Java Firebase cloud message . Send message to all

Question

I want to send a message to all device but I only send to one device this is how I send a message : I only can send message to one user , when I remove this at my method to send a message:

json.put("to", tokenId.trim());

a message is not send to nobody when I have this line I send a message to only one user . How I can send a message to every one ?

 static void send_FCM_Notification(String tokenId, String server_key, String message) {


        try {
            URL url = new URL(FCM_URL);
// create connection.
            HttpURLConnection conn;
            conn = (HttpURLConnection) url.openConnection();
            conn.setUseCaches(false);
            conn.setDoInput(true);
            conn.setDoOutput(true);
//set method as POST or GET
            conn.setRequestMethod("POST");
//pass FCM server key
            conn.setRequestProperty("Authorization", "key=" + server_key);
//Specify Message Format
            conn.setRequestProperty("Content-Type", "application/json");
//Create JSON Object & pass value
            JSONObject infoJson = new JSONObject();
            infoJson.put("title", "Wiadomosc z serwera");
            infoJson.put("sound", "default");
            infoJson.put("icon", "ic_launcher");
            infoJson.put("body", message);
            JSONObject json = new JSONObject();
            json.put("to", tokenId.trim());
            json.put("notification", infoJson);
            OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
            wr.write(json.toString());
            wr.flush();
            int status = 0;
            if (null != conn) {
                status = conn.getResponseCode();
            }
            if (status != 0) {
                if (status == 200) {
//SUCCESS message
                    BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                    System.out.println("Android Notification Response : " + reader.readLine());
                } else if (status == 401) {
//client side error
                    System.out.println("Notification Response : TokenId : " + tokenId + " Error occurred : 401");

                } else if (status == 501) {

//server side error

                    System.out.println("Notification Response : [ errorCode=ServerError ] TokenId : " + tokenId);

                } else if (status == 503) {

//server side error

                    System.out.println("Notification Response : FCM Service is Unavailable  TokenId : " + tokenId);

                }


            }

        } catch (MalformedURLException mlfexception) {

// Prototcal Error

            System.out.println("Error occurred while sending push Notification!.." + mlfexception.getMessage());

        } catch (IOException mlfexception) {

//URL problem

            System.out.println("Reading URL, Error occurred while sending push Notification!.." + mlfexception.getMessage());

        } catch (JSONException jsonexception) {

//Message format error

            System.out.println("Message Format, Error occurred while sending push Notification!.." + jsonexception.getMessage());

        } catch (Exception exception) {

//General Error or exception.

            System.out.println("Error occurred while sending push Notification!.." + exception.getMessage());

        }
    }

Answer 1

Firebase supports what is called topics

So you can send a message to a topic and all the devices subscribed to that topic will get the push.

You can have a topic called all and then register each device to that.

Here is how you register

FirebaseMessaging.getInstance().subscribeToTopic("all");

Then you can just fire notifications to that topic and all your users will get it.

Then replace this line

json.put("to", tokenId.trim());

with

json.put("to", "/topics/your-topic-name");

In this case your topic name is all

Answer 2

You can subscribe all devices to the same topic, and send a message to the topic. In this way you even don't need to keep track of the token ids in your server.

Check the dox here:

Subscribe the client app to a topic