FlexFactory Example

I'm wanting to use Spring for my backend for Flex Data Services. I
found the docs on using a class that implements the FlexFactory
interface, but the really is not enough detail in the docs to fully
understand how to fill out the FlexFactory implementation class.

Has anyone successfully used this class? Do I create a single
FlexFactory class for all of my destinations that I want to use Spring
with? Or do I create a FlexFactory impl for each destination?

Thanks
Bill