Going Reactive with RxJava EXTENDED - @ jPrime Sofia 2016

Reactive programming is here to stay, so you might as well learn it!
It already made its mark on languages like Swift or C#, and now with major companies such as Netflix and Microsoft backing it up, it's time to do the same in Java. In this lecture we'll talk about RxJava library and how it can be used to make our applications more Reactive.
We'll peak into RxJava API a little bit, but more importantly, we'll focus on the concepts and the ideas that drive RxJava, and the value it adds to our applications.
Once we understand that, RxJava will be yet another great tool in our toolbox.

Transcript

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4. •
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5. Reactive Manifesto
   

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6. •
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10. •
    

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11. • onNext
    • onCompleted
    • onError
    onNext
    onNext
    onNext
    onCompleted
    

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12. • onNext
    • onCompleted
    • onError
    onNext
    onNext
    onError
    

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13. • Observable.from
    • Observable.just
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    • 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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14. • 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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15. • 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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16. • 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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17. • observableInstance.subscribe
    observableInstance.subscribe(
    (SomeDataType message) -> {/*onNext*/},
    (Throwable error) -> {/*onError*/},
    () -> {/*onCompleted*/});
    

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21. • filter(Func1 predicate)
    • skip(int num)
    • take(int num)
    • elementAt(int index)
    • distinct()
    • ...
    observableInstance.filter(element -> element < 10)
    observableInstance.elementAt(5)
    observableInstance.take(5)
    observableInstance.skip(5)
    

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22. • throttleFirst(long duration, TimeUnit unit)
    • throttleLast(long duration, TimeUnit unit)
    • timeout(long duration, TimeUnit unit)
    • ...
    observableInstance.throttleFirst(100, TimeUnit.MILLISECONDS)
    observableInstance.timeout(100, TimeUnit.MILLISECONDS)
    observableInstance.throttleLast(100, TimeUnit.MILLISECONDS)
    

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23. • map(Func1 func)
    • flatMap(Func1> func)
    • ...
    observableInstance.map(number -> number * number)
    observableInstance.flatMap(line -> Observable.from(line.split(“\\.”)))
    

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24. • zip(Iterable seq, FuncN func)
    • merge(Iterable seq)
    • amb(Iterable seq)
    • ...
    Observable timedObservable = Observable.zip(
    Observable.from(Arrays.asList("Z", "I", "P", "P")),
    Observable.interval(300L, TimeUnit.MILLISECONDS),
    (value, i) -> value);
    Observable mergedObservable = Observable
    .merge(firstObservable, secondObservable, thirdObservable);
    Observable fasterObservable = Observable
    .amb(firstObservable, secondObservable);
    

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

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27. • try/catch
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    • onError
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    onNext
    onNext
    onError
    

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28. •
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    • 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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30. •
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31. •
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    Example
    

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32. main
    

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33. main
    observable.subscribe
    (onNext, onCompleted)
    

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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50. •
    • subscribe
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    • unsubscribe
    

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51. •
    Subscription subscription = observableInstance.subscribe(
    (Long message) -> {/*onNext*/},
    (Throwable error) -> {/*onError*/},
    () -> {/*onCompleted*/});
    // Do some logic;
    subscription.unsubscribe();
    

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52. •
    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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