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java实现的二级联动菜单效果

程序员文章站 2024-03-13 19:36:51
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" pagee...

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>

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希望本文所述对大家java程序设计有所帮助。