drag n drop desktop file to application as such in google

Is that possible to " Drag n drop file from desktop to upload " in Ruby on rails application

       for example : google (gmail) drag n drop attachments same as this feature .

        Drag and drop functionality working but how to upload the file to the application ? through ajax ? or other functionaltiy ?

         how to get file object through javascript which attributes suits for that ?

         how to implement this ?..........

        Any ideas greatly appreciated .....