找不到隐式...：akka.http.server.RoutingSetup答案

【问题标题】：could not find implicit ...: akka.http.server.RoutingSetup找不到隐式...：akka.http.server.RoutingSetup
【发布时间】：2015-05-07 18:23:52
【问题描述】：

在使用 akka-http 实验性 1.0-M2 时，我正在尝试创建一个简单的 Hello world 示例。

import akka.actor.ActorSystem
import akka.http.Http
import akka.http.model.HttpResponse
import akka.http.server.Route
import akka.stream.FlowMaterializer
import akka.http.server.Directives._

object Server extends App {

  val host = "127.0.0.1"
  val port = "8080"

  implicit val system = ActorSystem("my-testing-system")
  implicit val fm = FlowMaterializer()

  val serverBinding = Http(system).bind(interface = host, port = port)
  serverBinding.connections.foreach { connection ⇒
    println("Accepted new connection from: " + connection.remoteAddress)
    connection handleWith Route.handlerFlow {
      path("") {
        get {
          complete(HttpResponse(entity = "Hello world?"))
        }
      }
    }
  }
}

编译失败，could not find implicit value for parameter setup: akka.http.server.RoutingSetup

另外，如果我改变了

complete(HttpResponse(entity = "Hello world?"))

与

complete("Hello world?")

我收到另一个错误：type mismatch; found : String("Hello world?") required: akka.http.marshalling.ToResponseMarshallable

【问题讨论】：

标签： scala akka akka-http

【解决方案1】：

通过研究，我能够理解缺少Execution Context 的问题。为了解决这两个问题，我需要包含以下内容：

implicit val executionContext = system.dispatcher

查看akka/http/marshalling/ToResponseMarshallable.scala 我看到ToResponseMarshallable.apply 需要它，它返回一个Future[HttpResponse]。

另外，akka/http/server/RoutingSetup.scala、RoutingSetup.apply 需要它。

可能是akka 团队只需要添加更多@implicitNotFounds。我在direct use of Futures in Akka和spray Marshaller for futures not in implicit scope after upgrading to spray 1.2找到了不准确但相关的答案

【讨论】：

【解决方案2】：

很好 - Akka HTTP 1.0-RC2 仍然存在这个问题，因此现在的代码必须如下所示（考虑到他们的 API 更改）：

import akka.actor.ActorSystem
import akka.http.scaladsl.server._
import akka.http.scaladsl._
import akka.stream.ActorFlowMaterializer
import akka.stream.scaladsl.{Sink, Source}
import akka.http.scaladsl.model.HttpResponse
import Directives._
import scala.concurrent.Future

object BootWithRouting extends App {

  val host = "127.0.0.1"
  val port = 8080

  implicit val system = ActorSystem("my-testing-system")
  implicit val fm = ActorFlowMaterializer()
  implicit val executionContext = system.dispatcher

  val serverSource: Source[Http.IncomingConnection, Future[Http.ServerBinding]] =
    Http(system).bind(interface = host, port = port)

  serverSource.to(Sink.foreach {
    connection =>
      println("Accepted new connection from: " + connection.remoteAddress)
      connection handleWith Route.handlerFlow {
        path("") {
          get {
            complete(HttpResponse(entity = "Hello world?"))
          }
        }
      }
  }).run()
}

【讨论】：