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Ajax实现二级联动菜单

发布时间:2020-12-02 17:39 所属栏目:[移动互联] 来源:网络整理
导读:这篇文章主要为大家详细介绍了Ajax实现二级联动菜单,文中示例代码介绍的非常详细,具有一定的参考价值,感兴趣的小伙伴们可以参考一下

<%@ 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发生改变时调用该函数
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();//解析XML文档
}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;//获得返回的XML文档
var xSel = xmlDoc.getElementsByTagName('select');
//获得XML文档中的所有<select>标记
var select_root = document.getElementById('city');
//获得网页中的第二个下拉框
select_root.options.length=0;
//每次获得新的数据的时候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;
//获得每个<select>标记中的第一个标记的值,也就是<value>标记的值
var xText = xSel[i].childNodes[1].firstChild.nodeValue;
//获得每个<select>标记中的第二个标记的值,也就是<text>标记的值

var option = new Option(xText, xValue);
//根据每组value和text标记的值创建一个option对象

try{
select_root.add(option);//将option对象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);
// 获得请求中参数为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>朝阳</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
{// 如果是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

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