一 province.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <html> <head> <script type="text/javascript" language="javaScript"> var xmlHttp = false; //全局变量，用于记录XMLHttpRequest对象 function createXMLHttpRequest() { if(window.ActiveXObject) { //Internet Explorer时，创建XMLHttpRequest对象的方法 try { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch(e) { try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); //旧版本的Internet Explorer，创建XMLHttpRequest对象 } catch(e) { window.alert("创建XMLHttpRequest对象错误"+e); } } } else if(window.XMLHttpRequest) { //mozilla时，创建XMLHttpRequest对象的方法 xmlHttp = new XMLHttpRequest(); } if(!(xmlHttp)) { //未成功创建XMLHttpRequest对象 window.alert("创建XMLHttpRequest对象异常！"); } } //下拉列表项改变时的操作 function proChange(objVal) { createXMLHttpRequest(); //创建XMLHttpRequest对象 document.getElementById("city").length = 1; //根据ID获取指定元素，并赋值 xmlHttp.onreadystatechange = cityList; //指定onreadystatechange处理函数 var url="CityByXMLServlet?province="+objVal; //请求的URL地址 xmlHttp.open("POST",url,true); xmlHttp.send(null); } function cityList() { //onreadystatechange的处理函数 if(xmlHttp.readyState==4) { if(xmlHttp.status==200) { parseXML(xmlHttp.responseXML); //解析服务器返回的XML数据 } } } //解析xml信息，以添加地市 function parseXML(xmlDoc) { var len = xmlDoc.getElementsByTagName("city"); //获取XML数据中所有的“city”元素对象集合 var _citySel = document.getElementById("city"); //根据ID获取页面中的select元素 for(var i=0;i<len.length;i++) { //遍历XML数据并给select元素添加选项 var opt = document.createElement("OPTION"); //创建option对象 opt.text = xmlDoc.getElementsByTagName("city")[i].firstChild.data; //指定新创建元素的text属性值 opt.value = xmlDoc.getElementsByTagName("city")[i].firstChild.data; //指定新创建元素的value属性值 _citySel.add(opt); //为select元素添加option } } </script> <title>动态加载组合框</title> </head> <body> <table align="center" border=1 width="320"> <tr> <td>省份：</td> <td> <select id="province" onChange="proChange(this.value);" style="width:85"> <option value="gd">广东</option> <option value="gx">广西</option> <option value="hn">湖南</option> <option value="hb">湖北</option> <option value="ah">安徽</option> </select> </td> </tr> <tr> <td>城市：</td> <td> <select id="city" style="width:85"> <option value="">--请选择--</option> </select> </td> </tr> </table> </body> </html> 二、CityByXMLServlet.java
package servlet;import java.io.IOException;import java.io.PrintWriter;import java.util.*;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class CityByXMLServlet */@WebServlet("/CityByXMLServlet")public class CityByXMLServlet extends HttpServlet { private static final long serialVersionUID = 1L; private static final String CONTENT_TYPE = "text/xml; charset=UTF-8"; /** * @see HttpServlet#HttpServlet() */ public CityByXMLServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType(CONTENT_TYPE); //设置服务器响应类型 String province =request.getParameter("province"); StringBuffer city = new StringBuffer("<citys>"); //记录返回XML串的对象 if("gx".equals(province)){ List list=cityInit(); //获取城市列表 for(int i=0;i<list.size();i++){ city.append("<city>"+list.get(i)+"</city>"); } }else if("hn".equals(province)){ List list = cityInit1(); //获取城市列表 for(int j=0;j<list.size();j++){ city.append("<city>"+list.get(j)+"</city>"); } }else if("hb".equals(province)){ List list = cityInit2(); //获取城市列表 for(int j=0;j<list.size();j++){ city.append("<city>"+list.get(j)+"</city>"); } } city.append("</citys>"); PrintWriter out = response.getWriter(); out.println(city.toString()); out.flush(); //输出流刷新 out.close(); //关闭输出流 } /* * 初始化城市 */ public List<String> cityInit2() { List<String> cityList = new ArrayList<String>(); //添加城市列表 cityList.add("武汉"); cityList.add("襄阳"); cityList.add("黄冈"); cityList.add("荆门"); cityList.add("十堰"); cityList.add("黄石"); return cityList; } public List<String> cityInit(){ List<String> cityList = new ArrayList<String>(); //添加城市列表 cityList.add("南宁"); cityList.add("桂林"); cityList.add("北海"); cityList.add("河池"); cityList.add("梧州"); cityList.add("玉林"); return cityList; } public List<String> cityInit1() { List<String> cityList = new ArrayList<String>(); //添加城市列表 cityList.add("长沙"); cityList.add("湘潭"); cityList.add("岳阳"); cityList.add("常德"); cityList.add("衡阳"); cityList.add("邵阳"); return cityList; } /** *当前Servelt的初始化方法. <br> * * @throws ServletException发生ServletExceptio时抛出 */ public void init() throws ServletException { } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }}三 web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:web="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd http://xmlns.jcp.org/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.4"><servlet> <servlet-name>CityByXMLServlet</servlet-name> <servlet-class>servlet.CityByXMLServlet</servlet-class><!--类的位置 --></servlet><servlet-mapping> <servlet-name>CityByXMLServlet</servlet-name><!--你创建的类名 --> <url-pattern>/CityByXMLServlet</url-pattern></servlet-mapping>
总结
以上所述是小编给大家介绍的Ajax实现动态加载组合框的实例代码，希望对大家有所帮助，如果大家有任何疑问欢迎给我留言，小编会及时回复大家的！
Peter-Zhu
大家讲道理
