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[Java教程]第二十四章 springboot注入servlet


问:有了springMVC,为什么还要用servlet?有了servlet3的注解,为什么还要使用ServletRegistrationBean注入的方式?

使用场景:在有些场景下,比如我们要使用hystrix-dashboard,这时候就需要注入HystrixMetricsStreamServlet(第三方的servlet),该servlet是hystrix的组件。

一、代码

1、TestServlet(第一个servlet)

 1 package com.xxx.secondboot.servlet; 2  3 import java.io.IOException; 4  5 import javax.servlet.ServletException; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 public class TestServlet extends HttpServlet {11   12   private static final long serialVersionUID = -4619665430596950563L;13 14   @Override15   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {16     System.out.println("zhaojigang servlet");17   }18 19   @Override20   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {21     this.doGet(req, resp);22   }23 }

View Code

2、Testservlet2(第二个servlet)

 1 package com.xxx.secondboot.servlet; 2  3 import java.io.IOException; 4  5 import javax.servlet.ServletException; 6 import javax.servlet.http.HttpServlet; 7 import javax.servlet.http.HttpServletRequest; 8 import javax.servlet.http.HttpServletResponse; 9 10 public class TestServlet2 extends HttpServlet {11 12   private static final long serialVersionUID = 3788279972938793265L;13 14   @Override15   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {16     System.out.println("zhaojigang servlet2");17   }18 19   @Override20   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {21     this.doGet(req, resp);22   }23 }

View Code

3、ServletConfig(servlet注入配置类)

 1 package com.xxx.secondboot.servlet; 2  3 import org.springframework.boot.context.embedded.ServletRegistrationBean; 4 import org.springframework.context.annotation.Bean; 5 import org.springframework.context.annotation.Configuration; 6  7 @Configuration 8 public class ServletConfig { 9   10   @Bean11   public TestServlet testServlet(){12     return new TestServlet();13   }14   15   @Bean16   public ServletRegistrationBean testServletRegistrationBean(TestServlet testServlet){17     ServletRegistrationBean registration = new ServletRegistrationBean(testServlet);18     registration.setEnabled(true);19     registration.addUrlMappings("/servlet/test");20     return registration;21   }22   /********************************************/23   @Bean24   public TestServlet2 testServlet2(){25     return new TestServlet2();26   }27   28   @Bean29   public ServletRegistrationBean test2ServletRegistrationBean(TestServlet2 testServlet2){30     ServletRegistrationBean registration = new ServletRegistrationBean(testServlet2);31     registration.setEnabled(true);32     registration.addUrlMappings("/servlet/test2");33     return registration;34   }35   36 }

说明:使用ServletRegistrationBean来注入servlet,对于每一个servlet都有一个ServletRegistrationBean来注入。

注意:如果只是自己要使用servlet,可以直接只用servlet3的注解来声明servlet就好,但是像HystrixMetricsStreamServlet这样的第三方servlet,就只能通过上边这样的方式来搞了。

 

二、测试

启动服务,浏览器输入"http://localhost:8083/servlet/test","http://localhost:8083/servlet/test2",查看console的输出。