<html>
<head>
<title>Insert title here</title>
<script type="text/javascript" src="${pageContext.request.contextPath}/script/jquery-1.js"></script>
<script type="text/javascript">
$(function(){
$(":input[name='username']").change(function(){
var val = $(this).val();
val = $.trim(val);
if(val != ""){
var url = "${pageContext.request.contextPath}/valiateUsername";
var args = {"username":val,"time":new Date()};
$.post(url ,args ,function(data)){
$("#message").html(data);
}
}
})
})
</script>
</head>
<body>
<form action="" method="post">
username:<input type="text" name="username" />
<br>
<div id="message">
<font color="red"></font>
</div>
<input type="submit" value="Submit" />
</form>
</body>
</html>