//这是第三种开发servlet的方法，通过继承httpservlet

package com.tsinghua;

import javax.servlet.http.*;

import java.io.*;

public class HelloHttp extends HttpServlet{

    //处理get请求

     //req用于获得客户端(浏览器)的信息

     //res用于向 客户端(浏览器)返回信息

    public void doGet(HttpServletRequest req, HttpServletResponse res)

    {

        //业务逻辑

        try{

            PrintWriter pw = res.getWriter();

            pw.println("Hello,http!");

        }

        catch(Exception ex)

        {

            ex.printStackTrace();

        }

    }

     //处理get请求

     //req用于获得客户端(浏览器)的信息

     //res用于向 客户端(浏览器)返回信息

    public void doPost(HttpServletRequest req, HttpServletResponse res)

    {

        this.doGet(req,res);        

    }    

}

<?xml version="1.0" encoding="ISO-8859-1"?>

<!--

 Licensed to the Apache Software Foundation (ASF) under one or more

  contributor license agreements.  See the NOTICE file distributed with

  this work for additional information regarding copyright ownership.

  The ASF licenses this file to You under the Apache License, Version 2.0

  (the "License"); you may not use this file except in compliance with

  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software

  distributed under the License is distributed on an "AS IS" BASIS,

  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  See the License for the specific language governing permissions and

  limitations under the License.

-->

<web-app xmlns="http://java.sun.com/xml/ns/javaee"

   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"

   version="2.5">

  <display-name>Welcome to Tomcat</display-name>

  <description>

     Welcome to Tomcat

  </description>

  <!-- JSPC servlet mapping start -->

<servlet>

    <servlet-name>hello</servlet-name>

    <servlet-class>com.tsinghua.Hello</servlet-class>

</servlet>

  <servlet-mapping>

    <servlet-name>hello</servlet-name>

    <url-pattern>/sp</url-pattern>

  </servlet-mapping>

  <servlet>

    <servlet-name>hellogen</servlet-name>

    <servlet-class>com.tsinghua.HelloGen</servlet-class>

</servlet>

  <servlet-mapping>

    <servlet-name>hellogen</servlet-name>

    <url-pattern>/hellogen</url-pattern>

  </servlet-mapping>

    <servlet>

    <servlet-name>hellohttp</servlet-name>

    <servlet-class>com.tsinghua.HelloHttp</servlet-class>

</servlet>

  <servlet-mapping>

    <servlet-name>hellohttp</servlet-name>

    <url-pattern>/hellohttp</url-pattern>

  </servlet-mapping>

<!-- JSPC servlet mapping end -->

</web-app>