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responseXml is null

 
Greenhorn
Posts: 19
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Hi guys....
Im validating a jsp page....

but my call back responce object is keepgetting null...

My validation.js file is as below...

// holds an instance of XMLHttpRequest
var xmlHttp = createXmlHttpRequestObject();
// holds the remote server address
var serverAddress = "reg.jsp";
// when set to true, display detailed error messages
var showErrors = true;
// initialize the validation requests cache
var cache = new Array();

// creates an XMLHttpRequest instance
function createXmlHttpRequestObject()
{
// will store the reference to the XMLHttpRequest object
var xmlHttp;
// this should work for all browsers except IE6 and older
try
{
// try to create XMLHttpRequest object
xmlHttp = new XMLHttpRequest();
}
catch(e)
{
// assume IE6 or older
var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
"MSXML2.XMLHTTP.5.0",
"MSXML2.XMLHTTP.4.0",
"MSXML2.XMLHTTP.3.0",
"MSXML2.XMLHTTP",
"Microsoft.XMLHTTP");
// try every id until one works
for (var i=0; i<XmlHttpVersions.length && !xmlHttp; i++)
{
try
{
// try to create XMLHttpRequest object
xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
}
catch (e) {} // ignore potential error
}
}
// return the created object or display an error message
if (!xmlHttp)
displayError("Error creating the XMLHttpRequest object.");

else
return xmlHttp;
}

// function that displays an error message
function displayError(message)
{
// ignore errors if showErrors is false
if (showErrors)
{
// turn error displaying Off
showErrors = false;
// display error message

alert("Error encountered : \n" + message);
// retry validation after 10 seconds
setTimeout("validate();", 10000);
}
}

// the function handles the validation for any form field
function validate(inputValue, fieldID)
{
// only continue if xmlHttp isn't void
if (xmlHttp)
{
// if we received non-null parameters, we add them to cache in the
// form of the query string to be sent to the server for validation
if (fieldID)
{
// encode values for safely adding them to an HTTP request query string
inputValue = encodeURIComponent(inputValue);
fieldID = encodeURIComponent(fieldID);
// add the values to the queue
cache.push("inputValue=" + inputValue + "&fieldID=" + fieldID);
}
// try to connect to the server
try
{
// continue only if the XMLHttpRequest object isn't busy
// and the cache is not empty
if ((xmlHttp.readyState == 4 || xmlHttp.readyState == 0)
&& cache.length > 0)
{
// get a new set of parameters from the cache
var cacheEntry = cache.shift();
// make a server request to validate the extracted data
xmlHttp.open("POST", serverAddress, true);

xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded;");

xmlHttp.onreadystatechange = handleRequestStateChange;
xmlHttp.send(cacheEntry);
}
}
catch (e)
{
// display an error when failing to connect to the server
displayError(e.toString());
}
}
}

// function that handles the HTTP response
function handleRequestStateChange()
{
// when readyState is 4, we read the server response
if (xmlHttp.readyState == 4)
{
// continue only if HTTP status is "OK"
if (xmlHttp.status == 200)
{
try
{
// read the response from the server
readResponse();
}
catch(e)

{
// display error message
displayError(e.toString());
}
}
else
{
// display error message
displayError(xmlHttp.statusText);
}
}
}

// read server's response
function readResponse()
{
// retrieve the server's response
var response = xmlHttp.responseText;
// server error?

if (response.indexOf("ERRNO") >= 0
|| response.indexOf("error:") >= 0
|| response.length == 0)
throw(response.length == 0 ? "Server error." : response);

// get response in XML format (assume the response is valid XML)
responseXml = xmlHttp.responseXML;
// get the document element
xmlDoc = responseXml.documentElement;
result = xmlDoc.getElementsByTagName("result")[0].firstChild.data;
fieldID = xmlDoc.getElementsByTagName("fieldid")[0].firstChild.data;
// find the HTML element that displays the error
message = document.getElementById(fieldID + "Failed");
// show the error or hide the error
message.className = (result == "0") ? "error" : "hidden";
// call validate() again, in case there are values left in the cache
setTimeout("validate();", 250);
}

// sets focus on the first field of the form
function setFocus()
{
document.getElementById("txtUsername").focus();
}
 
author
Posts: 15385
6
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Use code tags!

Look at this old blog post of mine on causes of responseXML to be null: http://radio.javaranch.com/pascarello/2006/09/12/1158096122600.html

That Ajax code has a lot of bad practices in it, better to find a library that does Ajax calls for you.

Eric
 
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.
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