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Ajax二級聯(lián)動菜單實現(xiàn)原理及代碼_AJAX教程

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推薦：Ajax方式提交帶文件上傳的表單及隱藏iframe應用
一般的表單都是通過ajax方式提交，所以碰到帶文件上傳的表單就比較麻煩,基本原理就是在頁面增加一個隱藏iframe，然后通過ajax提交除文件之外的表單數(shù)據(jù),感興趣的你不妨了解一下，或許本文對你有所幫助

index.jsp:
復制代碼 代碼如下:hl5o.cn

<%@ page language="java" pageEncoding="UTF-8"%>
<html>
<head>
<title>二級菜單聯(lián)動演示</title>
<script type="text/javascript">
var req;
window.onload=function()
{//頁面加載時的函數(shù)
}
function Change_Select(){//當?shù)谝粋�下拉框的選項發(fā)生改變時調用該函數(shù)
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);
//指定回調函數(shù)為callback
req.onreadystatechange = callback;
req.send(null);
}
}
//回調函數(shù)
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(wǎng)頁中的第二個下拉框
select_root.options.length=0;
//每次獲得新的數(shù)據(jù)的時候先把每二個下拉框架的長度清0
for(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(jù)每組value和text標記的值創(chuàng)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(lián)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:
復制代碼 代碼如下:hl5o.cn

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);
// 獲得請求中參數(shù)為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>";
} else if (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>";
} else if (targetId.equalsIgnoreCase("2"))
{
xml = "<select><value>1</value><text>塘沽區(qū)</text></select>";
xml += "<select><value>2</value><text>漢沽區(qū)</text></select>";
xml += "<select><value>3</value><text>大港區(qū)</text></select>";
xml += "<select><value>4</value><text>東麗區(qū)</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);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
doGet(request, response);
}
public void init() throws ServletException
{
}
}

web.xml:
復制代碼 代碼如下:hl5o.cn

<?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>

分享：菜鳥蔡之Ajax復習第三篇(Ajax之無刷新登錄)
無刷新登錄大家也許沒寫過，但是一定都是聽說過的，很早以前就想用這個小技術在自己做的小項目中用一把了，但都沒有付出過實踐，在網(wǎng)上查也沒有查到具體完整的代碼，在這里，今天菜鳥蔡也來試了一把，獻丑了，希望對初學的童鞋有點幫助

來源：模板無憂//所屬分類：AJAX教程/更新時間：2013-04-22
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