JsonInput

Decoder used by Json during deserialization. This interface can be used to inject desired behaviour into a serialization process of Json.

Typical example of the usage:

// Class representing Either<Left|Right>
sealed class Either {
    data class Left(val errorMsg: String) : Either()
    data class Right(val data: Payload) : Either()
}

// Serializer injects custom behaviour by inspecting object content and writing
object EitherSerializer : KSerializer<Either> {
    override val descriptor: SerialDescriptor = SerialDescriptor("package.Either", PolymorphicKind.SEALED) {
         // ..
     }

    override fun deserialize(decoder: Decoder): Either {
        val input = decoder as? JsonInput ?: throw SerializationException("This class can be loaded only by Json")
        val tree = input.decodeJson() as? JsonObject ?: throw SerializationException("Expected JsonObject")
        if ("error" in tree) return Either.Left(tree.getPrimitive("error").content)
        return Either.Right(input.json.decodeJson(tree, Payload.serializer()))
    }

    override fun serialize(encoder: Encoder, value: Either) {
        val output = encoder as? JsonOutput ?: throw SerializationException("This class can be saved only by Json")
        val tree = when (value) {
          is Either.Left -> JsonObject(mapOf("error" to JsonLiteral(value.errorMsg)))
          is Either.Right -> output.json.toJson(value.data, Payload.serializer())
        }
        output.encodeJson(tree)
    }
}

Properties

Functions