Ajax
1.什么是Ajax？
asynchronous javascript and xml：异步的js和xml
它能使用js访问服务器，而且是异步访问！
服务器给客户端的响应一般是整个页面，一个html完整页面！但在ajax中因为是局部刷新，那么服务器就不用再响应整个页面！而只是数据！
>text：纯文本
>xml：
>json：它是js提供的数据交互格式，在Ajax中最受欢迎！
2.异步交互和同步交互
* 同步：
>发一个请求，就要等待服务器的响应结束，然后才能发第二个请求！中间这段时间就是一个“卡”
>刷新的是整个页面！
* 异步：
>发送一个请求后，无需等待服务器的响应，然后就可以发送第二个请求！
>可以使用js接收服务器的响应，然后使用js来局部刷新！
3.ajax应用场景
* 百度的搜索框
* 用户注册时（校验用户名是否被注册过）
4.ajax的优缺点
优点：
* 异步交互：增强了用户体验！
* 性能：因为服务器无需再响应整个页面，只需要响应部分内容，所以服务器的压力减轻了！
缺点：
* ajax不能应用在所有的场景！
* ajax无端的增多了对服务器的访问次数，给服务器带来了压力！
Ajax发送异步请求（四步操作）
1.第一步（得到XMLHttpRequest）
* ajax其实只需要学习一个对象：XMLHttpRequest，如果掌握了它，就掌握了ajax！！！
* 得到XMLHttpRequest
> 大多数浏览器都支持：var xmlHttp = new XMLHttpRequest();
> IE6.0：var xmlHttp = new ActiveXObject("Msxml2.0XMLHTTP");
> IE5.5及更早版本的IE：var xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
* 编写创建XMLHttpRequest对象的函数
function creatXMLHttpRequest(){ try { return new XMLHttpRequest(); } catch (e) { try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("不晓得你用的什么浏览器！"); throw e; } } } }
2.第二步（打开与服务器的连接）
* xmlHttp.open()：用来打开与服务器的连接，它需要三个参数：
> 请求方式：可以是GET或POST
> 请求的URL：指定服务器端资源，例如：/day23_1/AServlet
> 请求是否为异步：如果为true表示发送异步请求，否则同步请求！
* xmlHttp.open("GET", "/day23_1/AServlet", true);
3.第三步（发送请求）
* xmlHttp.send(null)：如果不给可能会造成部分浏览器无法发送！
>参数：就是请求体内容！如果是GET请求，必须给出null。
4.第四步（）
*在xmlHttp对象的一个事件上注册监听器：onreadystatechange
* xmlHttp对象一共有5个状态：
> 0状态：刚创建，还没有调用open()方法；
> 1状态：请求开始，调用了open()方法，但还没有调用send()方法
> 2状态：调用完了send()方法了；
> 3状态：服务器已经开始响应，但不表示响应结束了。
> 4状态：服务器响应结束！（通常我们只关心最后这个状态！！！）
* 得到xmlHttp对象的状态：
> var state = xmlHttp.readyState;//可能是0、1、2、3、4
* 得到服务器响应的状态吗
> var status = xmlHttp.status;//例如为200、404、500
* 得到服务器响应的内容
> var content = xmlHttp.responseText;//得到服务器的响应的文本格式的内容
> var content = xmlHttp.responseXML;//得到服务器的响应的XML响应的内容，它是Document对象了！
xmlHttp.onreadystatechange = function(){//xmlHttp的5种状态都会调用本方法
if(xmlHttp.readyState == 1 && xmlHttp.status == 200){//双重判断：判读是否为4状态，而且还有判断是否为200
//获取服务器响应内容
var text=xmlHttp.responseText;
}
};
JS示例：
<head>
<script type="text/javascript">
window.onload=function(){//在文档加载完 成之后马上执行！
//的带btn元素
var btn=document.getElementById("btn");
//给btn的click事件注册监听
btn.onclick=function(){//在按钮被点击时执行！
//获取h1元素对应的DOM对象
var h1=document.getElementById("h1");
//给h1添加内容
h1.innerHTML="hello JS!!";
};
};
</script>
</head>
<body>
<button id="btn">点击这里</button>
<h1 id="h1"></h1>
</body>
Ajax第一例：
AServlet：
package com.xjs.web.servlet; 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 AServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Hello AJAX!"); response.getWriter().print("Hello AJAX!"); } }
ajax1.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% 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 'ajax1.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"> //创建异步对象 function createXMLHttpRequest() { try { return new XMLHttpRequest(); } catch (e) { try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("不晓得你用的什么浏览器！"); throw e; } } } } window.onload = function() {//文档加载完毕后执行 var btn = document.getElementById("btn"); btn.onclick = function() {//给按钮的点击事件注册监听 /* ajax四步操作，得到服务器的响应 把响应结果显示到h1元素中 */ //1.得到异步对象 var xmlHttp = createXMLHttpRequest(); //2.打开与服务器 的连接 xmlHttp.open("GET", "/day23_1/AServlet", true); //3.发送请求 xmlHttp.send(null); //4.给异步对象的ontreadystatechange事件注册监听器 xmlHttp.onreadystatechange = function() {//当xmlHttp的状态发生变化时执行 if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { //获取服务器的响应内容 var text = xmlHttp.responseText; //获取h1元素 var h1 = document.getElementById("h1"); h1.innerHTML = text; } }; }; }; </script> </head> <body> <button id="btn">点击这里</button> <h1 id="h1"></h1> </body> </html>
第二例：发生POST请求(如果发送请求时需要带有参数，一般都用POST请求)
*open：xmlHttp.open("POST", ....);
*添加一步：设置Content-Type请求头：
> xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
*send：xmlHttp.send("username=zhangSan&password=123");//发送请求时指定请求体
AServlet：
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("UTF-8"); response.setContentType("text/html;charset=utf-8"); String username = request.getParameter("username"); System.out.println("(POST)Hello AJAX! "+username); response.getWriter().print(username); }
ajax2.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% 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 'ajax1.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"> //创建异步对象 function createXMLHttpRequest() { try { return new XMLHttpRequest(); } catch (e) { try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("不晓得你用的什么浏览器！"); throw e; } } } } window.onload = function() {//文档加载完毕后执行 var btn = document.getElementById("btn"); btn.onclick = function() {//给按钮的点击事件注册监听 /* ajax四步操作，得到服务器的响应 把响应结果显示到h1元素中 */ //1.得到异步对象 var xmlHttp = createXMLHttpRequest(); //2.打开与服务器 的连接 /*****************修改open方法，指定请求方式为POST*******************/ xmlHttp.open("POST", "<c:url value='/AServlet'/>", true); /********设置请求头：Content-Type*********/ xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); //3.发送请求 /************发送时指定请求体*************/ xmlHttp.send("username=金泰妍");//GET请求没有请求体，但也要给出null，不然FireFox可能会不能发送！ //4.给异步对象的ontreadystatechange事件注册监听器 xmlHttp.onreadystatechange = function() {//当xmlHttp的状态发生变化时执行 if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { //获取服务器的响应内容 var text = xmlHttp.responseText; //获取h1元素 var h1 = document.getElementById("h1"); h1.innerHTML = text; } }; }; }; </script> </head> <body> <button id="btn">点击这里</button> <h1 id="h1"></h1> </body> </html>
第三例：注册表单之校验用户是否注册！
1.编写页面：
* ajax3.jsp
>给出注册表单页面
>给用户名文本框添加onblur事件的监听
>获取文本框的内容，通过ajax 4步发送给服务器，得到响应结果
* 如果为1：在文本框后面显示 “用户名已被注册”
* 如果为0：什么都不做！
2.编写Servlet
* ValidateUsernameServlet
> 获取客户端传递的用户名参数
> 判断是否为itcast
* 是：返回1
* 否：返回0
ValidateUsernameServlet.java：
package com.xjs.web.servlet; 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 ValidateUsernameServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); request.setCharacterEncoding("UTF-8"); /* * 1.获取参数username 2.判断是否为itcast 3.是：响应1 4.否：响应0 */ String username = request.getParameter("username"); System.out.println(username); if (username.equalsIgnoreCase("itcast")) { System.out.println("1"); response.getWriter().print("1"); } else { System.out.println("0"); response.getWriter().print("0"); } } }
ajax3.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% 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 'ajax3.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"> //创建异步对象 function createXMLHttpRequest() { try { return new XMLHttpRequest(); } catch (e) { try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("不晓得你用的什么浏览器！"); throw e; } } } } window.onload = function() { //获取文本框，给它的失去焦点事件注册监听 var userEle = document.getElementById("usernameEle"); userEle.onblur = function() { //1.得到异步对象 var xmlHttp = createXMLHttpRequest(); //2.打开连接 xmlHttp.open("POST", "<c:url value='/ValidateUsernameServlet'/>", true); //3.设置请求头：Content-Type xmlHttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded"); //4.发送请求，给出请求体 xmlHttp.send("username=" + userEle.value); //5.给xmlHttp的onreadystatechange事件注册监听 xmlHttp.onreadystatechange = function() { if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { //获取服务器的响应，判断是否为1 //是：获取span,添加内容：“用户名已被注册”； var text = xmlHttp.responseText; var span = document.getElementById("errorSpan"); if (text == "1") { //得到span元素 span.innerHTML = "用户名已被注册！"; } else { span.innerHTML = ""; } } }; }; }; </script> </head> <body> <h1>演示用户名是否已被注册</h1> <form action="" method="post"> 用户名：<input type="text" name="username" id="usernameEle" /><span id="errorSpan"></span><br> 密码：<input type="password" name="password" /><br> <input type="submit" value="注册" /> </form> </body> </html>
第四例： 响应内容为xml数据
* 服务器端：
> 设置响应头：Content-Type，其值为：text/xml; charset=utf-8
* 客户端：
> var doc = xmlHttp.responseXML; //得到的是Document对象！
BServlet：
package com.xjs.web.servlet; 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 BServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/xml;charset=utf-8"); String xml="<students>"+ "<student number='ITCAST_1001'>"+ "<name>金泰妍</name>"+ "<age>23</age>"+ "<sex>女</sex>"+ "</student>"+ "</students>"; response.getWriter().print(xml); } }
ajax4.jsp：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% 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 'ajax1.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"> //创建异步对象 function createXMLHttpRequest() { try { return new XMLHttpRequest(); } catch (e) { try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try { return new ActiveXObject("Microsoft.XMLHTTP"); } catch (e) { alert("不晓得你用的什么浏览器！"); throw e; } } } } window.onload = function() {//文档加载完毕后执行 var btn = document.getElementById("btn"); btn.onclick = function() {//给按钮的点击事件注册监听 /* ajax四步操作，得到服务器的响应 把响应结果显示到h1元素中 */ //1.得到异步对象 var xmlHttp = createXMLHttpRequest(); //2.打开与服务器 的连接 xmlHttp.open("GET", "/day23_1/BServlet", true); //3.发送请求 xmlHttp.send(null); //4.给异步对象的ontreadystatechange事件注册监听器 xmlHttp.onreadystatechange = function() {//当xmlHttp的状态发生变化时执行 if (xmlHttp.readyState == 4 && xmlHttp.status == 200) { //获取服务器的响应内容(XML) var doc = xmlHttp.responseXML; //查询文档下名为student的所有元素，得到数组，再取下标0元素 var ele = doc.getElementsByTagName("student")[0]; var number=ele.getAttribute("number");//获取元素名为number的属性值 var name=ele.getElementsByTagName("name")[0].textContent;//IE支持 var age=ele.getElementsByTagName("age")[0].textContent; var sex=ele.getElementsByTagName("sex")[0].textContent; var text=number+","+name+","+age+","+sex; document.getElementById("h1").innerHTML=text; } }; }; }; </script> </head> <body> <button id="btn">点击这里</button> <h1 id="h1"></h1> </body> </html>
第五例：省市联动
1.页面
<select name="province">
<option>===请选择省份===</option>
</select>
<select name="city">
<option>===请选择城市===</option>
</select>
2.ProvinceServlet
* ProvinceServlet：当页面加载完毕后马上请求这个Servlet！
> 它需要加载china.xml文件，把所有的省的名称使用字符串发送给客户端！
3.页面的工作
* 获取这个字符串，使用逗号分隔，得到数组
* 循环遍历每个字符串（省份的名称），使用每个字符串创建一个<option>元素添加到<select name="province">这个元素中
4.CityServlet
* CityServlet：当页面选择某个省时，发送请求！
* 得到省份的名称，加载china.xml文件，查询出该省份对应的元素对象！把这个元素转换成xml字符串，发送给客户端
5.页面的工作
* 把<select name="city">中的所有子元素删除，但不要删除<option>===请选择城市===</option>
* 得到服务器的响应结果：doc！！！
* 获取所有的<city>子元素，循环遍历，得到<city>的内容
* 使用每个<city>的内容创建一个<option>元素，添加到<select name="city">
省份在src下的china.xml：
<?xml version="1.0" encoding="utf-8"?>
<china>
<province name="北京">
<city>东城区</city>
<city>西城区</city>
<city>崇文区</city>
<city>宣武区</city>
<city>朝阳区</city>
<city>丰台区</city>
<city>石景山区</city>
<city>海淀区</city>
<city>门头沟区</city>
<city>房山区</city>
<city>通州区</city>
<city>顺义区</city>
<city>昌平区</city>
<city>大兴区</city>
<city>怀柔区</city>
<city>平谷区</city>
<city>密云县</city>
<city>延庆县</city>
</province>
<province name="天津">
<city>和平区</city>
<city>河东区</city>
<city>河西区</city>
<city>南开区</city>
<city>河北区</city>
<city>红桥区</city>
<city>塘沽区</city>
<city>汉沽区</city>
<city>大港区</city>
<city>东丽区</city>
<city>西青区</city>
<city>津南区</city>
<city>北辰区</city>
<city>武清区</city>
<city>宝坻区</city>
<city>宁河县</city>
<city>静海县</city>
<city>蓟县</city>
</province>
<province name="河北">
<city>石家庄</city>
<city>唐山</city>
<city>秦皇岛</city>
<city>邯郸</city>
<city>邢台</city>
<city>保定</city>
<city>张家口</city>
<city>承德</city>
<city>沧州</city>
<city>廊坊</city>
<city>衡水</city>
</province>
<province name="山西">
<city>太原</city>
<city>大同</city>
<city>阳泉</city>
<city>长治</city>
<city>晋城</city>
<city>朔州</city>
<city>晋中</city>
<city>运城</city>
<city>忻州</city>
<city>临汾</city>
<city>吕梁</city>
</province>
<province name="内蒙古">
<city>呼和浩特</city>
<city>包头</city>
<city>乌海</city>
<city>赤峰</city>
<city>通辽</city>
<city>鄂尔多斯</city>
<city>呼伦贝尔</city>
<city>巴彦淖尔</city>
<city>乌兰察布</city>
<city>兴安盟</city>
<city>锡林郭勒盟</city>
<city>阿拉善盟</city>
</province>
<province name="辽宁">
<city>沈阳</city>
<city>大连</city>
<city>鞍山</city>
<city>抚顺</city>
<city>本溪</city>
<city>丹东</city>
<city>锦州</city>
<city>营口</city>
<city>阜新</city>
<city>辽阳</city>
<city>盘锦</city>
<city>铁岭</city>
<city>朝阳</city>
<city>葫芦岛</city>
</province>
<province name="吉林">
<city>长春</city>
<city>吉林</city>
<city>四平</city>
<city>辽源</city>
<city>通化</city>
<city>白山</city>
<city>松原</city>
<city>白城</city>
<city>延边</city>
</province>
<province name="黑龙江">
<city>哈尔滨</city>
<city>齐齐哈尔</city>
<city>鸡西</city>
<city>鹤岗</city>
<city>双鸭山</city>
<city>大庆</city>
<city>伊春</city>
<city>佳木斯</city>
<city>七台河</city>
<city>牡丹江</city>
<city>黑河</city>
<city>绥化</city>
<city>大兴安岭</city>
</province>
<province name="上海">
<city>黄浦区</city>
<city>卢湾区</city>
<city>徐汇区</city>
<city>长宁区</city>
<city>静安区</city>
<city>普陀区</city>
<city>闸北区</city>
<city>虹口区</city>
<city>杨浦区</city>
<city>闵行区</city>
<city>宝山区</city>
<city>嘉定区</city>
<city>浦东新区</city>
<city>金山区</city>
<city>松江区</city>
<city>青浦区</city>
<city>南汇区</city>
<city>奉贤区</city>
<city>崇明县</city>
</province>
<province name="江苏">
<city>南京</city>
<city>无锡</city>
<city>徐州</city>
<city>常州</city>
<city>苏州</city>
<city>南通</city>
<city>连云港</city>
<city>淮安</city>
<city>盐城</city>
<city>扬州</city>
<city>镇江</city>
<city>泰州</city>
<city>宿迁</city>
</province>
<province name="浙江">
<city>杭州</city>
<city>宁波</city>
<city>温州</city>
<city>嘉兴</city>
<city>湖州</city>
<city>绍兴</city>
<city>金华</city>
<city>衢州</city>
<city>舟山</city>
<city>台州</city>
<city>丽水</city>
</province>
<province name="安徽">
<city>合肥</city>
<city>芜湖</city>
<city>蚌埠</city>
<city>淮南</city>
<city>马鞍山</city>
<city>淮北</city>
<city>铜陵</city>
<city>安庆</city>
<city>黄山</city>
<city>滁州</city>
<city>阜阳</city>
<city>宿州</city>
<city>巢湖</city>
<city>六安</city>
<city>亳州</city>
<city>池州</city>
<city>宣城</city>
</province>
<province name="福建">
<city>福州</city>
<city>厦门</city>
<city>莆田</city>
<city>三明</city>
<city>泉州</city>
<city>漳州</city>
<city>南平</city>
<city>龙岩</city>
<city>宁德</city>
</province>
<province name="江西">
<city>南昌</city>
<city>景德镇</city>
<city>萍乡</city>
<city>九江</city>
<city>新余</city>
<city>鹰潭</city>
<city>赣州</city>
<city>吉安</city>
<city>宜春</city>
<city>抚州</city>
<city>上饶</city>
</province>
<province name="山东">
<city>济南</city>
<city>青岛</city>
<city>淄博</city>
<city>枣庄</city>
<city>东营</city>
<city>烟台</city>
<city>潍坊</city>
<city>济宁</city>
<city>泰安</city>
<city>威海</city>
<city>日照</city>
<city>莱芜</city>
<city>临沂</city>
<city>德州</city>
<city>聊城</city>
<city>滨州</city>
<city>荷泽</city>
</province>
<province name="河南">
<city>郑州</city>
<city>开封</city>
<city>洛阳</city>
<city>平顶山</city>
<city>安阳</city>
<city>鹤壁</city>
<city>新乡</city>
<city>焦作</city>
<city>濮阳</city>
<city>许昌</city>
<city>漯河</city>
<city>三门峡</city>
<city>南阳</city>
<city>商丘</city>
<city>信阳</city>
<city>周口</city>
<city>驻马店</city>
</province>
<province name="湖北">
<city>武汉</city>
<city>黄石</city>
<city>十堰</city>
<city>宜昌</city>
<city>襄樊</city>
<city>鄂州</city>
<city>荆门</city>
<city>孝感</city>
<city>荆州</city>
<city>黄冈</city>
<city>咸宁</city>
<city>随州</city>
<city>恩施</city>
<city>神农架</city>
</province>
<province name="湖南">
<city>长沙</city>
<city>株洲</city>
<city>湘潭</city>
<city>衡阳</city>
<city>邵阳</city>
<city>岳阳</city>
<city>常德</city>
<city>张家界</city>
<city>益阳</city>
<city>郴州</city>
<city>永州</city>
<city>怀化</city>
<city>娄底</city>
<city>湘西</city>
</province>
<province name="广东">
<city>广州</city>
<city>韶关</city>
<city>深圳</city>
<city>珠海</city>
<city>汕头</city>
<city>佛山</city>
<city>江门</city>
<city>湛江</city>
<city>茂名</city>
<city>肇庆</city>
<city>惠州</city>
<city>梅州</city>
<city>汕尾</city>
<city>河源</city>
<city>阳江</city>
<city>清远</city>
<city>东莞</city>
<city>中山</city>
<city>潮州</city>
<city>揭阳</city>
<city>云浮</city>
</province>
<province name="广西">
<city>南宁</city>
<city>柳州</city>
<city>桂林</city>
<city>梧州</city>
<city>北海</city>
<city>防城港</city>
<city>钦州</city>
<city>贵港</city>
<city>玉林</city>
<city>百色</city>
<city>贺州</city>
<city>河池</city>
<city>来宾</city>
<city>崇左</city>
</province>
<province name="海南">
<city>海口</city>
<city>三亚</city>
</province>
<province name="重庆">
<city>重庆</city>
<city>万州区</city>
<city>涪陵区</city>
<city>渝中区</city>
<city>大渡口区</city>
<city>江北区</city>
<city>沙坪坝区</city>
<city>九龙坡区</city>
<city>南岸区</city>
<city>北碚区</city>
<city>万盛区</city>
<city>双桥区</city>
<city>渝北区</city>
<city>巴南区</city>
<city>黔江区</city>
<city>长寿区</city>
<city>綦江县</city>
<city>潼南县</city>
<city>铜梁县</city>
<city>大足县</city>
<city>荣昌县</city>
<city>璧山县</city>
<city>梁平县</city>
<city>城口县</city>
<city>丰都县</city>
<city>垫江县</city>
<city>武隆县</city>
<city>忠县</city>
<city>开县</city>
<city>云阳县</city>
<city>奉节县</city>
<city>巫山县</city>
<city>巫溪县</city>
<city>石柱土家族自治县</city>
<city>秀山土家族苗族自治县</city>
<city>酉阳土家族苗族自治县</city>
<city>彭水苗族土家族自治县</city>
<city>江津</city>
<city>合川</city>
<city>永川</city>
<city>南川</city>
</province>
<province name="四川">
<city>成都</city>
<city>自贡</city>
<city>攀枝花</city>
<city>泸州</city>
<city>德阳</city>
<city>绵阳</city>
<city>广元</city>
<city>遂宁</city>
<city>内江</city>
<city>乐山</city>
<city>南充</city>
<city>眉山</city>
<city>宜宾</city>
<city>广安</city>
<city>达州</city>
<city>雅安</city>
<city>巴中</city>
<city>资阳</city>
<city>阿坝</city>
<city>甘孜</city>
<city>凉山</city>
</province>
<province name="贵州">
<city>贵阳</city>
<city>六盘水</city>
<city>遵义</city>
<city>安顺</city>
<city>铜仁</city>
<city>黔西南</city>
<city>毕节</city>
<city>黔东南</city>
<city>黔南</city>
</province>
<province name="云南">
<city>昆明</city>
<city>曲靖</city>
<city>玉溪</city>
<city>保山</city>
<city>昭通</city>
<city>丽江</city>
<city>思茅</city>
<city>临沧</city>
<city>楚雄</city>
<city>红河</city>
<city>文山</city>
<city>西双版纳</city>
<city>大理</city>
<city>德宏</city>
<city>怒江</city>
<city>迪庆</city>
</province>
<province name="西藏">
<city>拉萨</city>
<city>昌都</city>
<city>山南</city>
<city>日喀则</city>
<city>那曲</city>
<city>阿里</city>
<city>林芝</city>
</province>
<province name="陕西">
<city>西安</city>
<city>铜川</city>
<city>宝鸡</city>
<city>咸阳</city>
<city>渭南</city>
<city>延安</city>
<city>汉中</city>
<city>榆林</city>
<city>安康</city>
<city>商洛</city>
</province>
<province name="甘肃">
<city>兰州</city>
<city>嘉峪关</city>
<city>金昌</city>
<city>白银</city>
<city>天水</city>
<city>武威</city>
<city>张掖</city>
<city>平凉</city>
<city>酒泉</city>
<city>庆阳</city>
<city>定西</city>
<city>陇南</city>
<city>临夏</city>
<city>甘南</city>
</province>
<province name="青海">
<city>西宁</city>
<city>海东</city>
<city>海北</city>
<city>黄南</city>
<city>海南</city>
<city>果洛</city>
<city>玉树</city>
<city>海西</city>
</province>
<province name="宁夏">
<city>银川</city>
<city>石嘴山</city>
<city>吴忠</city>
<city>固原</city>
<city>中卫</city>
</province>
<province name="新疆">
<city>乌鲁木齐</city>
<city>克拉玛依</city>
<city>吐鲁番</city>
<city>哈密</city>
<city>昌吉</city>
<city>博尔塔拉</city>
<city>巴音郭楞</city>
<city>阿克苏</city>
<city>克孜勒苏</city>
<city>喀什</city>
<city>和田</city>
<city>伊犁</city>
<city>塔城</city>
<city>阿勒泰</city>
<city>石河子</city>
<city>阿拉尔</city>
<city>图木舒克</city>
<city>五家渠</city>
</province>
<province name="香港">
<city>香港</city>
</province>
<province name="澳门">
<city>澳门</city>
</province>
<province name="台湾">
<city>台湾</city>
</province>
</china>
ProvinceServlet：负责向页面响应所有的省份
package com.xjs.web.servlet; import java.io.IOException; import java.io.InputStream; import java.util.Iterator; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.dom4j.Document; import org.dom4j.DocumentException; import org.dom4j.Element; import org.dom4j.io.SAXReader; public class ProvinceServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { /* * 响应所有省份名称，使用逗号隔开！ */ /* * 1.Document对象 * 》创建解析器对象 * 》调用解析器的读方法，传递一个流对象，得到Document */ StringBuilder str=new StringBuilder(); SAXReader reader=new SAXReader(); InputStream in=this.getClass().getResourceAsStream("/china.xml"); Document doc; try { doc = reader.read(in); } catch (DocumentException e) { throw new RuntimeException(e); } Element root = doc.getRootElement();//根节点 Iterator<Element> ele = root.elementIterator(); while(ele.hasNext()){ //每个省份 Element province = ele.next(); //得到省份的名称--即该节点的属性值 String provinceName = province.attributeValue("name"); if(ele.hasNext()){ str=str.append(provinceName+","); }else{ str=str.append(provinceName); } } // System.out.println(str);在控制台显示所有的省份，省份 response.setContentType("text/html;charset=utf-8"); response.getWriter().print(str); } }
北京,天津,河北,山西,内蒙古,辽宁,吉林,黑龙江,上海,江苏,浙江,安徽,福建,江西,山东,河南,湖北,湖南,广东,广西,海南,重庆,四川,贵州,云南,西藏,陕西,甘肃,青海,宁夏,新疆,香港,澳门,台湾
CityServlet：根据选择的省份，去解析XML文件，找到该省的节点，直接使用asXML()转换成字符串，响应给页面
package com.xjs.web.servlet; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.dom4j.Document; import org.dom4j.DocumentException; import org.dom4j.Element; import org.dom4j.io.SAXReader; public class CityServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/xml;charset=utf-8"); request.setCharacterEncoding("utf-8"); /* * 获取省份名称，加载该省对应的<province>元素 * 把元素转换成字符串发送给客户端 */ /* * 1.获取省份的名称 * 2.使用省份名称查找到对应的<province>元素 * 3.把<province>元素转换成字符串，发送！ */ SAXReader reader=new SAXReader(); InputStream in=this.getClass().getResourceAsStream("/china.xml"); Document doc; try { doc = reader.read(in); } catch (DocumentException e) { throw new RuntimeException(e); } //获取参数 String pname = request.getParameter("pname"); //根据条件查节点元素 Element proEle=(Element) doc.selectSingleNode("//province[@name='"+pname+"']"); String xmlStr = proEle.asXML();//把元素转换成字符串 // System.out.println(xmlStr);在控制台显示该省中的市(XML格式) response.getWriter().print(xmlStr); } }
<province name="山东"> <city>济南</city> <city>青岛</city> <city>淄博</city> <city>枣庄</city> <city>东营</city> <city>烟台</city> <city>潍坊</city> <city>济宁</city> <city>泰安</city> <city>威海</city> <city>日照</city> <city>莱芜</city> <city>临沂</city> <city>德州</city> <city>聊城</city> <city>滨州</city> <city>荷泽</city> </province>
ajax5.jsp：负责显示页面，处理异步请求
1）请求ProvinceServlet，响应的文本信息，分隔得到数组，然后再添加option元素到select中
2）根据选择的省，去请求CityServlet，响应的是XML信息，直接得到Document对象，然后再去增option元素，
注意：2）中的首先要移除select中的option（除<option>===请选择市===</option>）元素，以免option元素的累加
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<%
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 'ajax5.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">
//创建异步对象
function createXMLHttpRequest() {
try {
return new XMLHttpRequest();
} catch (e) {
try {
return new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
return new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
alert("不晓得你用的什么浏览器！");
throw e;
}
}
}
}
/*
* 1.在文档加载完毕时发送请求，得到所有省份名称，显示在<select name="porvince"/>中
* 2.在选择了新的省份时，发送请求（参数为省份的名称），得到xml文档，即<province>元素
* 3.解析xml文档，得到其中所有的<city>,再得到每个<city>元素的内容，即市名，使用市名生成<option>，插入到<select name="city">元素中
*/
window.onload = function() {
/*
ajax四步，请求ProvinceServlet，得到所有的省份名称
使用每个省份名称创建一个<option>元素，添加到<select name="province">中
*/
var xmlHttp = createXMLHttpRequest();
xmlHttp.open("GET", "<c:url value='/ProvinceServlet'/>", true);
xmlHttp.send(null);
xmlHttp.onreadystatechange = function() {
if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
var text = xmlHttp.responseText;
//使用逗号分隔它，得到数组
var arr = text.split(",");
//循环遍历每个省份名称，每个名称生成一个option对象，添加到<select>元素中
for (var i = 0; i < arr.length; i++) {
var op = document.createElement("option");//创建指定名称的元素
op.value = arr[i];//设置op的实际值为当前的省份名称
var textNode = document.createTextNode(arr[i]);//创建文本节点
op.appendChild(textNode);//把文本子节点添加到op元素中，指定显示值
document.getElementById("p").appendChild(op);
}
}
};
/*
第二件事情：给<select name="province">添加改变监听器
使用选择的省份名称请求CityServlet，得到<province>元素(xml元素)！！！
获取<province>元素中所有的<city>元素，遍历之，获取每个<city>的文本内容，即市名称
使用每个市名称创建<option>元素添加到<select name="city">
*/
var proSelect = document.getElementById("p");
proSelect.onchange = function() {
var xmlHttp = createXMLHttpRequest();
xmlHttp.open("POST", "<c:url value='/CityServlet'/>", true);
xmlHttp.setRequestHeader("Content-Type",
"application/x-www-form-urlencoded");
xmlHttp.send("pname=" + proSelect.value);//把下拉列表中选择的值发送给服务器
xmlHttp.onreadystatechange = function() {
if (xmlHttp.readyState == 4 && xmlHttp.status == 200) {
//把select中的所有option移除（除了请选择）
var citySelect=document.getElementById("c");
//获取所有子元素
var optionEleList=citySelect.getElementsByTagName("option");
//循环遍历每个option元素，然后在citySelect中移除
while(optionEleList.length>1){
citySelect.removeChild(optionEleList[1]);//总是删除1下标，因为1删除了，2就变成1了
}
var doc = xmlHttp.responseXML;
//得到所有名为city的元素
var cityEleList = doc.getElementsByTagName("city");
//循环遍历每个city元素
for (var i = 0; i < cityEleList.length; i++) {
var cityEle = cityEleList[i];//得到每个city元素
var cityName;
//获取市名称
if (window.addEventListener) {
cityName = cityEle.textContent;
} else {
cityName = cityEle.text;//支持IE
}
//使用市名称创建option元素，添加到<select name="city">
var op = document.createElement("option");
op.value = cityName;
//创建文本节点
var textNode = document.createTextNode(cityName);
op.appendChild(textNode);
//把op添加到<select>中
citySelect.appendChild(op);
}
}
};
};
};
</script>
</head>
<body>
<h1>省市联动</h1>
<select name="porvince" id="p">
<option>===请选择省===</option>
</select>
<select name="porvince" id="c">
<option>===请选择市===</option>
</select>
</body>
</html>
