SP：SpringMVC架构

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业务流程图

架构（类图）

这里写图片描述

流程总结

DispatcherServlet：流程载体，首脑，总指挥官
Handler：具体处理请求
HandleMapping：匹配URL到具体的Handler
HandleAdapter：将匹配到的Handler适配至特定的接口
ModleAndView : 封装视图与数据
viewResolver：解析ModleAndView，得到具体的view

流程：
URL到达DispatcherServlet，
DispatcherServlet委派HandleMapping获取请求匹配到的Handler，
DispatcherServlet委派Handler处理请求获取ModelAndView，
DispatcherServlet委派viewResolver解析获取到的ModelAndView获得View，
DispatcherServlet使用Model渲染View返回客户端

问答

1 为什么请求会先到达DispatcherServlet？
简单的说是以上配置让tomcat将请求导向了这个DispatcherServlet

<servlet>  <servlet-name>xxx</servlet-name>  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  <init-param>    <param-name>contextConfigLocation</param-name>    <param-value>classpath*:/META-INF/spring/front-web.xml</param-value>  </init-param>  <load-on-startup>1</load-on-startup></servlet><servlet-mapping>  <servlet-name>xxx</servlet-name>  <url-patter`这里写代码片`n>/*</url-pattern></servlet-mapping>

2 HandleAdapter有什么用？
使用了适配器设计模式，目的是为了是程序在扩展时为了用一致的方式去处理请求，请求具体是由Handler处理的，Handler有很多种，如@RequestMapping和实现Controller接口，处理请求对于前者是执行被注解的方法，对于后者是调用Controller对象的handleRequest方法，形式不同，使用了HandleAdapter以后就请求处理程序就可以忽略这种不同，以后有新的Handler形式也不用修改程序，符合OCP原则

3 我的配置文件中没有配置 HandleMapping和HandleAdapter？

<mvc:annotation-driven/><!-- 由org.springframework.web.servlet.config.AnnotationDrivenBeanDefinitionParser解析 registers the following HandlerMappings:RequestMappingHandlerMapping ordered at 0 for mapping requests to annotated controller methods. BeanNameUrlHandlerMapping ordered at 2 to map URL paths to controller bean names. Note: Additional HandlerMappings may be registered as a result of using the <view-controller> or the <resources> MVC namespace elements. registers the following HandlerAdapters: RequestMappingHandlerAdapter for processing requests with annotated controller methods. HttpRequestHandlerAdapter for processing requests with HttpRequestHandlers. SimpleControllerHandlerAdapter for processing requests with interface-based Controllers. registers the following HandlerExceptionResolvers: ExceptionHandlerExceptionResolver for handling exceptions through @ExceptionHandler methods. ResponseStatusExceptionResolver for exceptions annotated with @ResponseStatus. DefaultHandlerExceptionResolver for resolving known Spring exception types -->

SpringMVC设计到的设计模式

HandleAdapter：适配器模式
viewResolver：模板方法

参考博客

http://jinnianshilongnian.iteye.com/blog/1594806

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