DefaultMarshallers missing with scala and spray-routing - scala

Question

I'm new to Scala, and trying to write a little REST API.
Here is my route definition :
package com.example
import akka.actor.Actor
import com.example.core.control.CrudController
import spray.routing._
class ServiceActor extends Actor with Service {
def actorRefFactory = context
def receive = runRoute(routes)
}
trait Service extends HttpService {
val crudController = new CrudController()
val routes = {
path("ads" / IntNumber) { id =>
get {
complete(
crudController.getFromElasticSearch(id)
)
}
}
}
}
and here is my controller
package com.example.core.control
import com.example._
import org.elasticsearch.action.search.SearchResponse
import scala.concurrent._
import ExecutionContext.Implicits.global
class CrudController extends elastic4s
{
def getFromElasticSearch (id:Integer) : Future[String] = {
val result: Future[SearchResponse] = get
result onFailure {
case t: Throwable => println("An error has occured: " + t)
}
result map { response =>
response.toString
}
}
}
When I try to run this code, I got the following exception :
Error:(22, 58) could not find implicit value for parameter marshaller: spray.httpx.marshalling.ToResponseMarshaller[scala.concurrent.Future[String]]
crudController.getFromElasticSearch(id)
I understand quite well this error, spray needs an implicit marshaller in order to marshall my Future[String] Object. But I'm a little bit confused because in the documentation we can read
Scala compiler will look for an in-scope implicit Marshaller for your type to do the job of converting your custom object to a representation accepted by the client. spray comes with the following marshallers already defined (as implicit objects in the DefaultMarshallers trait) Source https://github.com/spray/spray/wiki/Marshalling-and-Unmarshalling
The required marshallers in my case belongs to DefaultMarshallers, I should not have to implicit him by myself.. Should I ?