Going Reactive with RxJava - @ TopConf Linz 2016

Reactive programming is here to stay, so you might as well learn it!

It has already become a favourite tool in the toolboxes of many Swift or C# developers, and now with major companies such as Netflix and Microsoft backing it up, it is time to make it's mark on Java.

In this lecture we'll talk about RxJava library and how it can be used together with all the new nifty features from Java 8.

But more importantly, we'll try to get to the bottom of what it actually means to use the concepts of Reactive programming in our applications.
Once we understand that, RxJava will be yet another great tool in our toolbox.

Transcript

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3. Reactive Manifesto
   

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4. •
   •
   •
   •
   

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8. •
   

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9. • onNext
   • onCompleted
   • onError
   onNext
   onNext
   onNext
   onCompleted
   

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10. • onNext
    • onCompleted
    • onError
    onNext
    onNext
    onError
    

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11. • Observable.from
    • Observable.just
    •
    • Observable.interval , Observable.range , Observable.empty
    Observable intervalObservable = Observable.interval(500L, TimeUnit.MILLISECODS);
    Observable rangeObservable = Observable.range(1, 10);
    Observable justObservable = Observable.just('R', 'x', 'J', 'a', 'v', 'a');
    List list = Arrays.asList("blue", "red", "green", "yellow", "orange");
    Observable listObservable = Observable.from(list)
    

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12. • Observable.create
    public static Observable getData(String someParameter) {
    return Observable.create(subscriber -> {
    try {
    SomeDataType result = SomeService.getData(someParameter);
    subscriber.onNext(result);
    subscriber.onCompleted();
    } catch (Exception e) {
    subscriber.onError(e);
    }
    });
    }
    

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13. • observableInstance.subscribe
    observableInstance.subscribe(new Observer() {
    @Override
    public void onNext(SomeDataType message) {
    // Do something on each Message received
    }
    @Override
    public void onError(Throwable error) {
    // Do something on Error
    }
    @Override
    public void onCompleted() {
    // Do something when Observable completes
    }
    });
    

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14. • observableInstance.subscribe
    observableInstance.subscribe(
    (SomeDataType message) -> {/*onNext*/},
    (Throwable error) -> {/*onError*/},
    () -> {/*onCompleted*/});
    

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16. •
    •
    •
    •
    •
    •
    

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17. •
    •
    •
    •
    •
    •
    

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18. •
    •
    •
    •
    observableInstance.filter(element -> element < 10)
    observableInstance.timeout(100, TimeUnit.MILLISECONDS)
    observableInstance.map(number -> number * number)
    Observable mergedObservable = Observable
    .merge(firstObservable, secondObservable, thirdObservable);
    

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19. Observable.range(1,9)
    .skipWhile(element -> element < 5)
    .take(3)
    .reduce((elem1, elem2) -> elem1 + elem2)
    .subscribe(result -> /*do something*/)
    

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21. • try/catch
    •
    • onError
    •
    onNext
    onNext
    onError
    

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22. •
    •
    • onError , onErrorReturn , onErrorResumeNext, retry
    mainObservable.onErrorReturn(throwable -> {
    System.out.println("The original feed failed with" + throwable);
    return oneMoreMessage;
    }).subscribe(data -> {/* doSomething */});
    mainObservable.onErrorResumeNext(throwable -> {
    System.out.println("The original feed failed with" + throwable);
    return backupObservable;
    }).subscribe(data -> {/* doSomething */});
    

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24. •
    •
    •
    •
    

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25. main
    

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26. main
    observable.subscribe
    (onNext, onCompleted)
    

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27. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    

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28. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    remoteService.getData
    

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29. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    subscriber.onNext(data)
    

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30. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onNext
    

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31. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    

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32. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    subscriber.onCompleted
    

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33. main
    observable.subscribe
    (onNext, onCompleted)
    observable.subscribe
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    

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34. main
    observable.subscribe
    (onNext, onCompleted)
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    

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35. observable.subscribe
    (onNext, onCompleted)
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    

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36. • Observable
    • subscribeOn(Scheduler)
    • observeOn(Scheduler)
    • Schedulers
    • immediate –
    • newThread –
    • trampoline –
    • io –
    • computation –
    

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38. observable
    .subscribeOn(Schedulers.io())
    .observeOn(Schedulers.computation())
    .subscribe(onNext, onCompleted)
    

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39. observable
    .subscribeOn(Schedulers.io())
    .observeOn(Schedulers.computation())
    .subscribe(onNext, onCompleted)
    remoteService.getData()
    subscriber.onNext(data)
    

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40. observable
    .subscribeOn(Schedulers.io())
    .observeOn(Schedulers.computation())
    .subscribe(onNext, onCompleted)
    remoteService.getData()
    subscriber.onNext(data)
    

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41. observable
    .subscribeOn(Schedulers.io())
    .observeOn(Schedulers.computation())
    .subscribe(onNext, onCompleted)
    remoteService.getData()
    subscriber.onNext(data)
    subscriber.onCompleted()
    

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43. •
    • subscribe
    •
    • unsubscribe
    

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44. •
    Subscription subscription = observableInstance.subscribe(
    (Long message) -> {/*onNext*/},
    (Throwable error) -> {/*onError*/},
    () -> {/*onCompleted*/});
    // Do some logic;
    subscription.unsubscribe();
    

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45. •
    observableInstance.subscribe(new Subscriber() {
    @Override
    public void onNext(Long message) {
    // Do something on each Message received
    unsubscribe();
    }
    @Override
    public void onError(Throwable e) {
    // Do something on Error
    }
    @Override
    public void onCompleted() {
    // Do something when Observable completes
    }
    });
    

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