java实现的二级联动菜单效果

本文实例讲述了java实现的二级联动菜单效果。分享给大家供大家参考，具体如下：

JSP代码：

<%@ 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.onload=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>

Java代码：

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
  {
  }
}

XML代码：

<?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>

更多java相关内容感兴趣的读者可查看本站专题：《Java数据结构与算法教程》、《Java操作DOM节点技巧总结》、《Java文件与目录操作技巧汇总》和《Java缓存操作技巧汇总》

希望本文所述对大家java程序设计有所帮助。