Preserve order of fields while Deserializing using spray-json

package rest

/**
 * @author sjalipar
 */
import spray.json._
import scala.collection.immutable.ListMap

case class Response(time: String, a: Int, b: Int, c: Int, d: Int)

object restJsonProtocol extends DefaultJsonProtocol {

  implicit object customResponseJsonProtocol extends RootJsonFormat[Response] {
    def write(resp: Response): JsValue = JsObject(ListMap("time" -> JsString(resp.time),
      "a" -> JsNumber(resp.a),
      "b" -> JsNumber(resp.b),
      "c" -> JsNumber(resp.c),
      "d" -> JsNumber(resp.d)))

    def read(json: JsValue): Response = {
      json match {
        case obj: JsObject => obj.convertTo[Response]
        case _             => deserializationError("error occured in deserialization")
      }
    }
  }

}