AJAX File Upload in Java Web Application

File upload process involves data to be sent from client side to server, in html terms this means submitting form to server side method that gets the file from request object and saves it to the server. Most of the time, it is desirable to implement file upload in ajax way without refreshing the whole page while updating the user on the progress.

To make the job more easier, let us use this jQuery plugin called jQuery.AjaxFileUpload.jswhich exactly implements the hidden iframe technique behind the scenes along with progress update and cancelling options. The logic is simple, instead of submitting the form to the server which would cause a postback, we submit the contents of the form to an iframe that is created dynamically and let the iframe communicate with the server, once the upload is complete - iframe sends the response back to the form. Steve explains this technique here in a very neat manner, so I don't want to repeat this here again.