Error while calling an API using akka in scala-CodePudding

TO start with I am very new to Scala and also I don't have any Java experience also. I am trying to call an API using simple Scala code and running into the errors. Code looks like:

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._
import akka.stream.ActorMaterializer

import scala.concurrent.Future
import scala.util.{ Failure, Success }

object Client {
  def main(args: Array[String]): Unit = {
    implicit val system = ActorSystem()
    implicit val materializer = ActorMaterializer()
    // needed for the future flatMap/onComplete in the end
    implicit val executionContext = system.dispatcher

    val responseFuture: Future[HttpResponse] = Http().singleRequest(HttpRequest(uri = "https://akka.io"))

    responseFuture
      .onComplete {
        case Success(res) => println(res)
        case Failure(_)   => sys.error("something wrong")
      }
  }
}

Basically, I have just copied the code from Akka documentation and trying to run it.

I get the following errors:

not found: value ActorSystem implicit val system = ActorSystem()

not found: value ActorMaterializer implicit val materializer = ActorMaterializer()

Cannot find an implicit ExecutionContext. You might pass an (implicit ec: ExecutionContext) parameter to your method.

Also 'ActorMaterializer()' now seems to be deprecated. Is this the reason for errors?

Thanks in advance :)

CodePudding user response：

You may need to add akka-streams as a dependency in your build tool.

ActorMaterializer.apply should just be a warning, unrelated to your other error. Might be worth opening an issue on github asking for updated docs for this snippet though.

CodePudding user response：

This should get you going. In your build.sbt

scalaVersion := "2.13.8"

val akkaVersion = "2.6.19"
val akkaHTTPVersion = "10.2.9"

libraryDependencies   = Seq(
  "com.typesafe.akka" %% "akka-stream" % akkaVersion,
  "com.typesafe.akka" %% "akka-actor" % akkaVersion,
  "com.typesafe.akka" %% "akka-http" % akkaHTTPVersion
)

The code below is from the latest Doc, with the added line to consume the response entity as described in the Doc.

object HttpClientSingleRequest extends App {
  implicit val system: ActorSystem = ActorSystem()

  import system.dispatcher

  val responseFuture: Future[HttpResponse] = Http().singleRequest(HttpRequest(uri = "https://akka.io"))
  responseFuture
    .onComplete {
      case Success(res) =>
        // Even if we don’t care about the response entity, we must consume it 
        res.entity.discardBytes()
        println(s"Success: ${res.status}")
      case Failure(ex) => sys.error(s"Something wrong: ${ex.getMessage}")
    }
}