Scala GraphStageLogic类代码示例

//设置package包名称以及导入依赖的类
import java.nio.ByteBuffer

import akka.NotUsed
import akka.stream.scaladsl.Source
import akka.stream.stage.{GraphStage, GraphStageLogic, OutHandler}
import akka.stream.{Attributes, Outlet, SourceShape}
import akka.util.ByteString
import org.mongodb.scala.gridfs.GridFSDownloadStream

import scala.concurrent.{ExecutionContext, Future}




case class GridfsSource(stream: GridFSDownloadStream, chunkSize: Int)(implicit ec: ExecutionContext) extends GraphStage[SourceShape[Future[ByteBuffer]]] {
  val out: Outlet[Future[ByteBuffer]] = Outlet("File Stream")
  
  override def shape: SourceShape[Future[ByteBuffer]] = SourceShape(out)

  override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) {
    setHandler(out, new OutHandler {
      override def onPull(): Unit = {
        val buffer = ByteBuffer.allocate(chunkSize)
        val loaded = stream.read(buffer).toFuture().map(_ => buffer)
        push(out, loaded)
      }

      override def onDownstreamFinish(): Unit = {
        super.onDownstreamFinish()
        stream.close()
        complete(out)
      }
    })
  }
}

object GridfsSource {
  def apply(stream: GridFSDownloadStream)(implicit ec: ExecutionContext): Source[ByteString, NotUsed] = {
    Source.fromGraph(GridfsSource(stream, 512 * 1024)).mapAsync(1)(fb => fb.map { buffer => buffer.flip(); ByteString(buffer) }).takeWhile(_.nonEmpty)
  }
} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.ftp
package impl

import akka.stream.Shape
import akka.stream.stage.GraphStageLogic

import scala.util.control.NonFatal

private[ftp] abstract class FtpGraphStageLogic[T, FtpClient, S <: RemoteFileSettings](
    val shape: Shape,
    val ftpLike: FtpLike[FtpClient, S],
    val connectionSettings: S,
    val ftpClient: () => FtpClient
) extends GraphStageLogic(shape) {

  protected[this] implicit val client = ftpClient()
  protected[this] var handler: Option[ftpLike.Handler] = Option.empty[ftpLike.Handler]

  override def preStart(): Unit = {
    super.preStart()
    try {
      val tryConnect = ftpLike.connect(connectionSettings)
      if (tryConnect.isSuccess) {
        handler = tryConnect.toOption
      } else
        tryConnect.failed.foreach { case NonFatal(t) => throw t }
      doPreStart()
    } catch {
      case NonFatal(t) =>
        matFailure(t)
        failStage(t)
    }
  }

  override def postStop(): Unit = {
    matSuccess()
    disconnect()
    super.postStop()
  }

  protected[this] def doPreStart(): Unit

  protected[this] def disconnect(): Unit =
    handler.foreach(ftpLike.disconnect)

  protected[this] def matSuccess(): Boolean

  protected[this] def matFailure(t: Throwable): Boolean

} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.jms

import javax.jms.{MessageProducer, TextMessage}

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler}
import akka.stream.{ActorAttributes, Attributes, Inlet, SinkShape}

final class JmsSinkStage(settings: JmsSinkSettings) extends GraphStage[SinkShape[JmsTextMessage]] {

  private val in = Inlet[JmsTextMessage]("JmsSink.in")

  override def shape: SinkShape[JmsTextMessage] = SinkShape.of(in)

  override protected def initialAttributes: Attributes =
    ActorAttributes.dispatcher("akka.stream.default-blocking-io-dispatcher")

  override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with JmsConnector {

      private var jmsProducer: MessageProducer = _

      override private[jms] def jmsSettings = settings

      override def preStart(): Unit = {
        jmsSession = openSession()
        jmsProducer = jmsSession.session.createProducer(jmsSession.destination)
        if (settings.timeToLive.nonEmpty) {
          jmsProducer.setTimeToLive(settings.timeToLive.get.toMillis)
        }
        pull(in)
      }

      setHandler(
        in,
        new InHandler {
          override def onPush(): Unit = {
            val elem: JmsTextMessage = grab(in)
            val textMessage: TextMessage = jmsSession.session.createTextMessage(elem.body)
            elem.properties.foreach {
              case (key, v) =>
                v match {
                  case v: String => textMessage.setStringProperty(key, v)
                  case v: Int => textMessage.setIntProperty(key, v)
                  case v: Boolean => textMessage.setBooleanProperty(key, v)
                  case v: Byte => textMessage.setByteProperty(key, v)
                  case v: Short => textMessage.setShortProperty(key, v)
                  case v: Long => textMessage.setLongProperty(key, v)
                  case v: Double => textMessage.setDoubleProperty(key, v)
                }
            }
            jmsProducer.send(textMessage)
            pull(in)
          }
        }
      )

      override def postStop(): Unit =
        Option(jmsSession).foreach(_.closeSession())
    }

} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.s3.impl

import akka.stream.scaladsl.SubFlow
import akka.stream.scaladsl.Source
import akka.stream.stage.GraphStage
import akka.util.ByteString
import akka.stream.FlowShape
import akka.stream.Inlet
import akka.stream.Outlet
import akka.stream.stage.GraphStageLogic
import akka.stream.Attributes
import akka.stream.stage.OutHandler
import akka.stream.stage.InHandler
import akka.stream.scaladsl.RunnableGraph
import akka.stream.scaladsl.Flow


private[alpakka] object SplitAfterSize {
  def apply[I, M](minChunkSize: Long)(in: Flow[I, ByteString, M]): SubFlow[ByteString, M, in.Repr, in.Closed] =
    in.via(insertMarkers(minChunkSize)).splitWhen(_ == NewStream).collect { case bs: ByteString => bs }

  private case object NewStream

  private def insertMarkers(minChunkSize: Long) = new GraphStage[FlowShape[ByteString, Any]] {
    val in = Inlet[ByteString]("SplitAfterSize.in")
    val out = Outlet[Any]("SplitAfterSize.out")
    override val shape = FlowShape.of(in, out)

    override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
      new GraphStageLogic(shape) with OutHandler with InHandler {
        var count: Long = 0
        override def onPull(): Unit = pull(in)

        override def onPush(): Unit = {
          val elem = grab(in)
          count += elem.size
          if (count >= minChunkSize) {
            count = 0
            emitMultiple(out, elem :: NewStream :: Nil)
          } else emit(out, elem)
        }
        setHandlers(in, out, this)
      }
  }
} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.s3.impl

import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.stream.scaladsl.Source
import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.util.ByteString


private[alpakka] final class MemoryBuffer(maxSize: Int) extends GraphStage[FlowShape[ByteString, Chunk]] {
  val in = Inlet[ByteString]("MemoryBuffer.in")
  val out = Outlet[Chunk]("MemoryBuffer.out")
  override val shape = FlowShape.of(in, out)

  override def createLogic(attr: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with InHandler with OutHandler {
      var buffer = ByteString.empty
      override def onPull(): Unit = if (isClosed(in)) emit() else pull(in)

      override def onPush(): Unit = {
        val elem = grab(in)
        if (buffer.size + elem.size > maxSize) {
          failStage(new IllegalStateException("Buffer size of " + maxSize + " bytes exceeded."))
        } else {
          buffer ++= elem
          pull(in)
        }
      }

      override def onUpstreamFinish(): Unit = {
        if (isAvailable(out)) emit()
        completeStage()
      }

      def emit(): Unit = emit(out, Chunk(Source.single(buffer), buffer.size), () => completeStage())
      setHandlers(in, out, this)
    }

} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.csv

import akka.event.Logging
import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.util.ByteString

import scala.annotation.tailrec
import scala.util.control.NonFatal


private[csv] class CsvParsingStage(delimiter: Byte, quoteChar: Byte, escapeChar: Byte)
    extends GraphStage[FlowShape[ByteString, List[ByteString]]] {

  private val in = Inlet[ByteString](Logging.simpleName(this) + ".in")
  private val out = Outlet[List[ByteString]](Logging.simpleName(this) + ".out")
  override val shape = FlowShape(in, out)

  override protected def initialAttributes: Attributes = Attributes.name("CsvParsing")

  override def createLogic(inheritedAttributes: Attributes) =
    new GraphStageLogic(shape) with InHandler with OutHandler {
      private[this] val buffer = new CsvParser(delimiter, quoteChar, escapeChar)

      setHandlers(in, out, this)

      override def onPush(): Unit = {
        buffer.offer(grab(in))
        tryPollBuffer()
      }

      override def onPull(): Unit =
        tryPollBuffer()

      override def onUpstreamFinish(): Unit = {
        emitRemaining()
        completeStage()
      }

      private def tryPollBuffer() =
        try buffer.poll(requireLineEnd = true) match {
          case Some(csvLine) ? push(out, csvLine)
          case _ ?
            if (isClosed(in)) {
              emitRemaining()
              completeStage()
            } else pull(in)
        } catch {
          case NonFatal(ex) ? failStage(ex)
        }

      @tailrec private def emitRemaining(): Unit =
        buffer.poll(requireLineEnd = false) match {
          case Some(csvLine) ?
            emit(out, csvLine)
            emitRemaining()
          case _ ?
        }

    }
} 

//设置package包名称以及导入依赖的类
package akka.stream.alpakka.csv

import java.nio.charset.Charset

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.util.ByteString

import scala.collection.immutable


private[csv] class CsvToMapStage(columnNames: Option[immutable.Seq[String]], charset: Charset)
    extends GraphStage[FlowShape[immutable.Seq[ByteString], Map[String, ByteString]]] {

  override protected def initialAttributes: Attributes = Attributes.name("CsvToMap")

  private val in = Inlet[immutable.Seq[ByteString]]("CsvToMap.in")
  private val out = Outlet[Map[String, ByteString]]("CsvToMap.out")
  override val shape = FlowShape.of(in, out)

  override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with InHandler with OutHandler {
      private var headers = columnNames

      setHandlers(in, out, this)

      override def onPush(): Unit = {
        val elem = grab(in)
        if (headers.isDefined) {
          val map = headers.get.zip(elem).toMap
          push(out, map)
        } else {
          headers = Some(elem.map(_.decodeString(charset)))
          pull(in)
        }
      }

      override def onPull(): Unit = pull(in)
    }
} 

//设置package包名称以及导入依赖的类
package org.hpi.esb.datavalidator.validation.graphstage

import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}

import scala.collection.mutable


final class IgnoreLastElements[E](ignoreCount: Int)
  extends GraphStage[FlowShape[E, E]] {

  val in = Inlet[E]("IgnoreLastElement.in")
  val out = Outlet[E]("IgnoreLastElement.out")

  override def shape = FlowShape.of(in, out)

  override def createLogic(inheritedAttributes: Attributes) = new GraphStageLogic(shape) {

    var isBuffered = false
    val buffer: mutable.Queue[E] = new mutable.Queue[E]

    setHandlers(in, out, new InHandler with OutHandler {

      override def onPush(): Unit = {

        buffer.enqueue(grab(in))
        if(buffer.size == ignoreCount + 1) {
          push(out, buffer.dequeue())
        } else {
          // As long as the buffer is not full, nothing will be sent downstream.
          // As a result the downstream component will not call 'onPull' and we have
          // to manually pull upstream
          pull(in)
        }
      }

      override def onPull(): Unit = {
        pull(in)
      }

      override def onUpstreamFinish(): Unit = {
        completeStage()
      }
    })
  }
} 

//设置package包名称以及导入依赖的类
package org.hpi.esb.datavalidator.validation.graphstage

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}

import scala.collection.immutable


final class AccumulateWhileUnchanged[E, P](propertyExtractor: E => P)
  extends GraphStage[FlowShape[E, immutable.Seq[E]]] {

  val in = Inlet[E]("AccumulateWhileUnchanged.in")
  val out = Outlet[immutable.Seq[E]]("AccumulateWhileUnchanged.out")

  override def shape = FlowShape.of(in, out)

  override def createLogic(inheritedAttributes: Attributes) = new GraphStageLogic(shape) {

    private var currentState: Option[P] = None
    private val buffer = Vector.newBuilder[E]

    setHandlers(in, out, new InHandler with OutHandler {

      override def onPush(): Unit = {
        val nextElement = grab(in)
        val nextState = propertyExtractor(nextElement)

        if (currentState.isEmpty || currentState.contains(nextState)) {
          buffer += nextElement
          pull(in)
        } else {
          val result = buffer.result()
          buffer.clear()
          buffer += nextElement
          push(out, result)
        }

        currentState = Some(nextState)
      }

      override def onPull(): Unit = {
        pull(in)
      }

      override def onUpstreamFinish(): Unit = {
        val result = buffer.result()
        if (result.nonEmpty) {
          emit(out, result)
        }
        completeStage()
      }
    })

    override def postStop(): Unit = {
      buffer.clear()
    }
  }
} 

//设置package包名称以及导入依赖的类
package com.martinseeler.dtf.stages

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.util.ByteString
import com.martinseeler.dtf.{FactorizedDeltaTick, NonNegativeFactorizedDeltaTick}
import scodec.Attempt.{Failure, Successful}
import scodec.DecodeResult
import scodec.bits.BitVector

import scala.annotation.tailrec

class ByteStringToDeltaStage extends GraphStage[FlowShape[ByteString, FactorizedDeltaTick]] {

  val in = Inlet[ByteString]("ByteStringToDeltaStage.in")
  val out = Outlet[FactorizedDeltaTick]("ByteStringToDeltaStage.out")

  def shape: FlowShape[ByteString, FactorizedDeltaTick] = FlowShape(in, out)

  def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with OutHandler {

      def onPull(): Unit = if (!hasBeenPulled(in)) tryPull(in)
      setHandler(out, this)

      val inHandler = new InHandler {

        def decodeAllFromBits(bits: BitVector): (Vector[NonNegativeFactorizedDeltaTick], BitVector) = {

          @tailrec
          def compute(results: Vector[NonNegativeFactorizedDeltaTick], remainingBits: BitVector): (Vector[NonNegativeFactorizedDeltaTick], BitVector) = {
            NonNegativeFactorizedDeltaTick.nonNegFactorizedDeltaTickCodecV.decode(remainingBits) match {
              case Successful(DecodeResult(value, BitVector.empty)) =>
                (results :+ value, BitVector.empty)
              case Successful(DecodeResult(value, remainder)) if remainder.sizeGreaterThan(25) =>
                compute(results :+ value, remainder)
              case Successful(DecodeResult(value, remainder)) =>
                (results :+ value, remainder)
              case Failure(e) =>
                println("e = " + e)
                (results, BitVector.empty)
            }
          }

          compute(Vector.empty, bits)
        }

        private[this] var remainingBits = BitVector.empty

        def onPush(): Unit = {
          val bits = BitVector.view(grab(in).asByteBuffer)
          val (results, rest) = decodeAllFromBits(remainingBits ++ bits)
          emitMultiple(out, results.map(_.withNegatives))
          remainingBits = rest
        }
      }

      setHandler(in, inHandler)
    }

} 

//设置package包名称以及导入依赖的类
package com.martinseeler.dtf.stages

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.util.ByteString
import com.martinseeler.dtf.NonNegativeFactorizedDeltaTick.nonNegFactorizedDeltaTickCodecV
import com.martinseeler.dtf.{FactorizedDeltaTick, NonNegativeFactorizedDeltaTick}
import scodec.Attempt.{Failure, Successful}

class DeltaToByteStringStage extends GraphStage[FlowShape[FactorizedDeltaTick, ByteString]] {

  val in = Inlet[FactorizedDeltaTick]("DeltaToByteStringStage.in")
  val out = Outlet[ByteString]("DeltaToByteStringStage.out")

  def shape: FlowShape[FactorizedDeltaTick, ByteString] = FlowShape(in, out)

  def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with InHandler with OutHandler {

      def onPull(): Unit = if (!hasBeenPulled(in)) tryPull(in)
      setHandler(out, this)


      def onPush(): Unit = {
        val delta = grab(in)
        nonNegFactorizedDeltaTickCodecV.encode(delta.nonNegative) match {
          case Successful(x) => emit(out, ByteString(x.toByteBuffer))
          case Failure(err) => fail(out, new Exception(err.messageWithContext))
        }
      }
      setHandler(in, this)
    }

} 

//设置package包名称以及导入依赖的类
package com.martinseeler.dtf.stages

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import com.martinseeler.dtf.{FactorizedDeltaTick, FactorizedTick, Tick}

class TickToDeltaStage
    extends GraphStage[FlowShape[Tick, FactorizedDeltaTick]] {

  val in = Inlet[Tick]("FactorizeDeltaTickStage.in")
  val out = Outlet[FactorizedDeltaTick]("FactorizeDeltaTickStage.out")

  def shape: FlowShape[Tick, FactorizedDeltaTick] = FlowShape(in, out)

  def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
    new GraphStageLogic(shape) with OutHandler {

      def onPull(): Unit = if (!hasBeenPulled(in)) tryPull(in)
      setHandler(out, this)

      val firstTickInHandler: InHandler = new InHandler {
        def onPush(): Unit = {
          val tick = grab(in)
          val factorizedTick: FactorizedTick = tick.factorize
          emit(out, FactorizedDeltaTick(factorizedTick.time, factorizedTick.bid, factorizedTick.ask))
          setHandler(in, withPrevInHandler(tick))
        }
      }

      def withPrevInHandler(initialTick: Tick): InHandler = new InHandler {

        private[this] var prevTick = initialTick

        def onPush(): Unit = {
          val tick = grab(in)
          emit(out, tick.factorize.deltaTo(prevTick.factorize))
          prevTick = tick
          setHandler(in, withPrevInHandler(tick))
        }
      }

      setHandler(in, firstTickInHandler)
    }
} 

//设置package包名称以及导入依赖的类
package com.martinseeler.dtf.stages

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import com.martinseeler.dtf.{FactorizedDeltaTick, FactorizedTick, Tick}

class DeltaToTickStage
  extends GraphStage[FlowShape[FactorizedDeltaTick, Tick]] {

    val in = Inlet[FactorizedDeltaTick]("FactorizeDeltaTickStage.in")
    val out = Outlet[Tick]("FactorizeDeltaTickStage.out")

    def shape: FlowShape[FactorizedDeltaTick, Tick] = FlowShape(in, out)

    def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
      new GraphStageLogic(shape) with OutHandler {

        def onPull(): Unit = if (!hasBeenPulled(in)) tryPull(in)
        setHandler(out, this)

        val firstDeltaInHandler: InHandler = new InHandler {
          def onPush(): Unit = {
            val delta = grab(in)
            println("delta = " + delta)
            val newFactorizedTick: FactorizedTick = Tick(0L, 0, 0).factorize.withDelta(delta)
            emit(out, newFactorizedTick.normalize)
            setHandler(in, withPrevInHandler(newFactorizedTick))
          }
        }

        def withPrevInHandler(initialFactorizedTick: FactorizedTick): InHandler = new InHandler {

          private[this] var prevFactorizedTick = initialFactorizedTick

          def onPush(): Unit = {
            val delta = grab(in)
            val newFactorizedTick: FactorizedTick = prevFactorizedTick.withDelta(delta)
            emit(out, newFactorizedTick.normalize)
            prevFactorizedTick = newFactorizedTick
          }
        }

        setHandler(in, firstDeltaInHandler)
      }
  } 

//设置package包名称以及导入依赖的类
package utils.streams

import javax.crypto._

import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.stream.{Attributes, FlowShape, Inlet, Outlet}
import akka.util.ByteString
import utils.Utils


class FileCipher(cipher: Cipher) extends GraphStage[FlowShape[ByteString, ByteString]] {
  val in = Inlet[ByteString]("FileCipher.in")
  val out = Outlet[ByteString]("FileCipher.out")
  override val shape = FlowShape.of(in, out)

  override def createLogic(inheritedAttributes: Attributes): GraphStageLogic = new GraphStageLogic(shape) {
      setHandler(in, new InHandler {
        override def onPush(): Unit = {
          val bytes = grab(in)

          if (bytes.isEmpty)
            pull(in) // Should not happen, request more bytes
          else {
            val ciphered = ByteString(cipher.update(bytes.toArray))

            // En/Decryption (e.g. AES with CBC) will work with blocks, if the block is not completed
            // the cipher will return an empty ByteString. We won't send it because it mess up with
            // chucked encoding, so we pull to complete our block and push it when ready
            if(ciphered.nonEmpty)
              push(out, ciphered)
            else
              pull(in)
          }
        }

        override def onUpstreamFinish(): Unit = {
          val bs = ByteString(cipher.doFinal())
          if (bs.nonEmpty)
            emit(out, bs) // Complete if necessary
          complete(out)
        }
      })

      setHandler(out, new OutHandler {
        override def onPull(): Unit = {
          pull(in)
        }
      })
    }
}

object FileCipher {
  def apply(cipher: Cipher): FileCipher = new FileCipher(cipher)
} 

//设置package包名称以及导入依赖的类
package akka_in_action.streams

import akka.actor.ActorSystem
import akka.stream._
import akka.stream.scaladsl.{Balance, Broadcast, Flow, GraphDSL, Keep, Merge, RunnableGraph, Sink, Source, Tcp}
import GraphDSL.Implicits._
import akka.NotUsed
import akka.stream.scaladsl.Tcp.OutgoingConnection
import akka.stream.stage.{GraphStage, GraphStageLogic, InHandler, OutHandler}
import akka.util.ByteString

import scala.concurrent.{Await, Future}
import scala.concurrent.duration._

object MapShape_ extends App {
  implicit val system = ActorSystem()
  implicit val ec = system.dispatcher
  implicit val materializer = ActorMaterializer()

  class Map[A, B](f: A => B) extends GraphStage[FlowShape[A, B]] {
    val in = Inlet[A]("Map.in")
    val out = Outlet[B]("Map.out")

    override val shape = FlowShape.of(in, out)

    override def createLogic(inheritedAttributes: Attributes): GraphStageLogic =
      new GraphStageLogic(shape) {
        setHandler(in, new InHandler {
          @scala.throws[Exception](classOf[Exception])
          override def onPush(): Unit = {
            push(out, f(grab(in)))
          }
        })

        setHandler(out, new OutHandler {
          @scala.throws[Exception](classOf[Exception])
          override def onPull(): Unit = {
            pull(in)
          }
        })
      }
  }

  val flowGraph: Graph[FlowShape[Int, Int], NotUsed] = new Map[Int, Int]((a:Int) => a + 1)
  val result = Source.fromIterator(() => Iterator from 5).via(flowGraph).to(Sink.foreach(println))
  result.run()

  Thread.sleep(300)

  system.terminate()
}