Reactive Extensions for JVM

Transcript

1. Reactive extensions for JVM
2. “A library for composing asynchronous and event-based programs using observable sequences for the JVM” - RxJava
3. “ReactiveX is a combination of the best ideas from the Observer pattern, the Iterator pattern, and functional programming” - ReactiveX
4. Reactive
5. Problem
6. Limited method signature public Data getData(); What if the implementation needs to change from synchronous to asynchronous How should the client execute this method without blocking? Spawn a thread?
7. Let’s do it async public void getData(Callback<T> c); public Future<T> getData(); public Future<List<Future<T>>> getData();
8. Observable push onNext(T) onError(Exception) onCompleted() Iterable vs. Observable Iterable pull T next() throws Exception returns
9. Observable push onNext(T) onError(Exception) onCompleted() Iterable pull T next() throws Exception returns getDataFromLocalMemory() .skip(10) .take(5) .map({ s -> s + "_transformed" }) .forEach({ println "onNext => " + it }) getDataFromNetwork() .skip(10) .take(5) .map({ s -> s + "_transformed" }) .subscribe({ println "onNext => " + it })
10. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData();
11. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData(); String s = getData(); if(s.equals(x)) { // do something } else { // do something else }
12. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData(); Iterable<String> values = getData(); for(String s : values) { if(s.equals(x)) { // do sometinhg } else { // do something else } }
13. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData(); Future<String> s = getData(); if(s.get().equals(x)) { // do sometinhg } else { // do something else }
14. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData(); CompletableFuture<String> s = getData(); s.thenAply((v) -> { if(v.equals(x)) { // do something } else { // do something else } })
15. How to deal with data Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData(); Future<String> s = getData(); s.map({ s -> if(s.equals(x)) { // do something } else { // do something else } })
16. How to deal with data Observable<String> s = getData(); s.map({ s -> if(s.equals(x)) { // do something } else { // do something else } }) Single Multiple Sync T getData(); Iterable<T> getData(); Async Future<T> getData(); Observable<T> getData();
17. Code examples
18. Synchronous Observable with single value Observable.create({ observer -> try { Location location = /** get last location */ observer.onNext(location); observer.onCompleted(); } catch(Exception e) { observer.onError(e); } })
19. Asynchronous Observable with single value Observable.create({ observer -> executor.execute(new Runnable() { def void run() { try { Location location = /** get location */ observer.onNext(location); observer.onCompleted(); } catch(Exception e) { observer.onError(e); } } }) })
20. Synchronous Observable with multiple values Observable.create({ observer -> try { for(l in locations) { observer.onNext(l); } observer.onCompleted(); } catch(Exception e) { observer.onError(e); } })
21. Asynchronous Observable with multiple values Observable.create({ observer -> executor.execute(new Runnable() { def void run() { try { for(l in location) { location = /** resolve location */ observer.onNext(location); } observer.onCompleted(); } catch(Exception e) { observer.onError(e); } } }) })
22. Asynchronous Observer getLocations().subscribe( {location -> prinln "Location: " + location.name }, { error -> println "Error" }, { println "Completed" } )
23. Composable functions
24. Composable functions Transform: map, flatMap, reduce, scan, ... Filter: take, skip, sample, takeWhile, filter, .... Combine: count, merge, zip, combineLatest, multicast, publish, cache Concurrency: observeOn, subscribeOn Error Handling: onErrorReturn, onErrorResume, ...
25. Synchronous Observable with single value Observable.create({ observer -> try { Location location = /** get last location */ observer.onNext(location); observer.onCompleted(); } catch(Exception e) { observer.onError(e); } })
26. Combining via Merge
27. Combining via Merge Observable<Data> a = getDataA(); Observable<Data> b = getDataB(); Observable.merge(a, b) .subscribe( { element -> println "data: " + element})
28. Combining via Zip
29. Combining via Merge Observable<Data> a = getDataA(); Observable<String> b = getDataB(); Observable.zip(a, b, {x, y, -> [x, y]}) .subscribe( { pair -> println "a: " + pair[0] +"b: " + pair[1]})
30. Error handling Observable<Data> a = getDataA(); Observable<String> b = getDataB(); Observable.zip(a, b, {x, y, -> [x, y]}) .subscribe( { pair -> println "a: " + pair[0] +"b: " + pair[1]}, { exception -> println "Exception " + exception.getMessage})
31. Error handling
32. Error handling Observable<Data> a = getDataA(); Observable<String> b = getDataB() .onErrorResumeNext(getFallbackForB()); Observable.zip(a, b, {x, y, -> [x, y]}) .subscribe( { pair -> println "a: " + pair[0] +"b: " + pair[1]}, { exception -> println "Exception " + exception.getMessage})
33. Error handling
34. Thanks! me@blaz.solar @solarb