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)
...

[edonelezovic]

We made sure the Messages are not null and not empty.

Downgrading didn't prevent an error, but it was a different error, probably isn't handled in the newer version.

Older version:
java.util.concurrent.ExecutionException: com.google.firebase.messaging.FirebaseMessagingException: com.google.firebase.messaging.FirebaseMessaging

Newer version:
java.util.concurrent.ExecutionException: java.lang.NullPointerException

We needed to implement our custom solution using the Firebase Cloud Messaging API, because we didn't know which push messages were being sent and which weren't when the above method returned an exception. We knew that some of the messages were being sent.