由于SpringBoot默认是以jar包的方式启动嵌入式的Servlet容器来启动SpringBoot的web应用，那么没有web.xml文件，如何配置我们的三大Web基础组件呢？
通过使用XXXRegistrationBean如何注册Servlet：
如何注册Servlet：
@Bean public ServletRegistrationBean myServlet(){ ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myServlet"); return registrationBean; }
//Myservlet extends HttpServlet
如何注册Filter：
@Bean
public FilterRegistrationBean myFilter(){
FilterRegistrationBean registrationBean = new FilterRegistrationBean();
registrationBean.setFilter(new MyFilter());
registrationBean.setUrlPatterns(Arrays.asList("/hello","/myServlet"));
return registrationBean;
}
如何注册Listener：
@Bean
public ServletListenerRegistrationBean myListener(){
ServletListenerRegistrationBean<MyListener> registrationBean = new
ServletListenerRegistrationBean<>(new MyListener());
return registrationBean;
·}
//MyListener implements ServletContextListener等6大接口
