Ajax案例-基于XML，以POST方式，完成省份-城市二级下拉联动

时间：2022-01-07 15:47:32
<%@ page language="java" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

  <head>

    <title>基于XML，以POST方式，完成省份-城市二级下拉联动</title>

    <script type="text/javascript" src="js/ajax.js"></script>

  </head>

  <body>

    <select id="provinceID" style="width:111px">

        <option>选择省份</option>

        <option>湖南</option>

        <option>广东</option>

    </select>

    &nbsp;&nbsp;&nbsp;

    <select id="cityID" style="width:111px">

        <option>选择城市</option>

    </select>    

    <script type="text/javascript">

        //定位省份下拉框，同时添加内容改变事件

        document.getElementById("provinceID").onchange = function(){

            //清空城市下拉框中的内容，除第一项外

            var cityElement = document.getElementById("cityID");

            cityElement.options.length = 1;

            //获取选中option标签的索引号，从0开始

            var index = this.selectedIndex;

            //定位选中的option标签

            var optionElement = this[index];

            //获取选中的option标签中的内容，即省份

            var province = optionElement.innerHTML;

            //如果选中的内容不是"选择省份"

            if("选择省份" != province){

                //NO1)

                var ajax = createAJAX();

                //NO2)

                var method = "POST";

                var url = "${pageContext.request.contextPath}/ProvinceCityServlet?time="+new Date().getTime();

                ajax.open(method,url);

                //设置AJAX请求头

                ajax.setRequestHeader("content-type","application/x-www-form-urlencoded");

                //NO3)

                var content = "province=" + province;

                ajax.send(content);

                //---------------------------------等待

                //NO4)

                ajax.onreadystatechange = function(){

                    if(ajax.readyState == 4){

                        if(ajax.status == 200){

                            //NO5)从AJAX异步对象中获取服务器响应的xml文档

                            var xmlDocument = ajax.responseXML;

                            //NO6)按照DOM规则，解析XML文档

                            var cityElementArray = xmlDocument.getElementsByTagName("city");

                            var size = cityElementArray.length;

                            for(var i=0;i<size;i++){

                                //innerHTML只能用在html/jsp中，不能用在xml中

                                var city = cityElementArray[i].firstChild.nodeValue;

                                //<option></option>

                                var optionElement = document.createElement("option");

                                //<option>广州</option>

                                optionElement.innerHTML = city;

                                //<select><option>广州</option></select>

                                cityElement.appendChild(optionElement);

                            }

                        }

                    }

                }

            }

        }

    </script>

  </body>

</html>
package loaderman.provincecity;

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;

/**

 * 基于XML，以POST方式，完成省份-城市二级下拉联动

 * @author AdminTC

 */

public class ProvinceCityServlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");

        String province = request.getParameter("province");

        //通知AJAX异步对象，服务器响应的数据为xml格式的

        response.setContentType("text/xml;charset=UTF-8");

        //获取字符输出流

        PrintWriter pw = response.getWriter();

        pw.write("<?xml version='1.0' encoding='UTF-8'?>");

        pw.write("<root>");

        if("广东".equals(province)){

            pw.write("<city>广州</city>");

            pw.write("<city>深圳</city>");

            pw.write("<city>中山</city>");

        }else if("湖南".equals(province)){

            pw.write("<city>长沙</city>");

            pw.write("<city>株洲</city>");

            pw.write("<city>湘潭</city>");

            pw.write("<city>岳阳</city>");

        }

        pw.write("</root>");

        pw.flush();

        pw.close();

    }

}

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