Marshalling list of case class objects - scala

Question

I want to return list of json objects based on my case class objects.
Following is my spray router, which returns list of 'Appointment' objects.
trait GatewayService extends HttpService with SLF4JLogging {
import com.sml.apigw.protocols.AppointmentProtocol._
import spray.httpx.SprayJsonSupport._
implicit def executionContext = actorRefFactory.dispatcher
val router =
pathPrefix("api" / "v1") {
path("appointments") {
get {
complete {
val a = new Appointment("1", "2")
val l = List(a, a, a, a)
l
}
}
}
}
}
}
Following is the 'AppointmentProtocol'
import spray.json.DefaultJsonProtocol
case class Appointment(id: String, patient: String)
object AppointmentProtocol extends DefaultJsonProtocol {
implicit val appointmentFormat = jsonFormat2(Appointment.apply)
}
It gives the compilation error 'expression type of List[Appointment] doesn't confirms to expected type toResponseMarshallable'

Answer 1

Maybe you missed something in your example, but my brain-based compiler is telling me that your code should throw a compilation error since any directive in Spray requires a result of type Route, as i can see you have a List[Appointment]. Please read this article on Routes. Your route structure should be completed with complete, so i assume the this way would solve your issue:
get {
val a = new Appointment("1", "2")
val l = List(a, a, a, a)
complete(l)
}
Please note a complete directive which wraps the list. This should help, otherwise please provide the tree with resolved implicits by compiling your code with the flag -Xprint:typer, that should show where the problem with implicits is.

Answer 2

I think that you should use this library spray-json depending on your version of spay this will be your import and do not forget to add the imports to your code:
import MyJsonProtocol._
import spray.json._
for that be sure that you have imported:
libraryDependencies += "io.spray" %% "spray-json" % "1.3.2"
THen you can conver an object whith this, I also have problems having the case class in the same file but this was using testing:
case class Color(name: String, red: Int, green: Int, blue: Int)
object MyJsonProtocol extends DefaultJsonProtocol {
implicit val colorFormat = jsonFormat4(Color)
}
import MyJsonProtocol._
import spray.json._
val json = Color("CadetBlue", 95, 158, 160).toJson
val color = json.convertTo[Color]
and the list:
val jsonAst = List(1, 2, 3).toJson
This are extracted examples from the spray-json github project