Supplementary

createXHR
createXHRWrapper

doTxn
abort
getXHRObj

xHR_DbC

Calling this function simply creates an XMLHTTPRequest object that is appropriate to the browser on which the application is running.

It is the responsibility of any client code that calls this function to assign any event handlers to the object returned, as well as to call the open and send methods. Moreover, using this function means that the response handler must check the values of the readyState and status members of the XMLHTTPRequest object itself.

Given that the doTxn method of the XHRWrapper type manages all of these details, there is normally no need to use this method.

This method calls the 'open' and 'send' methods of the XHRWrapper's underlying XHR object, and manages other minutiae associated with this process. It also works around many of the bugs and inconsistencies that the various XHR implementations exhibit.

The method also implements a 'base' response handler that tests the readyState and status attributes of the underlying XHR object each time the server responds.

Given this, client code need not implement this logic itself in the response-handler function that it provides, and given that that function is called only if the transaction with the server was successful, it need contain only the logic needed to process the server's response.

This method returns the XMLHTTPRequest object that an XHRWrapper subsumes.

Some implementations of XMLHTTPRequest support methods such as onload, onerror and onprogress, as well as methods for event-listener manipulation. Should client code need to avail itself of these methods then it can do so by retrieving the XHR object that a given wrapper contains.

Stops a partially-completed transaction with the server.

Calling this function is a safe way of aborting a transaction, in that it ensures that the client-code response handler is not invoked, as happens on certain Gecko-based platforms.

Other than that, it has the same effect as calling the underlying XHR object's abort method, but applications that invoke a transaction using doTxn should use this method to abort that transaction, rather than by retrieving on the underlying XHR object and then calling the abort method on that.

Uses AspectJS to apply a suffix to createXHRWrapper. That suffix applies a prefix to the doTxn method of any XHRWrapper objects generated thereon, and that prefix checks for bad or missing arguments that client code passes to doTxn. Any such arguments generate an exception, thus alerting developers to incorrect calls.

Any application that uses XHRFactory_DbC must import an instance of the AspectJS AJS-object.

URL argument is undefined
URL argument is null
URL argument is not a string

Method argument is undefined
Method argument is null
Method argument is not a string

respHandler argument does not refer to a function

HTTP method is 'POST' and Data argument is undefined
HTTP method is 'POST' and Data argument is null
Data argument is not a string

ASync argument is null
ASync argument is not a boolean

MimeType argument is not a string

errHandler argument does not refer to a function

XHRFactory argument is undefined
XHRFactory argument is null
XHRFactory argument does not refer to an object

AJS argument is undefined
AJS argument is null
AJS argument does not refer to an object

Object referred to by the AJS argument has no getVersion method
AJS argument does not refer to version 1.1 of the AJS object

Repeated call made to xHR_DbC