AJAX（1）

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package test_main;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * Servlet implementation class Test2 */public class Test2 extends HttpServlet {private static final long serialVersionUID = 1L;private String usenames[] = { "as", "asd", "mkk" };protected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String usename = request.getParameter("usename");boolean b = false;for (String u : usenames) {if (u.equals(usename)) {b = true;break;}}response.setContentType("text/html;charset=utf-8");if (b) {// 这里是验证成功的response.getWriter().write("登录成功！");} else {response.getWriter().write("没有登录成功！");}}protected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubdoGet(request, response);}}

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><script type="text/javascript" src="jutil.js"></script><script type="text/javascript">window.onload=function(){//页面加载的时候就相应这个函数document.getElementById("usename").onblur=function(){//页面的id为usename的对象数去焦点的时候就去来相应这个函数if(this.value==""){//如果用户名是空alert("请输入用户名");this.focus();//把usenam从新回复焦点return ;}//下面开始发出异步请求//得到对象var xhr=getXHR();//2.注册监听器onreadystatechangexhr.onreadystatechange=function(){//如果发生变化，这相应这个函数readyStateif(xhr.readyState==4){//服务器相应结束statusif(xhr.status==200){//说明服务器相应success//TODUmsg.innerHTML=xhr.responseText;}}}//3.连接服务器xhr.open("GET","Test2?usename="+usename.value+"&time="+new Date().getTime());//4.发送正文xhr.send(null);}}</script><form action="Test2">usename:<input type="text" id="usename" name="usename"/><span id="msg"></span><br/>password:<input type="password" id="password" name="password"/><br/><input type="button" value="提交"/></form></body></html>

function getXHR() {var xmlHttp;try {// Firefox, Opera 8.0+, SafarixmlHttp = new XMLHttpRequest();} catch (e) {// Internet Explorertry {xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");} catch (e) {try {xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");} catch (e) {alert("您的浏览器不支持AJAX！");return false;}}}return xmlHttp;}

AJAX挺好玩的！

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