本文實例講述了java實現的二級聯動菜單效果。分享給大家供大家參考，具體如下：
JSP代碼：
<%@ 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(); }else if(window.ActiveXObject){ req = new ActiveXObject("Microsoft.XMLHTTP"); } if(req){ req.open("GET",url,true); //指定回調函數為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 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>Java代碼：
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>丰台</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</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); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } public void init() throws ServletException { }}XML代碼：
<?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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希望本文所述對大家java程序設計有所幫助。