Weird exception when using Protobuf messages

[mvh77]

Hi,

I have a Scala/ScalaJS project with Protobuf messages defined in a shared project (Play Framework). On the JVM I try to use the these messages as values in Kafka topics and I've defined appropriate Serializers and Deserializers. These work fine. When I use the KafkaProducerActor with the serializer I get the following in the logs:

2018-04-02 19:36:20,607 [error] a.actor.OneForOneStrategy - class x.y.ProtobufMessage in JavaMirror with DependencyClassLoader{file:/home/mvh/.ivy2/cache/org.scala-lang/scala-library/jars/scala-library-2.12.4.jar, 

.... gazillion more lines of classpath .... 

file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunjce_provider.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/zipfs.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/localedata.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/sunec.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/dnsns.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/jfxrt.jar,file:/usr/lib/jvm/java-8-oracle/jre/lib/ext/cldrdata.jar] and parent being primordial classloader with boot classpath [/usr/lib/jvm/java-8-oracle/jre/lib/resources.jar:/usr/lib/jvm/java-8-oracle/jre/lib/rt.jar:/usr/lib/jvm/java-8-oracle/jre/lib/sunrsasign.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jsse.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jce.jar:/usr/lib/jvm/java-8-oracle/jre/lib/charsets.jar:/usr/lib/jvm/java-8-oracle/jre/lib/jfr.jar:/usr/lib/jvm/java-8-oracle/jre/classes] not found.
        at scala.reflect.internal.Mirrors$RootsBase.staticClass(Mirrors.scala:122)
        at scala.reflect.internal.Mirrors$RootsBase.staticClass(Mirrors.scala:22)
        at x.y.z.KafkaProducer$$typecreator4$1.apply(KafkaTraits.scala:25)
        at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe$lzycompute(TypeTags.scala:230)
        at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe(TypeTags.scala:230)
        at cakesolutions.kafka.akka.ProducerRecords$$typecreator1$1.apply(ProducerRecords.scala:143)
        at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe$lzycompute(TypeTags.scala:230)
        at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe(TypeTags.scala:230)
        at scala.reflect.api.TypeTags.typeOf(TypeTags.scala:339)
        at scala.reflect.api.TypeTags.typeOf$(TypeTags.scala:339)

x.y.ProtobufMessage is the (ScalaPB) message I'm trying to push to Kafka and KafkaTraits.scala:25 is:

private val protobufMessageProducerActor = 
  context.actorOf(KafkaProducerActor.props(producerConfig, 
    new StringSerializer(), 
    ProtobufMessageSerde), 
  "ProtobufMessageProducer")

Is there some special classloader/macro stuff going on where it doesn't find the implementation for my class because it's in the shared project? Everything works fine if I setup the KafkaProducerActor with a ByteArraySerializer for the value and explicitly use my ProtobufMessageSerializer to serialize the message before sending it to the producer actor.

Thanks! Best Regards!