/**
* Copyright 2014 Netflix, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package rx.internal.operators;
import java.util.concurrent.*;
import rx.
Observable.
OnSubscribe;
import rx.
Subscriber;
import rx.exceptions.
Exceptions;
import rx.functions.
Action0;
import rx.internal.producers.
SingleProducer;
import rx.subscriptions.
Subscriptions;
/**
* Converts a {@code Future} into an {@code Observable}.
* <p>
* <img width="640" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/from.Future.png" alt="">
* <p>
* You can convert any object that supports the {@code Future} interface into an {@code Observable} that emits
* the return value of the {@code get} method of that object, by using this operator.
* <p>
* This is blocking so the {@code Subscription} returned when calling
* {@code Observable.unsafeSubscribe(Observer)} does nothing.
*/
public final class
OnSubscribeToObservableFuture {
private
OnSubscribeToObservableFuture() {
throw new
IllegalStateException("No instances!");
}
/* package accessible for unit tests */static class
ToObservableFuture<T> implements
OnSubscribe<T> {
final
Future<? extends T>
that;
private final long
time;
private final
TimeUnit unit;
public
ToObservableFuture(
Future<? extends T>
that) {
this.
that =
that;
this.
time = 0;
this.
unit = null;
}
public
ToObservableFuture(
Future<? extends T>
that, long
time,
TimeUnit unit) {
this.
that =
that;
this.
time =
time;
this.
unit =
unit;
}
@
Override
public void
call(
Subscriber<? super T>
subscriber) {
subscriber.
add(
Subscriptions.
create(new
Action0() {
@
Override
public void
call() {
// If the Future is already completed, "cancel" does nothing.
that.
cancel(true);
}
}));
try {
//don't block or propagate CancellationException if already unsubscribed
if (
subscriber.
isUnsubscribed()) {
return;
}
T
value = (
unit == null) ? (T)
that.
get() : (T)
that.
get(
time,
unit);
subscriber.
setProducer(new
SingleProducer<T>(
subscriber,
value));
} catch (
Throwable e) {
// If this Observable is unsubscribed, we will receive a CancellationException.
// However, CancellationException will not be passed to the final Subscriber
// since it's already subscribed.
// If the Future is canceled in other place, CancellationException will be still
// passed to the final Subscriber.
if (
subscriber.
isUnsubscribed()) {
//refuse to emit onError if already unsubscribed
return;
}
Exceptions.
throwOrReport(
e,
subscriber);
}
}
}
public static <T>
OnSubscribe<T>
toObservableFuture(final
Future<? extends T>
that) {
return new
ToObservableFuture<T>(
that);
}
public static <T>
OnSubscribe<T>
toObservableFuture(final
Future<? extends T>
that, long
time,
TimeUnit unit) {
return new
ToObservableFuture<T>(
that,
time,
unit);
}
}