<!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">
<script type="text/javascript">
var http_request=false;
function testID (username){
if(window.XMLHttpRequest){//mozilla
http_request=new XMLHttpRequest();
}else{
http_request=new ActiveXObject("Microsoft.XMLHTTP");
}
http_request.onreadystatechange = processRequest;
http_request.open("POST","../testID",true);//默認爲真時不繼續執行下面的代碼
http_request.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
http_request.send("username="+username);
}
// 處理返回信息的函數
function processRequest() {
if (http_request.readyState == 4) {// 判斷對象狀態
if (http_request.status == 200) {// 信息已經成功返回，開始處理信息
alert(http_request.responseText);
} else {//頁面不正常
alert("您所請求的頁面有異常。");
}
}
}
function checkUnique(){
var f=document.form1;
var username=f.username.value;
if(username==""){
alert("用戶名不能爲空");
f.username.focus;
return false;
}
else{
testID(username);
}
}
</script>
<title>Insert title here</title>
</head>
<body>
<form action="" method="post" name="form1">
<table>
<tr>
<td>用戶名</td>
<td><input type="text" name="username" ></td>
</tr>
<tr>
<td>密碼</td>
<td><input type="password" name="password" οnclick="checkUnique()"></td>
</tr>
</table>
</form>
</body>
</html>
、、、、、、、、、、、、、、、、、、、、、、、、、、、、、、、
server中的post方法
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
String userName=request.getParameter("username");
response.setContentType("text/plain");
System.out.println(userName);
Writer out=response.getWriter();
if(userName.equals("lsh")){
System.out.println("fff"+userName);
out.write("lsh已經被註冊，請註冊另外一個");
}
}