spray Collection ToResponseMarshallable

Question

I am trying to return a List from my complete directive in spray-routing.

complete {
  List("hello")
}

However, I am getting an error -

Expression of type List[String] doesn't conform to expected type ToResponseMarshallable

I am getting the same error with Seq. I see that marshallers for List and Seq are not provided by default in spray-httpx documentation. However, spray-json provides marshalling support in its DefaultJsonProtocol. I have imported spray.httpx.SprayJsonSupport._ and spray.json.DefaultJsonProtocol._ in my code, but that too hasn't helped.

Any idea how can I marshal a List/Seq using spray-json? Or will I have to write my own Marshaller?

(My scala version is 2.11.4)

Answer 1

Using spray 1.3.2 and spray-json 1.3.2 it should be possible.

Make sure you import (although you say you do, but double check).

import spray.httpx.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._

Consider following example:

import akka.actor.{ActorSystem, Props, Actor}
import akka.io.IO
import spray.can.Http
import spray.routing.HttpService
import akka.pattern.ask
import akka.util.Timeout
import scala.concurrent.duration._
import spray.httpx.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._

object Boot extends App {
  implicit val system = ActorSystem("so")

  val testActor = system.actorOf(Props[TestActor])

  implicit val timeout = Timeout(5.seconds)
  IO(Http) ? Http.Bind(testActor, interface = "0.0.0.0", port = 5000)

}

class TestActor extends Actor with HttpService {

  def receive  = runRoute(route)

  def actorRefFactory = context

  val route = get{
    path("ping") {
      complete(List("OK"))
    }
  }

}

Requesting /ping returns ["OK"] which looks okay.

Just for reference build.sbt bellow.

build.sbt

val akkaVersion = "2.3.5"

val sprayVersion = "1.3.2"

resolvers += "spray" at "http://repo.spray.io/"

scalaVersion := "2.11.5"

scalacOptions := Seq("-feature", "-unchecked", "-deprecation", "-encoding", "utf8")

libraryDependencies ++= Seq(
  "com.typesafe.akka"   %% "akka-actor"       % akkaVersion,
  "io.spray"            %% "spray-can"        % sprayVersion,
  "io.spray"            %% "spray-routing"    % sprayVersion,
  "io.spray"            %% "spray-client"     % sprayVersion,
  "io.spray"            %% "spray-json"       % "1.3.1"
)