http://www.blogjava.net/supercrsky/articles/203698.html
index.jsp:
<%
@ page language="java" pageEncoding="UTF-8"%>
<html><head><title>二級菜單聯動演示</title><script type="text/javascript">
var req; window.onload=function()
{//頁面加載時的函數
}function Change_Select(){//當第一個下拉框的選項發生改變時調用該函數var province = document.getElementById('province').value;var url ="select?id="+ escape(province);if(window.XMLHttpRequest){ req =new XMLHttpRequest(); }elseif(window.ActiveXObject){ req =new ActiveXObject("Microsoft.XMLHTTP"); }if(req){ req.open("GET",url,true);//指定回調函數爲callback req.onreadystatechange = callback; req.send(null); } }//回調函數function callback(){if(req.readyState ==4){if(req.status ==200){ parseMessage();//解析XML文檔 }else{ alert("不能得到描述信息:"+ req.statusText); } } }//解析返回xml的方法function parseMessage(){var xmlDoc = req.responseXML.documentElement;//獲得返回的XML文檔var xSel = xmlDoc.getElementsByTagName('select');//獲得XML文檔中的所有<select>標記var select_root = document.getElementById('city');//獲得網頁中的第二個下拉框 select_root.options.length=0;//每次獲得新的數據的時候先把每二個下拉框架的長度清0for(var i=0;i<xSel.length;i++){var xValue = xSel[i].childNodes[0].firstChild.nodeValue;//獲得每個<select>標記中的第一個標記的值,也就是<value>標記的值var xText = xSel[i].childNodes[1].firstChild.nodeValue;//獲得每個<select>標記中的第二個標記的值,也就是<text>標記的值var option =new Option(xText, xValue);//根據每組value和text標記的值創建一個option對象try{ select_root.add(option);//將option對象添加到第二個下拉框中 }catch(e){ } } }
</script></head><body><div align="center"><form name="form1" method="post" action=""><table width="70%" border="0" cellspacing="0" cellpadding="0"><tr><td align="center"> 二級聯動示例</td></tr><tr><td><select name="province" id="province" onChange="Change_Select()"><!--第一個下拉菜單--><option value="0"> 請選擇</option><option value="1"> 北京</option><option value="2"> 天津</option><option value="3"> 山東</option></select><select name="city" id="city"><!--第二個下拉菜單--><option value="0"> 請選擇</option></select></td></tr><tr><td></td><tr></table></form></div></body></html>SelectServlet:
package com;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** *//*** * * @author zdw **/publicclass SelectServlet extends HttpServlet{privatestaticfinallong serialVersionUID = 1L;public SelectServlet(){super(); }publicvoid destroy(){super.destroy(); }publicvoid doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException{// response.setCharacterEncoding("GBK"); response.setContentType("text/xml"); response.setHeader("Cache-Control", "no-cache"); request.setCharacterEncoding("GBK"); response.setCharacterEncoding("UTF-8"); String targetId = request.getParameter("id").toString(); System.out.println(targetId);// 獲得請求中參數爲id的值 String xml_start = "<selects>"; String xml_end = "</selects>"; String xml = "";if (targetId.equalsIgnoreCase("0")){ xml = "<select><value>0</value><text>請選擇</text></select>"; }elseif (targetId.equalsIgnoreCase("1")){ xml = "<select><value>1</value><text>昌平</text></select>"; xml += "<select><value>2</value><text>豐臺</text></select>"; xml += "<select><value>3</value><text>海淀</text></select>"; xml += "<select><value>4</value><text>朝陽</text></select>"; }elseif (targetId.equalsIgnoreCase("2")){ xml = "<select><value>1</value><text>塘沽區</text></select>"; xml += "<select><value>2</value><text>漢沽區</text></select>"; xml += "<select><value>3</value><text>大港區</text></select>"; xml += "<select><value>4</value><text>東麗區</text></select>"; }else{// 如果是3,則返回下面的字符 xml = "<select><value>1</value><text>濟南</text></select>"; xml += "<select><value>2</value><text>青島</text></select>"; xml += "<select><value>3</value><text>淄博</text></select>"; xml += "<select><value>4</value><text>棗莊</text></select>"; } String last_xml = xml_start + xml + xml_end; response.getWriter().write(last_xml); }publicvoid doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException{ doGet(request, response); }publicvoid init() throws ServletException{ }}web.xml:
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"><servlet><servlet-name>SelectServlet</servlet-name><servlet-class>com.SelectServlet</servlet-class></servlet><servlet-mapping><servlet-name>SelectServlet</servlet-name><url-pattern>/select</url-pattern></servlet-mapping><welcome-file-list><welcome-file>index.jsp</welcome-file></welcome-file-list></web-app>