FCM Cloud Messaging difference from Notifications and Message

Question

I implemented my backend service (using java and FCM) to send push-notifications to mobile apps.

I implemented my service using Java Firebase Admin-SDK (https://firebase.google.com/docs/reference/admin/java/reference/com/google/firebase/messaging/package-summary and https://firebase.google.com/docs/cloud-messaging/send-message#java) about this and I'm able to send (and receive) push notifications on iOS and Android mobile apps.

Now I received a request from mobile-developers that they needs to customize (client-side) the received push notifications (also when the app is in background mode).

Probably here is reported a same question: What is the difference between Firebase push-notifications and FCM messages?

Reading the documentation (https://firebase.google.com/docs/cloud-messaging/concept-options#notifications_and_data_messages) I understood that It's necessary to use a Data-message instead of a Notification message.

It's not clear for me what's necessary to change to support this delivery type. Do I change the Android-config of the FCM-message or Do I remove some unnecessary data (just set all info into the custom data without others info for example Android configuration etc..)

It's possible to have a small example?

Answer 1

If your json will have notification key, developers will not able to handle notifications in background. They will receive this notification only when app is in foreground. In case when developers should receive “silent pushes” or they need control all notifications, you should remove notification key, and use only data key.

Answer 2

This can be achieved by changing the key 'notification' to 'data' as follows:

   {
     "notification": {  //replace this line by "data"
     "title": "Hey Gajanan", 
     "body": "Thanks for visiting omnidecoder.com"
     },
     "to" : "YOUR-GENERATED-TOKEN"
    }