Akka Kafka Custom Serializer - scala

Question

I'm using Akka Kafka (Scala) and want to send custom objects.
class TweetsSerializer extends Serializer[Seq[MyCustomType]] {
override def configure(configs: util.Map[String, _], isKey: Boolean): Unit = ???
override def serialize(topic: String, data: Seq[MyCustomType]): Array[Byte] = ???
override def close(): Unit = ???
}
How can i correctly write my own serializer ? And, what should i do with field config ?

Answer 1

I would use the StringSerializer, I mean, I´d convert all my types to string before produce them. However that works:
case class MyCustomType(a: Int)
class TweetsSerializer extends Serializer[Seq[MyCustomType]] {
private var encoding = "UTF8"
override def configure(configs: java.util.Map[String, _], isKey: Boolean): Unit = {
val propertyName = if (isKey) "key.serializer.encoding"
else "value.serializer.encoding"
var encodingValue = configs.get(propertyName)
if (encodingValue == null) encodingValue = configs.get("serializer.encoding")
if (encodingValue != null && encodingValue.isInstanceOf[String]) encoding = encodingValue.asInstanceOf[String]
}
override def serialize(topic: String, data: Seq[MyCustomType]): Array[Byte] =
try
if (data == null) return null
else return {
data.map { v =>
v.a.toString
}
.mkString("").getBytes("UTF8")
}
catch {
case e: UnsupportedEncodingException =>
throw new SerializationException("Error when serializing string to byte[] due to unsupported encoding " + encoding)
}
override def close(): Unit = Unit
}
}
object testCustomKafkaSerializer extends App {
implicit val producerConfig = {
val props = new Properties()
props.setProperty("bootstrap.servers", "localhost:9092")
props.setProperty("key.serializer", classOf[StringSerializer].getName)
props.setProperty("value.serializer", classOf[TweetsSerializer].getName)
props
}
lazy val kafkaProducer = new KafkaProducer[String, Seq[MyCustomType]](producerConfig)
// Create scala future from Java
private def publishToKafka(id: String, data: Seq[MyCustomType]) = {
kafkaProducer
.send(new ProducerRecord("outTopic", id, data))
.get()
}
val input = MyCustomType(1)
publishToKafka("customSerializerTopic", Seq(input))
}