from the task execution is saved and the request dispatched in order to
* resume processing of that result. If the task raises an Exception then
* the saved result will be the raised Exception.
*
* @param callable a unit of work to be executed asynchronously
* @param processingContext additional context to save that can be accessed
* via {@link #getConcurrentResultContext()}
* @throws Exception If concurrent processing failed to start
*
* @see #getConcurrentResult()
* @see #getConcurrentResultContext()
*/
@SuppressWarnings({ "rawtypes", "unchecked" })
public void startCallableProcessing(final Callable<?> callable, Object... processingContext) throws Exception {
Assert.notNull(callable, "Callable must not be null");
startCallableProcessing(new WebAsyncTask(callable), processingContext);
}
/**
* Use the given {@link WebAsyncTask} to configure the task executor as well as
* the timeout value of the {@code AsyncWebRequest} before delegating to
* {@link #startCallableProcessing(Callable, Object...)}.
*
* @param webAsyncTask an WebAsyncTask containing the target {@code Callable}
* @param processingContext additional context to save that can be accessed
* via {@link #getConcurrentResultContext()}
* @throws Exception If concurrent processing failed to start
*/
public void startCallableProcessing(final WebAsyncTask<?> webAsyncTask, Object... processingContext) throws Exception {
Assert.notNull(webAsyncTask, "WebAsyncTask must not be null");
Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");
Long timeout = webAsyncTask.getTimeout();
if (timeout != null) {
this.asyncWebRequest.setTimeout(timeout);
}
AsyncTaskExecutor executor = webAsyncTask.getExecutor();
if (executor != null) {
this.taskExecutor = executor;
}
List<CallableProcessingInterceptor> interceptors = new ArrayList<CallableProcessingInterceptor>();
interceptors.add(webAsyncTask.getInterceptor());
interceptors.addAll(this.callableInterceptors.values());
interceptors.add(timeoutCallableInterceptor);
final Callable<?> callable = webAsyncTask.getCallable();
final CallableInterceptorChain interceptorChain = new CallableInterceptorChain(interceptors);
this.asyncWebRequest.addTimeoutHandler(new Runnable() {
public void run() {
logger.debug("Processing timeout");
Object result = interceptorChain.triggerAfterTimeout(asyncWebRequest, callable);
if (result != CallableProcessingInterceptor.RESULT_NONE) {
setConcurrentResultAndDispatch(result);
}
}
});
this.asyncWebRequest.addCompletionHandler(new Runnable() {
public void run() {
interceptorChain.triggerAfterCompletion(asyncWebRequest, callable);
}
});
interceptorChain.applyBeforeConcurrentHandling(asyncWebRequest, callable);
startAsyncProcessing(processingContext);
this.taskExecutor.submit(new Runnable() {
public void run() {
Object result = null;
try {
interceptorChain.applyPreProcess(asyncWebRequest, callable);
result = callable.call();
}
catch (Throwable t) {
result = t;
}
finally {
result = interceptorChain.applyPostProcess(asyncWebRequest, callable, result);
}
setConcurrentResultAndDispatch(result);
}
});
}
调用startDeferredResultProcessing方法
/**
* Start concurrent request processing and initialize the given
* {@link DeferredResult} with a {@link DeferredResultHandler} that saves
* the result and dispatches the request to resume processing of that
* result. The {@code AsyncWebRequest} is also updated with a completion
* handler that expires the {@code DeferredResult} and a timeout handler
* assuming the {@code DeferredResult} has a default timeout result.
*
* @param deferredResult the DeferredResult instance to initialize
* @param processingContext additional context to save that can be accessed
* via {@link #getConcurrentResultContext()}
* @throws Exception If concurrent processing failed to start
*
* @see #getConcurrentResult()
* @see #getConcurrentResultContext()
*/
public void startDeferredResultProcessing(
final DeferredResult<?> deferredResult, Object... processingContext) throws Exception {
Assert.notNull(deferredResult, "DeferredResult must not be null");
Assert.state(this.asyncWebRequest != null, "AsyncWebRequest must not be null");
Long timeout = deferredResult.getTimeoutValue();
if (timeout != null) {
this.asyncWebRequest.setTimeout(timeout);
}
List<DeferredResultProcessingInterceptor> interceptors = new ArrayList<DeferredResultProcessingInterceptor>();
interceptors.add(deferredResult.getInterceptor());
interceptors.addAll(this.deferredResultInterceptors.values());
interceptors.add(timeoutDeferredResultInterceptor);
final DeferredResultInterceptorChain interceptorChain = new DeferredResultInterceptorChain(interceptors);
this.asyncWebRequest.addTimeoutHandler(new Runnable() {
public void run() {
try {
interceptorChain.triggerAfterTimeout(asyncWebRequest, deferredResult);
}
catch (Throwable t) {
setConcurrentResultAndDispatch(t);
}
}
});
this.asyncWebRequest.addCompletionHandler(new Runnable() {
public void run() {
interceptorChain.triggerAfterCompletion(asyncWebRequest, deferredResult);
}
});
interceptorChain.applyBeforeConcurrentHandling(asyncWebRequest, deferredResult);
startAsyncProcessing(processingContext);
try {
interceptorChain.applyPreProcess(this.asyncWebRequest, deferredResult);
deferredResult.setResultHandler(new DeferredResultHandler() {
public void handleResult(Object result) {
result = interceptorChain.applyPostProcess(asyncWebRequest, deferredResult, result);
setConcurrentResultAndDispatch(result);
}
});
}
catch (Throwable t) {
setConcurrentResultAndDispatch(t);
}
}