首先写好前台页面testProvince.jsp，将请求通过open、send发送到服务器
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"https://www.jb51.net/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="https://www.jb51.net/<%=basePath%>" > <title>二级联动</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"> <style type="text/css"> select{ width:111px; } </style> </head> <body> <select> <option>选择省份</option> <option>湖南</option> <option>广东</option> </select> <select> <option>选择城市</option> </select> </body> <script type="text/javascript"> //创建ajax对象 function createAjax(){ var ajax = null; try{ ajax = new ActiveXObject("microsoft.xmlhttp"); }catch(e){ try{ ajax = new XMLHttpRequest(); }catch(e1){ alert("请更换浏览器"); } } return ajax; } </script> <script type="text/javascript"> document.getElementById("provinceID").onchange = function(){ //清空城市除了第一项 var cityElem = document.getElementById("cityID"); cityElem.options.length = 1; //获取选中的省份 var province = this.value; //进行编码处理 province = encodeURI(province); if("选择省份" != province){ var ajax = createAjax(); //提交方式为GET var method = "GET"; //提交路径为servlet路径 var url = "${pageContext.request.contextPath}/ProvinceServlet?time=" + new Date().getTime()+ "&province=" +province; //准备发送异步请求 ajax.open(method, url); //由于是get请求，所以不需要设置请求头 //发送请求 ajax.send(null); //监听服务器响应状态的变化 ajax.onreadystatechange = function(){ //响应状态为4 表示ajax已经完全接受到服务器的数据了 if(ajax.readyState == 4){ //接收到的数据正常 if(ajax.status == 200){ //获取服务器传来的html数据 var xmlDocument = ajax.responseXML; //进行dom操作解析xml //解析xml数据 var citys = xmlDocument.getElementsByTagName("city"); for(var i = 0; i< citys.length;i++){ //获取xml中的值 :不能用innerHTML,要用nodeValue var city = citys[i].firstChild.nodeValue; //创建option var optElement = document.createElement("option"); optElement.innerHTML = city; //获取city var cityElems = document.getElementById("cityID"); cityElems.appendChild(optElement); } } } } } } </script> </html>
然后在后台ProvinceServlet中通过GET方式获取请求，将返回的数据以O（输出）流的方式发送出去,上面代码的ajax.responseXML获取输出的数据，并进行dom操作
public class ProvinceServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("utf-8"); resp.setCharacterEncoding("utf-8"); String province = req.getParameter("province"); //重新编码 province = new String(province.getBytes("ISO-8859-1"),"utf-8"); //设置格式为xml resp.setContentType("text/xml;charset=utf-8"); //获取字符输出流 PrintWriter pw = resp.getWriter(); //拼接xml头 pw.write("<?xml version='1.0' encoding='UTF-8'?>"); pw.write("<citys>"); if ("湖南".equals(province)) { pw.write("<city>长沙</city>"); pw.write("<city>株洲</city>"); pw.write("<city>湘潭</city>"); pw.write("<city>岳阳</city>"); }else if("广东".equals(province)){ pw.write("<city>广州</city>"); pw.write("<city>深圳</city>"); pw.write("<city>中山</city>"); } pw.write("</citys>"); pw.flush(); pw.close(); } }
运行结果如下:
