前言
。
一、doService( )
将一些属性放入request中，如WebApplicationContext、localeResolver、themeResolver等，之后调用doDispatch( )方法进行请求的分发。
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
logRequest(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<>();
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.
//设置WebApplicationContext
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
//设置localeResolver
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
//设置themeResolver
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
//设置ThemeSource
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());
if (this.flashMapManager != null) {
FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);
if (inputFlashMap != null) {
//设置FlashMap
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);
}
RequestPath previousRequestPath = null;
if (this.parseRequestPath) {
previousRequestPath = (RequestPath) request.getAttribute(ServletRequestPathUtils.PATH_ATTRIBUTE);
ServletRequestPathUtils.parseAndCache(request);
}
try {
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);
}
}
if (this.parseRequestPath) {
ServletRequestPathUtils.setParsedRequestPath(previousRequestPath, request);
}
}
}
二、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 {
//处理文件上传请求
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
//获取handler的执行器链
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
//没有找到handler
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
//获取处理器适配器
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = HttpMethod.GET.matches(method);
if (isGet || HttpMethod.HEAD.matches(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
//GET请求，并且上次访问到现在没有被修改过，直接返回
return;
}
}
//拦截器链的预处理applyPreHandle
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
//处理业务
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
//拦截器链的后处理applyPostHandle
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);
}
//执行结果的处理，如视图的渲染，请求的跳转、重定向等
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
//拦截器链执行完毕回调
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.
//清理文件上传资源
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}