springMVC doDispatch方法

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
int interceptorIndex = -1;

// Expose current LocaleResolver and request as LocaleContext.
LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
LocaleContextHolder.setLocaleContext(buildLocaleContext(request), this.threadContextInheritable);

// Expose current RequestAttributes to current thread.
RequestAttributes previousRequestAttributes = RequestContextHolder.getRequestAttributes();
ServletRequestAttributes requestAttributes = new ServletRequestAttributes(request);
RequestContextHolder.setRequestAttributes(requestAttributes, this.threadContextInheritable);

if (logger.isTraceEnabled()) {
logger.trace("Bound request context to thread: " + request);
}

try {
ModelAndView mv = null;
boolean errorView = false;

try {
processedRequest = checkMultipart(request);//检查是否是multipartrequest请求，如果是，就形成将request封装为multipartrequest，如果不是就返回原request

// Determine handler for the current request.
mappedHandler = getHandler(processedRequest, false);//通过handlermapping得到mappedhandler
if (mappedHandler == null || mappedHandler.getHandler() == null) {
noHandlerFound(processedRequest, response);
return;
}

// Apply preHandle methods of registered interceptors.执行拦截器的prehandle方法。
HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
if (interceptors != null) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())) {
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
return;
}
interceptorIndex = i;
}
}

// Actually invoke the handler.得到handleradapter
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());//执行相关操作

// Do we need view name translation?
if (mv != null && !mv.hasView()) {
mv.setViewName(getDefaultViewName(request));
}

// Apply postHandle methods of registered interceptors.执行拦截器的posthandle方法。
if (interceptors != null) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);
}
}
}
catch (ModelAndViewDefiningException ex) {
logger.debug("ModelAndViewDefiningException encountered", ex);
mv = ex.getModelAndView();
}
catch (Exception ex) {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(processedRequest, response, handler, ex);
errorView = (mv != null);
}

// Did the handler return a view to render?//渲染视图
if (mv != null && !mv.wasCleared()) {
render(mv, processedRequest, 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");
}
}

// Trigger after-completion for successful outcome.
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);//执行拦截器的AfterCompletion方法。
}

catch (Exception ex) {
// Trigger after-completion for thrown exception.
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
throw ex;
}
catch (Error err) {
ServletException ex = new NestedServletException("Handler processing failed", err);
// Trigger after-completion for thrown exception.
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, ex);
throw ex;
}

finally {
// Clean up any resources used by a multipart request.
if (processedRequest != request) {
cleanupMultipart(processedRequest);
}

// Reset thread-bound context.
RequestContextHolder.setRequestAttributes(previousRequestAttributes, this.threadContextInheritable);
LocaleContextHolder.setLocaleContext(previousLocaleContext, this.threadContextInheritable);

// Clear request attributes.
requestAttributes.requestCompleted();
if (logger.isTraceEnabled()) {
logger.trace("Cleared thread-bound request context: " + request);
}
}
}