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;ilen.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;ilist.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;jlist.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;jlist.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 ListString> cityInit2() { ListString> cityList = new ArrayListString>(); //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 ListString> cityInit(){ ListString> cityList = new ArrayListString>(); //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 ListString> cityInit1() { ListString> cityList = new ArrayListString>(); //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!