Half pre-processing a POST

[Joshua Oransky]

I want to support uploading of files on some of my forms, but I want  
to do it in a generic kind of fashion. So what I would like to do is  
create a POST script that looks for files, but then passes the request  
back to sling to finish updating the properties. This way, I don't  
need to have a POST script for every for I want to have upload files,  
and I can easily change my forms and add text fields without having to  
constantly update the storage script.

Is this possible? Kind of like the Servlet Filter concept, where I can  
process some of the request than then pass it along.

-Josh