📄 form.jsp
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<%@ page language="java" contentType="text/html; charset=GBK"%>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GBK">
<title>Ajax示例1</title>
<script language="javascript">
var request;
function createRequest() {
try {
request = new XMLHttpRequest();
} catch(tryie) {
try {
request = new ActiveXObject("Msxml2.XMLHTTP");
} catch(other) {
try{
request = new ActiveXObject("MicroSoft.XMLHTTP");
} catch(failed) {
request = false;
}
}
}
if(!request)
alert("XMLHttpRequest对象初始化失败");
}
function confirmUserId() {
//create XMLHttpRequest instance
createRequest();
var userid = document.getElementById("USERID").value;
if(userid == "") {
alert("用户名不能为空！");
return;
}
var url = "confirm.a?USERID=" + userid;
request.open("POST", url, true);
request.onreadystatechange = showMessage;
request.send(null);
}
function showMessage() {
if(request.readyState == 4) {
if(request.status == 200) {
var message = request.responseText;
var msgSpan = document.getElementById("message");
msgSpan.style.color="red";
if(message == 1) {
msgSpan.innerHTML = "用户名已经被注册，请更换！";
} else if (message == 0) {
msgSpan.innerHTML = "用户名没有被注册，可以放心使用！"
}
}
}
}
</script>
<style>
body {font-size:9pt}
</style>
</head>
<body>
用户名：<input type="text" size="20" name="USERID" id="USERID"><br><br>
<a href="javascript:void(0)" onClick="confirmUserId()" title="验证用户名是否被使用">验证用户名</a><br><br>
<span id="message"></span>
</body>
</html>
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