Web开发使用 Controller 基本上可以完成大部分需求，但是我们还可能会用到 Servlet、Filter、Listener、Interceptor 等等。
当使用spring-Boot时，嵌入式Servlet容器通过扫描注解的方式注册Servlet、Filter和Servlet规范的所有监听器（如HttpSessionListener监听器）。
Spring boot 的主 Servlet 为DispatcherServlet，其默认的url-pattern为“/”。也许我们在应用中还需要定义更多的Servlet，该如何使用SpringBoot来完成呢？
在spring boot中添加自己的Servlet有两种方法，代码注册Servlet和注解自动注册（Filter和Listener也是如此）。
一、代码注册通过ServletRegistrationBean、 FilterRegistrationBean 和ServletListenerRegistrationBean 获得控制。
也可以通过实现 ServletContextInitializer 接口直接注册。
二、在SpringBootApplication 上使用@ServletComponentScan注解后，Servlet、Filter、Listener 可以直接通过 @WebServlet、@WebFilter、@WebListener 注解自动注册，无需其他代码。
1.通过代码注册Servlet示例代码：
package me.shijunjie.servlet;import java.io.IOException; import java.io.PrintWriter;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;public class MyServlet1 extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<");doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<");resp.setContentType("text/html"); PrintWriter out = resp.getWriter(); out.println("<html>"); out.println("<head>"); out.println("<title>HelloWorld</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>这是：MyServlet1</h1>"); out.println("</body>"); out.println("</html>");} }
package me.shijunjie.testspringboot2;import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.context.embedded.ServletRegistrationBean; import org.springframework.context.annotation.Bean;import me.shijunjie.servlet.MyServlet1; @SpringBootApplication public class App {/*** 注册Servlet.不需要添加注解：@ServletComponentScan* @return*/@Beanpublic ServletRegistrationBean myServlet1(){return new ServletRegistrationBean(new MyServlet1(),"/myServlet/*");}public static void main( String[] args ){SpringApplication.run(App.class, args);} }
测试
2.使用注解注册Servlet示例代码 添加@WebServlet注解
package me.shijunjie.servlet;import java.io.IOException; import java.io.PrintWriter;import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;@WebServlet(urlPatterns="/myServlet2/*",description="Servlet的说明") public class MyServlet2 extends HttpServlet {private static final long serialVersionUID = 1L;@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<");doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<");resp.setContentType("text/html"); PrintWriter out = resp.getWriter(); out.println("<html>"); out.println("<head>"); out.println("<title>HelloWorld</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>这是：MyServlet2</h1>"); out.println("</body>"); out.println("</html>");} }
添加@ServletComponentScan注解
package me.shijunjie.testspringboot2;import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.web.servlet.ServletComponentScan;/*** Hello world!**/ @SpringBootApplication @ServletComponentScan("me.shijunjie.servlet") public class App {/* *//*** 注册Servlet.不需要添加注解：@ServletComponentScan* @return*//*@Beanpublic ServletRegistrationBean myServlet1(){return new ServletRegistrationBean(new MyServlet1(),"/myServlet/*");}*/public static void main( String[] args ){SpringApplication.run(App.class, args);} }
测试
