package com.jsn.web.servlet;

package com.jsn.web.servlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class HelloServlet implements Servlet {

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
        System.out.println("hello");
    }

    @Override
    public ServletConfig getServletConfig() {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String getServletInfo() {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public void init(ServletConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("hello init");
    }

    @Override
    public void service(ServletRequest arg0, ServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().write("hello service response");
    }

}

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>dyweb</display-name>
  
  <servlet>
  <servlet-name>HelloServlet</servlet-name>
  <servlet-class>com.jsn.web.servlet.HelloServlet</servlet-class>
  
  
  
  </servlet>
  <servlet-mapping>
  <servlet-name>HelloServlet</servlet-name>
  <url-pattern>/hellworld</url-pattern>
  
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

servlet 三种方式   

1、implements Servlet

2、GenericServlet

3、HttpServlet    doget 

Servlet【接口】
GenericServlet【是 Servlet实现类】
httpservlet 是genericservlet的子类】

helloservlet 是 httpservlet 子类