基于XML，以POST方式，完成二级下拉联动【省份-城市】。效果当选择省份时，城市下拉框自动添加相对应的数据。
javascript代码：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<script type="text/javascript" src="js/createAjax.js"></script>
<title>My JSP 'index.jsp' starting page</title>
</head>
<body>
<select id="provinceID">
<option>请选择省份</option>
<option>广东</option>
<option>湖南</option>
</select>
<select id="cityID">
<option>请选择城市</option>
</select>
<script type="text/javascript">
//创建ajax对象
var ajax = createAjax();
//创建事件
document.getElementById("provinceID").onchange = function(){
//定位city下拉框节点
var citySelectElement = document.getElementById("cityID");
//再次选择省份时需先清空原来city下拉框之中的数据
var options = citySelectElement.options;
var size = options.length;
for(var i=1; i<size; i++){
citySelectElement.removeChild(options[1]);
}
//获取选中的节点的文本值
var province = this[this.selectedIndex].innerHTML;
//准备发送请求
var method = "post";
var url = "${pageContext.request.contextPath}/provinceServlet?id="+new Date().getTime();
ajax.open(method,url);
//真正发送请求
ajax.setRequestHeader("content-type","application/x-www-form-urlencoded");
var content = "province="+province;
ajax.send(content);
//监听服务器响应
ajax.onreadystatechange = function(){
//判断响应状态和响应码
if(ajax.readyState ==4){
if(ajax.status == 200){
//接收服务器响应回的字符串
var xmlDocument = ajax.responseXML;
//获取服务器传递过来的xml文档中的city节点
var cityElements = xmlDocument.getElementsByTagName("city");
var size = cityElements.length;
for(var i=0; i<size; i++){
//获取每个city节点之间的内容
var city = cityElements[i].firstChild.nodeValue;
//创建option节点
var optionElement = document.createElement("option");
//设置option节点之间的内容
optionElement.innerHTML=city;
//将option节点，条件到city下拉框之中
citySelectElement.appendChild(optionElement);
}
}
}
};
};
</script>
</body>
</html>
servlet代码：
package kerwin.ajax;
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;
public class provinceServlet extends HttpServlet {
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException {
request.setCharacterEncoding("utf-8");
//注意：这时向浏览器发送的是xml文件，所以这里应该写text/xml；而不是text/html
response.setContentType("text/xml;charset=UTF-8");
PrintWriter out = response.getWriter();
//接收参数
String province = request.getParameter("province");
out.write("<?xml version='1.0' encoding='UTF-8'?>");
out.write("<root>");
if("广东".equals(province)){
out.write("<city>广州</city>");
out.write("<city>中山</city>");
out.write("<city>深圳</city>");
}else if("湖南".equals(province)){
out.write("<city>长沙</city>");
out.write("<city>株洲</city>");
out.write("<city>湘潭</city>");
out.write("<city>张家界</city>");
}
out.write("</root>");
}
public void doPost(HttpServletRequest request,IOException {
doGet(request,response);
}
}
