XMLHttpRequest 对象用于在后台与服务器交换数据。

后台

package com.java1234.web;

import java.io.IOException;
import java.io.PrintWriter;

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

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class GetAjaxInfoServlet extends HttpServlet{

/\*\*  
 \*  
 \*/  
private static final long serialVersionUID = 1L;

@Override  
protected void doGet(HttpServletRequest request, HttpServletResponse response)  
        throws ServletException, IOException {  
    this.doPost(request, response);  
}

@Override  
protected void doPost(HttpServletRequest request, HttpServletResponse response)  
        throws ServletException, IOException {  
    response.setContentType("text/html;charset=utf-8");  
    String action=request.getParameter("action");  
    if("checkUserName".equals(action)){  
        this.checkUserName(request, response);  
    }else if("ejld".equals(action)){  
        this.ejld(request, response);  
    }

}

private void checkUserName(HttpServletRequest request, HttpServletResponse response)  
        throws ServletException, IOException {  
    PrintWriter out=response.getWriter();  
    String userName=request.getParameter("userName");  
    JSONObject resultJson=new JSONObject();  
    if("jack".equals(userName)){  
        resultJson.put("exist", true);  
    }else{  
        resultJson.put("exist", false);  
    }  
    out.println(resultJson);  
    out.flush();  
    out.close();  
}

private void ejld(HttpServletRequest request, HttpServletResponse response)  
        throws ServletException, IOException {  
    PrintWriter out=response.getWriter();  
    String shengId=request.getParameter("shengId");  
    JSONObject resultJson=new JSONObject();  
    JSONArray jsonArray=new JSONArray();  
    JSONObject temp=null;  
    switch(Integer.parseInt(shengId)){  
        case 1:{  
            temp=new JSONObject();temp.put("id", 1);temp.put("text", "南京");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 2);temp.put("text", "南通");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 3);temp.put("text", "泰兴");jsonArray.add(temp);  
            break;  
        }  
        case 2:{  
            temp=new JSONObject();temp.put("id", 4);temp.put("text", "济南");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 5);temp.put("text", "烟台");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 6);temp.put("text", "蓬莱");jsonArray.add(temp);  
            break;  
        }  
        case 3:{  
            temp=new JSONObject();temp.put("id", 7);temp.put("text", "杭州");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 8);temp.put("text", "宁波");jsonArray.add(temp);  
            temp=new JSONObject();temp.put("id", 9);temp.put("text", "温州");jsonArray.add(temp);  
            break;  
        }  
    }  
    resultJson.put("rows", jsonArray);  
    out.println(resultJson);  
    out.flush();  
    out.close();  
}

}

首页

<%@ page language="java" import="java.util.\*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>

<title>My JSP 'insex.jsp' starting page</title>

<!-- 控制缓存 -->  
<meta http-equiv="pragma" content="no-cache">  
<meta http-equiv="cache-control" content="no-cache">  
<meta http-equiv="expires" content="0">  
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
<meta http-equiv="description" content="This is my page">  
<!--  
<link rel="stylesheet" type="text/css" href="styles.css">  
-->

<br/>  
<br/>  
<br/>  
<a href="ejld.jsp">二级联动</a>  
<br/>  
<br/>  
<br/>  
<a href="checkUserName.jsp">ajax&json验证</a>  

验证姓名是否存在

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

用户注册
用户名：
密码：
确认密码：

二级联动

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

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