I'm running into an issue when testing a stream on the flink mini cluster in my integration test.
The stream maps a generated Avro SpecificRecord Pojo Class (Java).

The stream job is written in Scala.

The flink runtime is crashing because it cannot instantiate the `org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils`

Here is the stack trace:

```
stack: java.lang.ClassCastException: class org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils
java.lang.RuntimeException: Could not instantiate org.apache.flink.formats.avro.utils.AvroKryoSerializerUtils.
    at org.apache.flink.api.java.typeutils.AvroUtils.getAvroUtils(AvroUtils.java:53)
    at org.apache.flink.api.java.typeutils.runtime.kryo.KryoSerializer.buildKryoRegistrations(KryoSerializer.java:572)

```

I think the problem is that Flink is unable to serialize the Avro Pojo Class because the Class has multiple nested Avro Pojo Classes in it.

I tried to add all the type informations for all nested Pojo Class types but still running into the same issue.

So now I wonder if anyone made a Flink Job work with a generated Avro Pojo Class with nested Avro Pojo Classes. All classes inherit the type SpecificRecord and are generated from a avro schema.

Is there some kind of special Serializer that needs to be written? Is there any documentation or example out there for such a Serializer that deals with multiple nested Pojo Classes in Scala or Java?

Or is it a different problem altogether?

Many Thanks in advance for any help!