什么是springMVC？你会吗？看透Spring MVC源代码分析与实践 .pdf

组件概览

HandlerMapping

根据 request 找到对应的处理器 Handler 和 Interceptors。内部只有一个方法

HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;

HandlerAdapter

Handler 适配器，内部方法如下：

boolean supports(Object handler);//判断是否可以使用某个 Handler
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception; //具体使用
long getLastModified(HttpServletRequest request, Object handler);//获取资源上一次修改的时间

HandlerExceptionResolver

根据异常设置 ModelAndView ，再交给 render 方法进行渲染。

ModelAndView resolveException(
            HttpServletRequest request, HttpServletResponse response, @Nullable Object handler, Exception ex)

ViewResolver

用来将 String 类型的视图名和 Locale 解析为 View 类型的视图。

View resolveViewName(String viewName, Locale locale) throws Exception;

它的一个实现类 BeanNameViewResolver，它重写 resolveViewName 方法如下:

public View resolveViewName(String viewName, Locale locale) throws BeansException {
        ApplicationContext context = getApplicationContext();
        //如果应用上下文没有找到视图，返回 null
        if (!context.containsBean(viewName)) {
            if (logger.isDebugEnabled()) {
                logger.debug("No matching bean found for view name '" + viewName + "'");
            }
            // Allow for ViewResolver chaining...
            return null;
        }
        //如果找到的视图类型不匹配，也返回 null
        if (!context.isTypeMatch(viewName, View.class)) {
            if (logger.isDebugEnabled()) {
                logger.debug("Found matching bean for view name '" + viewName +
                        "' - to be ignored since it does not implement View");
            }
            // Since we're looking into the general ApplicationContext here,
            // let's accept this as a non-match and