NullPointerException when using cloud messaging

[edonelezovic]

• Library version: 9.4.3
• Firebase Product: cloud messaging

When we are sending messages in bulk to devices using device specific tokens, we randomly get the error below:

java.util.concurrent.ExecutionException: java.lang.NullPointerException
	at com.google.common.util.concurrent.AbstractFuture.getDoneValue(AbstractFuture.java:595)
	at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:574)
	at com.google.common.util.concurrent.FluentFuture$TrustedFuture.get(FluentFuture.java:91)
	at com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:67)
	at businessLayer.Messaging.sendPush(Messaging.java:777)
...

We are using the method sendEachAsync:
BatchResponse firebaseResponse = FirebaseMessaging.getInstance(firebaseApp).sendEachAsync(firebaseMessages, pushDryRun).get();

Besides the error showing up randomly when we are sending the messages, it seems that in older version of the library (<= 9.3.0), that the error is:

java.util.concurrent.ExecutionException: com.google.firebase.messaging.FirebaseMessagingException: com.google.firebase.messaging.FirebaseMessaging
	at com.google.common.util.concurrent.AbstractFuture.getDoneValue(AbstractFuture.java:594)
	at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:573)
	at com.google.common.util.concurrent.FluentFuture$TrustedFuture.get(FluentFuture.java:91)
	at com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:67)
	at businessLayer.Messaging.sendPush(Messaging.java:777)
...

The problem for us is that it seems that this error started showing up randomly last month.
At least some messages seem to be sent, because we have info that users are seeing and clicking on the notifications.
So, it seems that we are correctly calling the procedure.
Any help would be welcomed.

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[edonelezovic]

We have also started receiving a new error in the same method:

java.util.concurrent.ExecutionException: java.lang.ArrayIndexOutOfBoundsException: arraycopy: length -24 is negative
	at com.google.common.util.concurrent.AbstractFuture.getDoneValue(AbstractFuture.java:596)
	at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:575)
	at com.google.common.util.concurrent.FluentFuture$TrustedFuture.get(FluentFuture.java:91)
	at com.google.common.util.concurrent.ForwardingFuture.get(ForwardingFuture.java:67)
	at businessLayer.Messaging.sendPush(Messaging.java:777)
...

[Mohima6]

The error was caused by:
1)Null Firebase Messaging instance – [ FirebaseMessaging.getInstance(firebase App)] was not initialized properly.
2)Empty message list (firebase Messages) – The list passed to sendEachAsync() was sometimes empty, leading to execution failures.
3)Concurrency issue – Execution Exception was occurring when multiple messages were sent asynchronously.

I would fix it by-
1)Ensuring firebase Messages is not null or empty before calling sendEachAsync():
if (firebaseMessages == null || firebaseMessages.isEmpty()) {
throw new IllegalArgumentException("firebaseMessages list is empty");
}

2)Adding a try-catch block to handle execution errors.
try {
BatchResponse firebaseResponse = FirebaseMessaging.getInstance(firebaseApp)
.sendEachAsync(firebaseMessages, pushDryRun)
.get();
} catch (ExecutionException | InterruptedException e) {
e.printStackTrace();
}

3)Testing by downgrading Firebase Admin SDK to 9.3.0, confirming that the issue was introduced in 9.4.3.

Steps before fixing:
1)Using Firebase Admin SDK v9.4.3
2)Calling [ sendEachAsync() ] with an uninitialized firebaseApp or empty message list.
3)Observing NullPointerException or ExecutionException.