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Scala macros for compile-time generation of Kryo serializers
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Kryo Macros Build Status license version

Scala macros that generate com.esotericsoftware.kryo.Serializer implementations in compile time, based on compile time reflection.

Features and limitations

  • On top level only case classes are supported
  • Fields of case classes can be other case classes, Scala collections, options, primitive or AnyVal types & classes, tuples, Scala enums, standard types & classes: String, Either, BigDecimal, java.time.Instant, scala.concurrent.duration.FiniteDuration, org.joda.time.DateTime
  • Fields can be annotated as transient or just be not defined in constructor to avoid parsing and serializing
  • For nested structures need to generate serializers for all case classes
  • Implicitly defined mapping helpers are supported for ADT structures, simple alternative mappings, etc.
  • Manual serializers can be used in generated code when defined as implicits

How to use

Add the following resolver

resolvers += Resolver.bintrayRepo("evolutiongaming", "maven")

Add the library to your dependencies list

libraryDependencies += "com.evolutiongaming" %% "kryo-macros" % "1.2.0"

Generate some serializers for your case classes

import com.evolutiongaming.kryo.Serializer

case class Player(name: String)

val serializer = Serializer.make[Player]

That's it! You have generated a com.esotericsoftware.kryo.Serializer implementation for your Player. You must know what to do with it if you are here :)

To serialize objects that extends sealed traits/class use Serializer.makeCommon call:

import com.evolutiongaming.kryo.{ConstSerializer, Serializer}
sealed trait Reason
object Reason {
  case object Close extends Reason
  case object Pause extends Reason       

val reasonSerializer = Serializer.makeCommon[Reason] {
  case 0 => ConstSerializer(Reason.Close)
  case 1 => ConstSerializer(Reason.Pause)

sealed abstract class Message(val text: String)

object Message {
  case object Common extends Message("common")
  case object Notification extends Message("notification")

private implicit val messageSerializer = Serializer.makeMapping[Message] {
  case 0 => Message.Common   
  case 1 => Message.Notification

To see generated code just add the following line to your sbt build file

scalacOptions += "-Xmacro-settings:print-serializers"

For more examples, please, check out SerializerMacroSpec

How to develop

Run tests, check coverage & binary compatibility for both supported Scala versions

sbt ++2.11.12 clean coverage test coverageReport mimaReportBinaryIssues
sbt ++2.12.6 clean coverage test coverageReport mimaReportBinaryIssues
sbt ++2.13.0-M3 clean coverage test coverageReport mimaReportBinaryIssues
sbt ++2.13.0-M4 clean compile

Run benchmarks

sbt -no-colors clean 'benchmark/jmh:run -prof gc .*SerializerBenchmark.*' >results.txt


For version numbering use Recommended Versioning Scheme that is widely adopted in the Scala ecosystem.

Double-check binary & source compatibility and release using following command (credentials required):

sbt release
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