Unfortunately compojure
will directly invoke the function that is generated from your route definition after it has parsed the params.
AFAIC the only way to get in between is either to modify compojures codebase directly or to use Robert Hooke (by technomancy) on assoc-route-params
in https://github.com/weavejester/compojure/blob/master/src/compojure/core.clj#L30