Funny thing: I just came across the need to do this too. Here's how I solved it:
@RequestMapping(value = {"/someChildUrlIfYouWant/**"}
The "**"
here says 'grab anything at any sub-path of what's to the left of me.' If you want the path it actually matched to get to this method, you can use:
request.getAttribute( HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE )
You will get /someChildUrlIfYouWant/the/full/path/to/whatever.html
so if you just want the variable child path, you'll have to trim the front part of the string.
Make sense?