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副问题[/!--empirenews.page--]
<%@ page language="java" pageEncoding="UTF-8"%>
<html>
<head>
<title>二级菜单联动演示</title>
<script type="text/javascript">
var req;
window.οnlοad=function()
{//页面加载时的函数
}
function Change_Select(){//当第一个下拉框的选项产生改变时挪用该函数
var province = document.getElementById('province').value;
var url = "select?id="+ escape(province);
if(window.XMLHttpRequest){
req = new XMLHttpRequest();
}else if(window.ActiveXObject){
req = new ActiveXObject("Microsoft.XMLHTTP");
}
if(req){
req.open("GET",url,true);
//指定回调函数为callback
req.onreadystatechange = callback;
req.send(null);
}
}
//回调函数
function callback(){
if(req.readyState ==4){
if(req.status ==200){
parseMessage();//理会XML文档
}else{
alert("不能获得描写信息:" + req.statusText);
}
}
}
//理会返回xml的要领
function parseMessage(){
var xmlDoc = req.responseXML.documentElement;//得到返回的XML文档
var xSel = xmlDoc.getElementsByTagName('select');
//得到XML文档中的全部<select>标志
var select_root = document.getElementById('city');
//得到网页中的第二个下拉框
select_root.options.length=0;
//每次得到新的数据的时辰先把每二个下拉框架的长度清0
for(var i=0;i<xSel.length;i++){
var xValue = xSel[i].childNodes[0].firstChild.nodeValue;
//得到每个<select>标志中的第一个标志的值,也就是<value>标志的值
var xText = xSel[i].childNodes[1].firstChild.nodeValue;
//得到每个<select>标志中的第二个标志的值,也就是<text>标志的值
var option = new Option(xText, xValue);
//按照每组value和text标志的值建设一个option工具
try{
select_root.add(option);//将option工具添加到第二个下拉框中
}catch(e){
}
}
}
</script>
</head>
<body>
<div>
<form method="post" action="">
<table cellspacing="0" cellpadding="0">
<tr>
<td>
二级联动示例
</td>
</tr>
<tr>
<td>
<select onChange="Change_Select()">
<!--第一个下拉菜单-->
<option value="0">
请选择
</option>
<option value="1">
北京
</option>
<option value="2">
天津
</option>
<option value="3">
山东
</option>
</select>
<select>
<!--第二个下拉菜单-->
<option value="0">
请选择
</option>
</select>
</td>
</tr>
<tr>
<td>
</td>
<tr>
</table>
</form>
</div>
</body>
</html>
SelectServlet.java
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
*
*/
public class SelectServlet extends HttpServlet
{
private static final long serialVersionUID = 1L;
public SelectServlet()
{
super();
}
public void destroy()
{
super.destroy();
}
public void 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);
// 得到哀求中参数为id的值
String xml_start = "<selects>";
String xml_end = "</selects>";
String xml = "";
if (targetId.equalsIgnoreCase("0"))
{
xml = "<select><value>0</value><text>请选择</text></select>";
} else if (targetId.equalsIgnoreCase("1"))
{
xml = "<select><value>1</value><text>昌平</text></select>";
xml += "<select><value>2</value><text>丰台</text></select>";
xml += "<select><value>3</value><text>海淀</text></select>";
xml += "<select><value>4</value><text>向阳</text></select>";
} else if (targetId.equalsIgnoreCase("2"))
{
xml = "<select><value>1</value><text>塘沽区</text></select>";
xml += "<select><value>2</value><text>汉沽区</text></select>";
xml += "<select><value>3</value><text>大港区</text></select>";
xml += "<select><value>4</value><text>东丽区</text></select>";
} else
{// 假如是3,则返回下面的字符
xml = "<select><value>1</value><text>济南</text></select>";
xml += "<select><value>2</value><text>青岛</text></select>";
xml += "<select><value>3</value><text>淄博</text></select>";
xml += "<select><value>4</value><text>枣庄</text></select>";
}
String last_xml = xml_start + xml + xml_end;
response.getWriter().write(last_xml);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
public void init() throws ServletException
{
}
}
web.xml
（编辑：湖南网）
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