Send push notification from server to android device in Java

Question

I am struggling with the new FCM... I used FCM before, now I am trying FCM...

I am trying to send push notification for my app server to android device.

I wanna use the standard Java package, try not to use others such as Vert.x, apache's httpClient etc...

here is my code:

public void sendNotification(String messageBody)
{
    try
    {
        URL url = new URL("https://fcm.googleapis.com/fcm/send");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");

        String apiKey = "AI...wE";

        String credentials = "key=" + apiKey;
        //String basicAuth = "Basic " + Base64.getEncoder().encodeToString(credentials.getBytes());

        String basicAuth = "Basic " + new String(Base64.encodeBase64(credentials.getBytes()));

        conn.setRequestProperty ("Authorization", basicAuth);

        String notfnStr = "{\"body\": \"this is my body\", \"title\": \"this is my title\"}";
        String dataStr = "{\"key1\": \"value1\", \"key2\": \"value2\"}";

        String bodyStr = "{\"priority\": \"high\", \"to\": \"dFC8GW0N1Q8:APA91bHePPmC7QVV16LGnR6rqxwreHSv1GgawijZ_dZL9T70ZkiXIV8TW_ymAWkvFfXRiWJmtR_UGBXBv2iV2UhS8M-Tndw8sf8ZW6zIqfaiiVJao3G5HFbhqgA18ukNNtW_J7JaWkz8\", " +
                "\"notification\": " + notfnStr + ", \"data\": " + dataStr + "}";

        System.out.println("### input: " + bodyStr);

        OutputStream os = conn.getOutputStream();
        os.write(bodyStr.getBytes());
        os.flush();

        if (conn.getResponseCode() != HttpURLConnection.HTTP_CREATED) {
            throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
        }

        BufferedReader br = new BufferedReader(new InputStreamReader(
                (conn.getInputStream())));

        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }

        conn.disconnect();
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }
}

the response code i got is 401, which means unauthorized... i guess the format of credential is wrong...

The json string is in valid json format, so i don't bother to use JSONObject.

For the string credentials, i have tried "key:" + apiKey; but still got the same result.

The apiKey String is copied from the google-services.json I downloaded from Firebase console in google.

google didn't give a good example... just gave me this: https://firebase.google.com/docs/cloud-messaging/downstream

If any one knows how to do it, please reply. Thanks!!

Answer 1

FULL EXAMPLE USE THIS FOR SEND NOTIFICATION USING FCM IN JAVA

public class FCMNotification {

    // Method to send Notifications from server to client end.
    public final static String AUTH_KEY_FCM = "API_KEY_HERE";
    public final static String API_URL_FCM = "https://fcm.googleapis.com/fcm/send";

    public static void pushFCMNotification(String DeviceIdKey) throws Exception {

        String authKey = AUTH_KEY_FCM; // You FCM AUTH key
        String FMCurl = API_URL_FCM;

        URL url = new URL(FMCurl);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();

        conn.setUseCaches(false);
        conn.setDoInput(true);
        conn.setDoOutput(true);

        conn.setRequestMethod("POST");
        conn.setRequestProperty("Authorization", "key=" + authKey);
        conn.setRequestProperty("Content-Type", "application/json");

        JSONObject data = new JSONObject();
        data.put("to", DeviceIdKey.trim());
        JSONObject info = new JSONObject();
        info.put("title", "FCM Notificatoin Title"); // Notification title
        info.put("text", "Hello First Test notification"); // Notification body
        data.put("notification", info);

        OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
        wr.write(data.toString());
        wr.flush();
        wr.close();

        int responseCode = conn.getResponseCode();
        System.out.println("Response Code : " + responseCode);

        BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

    }

    @SuppressWarnings("static-access")
    public static void main(String[] args) throws Exception {
        FCMNotification.pushFCMNotification("USER_DEVICE_TOKEN");
    }
}

Answer 2

You mentioned that you got he key from the google-services.json file. That would be your Android API key, not the server key required to send FCM messages. In the Firebase console go to Settings > Cloud Messaging > Server key for the API key to be used for sending FCM messages.