Spring Boot（三）--Servlet

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。

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？

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。

通过代码注册Servlet示例代码：

SpringBootSampleApplication.java

package org.springboot.sample;  import org.springboot.sample.servlet.MyServlet; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.web.servlet.ServletComponentScan; import org.springframework.boot.web.servlet.ServletRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.web.servlet.DispatcherServlet;  @SpringBootApplication public class SpringBootSampleApplication {  	/** 	 *  	 * 使用代码注册Servlet（不需要@ServletComponentScan注解） 	 * @author gzm 	 * @date 2018年6月1日下午2:34:49 	 */     @Bean     public ServletRegistrationBean servletRegistrationBean() {         return new ServletRegistrationBean(new MyServlet(), "/xs/*");// ServletName默认值为首字母小写，即myServlet     }      	public static void main(String[] args) { 		SpringApplication.run(SpringBootSampleApplication.class, args); 	} }

MyServlet.java

package org.springboot.sample.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;  /**  * Servlet  * @author gzm  * @date 2018年6月1日 下午2:37:04  *  */ //@WebServlet(urlPatterns="/xs/*", description="Servlet的说明") public class MyServlet extends HttpServlet{      private static final long serialVersionUID = -8685285401859800066L;      @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         System.out.println(">>>>>>>>>>doGet()<<<<<<<<<<<");         doPost(req, resp);     }      @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         System.out.println(">>>>>>>>>>doPost()<<<<<<<<<<<");         resp.setContentType("text/html");          resp.setCharacterEncoding("utf-8");//不设置中文会乱码         PrintWriter out = resp.getWriter();           out.println("<html>");           out.println("<head>");           out.println("<title>Hello World</title>");           out.println("</head>");           out.println("<body>");           out.println("<h1>大家好，我的名字叫Servlet</h1>");           out.println("</body>");           out.println("</html>");      }  }

使用注解注册Servlet示例代码

SpringBootSampleApplication.java

package org.springboot.sample;  import org.springboot.sample.servlet.MyServlet; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.boot.web.servlet.ServletComponentScan; import org.springframework.boot.web.servlet.ServletRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.web.servlet.DispatcherServlet;  @SpringBootApplication @ServletComponentScan public class SpringBootSampleApplication {       	public static void main(String[] args) { 		SpringApplication.run(SpringBootSampleApplication.class, args); 	} }

MyServlet2.java

package org.springboot.sample.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;  /**  * @author gzm  * @date 2018年6月1日 下午2:45:27  *   */ @WebServlet(urlPatterns="/xs/myservlet", description="Servlet的说明") // 不指定name的情况下，name默认值为类全路径，即org.springboot.sample.servlet.MyServlet2 public class MyServlet2 extends HttpServlet{      private static final long serialVersionUID = -8685285401859800066L;      @Override     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         System.out.println(">>>>>>>>>>doGet2()<<<<<<<<<<<");         doPost(req, resp);     }      @Override     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {         System.out.println(">>>>>>>>>>doPost2()<<<<<<<<<<<");         resp.setContentType("text/html;charset=utf-8");           PrintWriter out = resp.getWriter();           out.println("<html>");           out.println("<head>");           out.println("<title>Hello World</title>");           out.println("</head>");           out.println("<body>");           out.println("<h1>大家好，我的名字叫Servlet2</h1>");           out.println("</body>");           out.println("</html>");  	    }  }

使用 @WebServlet 注解，其中可以设置一些属性。

http://localhost:8080/xs/myservlet http://localhost:8080/xs/abc

既然系统DispatcherServlet 默认拦截“/”，那么我们是否能做修改呢，答案是肯定的，我们在SpringBootSampleApplication中添加代码：

  @Bean     public ServletRegistrationBean dispatcherRegistration(DispatcherServlet dispatcherServlet) {         ServletRegistrationBean registration = new ServletRegistrationBean(dispatcherServlet);         registration.getUrlMappings().clear();         registration.addUrlMappings("*.do");         registration.addUrlMappings("*.json");         return registration;     }

当然，这里可以对DispatcherServlet做很多修改，并非只是UrlMappings。

文章来源: Spring Boot（三）--Servlet

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