spray Collection ToResponseMarshallable - scala

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"
)

Answer 2

API for marshalling seems to have changed since akka 2.3.5. For akka-2.4.11.2, SprayJsonSupport needs import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
1) Following is working sbt,
name := "some-project"
version := "1.0"
scalaVersion := "2.11.5"
scalacOptions := Seq("-unchecked", "-deprecation", "-encoding", "utf8")
val akkaVersion = "2.4.5"
libraryDependencies ++= {
Seq(
"com.typesafe.akka" %% "akka-http-experimental" % akkaVersion,
"com.typesafe.akka" % "akka-http-spray-json-experimental_2.11" % akkaVersion,
"com.typesafe.akka" %% "akka-slf4j" % akkaVersion,
"org.mongodb" % "mongo-java-driver" % "3.4.1",
"org.apache.kafka" %% "kafka" % "0.10.1.1",
"org.apache.kafka" % "kafka-clients" % "0.10.1.1",
//test
"org.scalatest" %% "scalatest" % "2.2.5" % "test",
"com.typesafe.akka" %% "akka-http-testkit" % "10.0.9" % "test",
"de.flapdoodle.embed" % "de.flapdoodle.embed.mongo" % "2.0.0" % "test"
)
}
parallelExecution in Test := false
2) And imports are,
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._
object GetMusicResources {
val music_get_api =
path("music") {
get {
complete {
List("my data1")
}
}
}
}
3) Tests
Get("/music") ~> GetMusicResources.music_get_api ~> check {
val response1: Future[ByteString] = response.entity.toStrict(300.millis).map {_.data }
response1.map(_.utf8String).map { responseString =>
responseString shouldBe """["my data1"]"""
}
}

Answer 3

In my case, I was missing the second import in :
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
import spray.json.DefaultJsonProtocol._ // <= this one
In case anyone stumble into the same issue