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！
