ToLowerCase

ToLowerCase.scala

object Test extends App {
  import DefaultJsonProtocol._

  trait ToLowerCase
  object ToLowerCase {
    def apply(str: String): String with ToLowerCase = str.toLowerCase.asInstanceOf[String with ToLowerCase]

    implicit val strWithToLowerCaseFormat: JsonFormat[String with ToLowerCase] =
      new JsonFormat[String with ToLowerCase] {
        def write(obj: String with ToLowerCase): JsValue = JsString(obj)
        def read(json: JsValue): String with ToLowerCase = ToLowerCase(json.convertTo[String])
      }
  }

  case class User(userId: String with ToLowerCase)
  object User {
    implicit val userFormat = jsonFormat1(User.apply _)
  }

  println(JsonParser("""{ "userId": "Joe" }""").convertTo[User])
}