日期:2014-05-16 浏览次数:20799 次
基本思路:前台的下拉框值改变时,AJAX将值传入后台的servlet进行处理,根据不同的值返回不同的JSON数据,然后前台进行解析成字符数组,添加到option中.
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> <script type="text/javascript"> var xmlHttpRequest; function createXmlHttpRequest() { if (window.XMLHttpRequest) { xmlHttpRequest = new XMLHttpRequest(); } else { xmlHttpRequest = new ActiveXObject("Microsoft.XMLHTTP"); } } function getCity(value) { createXmlHttpRequest(); xmlHttpRequest.open("POST", "cityAction?value="+value,true); //将value传递到后台的servlet xmlHttpRequest.onreadystatechange = showMsgCallback; xmlHttpRequest.send(null); } function showMsgCallback() { if (xmlHttpRequest.readyState == 4) { if (xmlHttpRequest.status == 200) { var str = eval("("+xmlHttpRequest.responseText+")"); //JSON格式转换为字符数组 if(str!=null&&str!=""){ document.getElementById("city").options.length=0; //将原有的选项清空 document.getElementById("city").options.add(new Option("--选择")); for(var i=0;i<str.length;i++){ //遍历数组 var option = document.createElement("option"); //创建一个 option option.text = str[i]; //设置显示的值 option.value = str[i]; //设置value属性值 document.getElementById("city").options.add(option); //将新建的option添加到select中 } }else{ document.getElementById("city").options.length=0; document.getElementById("city").options.add(new Option("--选择")); } } } } </script> </head> <body> 省: <select onchange="getCity(this.value)"> <option> --选择 </option> <option value="北京"> 北京 </option> <option value="深圳"> 深圳 </option> <option value="河南"> 河南 </option> </select> 城市: <select id="city"> <option> --选择 </option> </select> </body> </html> Servlet: CityAction.java
package com.org; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class CityAction extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); request.setCharacterEncoding("utf-8"); PrintWriter out = response.getWriter(); String province = request.getParameter("value"); StringBuffer buf = new StringBuffer("["); //数据只是测试 通常是从数据库中取出数据 if("北京".equals(province)){ buf.append("\"").append("海淀").append("\"").append(","); buf.append("\"").append("朝阳").append("\"").append(","); buf.append("\"").append("昌平").append("\"").append(","); buf.append("\"").append("大兴").append("\""); buf.append("]"); out.print(buf); System.out.println(buf); }else if("深圳".equals(province)){ buf.append("\"").append("福田").append("\"").