scalapb-circe

The structure of this project is hugely inspired by scalapb-json4s

Dependency

Include in your build.sbt file

core

libraryDependencies += "io.github.scalapb-json" %% "scalapb-circe" % "0.16.0"

for scala-js or scala-native

libraryDependencies += "io.github.scalapb-json" %%% "scalapb-circe" % "0.16.0"

macros

libraryDependencies += "io.github.scalapb-json" %% "scalapb-circe-macros" % "0.16.0"

Usage

JsonFormat

There are four functions you can use directly to serialize/deserialize your messages:

JsonFormat.toJsonString(msg) // returns String
JsonFormat.toJson(msg) // returns Json

JsonFormat.fromJsonString(str) // return MessageType
JsonFormat.fromJson(json) // return MessageType

Implicit Circe Codecs

You can also import codecs to support Circe's implicit syntax for objects of type GeneratedMessage and GeneratedEnum.

Assume a proto message:

message Guitar {
  int32 number_of_strings = 1;
}

import io.circe.syntax._
import io.circe.parser._
import scalapb_circe.codec._

Guitar(42).asJson.noSpaces // returns {"numberOfStrings":42}

decode[Guitar]("""{"numberOfStrings": 42}""") // returns Right(Guitar(42))
Json.obj("numberOfStrings" -> Json.fromInt(42)).as[Guitar] // returns Right(Guitar(42))

You can define an implicit scalapb_circe.Printer and/or scalapb_circe.Parser to control printing and parsing settings. For example, to include default values in Json:

import io.circe.syntax._
import io.circe.parser._
import scalapb_circe.codec._
import scalapb_circe.Printer

implicit val p: Printer = new Printer(includingDefaultValueFields = true)

Guitar(0).asJson.noSpaces // returns {"numberOfStrings": 0}

Finally, you can include scalapb GeneratedMessage and GeneratedEnums in regular case classes with semi-auto derivation:

import io.circe.generic.semiauto._
import io.circe.syntax._
import io.circe._
import scalapb_circe.codec._ // IntelliJ might say this is unused.

case class Band(guitars: Seq[Guitar])
object Band {
  implicit val dec: Decoder[Band] = deriveDecoder[Band]
  implicit val enc: Encoder[Band] = deriveEncoder[Band]
}
Band(Seq(Guitar(42))).asJson.noSpaces // returns {"guitars":[{"numberOfStrings":42}]}

Credits

• https://github.com/whisklabs/scalapb-playjson
• https://github.com/scalapb/scalapb-json4s