Use gcm-server from clojure

gcm-clojure.clj

;;; Project here: https://github.com/seymores/gcm-clj
;;; 
;;;  Note: you need to specify the custom repo to get gcm-server.jar
;;;  :repositories [["google" "https://github.com/slorber/gcm-server-repository/raw/master/releases"]]
;;;  :dependencies [[com.google.android.gcm/gcm-server "1.0.2"]]
;;;
;;; See http://developer.android.com/google/gcm/gs.html#server-app

;; Import all the needed classes from gcm-server.jar
(import (com.google.android.gcm.server Sender Message Message$Builder MulticastResult))

(def API_KEY "xxxxxxxxxxxxxxxxxxxxxxxx...vz") ;Use your API KEY here
(def sender (Sender. API_KEY))

(defn notify
    "Send notification with the given message to the specific device"
    [message deviceRegId retryCount]
    (.send sender message deviceRegId retryCount))
    
(def devId "1jGmalO_K9bPrprKlH4...GTX9EtRDbCZDocdRR5qxxxxxx") ; Get from your device during gcm registration
(def msg (-> (Message$Builder.) (.addData "key" "Updates") .build))

;; Look ma, no classes!
(notify msg devId 2)