Preventing multiple form submits in ICEFaces by disabling commandButton

I created a form in ICEFaces 2 to upload a file. ICEFaces 2 has a new component for files, called the fileEntry (see http://wiki.icefaces.org/display/ICE/FileEntry). The old inputFile component has been removed from ICEFaces 2. Uploading a file takes a while, and I quickly noticed the user could click the "upload" button multiple times while the upload was in progress. This is obviously something you want to prevent. There is a very easy approach to this: just disable the submit button once it has been pressed. All you need to do is add this code to the commandButton tag:

onclick="this.disabled=true"

This works fine, and if you always go to a new page after the form has been submitted this is all you have to do. In most applications this unfortunately won't be the case: if something goes wrong with the file upload or if some other form components fail validation, you will want to stay on the same page, giving the user a warning message and allowing him to try again. The problem is that your commandButton is now disabled, so the user can't try again...
Re-enabling the commandButton when the action finishes is not as easy as it may seem: there's no "onAfterSubmit" action or something similar on the form. My first try was to add the disabled property with a value of "false":

disabled="false"

I thought that ICEFaces would re-evaluate the form after the submit, causing it to reset the disabled property to false. Unfortunately ICEFaces is smarter than that, and uses a technique called "partial dom updates". What this means is it checks if any of the components properties were changed in the action and it will only update those components whose properties have actually changed. This is a smart technique, since it reduces http traffic. It also means that our commandButton will not be updated, since for ICEFaces nothing changed to this component (it isn't aware of the JavaScript function we performed on it). This means we will have to trick ICEFaces into thinking a property of our commandButton has actually changed, causing it to refresh the commandButton. I choose to "abuse" the styleClass property for this use. I set it to:

styleClass="#{backingBean.randomValue}"

Then in my backing bean I implemented the getter for this value as follows:

public String getRandomValue() {
return "a" + System.currentTimeMillis();
}

This ensures we will get a different value for the styleClass property on each form submit. This will trick ICEFaces into thinking the commandButton has changed, causing it to refresh it and setting the disabled value to false, effectively re-enabling our commandButton.

I agree this approach isn't very clean, but it's the only technique I found to accomplish this in ICEFaces. If anyone knows of a better way, I'd be glad to know!