Hi:

I am facing a problem in ajax.

My code functionality is retrieving data from database. For it i am using ajax.

i am including the code below which contains ajax function:

<script>
var req;
var which;
function fetchCorpClassTaxonomy(url) {
alert("entered into Ajax function");
if (window.XMLHttpRequest) { // Non-IE browsers
alert("NON IE Block is Invoked");
req = new XMLHttpRequest();
req.onreadystatechange = processStateChange;
try {
req.open("GET", url, true);
} catch (e) {
alert(e);
}
req.send(null);
} else if (window.ActiveXObject) { // IE
alert("entered into IE block");
req = new ActiveXObject("Microsoft.XMLHTTP");
if (req) {
alert("entered into if(req)");
req.onreadystatechange = processStateChange;
req.open("GET", url, true);
alert("readystate: "+ req.readyState);
req.send();
}
}
}
function processStateChange() {
alert("entered into processStateChange()");
if (req.readyState == 4) { // Complete
if (req.status == 200) { // OK response
alert("response received from server is "+req.responseText);
var serverResponse = req.responseText;
var fieldName = serverResponse.substring(0,serverResponse.indexOf ("|"));
//alert("fieldname string "+fieldName);
var restResponse = serverResponse.substring(serverResponse.indexOf ("|")+1,serverResponse.length);
//alert("rest of Response is "+restResponse);
if(fieldName == "classification"){
document.getElementById("subclassification").innerHTML = restResponse;
}
} else {
alert("Problem: " + req.statusText);
}
}
}
</script>

I am getting response from action class so there is no problem in my other code.

when fetchCorpClassTaxonomy(url) function is called it is going to IE block since i am using IE 7.0

After that
alert("readystate: "+ req.readyState);
is also coming.

but the function processStateChange() is not called.
The alert just inside the function :

alert("entered into processStateChange()"); is also not executing.


The problem is function processStateChange() is not called.


Please give me your valuable suggestions As Soon As Possible for solving the problem. Since i am new to Ajax I am not able to find the solution.

Thanks.....

Calling the open method initializes the request object. If you have set properties (such as onreadystatechange) it is reset to initial default values (NULL). So, do all your initialization between OPEN and the final call to SEND.

It seems that there's also an issue with load balancing (using the IIS load balancer) and NTLM authentication on IE. Basically, you either get prompted to log in, or nothing happens at all (and an error is thrown: "The download of the specified resource has failed."

I've also seen this happen when using AJAX resources through a router or firewall that requires NTLM authentication.

Two things that may be obvious but that are overlooked. May be helpful.

1. POST works properly with multiple requessts to the same object. GET does not. So try POST when you experience problems.
2. Returning values from a function that uses a request object may result in the caller proceeding before the callee is ready to return a value. For correct operation the callee needs a loop or event to delay/synchronize to the callee completion.

if (window.XMLHttpRequest)
{
   var oReq = new XMLHttpRequest();
   oReq.open("GET", "http://localhost/test.xml");
   oReq.send();
   alert(oReq.statusText); // fails
}

The request is asynchronous, it will run only after the calling current script completes.

CLASS T3REQ4CALL4BACK
DIM M3REQ
PUBLIC DEFAULT PROPERTY GET HANDLER
IF M3REQ. READYSTATE = &O4 THEN MSGBOX M3REQ. STATUSTEXT,, "STATUS"
END PROPERTY
END CLASS

SET A3REQ = WINDOW. XMLHTTPREQUEST. CREATE
A3REQ. OPEN "HEAD", "http://msdn.microsoft.com/"
A3REQ. SEND
SET A4CALL4BACK = NEW T3REQ4CALL4BACK
SET A4CALL4BACK. M3REQ = A3REQ
A3REQ. ONREADYSTATECHANGE = A4CALL4BACK
REM AMAZINGLY, "SET" IS NOT NEEDED AND FAILS HERE

REM REMINDER: DO NOT WAIT FOR THE REPLY HERE, 
REM IT WILL NOT ARRIVE AS LONG AS YOUR SCRIPT IS BUSY!