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[英]How to check whether a value already exists using AJAX in jQuery validator?
[英]Ajax How to check whether the username already exists?
<script type="text/javascript">
function createXMLHttpRequest() {
try {
return new XMLHttpRequest();
} catch (e) {
try {
return ActiveXObject("Msxm12.XMLHTTP");
} catch (e) {
try {
return ActiveXObject("Microsoft.XMLHTTP");
} catch (e) {
alert("dude,What kind of browser you have?");
throw e;
}
}
}
}
window.onload = function () {
var username = document.getElementById("loginname");
username.onblur = function () {
var xmlHttp = createXMLHttpRequest();
xmlHttp.open("POST", "<c:url value='/ajaxValidateLoginname'/>", true);
xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
xmlhttp.send("loginname=" + username.value);
xmlhttp.onreadystatechange = function () {
if (xmlhttp.readyState === 4 && xmlhttp.status === 200) {
var text = xmlhttp.responseText;
var label = document.getElementById("loginnameError");
if (text === false) {
label.innerHTML = "The user name has been registered!";
}else{
label.innerHTML = "";
}
}
};
};
};
這是驗證登錄名是否已經存在的 servlet。
public void doPost ajaxValidateLoginname(HttpServletRequest request, HttpServletResponse response) throws IOException {
String loginname = request.getParameter("loginname");
boolean flag = us.ajaxValidateLoginname(loginname);
response.getWriter().print(flag);
return null;
}
問題是什么? 我認為代碼是正確的。 只刪除返回空值; 在 servlet 中。
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