如何使用Cloud Messaging Firebase从服务器推送通知

Question

I already have an app and I want to start sending notification to the users. I already set up everything in the app(using react native) and I checked manually that I can send notification to the devices and it works. Now I want to run a job in the server who will push the message (with the device token) to the cloud messaging in firebase. I can't find a lot of details about how to do it. I would like if someone can give me any guide I can use with. my server is in Kotlin(java can be good too) and I m working with gradle.

Thank you so much for the help

Answer 1

From a Java server you can use the Firebase Admin SDK to send messages . From that documentation comes this minimal example:

// This registration token comes from the client FCM SDKs.
String registrationToken = "YOUR_REGISTRATION_TOKEN";

// See documentation on defining a message payload.
Message message = Message.builder()
    .putData("score", "850")
    .putData("time", "2:45")
    .setToken(registrationToken)
    .build();

// Send a message to the device corresponding to the provided
// registration token.
String response = FirebaseMessaging.getInstance().send(message);
// Response is a message ID string.
System.out.println("Successfully sent message: " + response);

Note that this sends a data message, so that will always be delivered to your code , where you can decide to display a notification or not. To send a notification message, which is what the Firebase console does, you'd use:

Message message = Message.builder()
    .setNotification(new Notification("This is the title", "This is the body"))
    .setToken(registrationToken)
    .build();

Both of these send the message to a specific registration token, so only to a single device/app instance. This means you will need to maintain a list of these tokens, in a way that allows you to send the messages to fit your needs. Eg a common way is to store the tokens per user. For an example of that, see the functions-samples repo . While this example is in Node.js, the same logic could be applied to a Java server.

Finally: you can also send message to topics. For an example of that (again: using a Node.js server), have a look at this blog post Sending notifications between Android devices with Firebase Database and Cloud Messaging .