四、SpringMVC前端控制器

1.前端控制器接收請求，調用doDispatch方法

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
	HttpServletRequest processedRequest = request;
	HandlerExecutionChain mappedHandler = null;
	boolean multipartRequestParsed = false;
	...
}

2.前端控制器調用HandlerMapping（處理器映射器）根據url查找Handler

mappedHandler = getHandler(processedRequest);

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;
}

3.調用處理器適配器執行Handler,獲得執行的結果ModelAndView mv。在doDispatch方法中

mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

4.視圖渲染。doDispatch->processDispatchResult->render。在render方法中,視圖解析獲得view。

view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);

調用view的渲染方法，將model數據填充到request域。在render方法中,調用View接口的render方法

view.render(mv.getModelInternal(), request, response);