第一種：傳統(tǒng)的ajax異步請(qǐng)求，后臺(tái)代碼以及效果在最下邊
首先我們?cè)趀clipse中創(chuàng)建一個(gè)注冊(cè)頁(yè)面regist.jsp,創(chuàng)建一個(gè)form表單，注意，由于我們只是實(shí)現(xiàn)用戶名校驗(yàn)的效果，下邊紅色部門是我們需要研究對(duì)象，所以其他的部門可以忽略不看。
內(nèi)容如下：
<%@ page language="java" contentType="text/html; charset=UTF-8"pageEncoding="UTF-8"%><!DOCTYPE html><html><head><meta charset="UTF-8"><title>用戶注冊(cè)</title><link rel="stylesheet" type="text/css" href="${pageContext.request.contextPath }/css/login.css" rel="external nofollow" ><script type="text/javascript">//第三步：ajax異步請(qǐng)求用戶名是否存在 function checkUsername(){// 獲得文本框值:var username = document.getElementById("username").value;// 1.創(chuàng)建異步交互對(duì)象var xhr = createXmlHttp();//第二步中已經(jīng)創(chuàng)建xmlHttpRequest,這里直接調(diào)用函數(shù)就可以了。// 2.設(shè)置監(jiān)聽xhr.onreadystatechange = function(){if(xhr.readyState == 4){if(xhr.status == 200){//把返回的數(shù)據(jù)放入到span中document.getElementById("span").innerHTML = xhr.responseText;//responseText是后臺(tái)返回的數(shù)據(jù)}}}// 3.打開連接xhr.open("GET","${pageContext.request.contextPath}/user_findByName.action?time="+new Date().getTime()+"&username="+username,true);// 4.發(fā)送xhr.send(null);} //第二部：創(chuàng)建xmlHttp對(duì)象function createXmlHttp(){var xmlHttpRequest;try{ // Firefox, Opera 8.0+, SafarixmlHttp=new XMLHttpRequest();}catch (e){try{// Internet ExplorerxmlHttp=new ActiveXObject("Msxml2.XMLHTTP");}catch (e){try{xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");}catch (e){}}}return xmlHttpRequest;} function change(){var img1 = document.getElementById("checkImg");img1.src="${pageContext.request.contextPath}/checkImg.action?"+new Date().getTime();}</script></head><body><form action="${pageContext.request.contextPath }/user_regist.action" method="post" onsubmit="return checkForm()";><div class="regist"><div class="regist_center"><div class="regist_top"><div class="left fl">會(huì)員注冊(cè)</div><div class="right fr"><a href="${pageContext.request.contextPath }/index.jsp" rel="external nofollow" target="_self">小米商城</a></div><div class="clear"></div><div class="xian center"></div></div><div class="regist_main center">//第一步：首先，我們創(chuàng)建一個(gè)用戶名input輸入框，并添加一個(gè)onblur="checkUsername()"事件<div class="username">用 戶 名: <input class="shurukuang" type="text" id="username" name="username" onblur="checkUsername()"/><span id="span"></span></div><div class="username">密 碼: <input class="shurukuang" type="password" id="password" name="password"/></div> <div class="username">確認(rèn) 密碼: <input class="shurukuang" type="password" id="repassword" name="repassword" /></div><div class="username">郵 箱 號(hào): <input class="shurukuang" type="email" id="email" name="email" /></div><div class="username">姓 名: <input class="shurukuang" type="text" id="name" name="name"/></div><div class="username">手 機(jī) 號(hào): <input class="shurukuang" type="text" id="phone" name="phone"/></div><div class="username">地 址: <input class="shurukuang" type="text" id="addr" name="addr"/></div><div class="username"><div class="left fl">驗(yàn) 證 碼: <input class="yanzhengma" type="text" id="checkcode" name="checkcode" maxlength="4"/></div><div class="right fl"><img id="checkImg" class="captchaImage" src="${pageContext.request.contextPath}/checkImg.action" onclick="change()" title="點(diǎn)擊更換驗(yàn)證碼"></div><div class="clear"></div></div></div><div class="regist_submit"><input class="submit" type="submit" name="submit" value="立即注冊(cè)" ></div> </div></div></form></body></html>
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