akka-http.scala

package com.example

import akka.actor.ActorSystem
import akka.http.scaladsl.Http
import akka.http.scaladsl.model._
import akka.http.scaladsl.server.Directives._
import akka.stream.{ActorMaterializer, Materializer}
import akka.stream.scaladsl.{Sink, Source, StreamConverters}
import akka.util.ByteString

import scala.io.StdIn

object WebServer {
  def main(args: Array[String]) {

    implicit val system = ActorSystem("my-system")
    implicit val materializer = ActorMaterializer()
    implicit val executionContext = system.dispatcher

    val route =
      path("stream") {
        get {
          source.runWith(Sink.foreach(str => println(s"Some string: ${str.utf8String}")))
          val httpEntity = HttpEntity(ContentTypes.`text/plain(UTF-8)`, source)

          complete(httpEntity)
        }
      }

    val bindingFuture = Http().bindAndHandle(route, "localhost", 8080)

    println(s"Server online at http://localhost:8080/\nPress RETURN to stop...")
    StdIn.readLine() // let it run until user presses return
    bindingFuture
      .flatMap(_.unbind()) // trigger unbinding from the port
      .onComplete(_ => system.terminate()) // and shutdown when done
  }

  private def source: Source[ByteString, Unit] = {
    StreamConverters.asOutputStream().mapMaterializedValue { os =>
      os.write("test hello 33".getBytes)
      os.close()
    }
  }
}