没有找到喷雾清单Marshaller

Question

此代码导致编译错误could not find implicit value for parameter marshaller: spray.httpx.marshalling.ToResponseMarshaller[List[akka.actor.ActorRef]].

我不认为问题是ActorRef,因为改变它.mapTo[List[String]]显示相同的编译错误

一般来说,喷雾如何编组与所有暗示有点混淆 - 有没有办法使这个明确,例如ListProtocol.marshal(value)？

import akka.actor.Actor
import spray.http.HttpResponse
import spray.http.HttpRequest
import spray.http.Uri
import spray.http._
import spray.routing._
import HttpMethods._
import akka.actor.ActorRef
import akka.pattern.ask
import scala.concurrent.duration._
import scala.concurrent.ExecutionContext.Implicits.global
import scala.util.Success
import scala.util.Failure
import spray.http.StatusCodes.InternalServerError
import spray.json.DefaultJsonProtocol
import spray.httpx.SprayJsonSupport._
import spray.httpx.marshalling._
import spray.http._

class HttpApi(val manager: ActorRef) extends HttpServiceActor {

  def receive = runRoute {
    path("nodes") {
      get {
        onComplete(manager.ask(NodeList())(3.seconds).mapTo[List[ActorRef]]) {
          case Success(value) => {
            // Compile error happens here
            complete(value)
          }
          case Failure(ex) => {
            complete(InternalServerError, s"An error occurred: ${ex.getMessage}")
          }
        }
      }
    }
  }
}

Answer 1

更改此导入

import spray.json.DefaultJsonProtocol

至

import spray.json.DefaultJsonProtocol._

也就是说,您要导入该对象中定义的implicits,而不是对象本身.

或者,您可以扩展特征以获取隐含:

class HttpApi(val manager: ActorRef) extends HttpServiceActor
                                        with DefaultJsonProtocol {