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Ajax实现动态加载组合框的实例代码

程序员文章站 2022-06-25 10:47:55
一  province.jsp <%@ page language="java" import="java.util.*" pageencodin...

一  province.jsp

<%@ page language="java" import="java.util.*" pageencoding="utf-8"%>
 <html>
  <head>
   <script type="text/javascript" language="javascript">
    var xmlhttp = false; //全局变量,用于记录xmlhttprequest对象
    function createxmlhttprequest() {
     if(window.activexobject) { //internet explorer时,创建xmlhttprequest对象的方法
      try {
      xmlhttp = new activexobject("msxml2.xmlhttp");
     } catch(e) {
      try {       xmlhttp = new activexobject("microsoft.xmlhttp");
       //旧版本的internet explorer,创建xmlhttprequest对象
      } catch(e) {
       window.alert("创建xmlhttprequest对象错误"+e);
      } 
     }
    } else if(window.xmlhttprequest) { //mozilla时,创建xmlhttprequest对象的方法
      xmlhttp = new xmlhttprequest();
     } 
    if(!(xmlhttp)) { //未成功创建xmlhttprequest对象
      window.alert("创建xmlhttprequest对象异常!");
    } 
    }
   //下拉列表项改变时的操作
   function prochange(objval) {
     createxmlhttprequest(); //创建xmlhttprequest对象
     document.getelementbyid("city").length = 1;   //根据id获取指定元素,并赋值
     xmlhttp.onreadystatechange = citylist; //指定onreadystatechange处理函数
     var url="citybyxmlservlet?province="+objval; //请求的url地址
     xmlhttp.open("post",url,true);
     xmlhttp.send(null);
    }
    function citylist() { //onreadystatechange的处理函数
    if(xmlhttp.readystate==4) {
      if(xmlhttp.status==200) {
       parsexml(xmlhttp.responsexml);   //解析服务器返回的xml数据
     }
     }
   }
    //解析xml信息,以添加地市
    function parsexml(xmldoc) {
    var len = xmldoc.getelementsbytagname("city");
    //获取xml数据中所有的“city”元素对象集合
     var _citysel = document.getelementbyid("city");   //根据id获取页面中的select元素
     for(var i=0;i<len.length;i++) { //遍历xml数据并给select元素添加选项
     var opt = document.createelement("option");   //创建option对象
     opt.text = xmldoc.getelementsbytagname("city")[i].firstchild.data;
     //指定新创建元素的text属性值
     opt.value = xmldoc.getelementsbytagname("city")[i].firstchild.data;
    //指定新创建元素的value属性值
     _citysel.add(opt); //为select元素添加option
    }
    }
   </script>
   <title>动态加载组合框</title>
  </head>
  <body>
   <table align="center" border=1 width="320">
    <tr>
     <td>省份:</td>
    <td>
     <select id="province" onchange="prochange(this.value);" style="width:85">
      <option value="gd">广东</option>
       <option value="gx">广西</option>
       <option value="hn">湖南</option>
      <option value="hb">湖北</option>
      <option value="ah">安徽</option>
     </select>
    </td>
    </tr>
   <tr>
    <td>城市:</td>
    <td>
     <select id="city" style="width:85">
       <option value="">--请选择--</option>
     </select>
    </td>
    </tr>
   </table>
 </body>
 </html> 

二、citybyxmlservlet.java

package servlet;
import java.io.ioexception;
import java.io.printwriter;
import java.util.*;
import javax.servlet.servletexception;
import javax.servlet.annotation.webservlet;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
/**
 * servlet implementation class citybyxmlservlet
 */
@webservlet("/citybyxmlservlet")
public class citybyxmlservlet extends httpservlet {
 private static final long serialversionuid = 1l;
  private static final string content_type = "text/xml; charset=utf-8";
  /**
   * @see httpservlet#httpservlet()
   */
  public citybyxmlservlet() {
    super();
    // todo auto-generated constructor stub
  }
 /**
 * @see httpservlet#doget(httpservletrequest request, httpservletresponse response)
 */
  public void doget(httpservletrequest request, httpservletresponse response)
         throws servletexception, ioexception {
      response.setcontenttype(content_type); //设置服务器响应类型
       string province =request.getparameter("province");
       stringbuffer city = new stringbuffer("<citys>"); //记录返回xml串的对象
       if("gx".equals(province)){
       list list=cityinit(); //获取城市列表
        for(int i=0;i<list.size();i++){
           city.append("<city>"+list.get(i)+"</city>");
        }      
       }else if("hn".equals(province)){
       list list = cityinit1(); //获取城市列表
       for(int j=0;j<list.size();j++){
           city.append("<city>"+list.get(j)+"</city>");
       }
        }else if("hb".equals(province)){
        list list = cityinit2(); //获取城市列表
        for(int j=0;j<list.size();j++){
           city.append("<city>"+list.get(j)+"</city>");
        } 
       }
      city.append("</citys>");
      printwriter out = response.getwriter();
      out.println(city.tostring());
      out.flush(); //输出流刷新
      out.close(); //关闭输出流
     }
     /*
     * 初始化城市
     */
  public list<string> cityinit2() {
    list<string> citylist = new arraylist<string>();
   //添加城市列表
    citylist.add("武汉");
    citylist.add("襄阳");
    citylist.add("黄冈");
    citylist.add("荆门");
    citylist.add("十堰");
    citylist.add("黄石");
    return citylist;
  }
     public list<string> cityinit(){
       list<string> citylist = new arraylist<string>();
     //添加城市列表
       citylist.add("南宁");
       citylist.add("桂林");
       citylist.add("北海");
       citylist.add("河池");
       citylist.add("梧州");
       citylist.add("玉林");
    return citylist;
   }
    public list<string> cityinit1() {
    list<string> citylist = new arraylist<string>();
   //添加城市列表
    citylist.add("长沙");
    citylist.add("湘潭");
    citylist.add("岳阳");
    citylist.add("常德");
    citylist.add("衡阳");
    citylist.add("邵阳");
    return citylist;
  }
    /**
     *当前servelt的初始化方法. <br>
     *
     * @throws servletexception发生servletexceptio时抛出
     */
    public void init() throws servletexception {
    }
 protected void dopost(httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
 doget(request, response);
 }
}

三 web.xml

<?xml version="1.0" encoding="utf-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/xmlschema-instance" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:web="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemalocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd http://xmlns.jcp.org/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.4">
<servlet>
  <servlet-name>citybyxmlservlet</servlet-name>
  <servlet-class>servlet.citybyxmlservlet</servlet-class><!--类的位置 -->
</servlet>
<servlet-mapping>
  <servlet-name>citybyxmlservlet</servlet-name><!--你创建的类名 -->
  <url-pattern>/citybyxmlservlet</url-pattern>
</servlet-mapping>

总结

以上所述是小编给大家介绍的ajax实现动态加载组合框的实例代码,希望对大家有所帮助