MongoDB Codec in Scala broken? - mongodb

Question

I have an app written in Scala to access a Mongo database in which I can query and insert data perfectly fine.
However when I try to use collection.distinct("user") I get the error:
Unknown Error org.bson.codecs.configuration.CodecConfigurationException:
Can't find a codec for class scala.runtime.Nothing$.
After doing some googling I found that I would need to specify a codec, so I initalised the MongoClient with one:
val clusterSettings = ClusterSettings
.builder()
.hosts(scala.collection.immutable.List(new com.mongodb.ServerAddress(addr)).asJava)
.build()
val settings = MongoClientSettings.builder()
.codecRegistry(MongoClient.DEFAULT_CODEC_REGISTRY)
.clusterSettings(clusterSettings)
.build()
val mongoClient: MongoClient = MongoClient(settings)
Still no luck, got the same error.
I figured I would need to make a custom codec as per this web page:
class NothingCodec extends Codec[Nothing] {
override def encode(writer:BsonWriter, value:Nothing, encoderContext:EncoderContext)={}
override def decode(reader: BsonReader, decoderContext: DecoderContext): Nothing = {
throw new Exception
}
override def getEncoderClass(): Class[Nothing] = {
classOf[Nothing]
}
}
But this doesn't work nor doesn't make sense, Nothing is not a valid return type; there exist no instances of this type.
As a result this obvisouly does not work with a new error of Unknown Error java.lang.Exception(Obviously!)
Am I missing something with the Mongo Scala Driver? Or is it just broken?

Answer 1

Use Document instead:
collection.distinct[Document]("user")
// i.e.
case class User(name: String, id: String)
records.distinct[Document]("user")
.toFuture()
.map(_ map { doc => getUserFromBson(doc).get })
def getUserFromBson(doc: Document): Option[User] = {
for {
name <- doc.get("name") map { x => x.asString().getValue }
id <- doc.get("id") map { x => x.asString().getValue }
}yield(User(name, id))
}
hope this helps.