Usage of spray json in Scala hierarchy of classes

sprayjsonInClasses.scala

import spray.json.JsonParser

val msg =
  """
    | {"action":"move","data":{"direction":"left"}}
  """.stripMargin

JsonParser(msg).asJsObject.getFields("action","data")(1).asJsObject.getFields("direction")

case class B(val afieldOfb: String)
case class A(val afieldOfa: String, val bFieldOfA: B)

val a = A("hola",B("soy b"))

import spray.json._
import DefaultJsonProtocol._

implicit val aFormat: RootJsonFormat[A] = jsonFormat2(A)
implicit val bFormat: RootJsonFormat[B] = jsonFormat1(B)

val b = a.toJson

b.convertTo[A]

//====== with traits and hierarchy of class

// a hierarchy of case classes
class C()
case class E(efield: String) extends C
case class F(ffield: String, f2field: String) extends C

// one that contains
case class Container(c: C)

val a1 = Container(E("evalue"))
val a2 = Container(F("fvalue","fvalue2"))

//implicit val containerFormat: RootJsonFormat[Container] = jsonFormat1(Container)
implicit val eFormat = jsonFormat1(E)
implicit val fFormat = jsonFormat2(F)

object MyJsonProtocol extends DefaultJsonProtocol {
  implicit object ContainerJsonFormat extends RootJsonFormat[Container] {
    override def write(obj: Container) = {
      obj match {
        case Container(x: E) => JsObject(
          "type" -> JsString("E"),
          "data" -> x.toJson
        )
        case Container(x: F) => JsObject(
          "type" -> JsString("F"),
          "data" -> x.toJson
        )
        case _ => JsObject(
          "type" -> JsString("X"),
          "data" -> JsString("")
        )
      }
    }

    override def read(json: JsValue) = {
      json.asJsObject.getFields("type","data") match {
        case Seq(JsString("E"),x) => Container( x.convertTo[E])
        case Seq(JsString("F"),x) => Container( x.convertTo[F])
      }
    }
  }
}

import MyJsonProtocol._

a1
a2

val a1j = a1.toJson
val a2j = a2.toJson

a1j.convertTo[Container]
a2j.convertTo[Container]



val msg2 =
  """
    | {"type":"E","data":{"efield":"left","extra":"willnotapper"}}
  """.stripMargin

JsonParser(msg2).convertTo[Container]