Serialization / Deserialization

Serializer and deserializer are defined under com.anymindgroup.pubsub.serde.

A Deserializer basically represents a function that takes a message with array of bytes as input and returns type T by using environment R.
Other meta information under ReceivedMessage can be included into building type T apart from the message body.
Defined as follows:

trait Deserializer[-R, +T] {
  def deserialize(message: ReceivedMessage[Array[Byte]]): RIO[R, T]
}

Serializer works the other way around, given input of type T, return an array of bytes using environmet R:

trait Serializer[-R, -T] {
  def serialize(data: T): RIO[R, Array[Byte]]
}

Serde is a combination of both:

trait Serde[-R, T] extends Serializer[R, T] with Deserializer[R, T] {}

The object com.anymindgroup.Serde contains built-in serializers/deserializers. Currently available:

• Serde.byteArray
• Serde.int
• Serde.utf8String

Serializer/Deserializer for custom data types

Example of creating a serializer / deserializer for a data type from/to a JSON string using zio-json:

import com.anymindgroup.pubsub.*, zio.*, zio.json.*

// given data structure with a json codec like
case class MyData(name: String, age: Int) derives JsonCodec

// a deserializer implementation can look like
val myDataDes: Deserializer[Any, MyData] =
  message =>
    String(message.data).fromJson[MyData] match
      case Left(err)    => ZIO.fail(Throwable(s"Failed to deserialize: $err"))
      case Right(value) => ZIO.succeed(value)

// and a serializer like
val myDataSer: Serializer[Any, MyData] = data => ZIO.succeed(data.toJson.getBytes())

Handling deserialization errors

Example for handling deserialization errors in a subsription process:

import com.anymindgroup.pubsub.*, zio.*, zio.json.*

case class MyData(name: String, age: Int) derives JsonCodec

// deserializer returning the result as Either instead of failing
val myDataDes: Deserializer[Any, Either[String, MyData]] = message =>
  ZIO.succeed(String(message.data).fromJson[MyData])

// result can be handled in the subscription process e.g. like
val subStream =
  Subscriber.subscribe("my_sub_name", myDataDes).mapZIO { (message, reply) =>
    message.data match
      case Left(err)   => reply.nack() *> ZIO.logError(s"Failed to deserialize: $err")
      case Right(data) => reply.ack() *> ZIO.logInfo(s"Data ok $data")
}