SpringMVC 之DispatchServlet 原理梳理

目录

• DispatchServlet
  • 启动时：onRefresh()
    • 初始化各种配置 initStrategies()
  • 请求时：doService()
    • doDispatch()
      • 根据请求选择合适的HandlerExecutionChain mappedHandler = this.getHandler(processedRequest);
        • 遍历所有初始化的HanderMapping.getHandler()
      • 再根据hander选择适配器 HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());
      • 执行拦截器HandlerInterceptor前置方法 mappedHandler.applyPreHandle(processedRequest, response)
      • 通过适配器执行具体内容 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
      • 执行拦截器HandlerInterceptor后置方法 mappedHandler.applyPostHandle(processedRequest, response, mv);

DispatchServlet

主要梳理了一下源码中几个方法

启动时：onRefresh()

初始化各种配置 initStrategies()

• this.initMultipartResolver(context);

• this.initLocaleResolver(context);

• this.initThemeResolver(context);

• this.initHandlerMappings(context);

• this.initHandlerAdapters(context);

• this.initHandlerExceptionResolvers(context);

• this.initRequestToViewNameTranslator(context);

• this.initViewResolvers(context);

• this.initFlashMapManager(context);

请求时：doService()

doDispatch()

根据请求选择合适的HandlerExecutionChain mappedHandler = this.getHandler(processedRequest);

遍历所有初始化的HanderMapping.getHandler()

1. SimpleUrlHanderMapping

2. PropertySourcedRequestMappinglHanderMapping

3. RequestMappinglHanderMapping

• 父类：AbstractHandlerMethodMapping .getHandlerInternal(request)

• 根据请求路径 lookupPath 获取对应的controller的方法 lookupHandlerMethod(String lookupPath, HttpServletRequest request)

  1. 其实初始化的时候就已经把RequestMap储存到集合中了 所以第一步先根据key找这个集合 this.urlLookup 获取RequestMappingInfo

  2. 如果没有找到，再遍历这个进行匹配 this.mappingLookup 可以匹配到具体的HandMethod

     • 匹配规则：RequestMappingInfo .getMatchingCondition(HttpServletRequest request)

4. BeanNameHanderMapping

5. SimpleUrlHanderMapping 居然有第二个？

6. WelcomePageHanderMapping

再根据hander选择适配器 HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler());

执行拦截器HandlerInterceptor前置方法 mappedHandler.applyPreHandle(processedRequest, response)

通过适配器执行具体内容 mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

1. HttpRequestHandlerAdapter:

2. RequestMappingHandlerAdapter:

• 会调用该方法 handleInternal()

• 执行具体的方法invokeHandlerMethod mav = this.invokeHandlerMethod(request, response, handlerMethod);

• ServletInvocableHandlerMethod.class invocableMethod.invokeAndHandle(webRequest, mavContainer);

• InvocableHandlerMethod.class Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);

  1. 获取请求参数 Object[] args = this.getMethodArgumentValues(request, mavContainer, providedArgs);

     • 会先从privatedArgs中取看看，但是一般都是取不到的 args[i] = findProvidedArgument(parameter, providedArgs);

     • args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);

     * HandlerMethodArgumentResolverComposite.class resolveArgument()

     * 根据参数从this.argumentResolvers中指定解析器 HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter);

     * 使用解析指定解析器 获取参数 resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory);

  2. 调用执行方法 this.doInvoke(args);

3. SimpleControllerHandlerAdapter

4. 一般不用被初始化，只有上面三个 SimpleServletHandlerAdapter: servlet时使用

执行拦截器HandlerInterceptor后置方法 mappedHandler.applyPostHandle(processedRequest, response, mv);