Ajax实现二级联动菜单-学习AJAX-JavaScript编程-硕编程

Ajax实现二级联动菜单

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>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持硕编程。

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