1.springmvc的基本流程(不多赘述)
2.主要涉及到的类
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; }
在DispatcherServlet类中通过getHandler方法去遍历我们配置文件中写入的handlerMapping 从而找到我们的handle handle会有多种形态 此时需要我们的handleadapter去适配
在doDisdapch方法中 通过handle去找对应的适配器
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 { processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // Determine handler for the current request. mappedHandler = getHandler(processedRequest); if (mappedHandler == null || mappedHandler.getHandler() == null) { noHandlerFound(processedRequest, response); return; } // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
通过上面红色的部分 进入getHandlerAdapter
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException { for (HandlerAdapter ha : this.handlerAdapters) { if (logger.isTraceEnabled()) { logger.trace("Testing handler adapter [" + ha + "]"); } if (ha.supports(handler)) { return ha; } } throw new ServletException("No adapter for handler [" + handler + "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler"); }
通过对handlerAdapters遍历的方法去找到适配的handler 找到后基于HandlerAdapter中的handler方法返回我们的ModelAndView
ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception;
接收到返回ModelAndView以后 再去找DispatcherServlet类中的resolveViewName方法
protected View resolveViewName(String viewName, Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception { for (ViewResolver viewResolver : this.viewResolvers) { View view = viewResolver.resolveViewName(viewName, locale); if (view != null) { return view; } } return null; }
然后通过我们的render 去执行我们的视图
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception { // Determine locale for request and apply it to the response. Locale locale = this.localeResolver.resolveLocale(request); response.setLocale(locale); View view; if (mv.isReference()) { // We need to resolve the view name. view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request); if (view == null) { throw new ServletException("Could not resolve view with name '" + mv.getViewName() + "' in servlet with name '" + getServletName() + "'"); } } else { // No need to lookup: the ModelAndView object contains the actual View object. view = mv.getView(); if (view == null) { throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " + "View object in servlet with name '" + getServletName() + "'"); } } // Delegate to the View object for rendering. if (logger.isDebugEnabled()) { logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'"); } try { if (mv.getStatus() != null) { response.setStatus(mv.getStatus().value()); } view.render(mv.getModelInternal(), request, response); } catch (Exception ex) { if (logger.isDebugEnabled()) { logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'", ex); } throw ex; } }
HandlerMapping详解
目前主流的三种mapping 如下:
BeanNameUrlHandlerMapping: 基于ioc name 中已 "/" 开头的Bean时行 注册至映谢.
SimpleUrlHandlerMapping:基于手动配置 url 与control 映谢
RequestMappingHandlerMapping:基于@RequestMapping注解配置对应映谢
HandlerAdapter详解
这里spring mvc 采用适配器模式来适配调用指定Handler,根据Handler的不同种类采用不同的Adapter,其Handler与 HandlerAdapter 对应关系如下:
Handler类别 |
对应适配器 |
描述 |
Controller |
SimpleControllerHandlerAdapter |
标准控制器,返回ModelAndView |
HttpRequestHandler |
HttpRequestHandlerAdapter |
业务自行处理 请求,不需要通过modelAndView 转到视图 |
Servlet |
SimpleServletHandlerAdapter |
基于标准的servlet 处理 |
HandlerMethod |
RequestMappingHandlerAdapter |
基于@requestMapping对应方法处理 |
HandlerAdapter 接口方法
ViewResolver 与View 详解
找到应的Adapter 之后就会基于适配器调用业务处理,处理完之后业务方会返回一个ModelAndView ,在去查找对应的视图进行处理。其在org.springframework.web.servlet.DispatcherServlet#resolveViewName() 中遍历 viewResolvers 列表查找,如果找不到就会报一个 Could not resolve view with name 异常。
在下一步就是基于ViewResolver.resolveViewName() 获取对应View来解析生成Html并返回 。对应VIEW结构如下: