ajax验证用户名是否存在

blgaici1

<script>
var xmlHttpRequest;
function getXmlHttpRequset(){
try{
if( window.ActiveXObject ){
for( var i = 5; i; i-- ){
try{
if( i == 2 ){
xmlHttpRequest = new ActiveXObject( "Microsoft.XMLHTTP" );
}else{
xmlHttpRequest = new ActiveXObject( "Msxml2.XMLHTTP." + i + ".0" );
xmlHttpRequest.setRequestHeader("Content-Type","text/xml");
xmlHttpRequest.setRequestHeader("Charset","gbk"); }
break;
}
catch(e){
xmlHttpRequest = false;
}
}
}else if( window.XMLHttpRequest ){
xmlhttp_request = new XMLHttpRequest();
if (xmlHttpRequest.overrideMimeType){
xmlHttpRequest.overrideMimeType('text/xml');
}
}
}catch(e){
xmlHttpRequest = false;
}
return xmlHttpRequest;
}

function checkUserName(url){
document.getElementById("checkUserName").innerHTML="正在检查用户名...";
if(document.getElementById("userName").value==""||document.getElementById("userName").value==null){
document.getElementById("checkUserName").innerHTML="请输入用户名！";
}else{
xmlHttpRequest=getXmlHttpRequset();
xmlHttpRequest.open("POST",url+document.getElementById("userName").value,false);
xmlHttpRequest.send(null);

xmlHttpRequest.onreadystatechange=changeView(xmlHttpRequest);
}
}

function changeView(xmlHttpRequest){
if(xmlHttpRequest.readyState==4&&xmlHttpRequest.status==200){
if(xmlHttpRequest.responseText==1){
document.getElementById("checkUserName").innerHTML="该用户名可以使用！";
}else if(xmlHttpRequest.responseText==2){
document.getElementById("checkUserName").innerHTML="该用户名已经存在！";
}else{
document.getElementById("checkUserName").innerHTML="系统错误！";
}
}
}
</script>

web.xml

<servlet>
<servlet-name>studyRoom</servlet-name>
<servlet-class>
hbu.hicc.crms.servlet.StudyRoomServlet
</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>studyRoom</servlet-name>
<url-pattern>/StudyRoom/studyRoomSelect</url-pattern>
</servlet-mapping>

url="../RoomSystem/StudyRoom/studyRoomSelect";