找不到参数封送器的隐式值: spray.httpx.marshalling.ToResponseMarshaller[Unit]

Question

我有以下代码要执行：

import akka.actor.ActorSystem
import spray.routing.SimpleRoutingApp
import spray.json.DefaultJsonProtocol._
object Server1 extends App with SimpleRoutingApp{
def testing(p:String,q:String){
println(p+"  "+q)
}
implicit val actorSystem = ActorSystem()        
var state:String=""
startServer(interface="localhost",port = 8080){
println("Listening...")         
    get{
        println("incoming..")
        path("state"){
            parameters("alertC".as[String],"alertB".as[String]){   (alertC,alertB)=>{

                    complete{
                        testing(alertC,alertB)
                    }


                }   
            }
        } 
    }
}

}

复杂时，错误是:无法为参数封送器找到隐式值: spray.httpx.marshalling.ToResponseMarshallerUnit错误at: testing(alertC，alertB)

Answer 1

喷雾无法找到用于Unit的封送器。例如，从testing返回一个字符串。