点击各按钮无结果，并且在页面报错

来源：2-8 自由编程

qq_cookies_oqrHNO

2019-04-09 12:00:02

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<table width="100%">
        <tr>
            <td width="33%"><button id="y" style="width:100%;">员工列表</button></td>
            <td width="33%"><button id="z" style="width:100%;" >职位列表</button></td>
            <td width="33%"><button id="b" style="width:100%;">部门列表</button></td>
        </tr>
    </table>
<div id="content" style="text-align: center;"></div>
<script type="text/javascript" src="js/jquery-3.3.1.js"></script>
<script type="text/javascript">
//1.创建ajax对象
var xmlhttp;
if(window.XMLHttpRequest){
   xml=new XMLHttpRequest();
}else{
   xmlhttp=new ActiveObject("Microsoft.XMLHTTP");
}
$("#y,#b,#z").click(function(){
   var url = "/ajax_practice/content?id=" + this.id;
   //2.发送ajax请求
   xmlhttp.open("GET",url,true);
   xmlhttp.send();
   //3.处理服务器响应
   xmlhttp.onreadystatechange=function(){
       if(xmlhttp.readyState==4 && xmlhttp.status==200){
           var t=xmlhttp.responseText;
           var json=JSON.parse(t);
           var html="";
           for(var i=0;i<json.length;i++){
               html=html+json[i];
               html=html+"<hr>";
           }
           document.getElementById("content").innerHTML=html;
       }
   }
});
</script>
</body>
</html>

package com.imooc.ajax;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.alibaba.fastjson.JSON;

/**
* Servlet implementation class ContentServlet
*/
@WebServlet("/content")
public class ContentServlet extends HttpServlet {
   private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ContentServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

   /**
   * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       List yList=new ArrayList();
       List bList=new ArrayList();
       List zList=new ArrayList();
       yList.add("小红");
       yList.add("小明");
       yList.add("小白");
       bList.add("人事部");
       bList.add("技术部");
       bList.add("无线事业部");
       zList.add("职员");
       zList.add("经理");
       String jsony=JSON.toJSONString(yList);
       String jsonb=JSON.toJSONString(bList);
       String jsonz=JSON.toJSONString(zList);
       response.setContentType("text/html;charset=UTF-8");
       if( request.getParameter("id").equals("y") ) {
            System.out.println(jsony);
            response.getWriter().println(jsony);
        }else if( request.getParameter("id").equals("b") ) {
            System.out.println(jsonb);
            response.getWriter().println(jsonb);
        }else if( request.getParameter("id").equals("z")) {
            System.out.println(jsonz);
            response.getWriter().println(jsonz);
        }
   }

}