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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）
package com.xxx.secondboot.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestServlet extends HttpServlet {
private static final long serialVersionUID = -4619665430596950563L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("zhaojigang servlet");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}
</div>
2、Testservlet2（第二个servlet）
package com.xxx.secondboot.servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class TestServlet2 extends HttpServlet {
private static final long serialVersionUID = 3788279972938793265L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
System.out.println("zhaojigang servlet2");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
this.doGet(req, resp);
}
}
</div>
3、ServletConfig（servlet注入配置类）
package com.xxx.secondboot.servlet;
import org.springframework.boot.context.embedded.ServletRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class ServletConfig {
@Bean
public TestServlet testServlet(){
return new TestServlet();
}
@Bean
public ServletRegistrationBean testServletRegistrationBean(TestServlet testServlet){
ServletRegistrationBean registration = new ServletRegistrationBean(testServlet);
registration.setEnabled(true);
registration.addUrlMappings("/servlet/test");
return registration;
}
/********************************************/
@Bean
public TestServlet2 testServlet2(){
return new TestServlet2();
}
@Bean
public ServletRegistrationBean test2ServletRegistrationBean(TestServlet2 testServlet2){
ServletRegistrationBean registration = new ServletRegistrationBean(testServlet2);
registration.setEnabled(true);
registration.addUrlMappings("/servlet/test2");
return registration;
}
}
</div>
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。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。