Get ready for java.util.concurrent.Flow!

Slides from the presentation regarding Reactive Streams implementations and Reactive Streams standard introduced in Java 9. This presentation was shown during JDD Conference on the 3rd of October 2017. I've also presented this talk during JUG meetup in Kraków on 4th of December 2017, infoMEET conference in Wrocław on 16th of December 2017 and Hackin' Gliwice mini-conference in Gliwice on 15th of March 2018.

Transcript

1. View Slide

2. ●
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3. List list = Arrays.asList(1, 2, 3, 4, 5);
   for (Integer n : list) {
   if (n % 2 == 0) {
   operate(n);
   }
   }
   

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4. ●
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5. View Slide

6. Publisher pushes data to Subscriber
   onSubscribe
   onNext
   onError
   onComplete
   

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7. View Slide

8. List list = Arrays.asList(1, 2, 3, 4, 5);
   for (Integer n : list) {
   if (n % 2 == 0) {
   operate(n);
   }
   }
   

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9. List list = Arrays.asList( , , , , );
   for (Integer n : list) {
   if (n % 2 == 0) {
   operate(n);
   }
   }
   1 2 4
   3 5
   

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10. 1 2 4
    3 5
    filter(n -> n % 2 == 0)
    2 4
    

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11. 1 2 4
    3 5
    Flowable.fromArray( , , , , )
    .filter(n -> n % 2 == 0)
    .subscribe(n -> operate(n));
    

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12. Flowable.fromArray(1, 2, 3, 4, 5)
    .filter(n -> n % 2 == 0)
    .subscribe(n -> operate(n));
    

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13. View Slide

14. View Slide

15. ● RxJava 1
    ○
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    ○
    ● RxJava 2
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16. ● Observable
    ○
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    ● Completable
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    ● Flowable
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    ● Single
    ○
    ● Maybe
    ○
    

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17. Observable.range(1, 10)
    .map(i -> i * 100)
    .doOnNext(i -> printNumberWithThreadInfo("emitting", i))
    .map(i -> i * 10)
    .subscribeOn(Schedulers.computation())
    .observeOn(Schedulers.newThread())
    .subscribe(integer -> printNumberWithThreadInfo("received", integer));
    

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18. Observable.range(1, 10)
    .map(i -> i * 100)
    .doOnNext(i -> printNumberWithThreadInfo("emitting", i))
    .map(i -> i * 10)
    .subscribeOn(Schedulers.computation())
    .observeOn(Schedulers.newThread())
    .subscribe(integer -> printNumberWithThreadInfo("received", integer));
    observeOn(...)
    observeOn(...) subscribeOn(...)
    

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19. View Slide

20. List list = new ArrayList<>();
    new Thread(() -> ((Callback) () -> {
    list.add("one");
    ((Callback) () -> {
    list.add("two");
    ((Callback) () -> {
    list.add("three");
    System.out.println(list.stream().collect(Collectors.joining(" ")));
    }).execute();
    }).execute();
    }).execute()).start();
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21. Flowable
    .fromCallable(() -> "one")
    .flatMap(name -> Flowable.fromCallable(() -> name.concat(" two")))
    .flatMap(name -> Flowable.fromCallable(() -> name.concat(" three")))
    .subscribe(System.out::println);
    

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22. flowable.subscribe(new Subscriber() {
    @Override public void onSubscribe(Subscription s) {
    }
    @Override public void onNext(Object o) {
    }
    @Override public void onError(Throwable throwable) {
    System.out.println(throwable.getMessage());
    }
    @Override public void onComplete() {
    }
    });
    Subscriber
    

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23. Map words = new HashMap();
    Flowable
    .fromArray(1, 2, 3, 4, 5)
    .flatMap(i -> Flowable.just(i * 2))
    .map(words::get)
    .throttleWithTimeout(1, TimeUnit.SECONDS)
    .lastElement()
    .subscribe(System.out::println);
    

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24. sample( ) throttleLast( ) throttleFirst( )
    throttleWithTimeout( ) debounce( )
    BUFFER LATEST DROP
    Flowable
    

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25. View Slide

26. View Slide

27. View Slide

28. Flux.just(1, 2, 3, 4)
    .subscribe(System.out::println);
    Mono.just("foo")
    .subscribe(System.out::println);
    Flowable
    Single
    

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29. List list = new ArrayList<>();
    ActorSystem actorSystem = ActorSystem.create();
    ActorMaterializer mat = ActorMaterializer.create(actorSystem);
    Source source = Source.range(1, 5);
    source.runForeach(list::add, mat);
    

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30. Flowable flowable = Flowable.just(1, 2, 3, 4);
    Flux flux = Flux.just(5, 6, 7, 8);
    flowable
    .mergeWith(flux)
    .sorted()
    .subscribe(System.out::println);
    io.reactivex.Flowable reactor.core.publisher.Flux
    org.reactivestreams.Publisher java.util.concurrent.Flow.Publisher
    

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31. ●
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    ● provide interfaces
    are their implementations
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32. Publisher pushes data to Subscriber
    onSubscribe
    onNext
    onError
    onComplete
    java.util.concurrent.Flow
    

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33. Flow.Publisher publisher = subscriber -> {
    … // to be implemented
    };
    publisher.subscribe(new Flow.Subscriber<>() {
    @Override public void onSubscribe(Flow.Subscription subscription) {
    ...
    }
    @Override public void onNext(Integer item) {
    ...
    }
    @Override public void onError(Throwable throwable) {
    ...
    }
    @Override public void onComplete() {
    ...
    }
    });
    Publisher
    Subscriber
    

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34. Just for a presentation demo it’s better to use
    production ready libraries
    has to pass TCK (Technology
    Compatibility Kit) tests to keep RS ecosystem healthy!
    

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35. View Slide

36. View Slide

37. ● part of Java 9 language
    ● interfaces for reactive applications without implementations
    ● external production ready implementations RxJava Reactor Akka Stream
    ● have to be compatible with TCK
    ● data transformation
    ● callback hell
    ● asynchronous operations
    ● efficient consumption of the hardware resources
    ● error handling API
    ● can be used anywhere
    ● clean maintainable concise modern
    

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38. Thank you for the attention!
    https://github.com/pwittchen/java-flow-experiments
    https://speakerdeck.com/pwittchen
    

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