How to attach multiple actors as sources to an Akka stream?

Question

I am trying to build and run an akka stream flow (in Java DSL) with 2 actors as sources, then a merge junction and then 1 sink:

    Source<Integer, ActorRef> src1 = Source.actorRef(100, OverflowStrategy.backpressure());
    Source<Integer, ActorRef> src2 = Source.actorRef(100, OverflowStrategy.backpressure());
    Sink<Integer, BoxedUnit> sink = Flow.of(Integer.class).to(Sink.foreach(System.out::println));

    RunnableFlow<BoxedUnit> closed = FlowGraph.factory().closed(sink, (b, out) -> {
        UniformFanInShape<Integer, Integer> merge = b.graph(Merge.<Integer>create(2));
        b.from(src1).via(merge).to(out);
        b.from(src2).to(merge);
    });

    closed.run(mat);

My question is how do I obtain ActorRef references to the source actors in order to send them messages? In case of 1 actor, I wouldn't be using graph builder, and then the .run() or runWith() method would return the ActorRef object. But what to do in case of many source actors? Is it even possible to materialize such a flow?

Answer 1

Answering my own question in case someone needs it.

Using jrudolph's advice, I was able to use actors like this (in actual code I did something nicer than a list of 2 ActorRefs):

    Source<Integer, ActorRef> src1 = Source.actorRef(100, OverflowStrategy.fail());
    Source<Integer, ActorRef> src2 = Source.actorRef(100, OverflowStrategy.fail());
    Sink<Integer, BoxedUnit> sink = Flow.of(Integer.class).to(Sink.foreach(System.out::println));

    RunnableFlow<List<ActorRef>> closed = FlowGraph.factory().closed(src1, src2, (a1, a2) -> Arrays.asList(a1, a2), (b, s1, s2) -> {
        UniformFanInShape<Integer, Integer> merge = b.graph(Merge.<Integer>create(2));
        b.from(s1).via(merge).to(sink);
        b.from(s2).to(merge);
    });

    List<ActorRef> stream = closed.run(mat);
    ActorRef a1 = stream.get(0);
    ActorRef a2 = stream.get(1);