Ajax实现二级联动菜单

2024-09-01 08:31:18

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本文实例为大家分享了Ajax二级联动菜单的具体代码，供大家参考，具体内容如下

index.jsp

<%@ 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 align="center">   <form name="form1" method="post" action="">    <table width="70%" border="0" cellspacing="0" cellpadding="0">     <tr>      <td align="center">       二级联动示例      </td>     </tr>     <tr>      <td>       <select name="province" id="province" 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 name="city" id="city">        <!--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

<?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>

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