1。servlet代码：

如果用包直接加上包就好：例如 package lcy;

import javax.servlet.http.*;
import java.io.*;

public class HelloHttp extends HttpServlet {
    
     public void doGet(HttpServletRequest request, HttpServletResponse response) {
        
         try {
             PrintWriter pw = response.getWriter();
             pw.println(encoding("welcome java"));
         }
         catch(Exception ex) {
             ex.printStackTrace();
         }
        
     }
    
     public void doPost(HttpServletRequest request, HttpServletResponse response) {
        
         this.doGet(request, response);
       
     }
    
     private String encoding(String str)
   {
    try
    {
     str = new String(str.getBytes("ISO-8859-1"),"GB2312");
    }
    catch(UnsupportedEncodingException uee)
    {
     System.out.println("" + uee.getMessage());
    
    }
    return str;
   
   
   }
}

2。web.xml配置：

<servlet>
        <servlet-name>helloHttp </servlet-name> //调用时的真实名字
        <servlet-class>HelloHttp </servlet-class>//servlet名字，如果有包加上包名，例如：lcy.HelloHttp
    </servlet>

    <servlet-mapping>
        <servlet-name>helloHttp</servlet-name> //调用时的真实名字
        <url-pattern>/HelloHttp </url-pattern>//servlet的具体路径，根目录下要找到才行
    </servlet-mapping>

3.地址栏输入

http://localhost:8080/helloHttp   

即可执行