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

3. Reactive Manifesto
4. • • • •
8. •
9. • onNext • onCompleted • onError onNext onNext onNext onCompleted
10. • onNext • onCompleted • onError onNext onNext onError
11. • 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)
12. • 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); } }); }
13. • 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 } });
14. • observableInstance.subscribe observableInstance.subscribe( (SomeDataType message) -> {/*onNext*/}, (Throwable error) -> {/*onError*/}, () -> {/*onCompleted*/});
16. • • • • • •
17. • • • • • •
18. • • • • observableInstance.filter(element -> element < 10) observableInstance.timeout(100, TimeUnit.MILLISECONDS) observableInstance.map(number -> number * number) Observable<String> mergedObservable = Observable .merge(firstObservable, secondObservable, thirdObservable);
19. Observable.range(1,9) .skipWhile(element -> element < 5) .take(3) .reduce((elem1, elem2) -> elem1 + elem2) .subscribe(result -> /*do something*/)
21. • try/catch • • onError • onNext onNext onError
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 */});
24. • • • •
25. main
26. main observable.subscribe (onNext, onCompleted)
27. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData()
28. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() remoteService.getData
29. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data)
30. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onNext
31. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
32. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted() subscriber.onCompleted
33. main observable.subscribe (onNext, onCompleted) observable.subscribe remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
34. main observable.subscribe (onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
35. observable.subscribe (onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
36. • Observable • subscribeOn(Scheduler) • observeOn(Scheduler) • Schedulers • immediate – • newThread – • trampoline – • io – • computation –
38. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted)
39. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data)
40. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data)
41. observable .subscribeOn(Schedulers.io()) .observeOn(Schedulers.computation()) .subscribe(onNext, onCompleted) remoteService.getData() subscriber.onNext(data) subscriber.onCompleted()
43. • • subscribe • • unsubscribe
44. • Subscription subscription = observableInstance.subscribe( (Long message) -> {/*onNext*/}, (Throwable error) -> {/*onError*/}, () -> {/*onCompleted*/}); // Do some logic; subscription.unsubscribe();
45. • 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 } });