1. 앱 구동시 FCM SDK에서 토큰 발행 및 서버에 저장(android)

public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {
    private static final String TAG = MyFirebaseInstanceIDService.class.getSimpleName();

    // 토큰 재생성
    @Override
    public void onTokenRefresh() {
        // Get updated InstanceID token.
        String token = FirebaseInstanceId.getInstance().getToken();
        Log.d(TAG, "token = " + token);

        sendTokenToServer(token);
    }

    private void sendTokenToServer(String token){

        OkHttpClient client = new OkHttpClient();
        RequestBody body = new FormBody.Builder()
                .add("token", token)
                .build();

        Request request = new Request.Builder()
                .url("서버URL")  /* 서버에 발행된 토큰을 저장 */
                .post(body)
                .build();

        try {
            client.newCall(request).execute();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

2. push.jsp / 푸시메시지 전송할 화면(spring / jsp)

<form action="/sendPush" method="post">

<input type="text" id="title" name="title"/>

<input type="text" id="content" name="content"/>

<input type="submit" value="push"/>

<input type="reset" value="cancel"/>

</form>

3.  푸시메시지 전송하기(spring / controller)

@RequestMapping(value ="/sendPush", method = {RequestMethod.GET,RequestMethod.POST})

public String sendPush(HttpServletRequest request, Model model) {

System.out.println("sendPush.......");

String token = getPushToken(); // 서버에 저장된 토큰 가져오기

String title = request.getParameter("title");

if(StringUtils.isEmpty(title)) title = "Push Default title";

String content = request.getParameter("content");

if(StringUtils.isEmpty(content)) title = "Push Default content";

try {

title   = URLEncoder.encode(title  ,"UTF-8"); // 한글깨짐으로 URL인코딩해서 보냄

content = URLEncoder.encode(content,"UTF-8");

System.out.println(String.format("title : %s, content : %s", title, content));

} catch (UnsupportedEncodingException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

ResponseEntity<String> result = sendHttp(token, title, content);

model.addAttribute("serverTime", token);

model.addAttribute("result", result.getBody());

return "push";

}

private ResponseEntity<String> sendHttp(String token, String title, String content){

RestTemplate template = new RestTemplate();

HttpHeaders headers = new HttpHeaders(); 

headers.setContentType(MediaType.APPLICATION_JSON);

headers.add("Authorization", "key="+API_KEY); // API_KEY : Firebase 내 프로젝트의 서버키

JSONObject json  = new JSONObject();

json.put("to", token);

JSONObject data = new JSONObject();

data.put("title"  , title);

data.put("content", content);

json.put("data"   ,data);

HttpEntity entity = new HttpEntity(json.toJSONString(), headers);

return template.exchange("https://fcm.googleapis.com/fcm/send", HttpMethod.POST, entity, String.class);

}

4. MyFirebaseMessagingService.class(android)

public void onMessageReceived(RemoteMessage remoteMessage) {
    Log.i(TAG, "onMessageReceived..");

    Map<String, String> data = remoteMessage.getData();
    String title   = data.get("title");
    String content = data.get("content");
    try {
        if(!TextUtils.isEmpty(title))   title   = URLDecoder.decode(title,"UTF-8");  // 한글깨짐으로 서버에서 URLEncoding해서 보냄..
        if(!TextUtils.isEmpty(content)) content = URLDecoder.decode(content,"UTF-8");
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    Log.i(TAG, String.format("title : $s , content : %s",title,content));
    sendNotification(title, content);
}

* https://fcm.googleapis.com/fcm/send로 보낼 때의 json 형태

{

 "to": "etBbtvcHFZ4:APA91bF7I4BvHftRRpZ8qzA3by9kJJBSV2nT4_5vLkvk00-oKyyAXtFKxu2ybyJeTiTqoy4rTYOZzO6kkK74zqLFd5XCgO...",

"data": {

  "title" : "title내용",

  "content" : "content내용"

 }

}

* 특정 단말에만 푸시 보낼 때 : json의 "to"에 단말 토큰 설정

* 모든 단말에 푸시 보낼 때 : json의 "to"에 "/topics/all" 설정

  (단, android에서 subscribeToTopic("all")로 설정되어 있어야 함.)

  => MainActivity.class(android)에서

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
   
    FirebaseMessaging.getInstance().subscribeToTopic("all");

    if(FirebaseInstanceId.getInstance().getToken() != null)
        Log.d(TAG+"_token : ",FirebaseInstanceId.getInstance().getToken());
}

출처: http://devmason.tistory.com/147 [With IT]