Sttp, Circe, Json - how to deserialize Json to custom object?

Question

I have a simple case class which models Http response:

case class Other(name: String, age: Int)
case class MyResponse(id: String, name: String, others: List[Other])

I created decoders for them:

implicit val decoderOther: Decoder[Other] = deriveDecoder[Other]
implicit val decoderMyResponse: Decoder[MyResponse] = deriveDecoder[MyResponse]

But when I call it on sttp http client:

basicRequest.(...).get(...).response(asJson[MyResponse].getRight).send(backend).map(_) 

I got a Desarialization error:

sttp.client3.DeserializationException: DecodingFailure at .id Missing required field

I don't know why it cannot be parsed correctly. Decoders seems fine. When I change MyResponse to circe Json class it works fine:

Response([{ "id": "121", "name": "test", "others": [] }])

but I would like to parse it to my model. Can you help me?

Answer 1

If you write asJson[MyResponse] you need Encoder rather than Decoder.

So add

implicit val encoderOther: Encoder[Other]           = deriveEncoder[Other]
implicit val encoderMyResponse: Encoder[MyResponse] = deriveEncoder[MyResponse]

You can replace Encoder and Decoder with Codec

implicit val codecOther: Codec[Other]           = deriveCodec[Other]
implicit val codecMyResponse: Codec[MyResponse] = deriveCodec[MyResponse]

MyResponse("121", "test", List()).asJson.noSpaces
// {"id":"121","name":"test","others":[]}

https://scastie.scala-lang.org/DmytroMitin/W3wgn0gbRXyA1vRI6OyoUg/1