斯卡拉 – 喷雾/阿卡失踪隐含

发布时间：2020-12-16 08:51:12 所属栏目：安全来源：网络整理

导读：MyService. scala：33：找不到参数eh的隐式值：spray.routing.ExceptionHandler 我在使用Akka时遇到了“缺少隐式”编译错误,在spray.io代码中,对一个单独的后端服务器进行http调用,作为响应http get的一部分.代码需要导入相当多的Spray和Akka库,因此有点难以

MyService. scala：33：找不到参数eh的隐式值：spray.routing.ExceptionHandler

我在使用Akka时遇到了“缺少隐式”编译错误,在spray.io代码中,对一个单独的后端服务器进行http调用,作为响应http get的一部分.代码需要导入相当多的Spray和Akka库,因此有点难以确定是否存在导致此问题的库冲突,我宁愿想出如何在这个和其他情况下逻辑地跟踪这类问题.

调用runRoute(myRoute)时遇到缺少的隐式

这是代码：

import spray.routing._
import akka.actor.Actor
import akka.actor.ActorSystem
import spray.http._
import MediaTypes._
import akka.io.IO
import spray.httpx.RequestBuilding._
import scala.concurrent.Future
import spray.can.Http
import spray.http._
import akka.util.Timeout
import HttpMethods._
import akka.pattern.ask
import akka.event.Logging
import scala.concurrent.duration._


// we don't implement our route structure directly in the service actor because
// we want to be able to test it independently,without having to spin up an actor
class MyServiceActor extends Actor with MyService with akka.actor.ActorLogging {

  log.info("Starting")

  // the HttpService trait defines only one abstract member,which
  // connects the services environment to the enclosing actor or test
  def actorRefFactory = context

  // this actor only runs our route,but you could add
  // other things here,like request stream processing
  // or timeout handling
  def receive = runRoute(myRoute)
}

// this trait defines our service behavior independently from the service actor
trait MyService extends HttpService {

  implicit val system: ActorSystem = ActorSystem()

  implicit val timeout: Timeout = Timeout(15.seconds)

  import system.dispatcher // implicit execution context

  //val logger = context.actorSelection("/user/logger")
  val logger = actorRefFactory.actorSelection("../logger")

  val myRoute =
  {
    def forward(): String = {
      logger ! Log("forwarding to backend")  
      val response: Future[HttpResponse] =
      (IO(Http) ? Get("http:3080//localhost/backend")).mapTo[HttpResponse]    
      "<html><body><h1>api response after backend processing</h1></body></html>"
    }

    path("") {
      get {
        respondWithMediaType(`text/html`) { // XML is marshalled to `text/xml` by default,so we simply override here
          complete(forward)
        }
      }
    }
  }
}

我想知道解决这个问题的最佳方法是什么,希望能够提供有关如何解决类似问题的洞察力,因为它们在某种程度上并不能直接追踪.

编辑：当试图直接传递implicits,如下面的@ christian的答案,我得到：

MyService.scala：35：含糊不清的隐含值：
特征中的值上下文类型=>的元素akka.actor.ActorContext
特征中的价值体系MyService of type => akka.actor.ActorSystem
匹配预期类型akka.actor.ActorRefFactory
RoutingSettings.default,LoggingContext.fromActorRefFactory)
????????????????^

不太确定为什么具体如@ christian的答案为编译器留下了歧义的空间……

解决方法

runRoute期待一些暗示.您缺少导入：

import spray.routing.RejectionHandler.Default

更新：
我认为我们也确实遇到了runRoute的一些问题,因为我们明确地提供了隐式参数：

runRoute(route)(ExceptionHandler.default,RejectionHandler.Default,context,RoutingSettings.default,LoggingContext.fromActorRefFactory)

UPDATE2：
要修复上一个错误,请删除ActorSystem的创建(在MyService中,您从MyServiceActor获取actor系统 – 因此您必须使用自我类型注释).这编译：

import akka.actor.Actor
import akka.io.IO
import spray.httpx.RequestBuilding._
import spray.http.MediaTypes._
import spray.routing.{RoutingSettings,RejectionHandler,ExceptionHandler,HttpService}
import spray.util.LoggingContext
import scala.concurrent.Future
import spray.can.Http
import spray.http._
import akka.util.Timeout
import HttpMethods._
import akka.pattern.ask
import akka.event.Logging
import scala.concurrent.duration._


// we don't implement our route structure directly in the service actor because
// we want to be able to test it independently,which
  // connects the services environment to the enclosing actor or test
  implicit def actorRefFactory = context

  // this actor only runs our route,like request stream processing
  // or timeout handling
  def receive = runRoute(myRoute)(ExceptionHandler.default,LoggingContext.fromActorRefFactory)
}

// this trait defines our service behavior independently from the service actor
trait MyService extends HttpService { this: MyServiceActor =>

  implicit val timeout: Timeout = Timeout(15.seconds)

  implicit val system = context.system

  //val logger = context.actorSelection("/user/logger")
  val logger = actorRefFactory.actorSelection("../logger")

  val myRoute =
  {
    def forward(): String = {
      //logger ! Log("forwarding to backend")
      val response: Future[HttpResponse] =
        (IO(Http) ? Get("http:3080//localhost/backend")).mapTo[HttpResponse]
      "<html><body><h1>api response after backend processing</h1></body></html>"
    }

    path("") {
      get {
        respondWithMediaType(`text/html`) { // XML is marshalled to `text/xml` by default,so we simply override here
          complete(forward)
        }
      }
    }
  }
}

（编辑：李大同）

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