SpringBoot注册Servlet、Filter、Listener

SpringBoot默认是以jar包的方式启动嵌入式的Servlet容易来启动SpringBoot的Web应用，没有web.xml文件

因此我们可以使用以下方式来注册Servlet、Filter、Listener。

（1）、注册Servlet

 package cn.coreqi.servlet;

 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import java.io.IOException;
 import java.io.PrintWriter;

 public class MyServlet extends HttpServlet {
     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         // 设置响应内容类型
         resp.setContentType("text/html");

         // 实际的逻辑是在这里
         PrintWriter out = resp.getWriter();
         out.println("<h1>MyServlet</h1>");
     }
 }

     //注册Servlet
     @Bean
     public ServletRegistrationBean myServlet(){
         ServletRegistrationBean registrationBean = new ServletRegistrationBean(new MyServlet(),"/myservlet");
         return registrationBean;
     }

（2）、注册Filter

 package cn.coreqi.filter;

 import javax.servlet.*;
 import java.io.IOException;
 import java.io.PrintWriter;

 public class MyFilter implements Filter {
     @Override
     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
         PrintWriter out = servletResponse.getWriter();
         out.println("<h1>MyFilter</h1>");
         filterChain.doFilter(servletRequest,servletResponse);
     }
 }

     @Bean
     public FilterRegistrationBean myFilter(){
         FilterRegistrationBean registrationBean = new FilterRegistrationBean();
         registrationBean.setFilter(new MyFilter());
         registrationBean.setUrlPatterns(Arrays.asList("/myservlet"));
         return registrationBean;
     }

（3）、注册Listener

 package cn.coreqi.listener;

 import javax.servlet.ServletContextEvent;
 import javax.servlet.ServletContextListener;

 public class MyListener implements ServletContextListener {
     @Override
     public void contextInitialized(ServletContextEvent sce) {
         System.out.println("contextInitialized");
     }
 }

     @Bean
     public ServletListenerRegistrationBean myListener(){
         ServletListenerRegistrationBean registrationBean = new ServletListenerRegistrationBean();
         registrationBean.setListener(new MyListener());
         return registrationBean;
     }