middleware.clj

(defn append-user-data [handler]
  (fn [request]
    (clutch/with-db database-address
      (let [access-token (get-in request [:headers "token"])
            view-data (clutch/get-view "api" "users-by-token" {:keys [access-token]})]
        (if (= 1 (count view-data))
          (handler (assoc request :api-user (:value (first view-data))))
          {:status 403
           :body "Invalid access token"})))))