Is there true asynchronous/ajax file uploading in grails that hooks into the default "busy" spinner (the one that shows on other ajax calls)?
Or if I wanted to show that spinner during a file upload would I need to call is explicitly?
This is one of those things that you usually want some help from a third party because of some of the complexities and restrictions behind the exchange.
Some plugins are available for jquery that use Flash to accomplish this but I prefer to avoid anything that uses Flash (personal preference). Check out Valums Ajax-Upload I've used it now for about a year in my production site and it works well and was easy to use. My favorite thing about the plug-in is that it's unobtrusive to the design and layout of most any site.
Also, this is a commonly asked question. Check out these answers as well...