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

4. • • • • • • •
5. Reactive Manifesto
6. • • • •
10. •
11. • onNext • onCompleted • onError onNext onNext onNext onCompleted
12. • onNext • onCompleted • onError onNext onNext onError
13. • Observable.from • Observable.just • • Observable.interval , Observable.range , Observable.empty Observable<Long> intervalObservable = Observable.interval(500L, TimeUnit.MILLISECODS); Observable<Integer> rangeObservable = Observable.range(1, 10); Observable<Character> justObservable = Observable.just('R', 'x', 'J', 'a', 'v', 'a'); List<String> list = Arrays.asList("blue", "red", "green", "yellow", "orange"); Observable<String> listObservable = Observable.from(list)
14. • Observable.create public static Observable<SomeDataType> getData(String someParameter) { return Observable.create(subscriber -> { try { SomeDataType result = SomeService.getData(someParameter); subscriber.onNext(result); subscriber.onCompleted(); } catch (Exception e) { subscriber.onError(e); } }); }
15. • Observable.create public static Observable<SomeDataType> getData(String someParameter) { return Observable.create(subscriber -> { try { SomeDataType result = SomeService.getData(someParameter); subscriber.onNext(result); subscriber.onCompleted(); } catch (Exception e) { subscriber.onError(e); } }); }
16. • observableInstance.subscribe observableInstance.subscribe(new Observer<SomeDataType>() { @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 } });
17. • observableInstance.subscribe observableInstance.subscribe( (SomeDataType message) -> {/*onNext*/}, (Throwable error) -> {/*onError*/}, () -> {/*onCompleted*/});
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21. • filter(Func1<T, Boolean> 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)
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)
23. • map(Func1<T,R> func) • flatMap(Func1<T,Observable<R>> func) • ... observableInstance.map(number -> number * number) observableInstance.flatMap(line -> Observable.from(line.split(“\\.”)))
24. • zip(Iterable<Observable> seq, FuncN<R> func) • merge(Iterable<Observable> seq) • amb(Iterable<Observable> seq) • ... Observable<String> timedObservable = Observable.zip( Observable.from(Arrays.asList("Z", "I", "P", "P")), Observable.interval(300L, TimeUnit.MILLISECONDS), (value, i) -> value); Observable<String> mergedObservable = Observable .merge(firstObservable, secondObservable, thirdObservable); Observable<String> fasterObservable = Observable .amb(firstObservable, secondObservable);
25. Observable.range(1,9) .skipWhile(element -> element < 5) .take(3) .reduce((elem1, elem2) -> elem1 + elem2) .subscribe(result -> /*do something*/)
27. • try/catch • • onError • onNext onNext onError
28. • • • 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 */});
30. • • • •
31. • • • Example
32. main
33. main observable.subscribe (onNext, onCompleted)
34. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData()
35. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() remoteService.getData
36. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data)
37. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onNext
38. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
39. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted() subscriber.onCompleted
40. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
41. main observable.subscribe (onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
42. observable.subscribe (onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
43. • Observable • subscribeOn(Scheduler) • observeOn(Scheduler) • Schedulers • immediate – • newThread – • trampoline – • io – • computation –
45. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted)
46. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data)
47. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data)
48. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
50. • • subscribe • • unsubscribe
51. • Subscription subscription = observableInstance.subscribe( (Long message) -> {/*onNext*/}, (Throwable error) -> {/*onError*/}, () -> {/*onCompleted*/}); // Do some logic; subscription.unsubscribe();
52. • observableInstance.subscribe(new Subscriber<Long>() { @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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