Looking Ahead To RxJava 2 (Droidcon NYC 2016)

Looking Ahead To
 
RxJava 2
Jake Wharton

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Reactive Streams
...is an initiative to provide a standard
for asynchronous stream processing
with non-blocking back pressure.

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Reactive Streams
interface Publisher { 
void subscribe(Subscriber super T> s); 
}A

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Reactive Streams
}A
interface Subscriber { 
void onNext(T t); 
void onComplete(); 
void onError(Throwable t); 
}B

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Reactive Streams
}A
void onSubscribe(Subscription s); 
}B

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Reactive Streams
}A
}B
interface Subscription { 
void request(long n); 
void cancel(); 
}C

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Reactive Streams
}A
}B
void request(long n); 
void cancel(); 
}C
interface Processor extends Subscriber, Publisher { 
}D 

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Reactive Streams
class RxReactiveStreams { 
static Publisher toPublisher(Observable o) { … } 
static Observable toObservable(Publisher p) { … } 
static Publisher toPublisher(Single o) { … } 
static Single toSingle(Publisher p) { … } 
static Publisher toPublisher(Completable o) { … } 
static Completable toCompletable(Publisher> p) { … } 
}

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Reactive Streams
class RxReactiveStreams { 
static Publisher toPublisher(Observable o) { … } 
static Observable toObservable(Publisher p) { … } 
static Publisher toPublisher(Single o) { … } 
static Single toSingle(Publisher p) { … } 
static Publisher toPublisher(Completable o) { … } 
static Completable toCompletable(Publisher> p) { … } 
}
github.com/ReactiveX/RxJavaReactiveStreams

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Reactive Streams
}B

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Reactive Streams
}B
Calling onSubscribe, onNext, onError or
onComplete MUST return normally

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Reactive Streams
}B
Calling onSubscribe, onNext, onError or
onComplete MUST return normally except when any
provided parameter is null in which case it MUST throw
a java.lang.NullPointerException to the caller

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Flowable

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Flowable
ALL
NEW!!!!!

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Flowable
• Implementation of Reactive Streams Publisher.
ALL
NEW!!!!!

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Flowable
• Observed with Reactive Streams Subscriber.
ALL
NEW!!!!!

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Flowable
• 0 to many items, completes or errors.
ALL
NEW!!!!!

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Flowable
• Handles backpressure to slow down events 
with Reactive Streams Subscription.
ALL
NEW!!!!!

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Flowable
• Hundreds of convenience methods for 
transforming and composing data.
ALL
NEW!!!!!

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Flowable (aka RxJava 1.x's Observable)
• Hundreds of convenience methods for 
transforming and composing data.

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FlowableProcessor

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FlowableProcessor
ALL
NEW!!!!!

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FlowableProcessor
• Implementation of Reactive Streams Processor 
(aka Publisher via Flowable + Subscriber).
ALL
NEW!!!!!

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FlowableProcessor (aka 1.x's Subject)
• Implementation of Reactive Streams Processor 
(aka Publisher via Flowable + Subscriber).

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Observable? Subject?

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Observable
• Observed with an Observer (not Reactive Streams type).
• No backpressure support.
• Hundreds of convenience methods for transforming and 
composing data.

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Subject
• Implementation of Observable and Observer.

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Flowable vs. Observable

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• RxJava 1.x added backpressure late in the design process.

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• All types exposed backpressure but not all sources respected it.

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• All types exposed backpressure but not all sources respected it.
• Backpressure, like inheritance, must be designed for.

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RxView.touches(paintView)
.subscribe(e -> draw(e));

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db.createQuery("SELECT * …")
.subscribe(e -> update(e));

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Observable Observable

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Observable Observable
MissingBackpressureException

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Observable Flowable

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Observable Flowable
}B
interface Observer { 
void onSubscribe(Disposable d); 
}B

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Observable Flowable
}B
}B
interface Disposable { 
void dispose(); 
}B
void cancel(); 
void request(long r); 
}B

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Converting

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Converting
Observable

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Converting
1 2 3 4 5 6 7 8 9 10 11
Observable

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Converting
Observable
toFlowable()X

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Converting
Observable
toFlowable(DROP)X

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Converting
Observable
toFlowable(DROP)X
Flowable

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Converting
Observable
Flowable
toFlowable(DROP)X
request(5)

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Converting
1 2 3 4 5
Observable
Flowable
toFlowable(DROP)X
1 2 3 4 5
request(5)

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable
toFlowable(DROP)X
1 2 3 4 5
request(5)

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable
toFlowable(DROP)X
1 2 3 4 5
request(5) request(2)

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Converting
1 2 3 4 5 6 7 8 9 10 11
Observable
Flowable
toFlowable(DROP)X
1 2 3 4 5 9 10

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Converting
Observable
toFlowable(LATEST)X
Flowable

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Converting
Observable
Flowable
request(5)
toFlowable(LATEST)X

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Converting
1 2 3 4 5
Observable
Flowable 1 2 3 4 5
request(5)
toFlowable(LATEST)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
request(5)
toFlowable(LATEST)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
toFlowable(LATEST)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
toFlowable(LATEST)X
8

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Converting
1 2 3 4 5 6 7 8 9 10 11
Observable
Flowable 1 2 3 4 5 9
toFlowable(LATEST)X
8

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Converting
Observable
BUFFER
Flowable
toFlowable( )X

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Converting
Observable
Flowable
request(5)
toFlowable(BUFFER)X

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Converting
1 2 3 4 5
Observable
Flowable 1 2 3 4 5
request(5)
toFlowable(BUFFER)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
request(5)
toFlowable(BUFFER)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
toFlowable(BUFFER)X

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Converting
1 2 3 4 5 6 7 8
Observable
Flowable 1 2 3 4 5
toFlowable(BUFFER)X
6 7

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Converting
1 2 3 4 5 6 7 8 9 10 11
Observable
Flowable 1 2 3 4 5
toFlowable(BUFFER)X
6 7

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Converting
toObservable()
Observable
Flowable

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Converting
Observable
Flowable
request(Long.MAX_VALUE)
toObservable()

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Converting
1 2 3 4 5 6 7 8 9 10 11
Observable
Flowable
1 2 3 4 5
request(Long.MAX_VALUE)
6 7 8 9 10 11
toObservable()

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Specializations

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Specializations
• Encoding subsets of Observable into the type system.

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Single

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Single
• Either succeeds with an item or errors.
• Convenience methods for transforming and composing data.

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Single
• Either succeeds with an item or errors.
• Think "reactive scalar".

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Completable

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Completable
• Either completes or errors. Has no items!

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Completable
• Either completes or errors. Has no items!
• Think "reactive runnable".

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Maybe

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Maybe
ALL
NEW!!!!!

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Maybe
• Either succeeds with an item, completes with no items, or errors.
• Convenience methods for transforming 
and composing data. ALL
NEW!!!!!

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Maybe
• Either succeeds with an item, completes with no items, or errors.
• Convenience methods for transforming 
and composing data.
• Think "reactive optional".
ALL
NEW!!!!!

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Specializations
• Encoding subsets of Observable into the type system.
• Single – Item or error. Think "scalar".
• Completable – Complete or error. Think "runnable".
• Maybe – Item, complete, or error. Think "optional".

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Operator Specialization

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first()
Observable

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first()
Observable
Observable

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1 2 3 4 5 6 7 8 9 10 11
first()
1
Observable
Observable

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first()
Observable
Single

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1 2 3 4 5 6 7 8 9 10 11
first()
1
Observable
Single

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first()
Observable
Single
NoSuchElementException

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firstElement()
Observable

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firstElement()
Observable
Maybe

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ignoreElements()
Observable

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ignoreElements()
Observable
Completable

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1 2 3 4 5 6 7 8 9
ignoreElements()
Observable
Completable

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ignoreElements()
Flowable
Completable

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1 2 3 4 5 6 7 8 9
ignoreElements()
Flowable
Completable

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firstElement()
Flowable
Maybe

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first()
Flowable
Single

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Flowable Observable Maybe Single Completable
Flowable toObservable()
reduce()
elementAt()
firstElement()
lastElement()
singleElement()
scan()
elementAt()
first()/firstOrError()
last()/lastOrError()
single/singleOrError()
all()/any()/count()
(and more)
ignoreElements()
Observable toFlowable()
reduce()
elementAt()
firstElement()
lastElement()
singleElement()
scan()
elementAt()
first()/firstOrError()
last()/lastOrError()
single/singleOrError()
all()/any()/count()
(and more)
ignoreElements()
Maybe toFlowable() toObservable()
toSingle()
sequenceEqual()
toCompletable()
Single toFlowable() toObservable() toMaybe() toCompletable()
Completable toFlowable() toObservable() toMaybe()
toSingle()
toSingleDefault()
From
To

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Creating Sources

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Creating Sources
Flowable.just("Hello"); 
Flowable.just("Hello", "World");
 
Observable.just("Hello"); 
Observable.just("Hello", "World"); 
Maybe.just("Hello"); 
Single.just("Hello");

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Creating Sources
String[] array = { "Hello", "World" }; 
List list = Arrays.asList(array); 
Flowable.fromArray(array);
Flowable.fromIterable(list);
Observable.fromArray(array);
Observable.fromIterable(list);

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Creating Sources
Future future = CompletableFuture.completedFuture("Hello"); 
Flowable.fromFuture(future); 
Observable.fromFuture(future);

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Creating Sources
Flowable.empty(); 
 
Observable.empty(); 
 
Maybe.empty(); 
 
Completable.complete();

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Creating Sources
Flowable.never(); 
 
Observable.never(); 
 
Maybe.never();
Single.never(); 
 
Completable.never();

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Creating Sources
Flowable.error(new RuntimeException()); 
Observable.error(new RuntimeException()); 
Maybe.error(new RuntimeException()); 
Single.error(new RuntimeException()); 
Completable.error(new RuntimeException());

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Creating Sources
Observable.fromCallable(new Callable() { 
@Override public String call() {Y 
return getName(); 
}X 
});

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Creating Sources
@Override public String call() throws Exception {Y 
return getName();Z 
}X 
});

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Creating Sources
OkHttpClient client = // …
Request request = // …
@Override public String call() throws Exception {Y 
return client.newCall(request).execute();Z 
}X 
});
 
 
getName()

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Creating Sources
Flowable.fromCallable(() -> "Hello"); 
 
Observable.fromCallable(() -> "Hello"); 
 
Maybe.fromCallable(() -> "Hello"); 
Maybe.fromAction(() -> System.out.println("Hello")); 
Maybe.fromRunnable(() -> System.out.println("Hello")) 
 
Single.fromCallable(() -> "Hello"); 
 
Completable.fromCallable(() -> "Ignored!"); 
Completable.fromAction(() -> System.out.println("Hello")); 
Completable.fromRunnable(() -> System.out.println("Hello"));

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Creating Sources
Observable.create();

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Creating Sources
Observable.create();
100% LESS
AWFUL!!!

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Creating Sources
Observable.create(new ObservableOnSubscribe() { 
@Override 
public void subscribe(ObservableEmitter e) throws Exception { 
e.onNext("Hello"); 
e.onComplete(); 
}X 
});

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Creating Sources
Observable.create(e -> { 
e.onNext("Hello"); 
e.onComplete(); 
});
new ObservableOnSubscribe() 
@Override 
public void subscribe(ObservableEmitter ) throws Exception { 
 
 
}X 

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Creating Sources
Observable.create(e -> { 
e.onNext("Hello");
e.onNext("World"); 
e.onComplete(); 
});

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Creating Sources
Observable.create(e -> {
client.newCall(request).enqueue(new Callback() {
@Override public void onResponse(Response r) throws IOException {
e.onNext(r.body().string());
e.onComplete();
}A
@Override public void onFailure(IOException e) {
e.onError(e);
}B
}); 
});
 
e.onNext("Hello");
e.onNext("World"); 
e.onComplete();

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Creating Sources
Call call = client.newCall(request);
call.enqueue(new Callback() {
e.onComplete();
}A
e.onError(e);
}B
}); 
});

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Creating Sources
e.setCancelation(() -> call.cancel());
e.onComplete();
}A
e.onError(e);
}B
}); 
});

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Creating Sources
View view = // …
e.setCancelation(() -> view.setOnClickListener(null));
view.setOnClickListener(v -> e.onNext(v)); 
});
OkHttpClient client = // ...
Request request = // ...
e.setCancelation(() -> call.cancel());
e.onComplete();
}A
e.onError(e);
}B
}); 

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Creating Sources
Flowable.create(e -> { … });
Observable.create(e -> { … });
Maybe.create(e -> { … });
Single.create(e -> { … });
Completable.create(e -> { … });

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Observing Sources

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Observing Sources
Observable Flowable
}B
}B

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Observing Sources
Observable Flowable
}B
void onNext(T t);A 
void onComplete();B 
void onError(Throwable t);C 
void onSubscribe(Disposable d);D 
}B
void dispose(); 
}B
void cancel(); 
}B

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Observing Sources
Observable o = Observable.just("Hello");
o.subscribe(new Observer() { 
@Override public void onNext(String s) { … } 
@Override public void onComplete() { … } 
@Override public void onError(Throwable t) { … }
 
@Override public void onSubscribe(Disposable d) {
???
}B 
});
Flowable
}B
void dispose(); 
}B
void cancel(); 
}B
interface T 
T t ;A 
;B 
;C 
;D 

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Observing Sources
o.subscribe(new DisposableObserver() { 
@Override public void onError(Throwable t) { … } 
});
 
 
 
 
@Override public void onSubscribe(Disposable d) {
???
}B 

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Observing Sources
});Z
unsubscribe???

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Observing Sources
DisposableObserver observer = new DisposableObserver() { 
}
o.subscribe(observer);Z
unsubscribe???

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Observing Sources
DisposableObserver observer = new DisposableObserver() { 
}
o.subscribe(observer);Z
observer.dispose();

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Observing Sources
});Z

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Observing Sources
o.subscribeWith(new DisposableObserver() { 
});Z

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Observing Sources
Disposable d = o.subscribeWith(new DisposableObserver() { 
});Z
d.dispose();

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Observing Sources
CompositeDisposable disposables = new CompositeDisposable();
});Z
disposables.add(d);
 
 
 
 
d.dispose();

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Observing Sources
CompositeDisposable disposables = new CompositeDisposable();
});Z
disposables.add(d);
disposables.dispose();

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Observing Sources
o.subscribeWith(new DisposableObserver() { … });Z
Maybe m = Maybe.just("Hello");
m.subscribeWith(new DisposableMaybeObserver() { … });Z
Single s = Single.just("Hello");
s.subscribeWith(new DisposableSingleObserver() { … });Z
Completable c = Completable.completed();
c.subscribeWith(new DisposableCompletableObserver() { … });Z

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Observing Sources
Flowable f = Flowable.just("Hello");
f.subscribeWith(new DisposableSubscriber() { … });
o.subscribeWith(new DisposableObserver() { … });
m.subscribeWith(new DisposableMaybeObserver() { … });
s.subscribeWith(new DisposableSingleObserver() { … });
c.subscribeWith(new DisposableCompletableObserver() { … });

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Observing Sources
Flowable f = Flowable.just("Hello");
Disposable d1 = f.subscribeWith(new DisposableSubscriber() { … });
Disposable d2 = o.subscribeWith(new DisposableObserver() { … });
Disposable d3 = m.subscribeWith(new DisposableMaybeObserver() { … });
Disposable d4 = s.subscribeWith(new DisposableSingleObserver() { … });
Disposable d5 = c.subscribeWith(new DisposableCompletableObserver() { … });

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RxJava

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RxJava
• 2.0.0-RC3 was released 2016-09-23.

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RxJava
• 2.0.0-RC3 was released 2016-09-23.
• Releases are more like developer previews than release candidates.

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RxJava
• 2.0.0-RC3 was released 2016-09-23.
• Next two are scheduled for 2016-10-07 and 2016-10-21.

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RxJava
• 2.0.0-RC3 was released 2016-09-23.
• Next two are scheduled for 2016-10-07 and 2016-10-21.
• Final release scheduled for 2016-10-29.

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RxJava
• Package name is io.reactivex.*.

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RxJava
• Maven coordinates are io.reactivex.rxjava2:rxjava.

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RxJava
• Maven coordinates are io.reactivex.rxjava2:rxjava.
• Why the change? See http://jakes.link/major-versions

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RxAndroid

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RxAndroid
• 2.0.0-RC1 was released 2016-08-25.

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RxAndroid
• 2.0.0-RC1 was released 2016-08-25.
• Provides facilities for dealing with the main thread (or any Looper).

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RxAndroid
• 2.0.0-RC1 was released 2016-08-25.
• Package name is io.reactivex.android.*.

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RxAndroid
• 2.0.0-RC1 was released 2016-08-25.
• Package name is io.reactivex.android.*.
• Maven coordinates are io.reactivex.rxjava2:rxandroid.

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Living with 1.x and 2.x

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class RxJavaInterop { 
static Flowable toV2Flowable(rx.Observable o) { … } 
static Observable toV2Observable(rx.Observable o) { … }
static Maybe toV2Maybe(rx.Single s) { … }
static Maybe toV2Maybe(rx.Completable c) { … } 
static Single toV2Single(rx.Single s) { … } 
static Completable toV2Completable(rx.Completable c) { … }
 
static rx.Observable toV1Observable(Publisher p) { … }
static rx.Observable toV1Observable(Observable o, …) { … } 
static rx.Single toV1Single(Single o) { … }
static rx.Single toV1Single(Maybe m) { … } 
static rx.Completable toV1Completable(Completable c) { … }
static rx.Completable toV1Completable(Maybe m) { … } 
}X

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class RxJavaInterop { 
static Flowable toV2Flowable(rx.Observable o) { … } 
static Observable toV2Observable(rx.Observable o) { … }
static Maybe toV2Maybe(rx.Single s) { … }
static Maybe toV2Maybe(rx.Completable c) { … } 
static Single toV2Single(rx.Single s) { … } 
static Completable toV2Completable(rx.Completable c) { … }
 
static rx.Observable toV1Observable(Publisher p) { … }
static rx.Observable toV1Observable(Observable o, …) { … } 
static rx.Single toV1Single(Single o) { … }
github.com/akarnokd/RxJava2Interop

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dependencies { 
compile 'io.reactivex.rxjava2:rxjava:2.0.0-RC3' 
compile 'io.reactivex.rxjava2:rxandroid:2.0.0-RC1'
// Optionally... 
compile 'com.github.akarnokd:rxjava2-interop:0.3.0'
}

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Looking Ahead To RxJava 2 (Droidcon NYC 2016)

Looking Ahead To RxJava 2 (Droidcon NYC 2016)

Jake Wharton
PRO

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Transcript

Looking Ahead To RxJava 2 (Droidcon NYC 2016)

Looking Ahead To RxJava 2 (Droidcon NYC 2016)

Jake Wharton PRO

More Decks by Jake Wharton

Other Decks in Programming

Featured

Transcript

Jake Wharton
PRO