SpringMVC请求处理大致流程源码学习笔记

请求处理大致流程：doDispatch()详细细节

@SuppressWarnings("serial")
public class DispatcherServlet extends FrameworkServlet {

	@Override
	protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
		try {
			doDispatch(request, response);
		}
	}
	
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HttpServletRequest processedRequest = request;
		HandlerExecutionChain mappedHandler = null;
		boolean multipartRequestParsed = false;
		
		//异步管理器
		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

		try {
			ModelAndView mv = null;
			Exception dispatchException = null;
			try {
				//1.检查多部件，检查当前请求是否文件上传请求
				processedRequest = checkMultipart(request);
				//如果是文件上传请求，就不能用原来的request，如果是就用原来的
				multipartRequestParsed = (processedRequest != request);

				// Determine handler for the current request.
				//2.根据当前请求地址，找到用哪个(处理器)Handler
				mappedHandler = getHandler(processedRequest);
				
				//3.如果没有找到哪个处理器（控制器）能处理这个请求就404，或者抛异常
				if (mappedHandler == null || mappedHandler.getHandler() == null) {
					noHandlerFound(processedRequest, response);
					return;
				}

				// Determine handler adapter for the current request.
				//4.拿到能执行这个类的所有方法的适配器(反射工具)。决定当前请求用哪个处理器的适配器
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				// Process last-modified header, if supported by the handler.
				//获取了请求方式
				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.
				//5.用适配器真正执行处理器的方法，将目标方法执行完成后的返回值作为视图名，设置保存到ModelAndView中
				//无论目标方法怎写，最终适配器执行完成以后都会将执行后的信息封装成ModelAndView
				//处理（控制器）器的方法被调用
				//控制器(Controller)，处理器(Handler)
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
				
				//异步处理器判断，是否是异步方法
				if (asyncManager.isConcurrentHandlingStarted()) {
					return;
				}
				
				//如果没有视图名，使用默认的视图名字
				applyDefaultViewName(request, mv);
				mappedHandler.applyPostHandle(processedRequest, response, mv);
			}
			catch (Exception ex) {
				dispatchException = ex;
			}
			//转发到目标页面，页面渲染
			//6.根据方法最终执行后封装的ModelAndView，转发到对应页面，而且ModelAndView中的数据可以从请求域中获取
			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);
				}
			}
		}
	}
}

noHandlerFound

	源码：
	protected void noHandlerFound(HttpServletRequest request, HttpServletResponse response) throws Exception {
		if (pageNotFoundLogger.isWarnEnabled()) {
			pageNotFoundLogger.warn("No mapping found for HTTP request with URI [" + getRequestUri(request) +
					"] in DispatcherServlet with name '" + getServletName() + "'");
		}
		if (this.throwExceptionIfNoHandlerFound) {
			ServletServerHttpRequest sshr = new ServletServerHttpRequest(request);
			throw new NoHandlerFoundException(
					sshr.getMethod().name(), sshr.getServletRequest().getRequestURI(), sshr.getHeaders());
		}
		else {
			response.sendError(HttpServletResponse.SC_NOT_FOUND);
		}
	}