How to send Firebase Cloud Message from Google App Engine App

Question

How can you send a Firebase Cloud Message from a Google App Engine/Cloud Endpoints App?

Android Studio automatically generates the following code to send a Google Cloud Message. While you can use the same code to send a FCM, you can't set the "notification" or "priority" or anything like that which the new FCM uses.

Is there a gradle import for this or an example of how to use Firebase Cloud Messaging inside of an App Engine app so you can easily do things like set the message, notification, priority, etc?

This is what Android Studio Cloud Endpoints auto generates for you currently:

// Gradle dependency:
compile 'com.google.gcm:gcm-server:1.0.0'

/**
     * Api Keys can be obtained from the google cloud console
     */
    private static final String API_KEY = System.getProperty("gcm.api.key");

    /**
     * Send to the first 10 devices (You can modify this to send to any number of devices or a specific device)
     *
     * @param message The message to send
     */
    public void sendMessage(@Named("message") String message) throws IOException {
        if (message == null || message.trim().length() == 0) {
            log.warning("Not sending message because it is empty");
            return;
        }
        // crop longer messages
        if (message.length() > 1000) {
            message = message.substring(0, 1000) + "[...]";
        }
        Sender sender = new Sender(API_KEY);

        Message msg = new Message.Builder().addData("message", message).build();
        List<RegistrationRecord> records = ofy().load().type(RegistrationRecord.class).limit(10).list();
        for (RegistrationRecord record : records) {
            Result result = sender.send(msg, record.getRegId(), 5);
            if (result.getMessageId() != null) {
                log.info("Message sent to " + record.getRegId());
                String canonicalRegId = result.getCanonicalRegistrationId();
                if (canonicalRegId != null) {
                    // if the regId changed, we have to update the datastore
                    log.info("Registration Id changed for " + record.getRegId() + " updating to " + canonicalRegId);
                    record.setRegId(canonicalRegId);
                    ofy().save().entity(record).now();
                }
            } else {
                String error = result.getErrorCodeName();
                if (error.equals(Constants.ERROR_NOT_REGISTERED)) {
                    log.warning("Registration Id " + record.getRegId() + " no longer registered with GCM, removing from datastore");
                    // if the device is no longer registered with Gcm, remove it from the datastore
                    ofy().delete().entity(record).now();
                } else {
                    log.warning("Error when sending message : " + error);
                }
            }
        }
    }

Answer 1

There's currently no Firebase client for sending messages from an app server. You should just send raw HTTP requests with JSON payloads from your endpoint using the protocol documented here. The server reference shows what parameters you can use, which includes priority.