SpringMVC底层实现原理

       当项目启动了Tomcat后，服务器会去当前wabapp的路径下去读取配置文件，然后解析其中配置的DispathServlet，在DispathServlet中会创建一个Spring容器，去扫描我们的Contorller等各个由Spring管理的bean对象，在DispathServlet的源码中，是需要将Spring容器给到DispathServlet当中，也就相当于在DispathServlet中内嵌一个Spring容器，从而实现对目标资源的调用。

XML配置方式：

<web-app> 
<listener>
     <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
 </listener>
 
 <context-param> 
     <param-name>contextConfigLocation</param-name> 
     <param-value>/WEB-INF/app-context.xml</param-value>
 </context-param>
 
<servlet> <servlet-name>app</servlet-name> 
    <servlet-class>org.springframework.web.servlet.DispatcherServlet
</servlet-class>
 
<init-param> 
    <param-name>contextConfigLocation</param-name> 
    <param-value></param-value> 
</init-param> 
<load-on-startup>1</load-on-startup> 
 
</servlet> 
    <servlet-mapping> 
        <servlet-name>app</servlet-name> <url-pattern>/app/*</url-pattern> 
    </servlet-mapping> 
</web-app>

JavaConfig配置方式：

public class MyWebApplicationInitializer implements WebApplicationInitializer {
 
    @Override
    public void onStartup(ServletContext servletContext) {
 
        // Load Spring web application configuration
        AnnotationConfigWebApplicationContext context = new AnnotationConfigWebApplicationContext();
        context.register(AppConfig.class);
 
        // Create and register the DispatcherServlet
        DispatcherServlet servlet = new DispatcherServlet(context);
        ServletRegistration.Dynamic registration = servletContext.addServlet("app", servlet);
        registration.setLoadOnStartup(1);
        registration.addMapping("/app/*");
    }
}