01. Working with Graphs

        <dependency>
            <groupId>com.typesafe.akka</groupId>
            <artifactId>akka-stream_2.12</artifactId>
            <version>${akka.version}</version>
        </dependency>        

package com.psmon.cachedb.actortest;

import org.springframework.stereotype.Component;
import akka.*;
import akka.stream.*;
import akka.stream.javadsl.*;
import java.util.Arrays;
import java.util.concurrent.CompletionStage;

/*
  ActorStream class
 */
@Component
public class ActorStream extends ActorBase{
  public void runAll() {
    runBasic1();          
  }
  
  protected void runBasic1() {
    // Stream을 실행시킬수 있는곳 ( 액터시스템이 가지고 있음 )
    final Materializer materializer = ActorMaterializer.create(system);

    final Source<Integer, NotUsed> source =
    Source.from(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10));
    // note that the Future is scala.concurrent.Future

    final Sink<Integer, CompletionStage<Integer>> sink =
        Sink.<Integer, Integer> fold(0, (aggr, next) -> aggr + next);

    // connect the Source to the Sink, obtaining a RunnableFlow
    final RunnableGraph<CompletionStage<Integer>> runnable =
        source.toMat(sink, Keep.right());  //Left:읽은쪽을 유지 , Right:기록한쪽을 유지 . Both:둘다 유지 , None : 유지없음

    // materialize the flow
    final CompletionStage<Integer> sum = runnable.run(materializer);

    try {      
      log.info("==> {}",sum.toCompletableFuture().get());    
    } catch (Exception e) {
      //TODO: handle exception
    }
  }
}

  protected void runBasic2(){
    final Materializer materializer = ActorMaterializer.create(system);
    Source.range(1, 3)
      .map(x -> x + 1).async()
      .map(x -> x * 2)
      .to( Sink.foreach( result ->{
        log.info("runBasic2 ==> {}", result );
      }))
      .run(materializer);
  }

  protected void runBasic3(){
    final Materializer materializer = ActorMaterializer.create(system);
    final Source<Integer, NotUsed> in = Source.from(Arrays.asList(1, 2, 3, 4, 5));
    final Sink<List<String>, CompletionStage<List<String>>> sink = Sink.head();
    final Flow<Integer, Integer, NotUsed> f1 = Flow.of(Integer.class).map(elem -> elem + 10);
    final Flow<Integer, Integer, NotUsed> f2 = Flow.of(Integer.class).map(elem -> elem + 20);
    final Flow<Integer, String, NotUsed> f3 = Flow.of(Integer.class).map(elem -> elem.toString());
    final Flow<Integer, Integer, NotUsed> f4 = Flow.of(Integer.class).map(elem -> elem + 30);


    final RunnableGraph<CompletionStage<List<String>>> result =
            RunnableGraph.fromGraph(
                    GraphDSL     // create() function binds sink, out which is sink's out port and builder DSL
                            .create(   // we need to reference out's shape in the builder DSL below (in to() function)
                                    sink,                // previously created sink (Sink)
                                    (builder, out) -> {  // variables: builder (GraphDSL.Builder) and out (SinkShape)
                                      final UniformFanOutShape<Integer, Integer> bcast = builder.add(Broadcast.create(2));
                                      final UniformFanInShape<Integer, Integer> merge = builder.add(Merge.create(2));

                                      final Outlet<Integer> source = builder.add(in).out();
                                      builder.from(source).via(builder.add(f1))
                                              .viaFanOut(bcast).via(builder.add(f2)).viaFanIn(merge)
                                              .via(builder.add(f3.grouped(1000))).to(out);  // to() expects a SinkShape
                                      builder.from(bcast).via(builder.add(f4)).toFanIn(merge);

                                      return ClosedShape.getInstance();
                                    }));

      result.run(materializer);
  }