Copyright (c) 2016-present, RxJava Contributors.
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.
/**
* Copyright (c) 2016-present, RxJava Contributors.
*
* 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 io.reactivex.subscribers;
import java.util.concurrent.atomic.AtomicReference;
import org.reactivestreams.Subscription;
import io.reactivex.FlowableSubscriber;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.EndConsumerHelper;
An abstract Subscriber that allows asynchronous, external cancellation by implementing Disposable.
All pre-implemented final methods are thread-safe.
The default onStart() requests Long.MAX_VALUE by default. Override the method to request a custom positive amount. Use the protected request(long) to request more items and cancel() to cancel the sequence from within an onNext implementation.
Note that calling request(long) from onStart() may trigger an immediate, asynchronous emission of data to Subscriber.onNext(Object). Make sure all initialization happens before the call to request() in onStart(). Calling request(long) inside Subscriber.onNext(Object) can happen at any time because by design, onNext calls from upstream are non-reentrant and non-overlapping.
Like all other consumers, DisposableSubscriber can be subscribed only once. Any subsequent attempt to subscribe it to a new source will yield an IllegalStateException with message "It is not allowed to subscribe with a(n) <class name> multiple times.".
Implementation of onStart(), Subscriber.onNext(Object), Subscriber.onError(Throwable) and Subscriber.onComplete() are not allowed to throw any unchecked exceptions. If for some reason this can't be avoided, use Flowable.safeSubscribe(Subscriber) instead of the standard subscribe() method.
Example
Disposable d =
Flowable.range(1, 5)
.subscribeWith(new DisposableSubscriber<Integer>() {
@Override public void onStart() {
request(1);
}
@Override public void onNext(Integer t) {
if (t == 3) {
cancel();
}
System.out.println(t);
request(1);
}
@Override public void onError(Throwable t) {
t.printStackTrace();
}
@Override public void onComplete() {
System.out.println("Done!");
}
});
// ...
d.dispose();
Type parameters: - <T> – the received value type.
/**
* An abstract Subscriber that allows asynchronous, external cancellation by implementing Disposable.
*
* <p>All pre-implemented final methods are thread-safe.
*
* <p>The default {@link #onStart()} requests Long.MAX_VALUE by default. Override
* the method to request a custom <em>positive</em> amount. Use the protected {@link #request(long)}
* to request more items and {@link #cancel()} to cancel the sequence from within an
* {@code onNext} implementation.
*
* <p>Note that calling {@link #request(long)} from {@link #onStart()} may trigger
* an immediate, asynchronous emission of data to {@link #onNext(Object)}. Make sure
* all initialization happens before the call to {@code request()} in {@code onStart()}.
* Calling {@link #request(long)} inside {@link #onNext(Object)} can happen at any time
* because by design, {@code onNext} calls from upstream are non-reentrant and non-overlapping.
*
* <p>Like all other consumers, {@code DisposableSubscriber} can be subscribed only once.
* Any subsequent attempt to subscribe it to a new source will yield an
* {@link IllegalStateException} with message {@code "It is not allowed to subscribe with a(n) <class name> multiple times."}.
*
* <p>Implementation of {@link #onStart()}, {@link #onNext(Object)}, {@link #onError(Throwable)}
* and {@link #onComplete()} are not allowed to throw any unchecked exceptions.
* If for some reason this can't be avoided, use {@link io.reactivex.Flowable#safeSubscribe(org.reactivestreams.Subscriber)}
* instead of the standard {@code subscribe()} method.
*
* <p>Example<pre><code>
* Disposable d =
* Flowable.range(1, 5)
* .subscribeWith(new DisposableSubscriber<Integer>() {
* @Override public void onStart() {
* request(1);
* }
* @Override public void onNext(Integer t) {
* if (t == 3) {
* cancel();
* }
* System.out.println(t);
* request(1);
* }
* @Override public void onError(Throwable t) {
* t.printStackTrace();
* }
* @Override public void onComplete() {
* System.out.println("Done!");
* }
* });
* // ...
* d.dispose();
* </code></pre>
* @param <T> the received value type.
*/
public abstract class DisposableSubscriber<T> implements FlowableSubscriber<T>, Disposable {
final AtomicReference<Subscription> upstream = new AtomicReference<Subscription>();
@Override
public final void onSubscribe(Subscription s) {
if (EndConsumerHelper.setOnce(this.upstream, s, getClass())) {
onStart();
}
}
Called once the single upstream Subscription is set via onSubscribe.
/**
* Called once the single upstream Subscription is set via onSubscribe.
*/
protected void onStart() {
upstream.get().request(Long.MAX_VALUE);
}
Requests the specified amount from the upstream if its Subscription is set via
onSubscribe already.
Note that calling this method before a Subscription is set via onSubscribe
leads to NullPointerException and meant to be called from inside onStart or
onNext.
Params: - n – the request amount, positive
/**
* Requests the specified amount from the upstream if its Subscription is set via
* onSubscribe already.
* <p>Note that calling this method before a Subscription is set via onSubscribe
* leads to NullPointerException and meant to be called from inside onStart or
* onNext.
* @param n the request amount, positive
*/
protected final void request(long n) {
upstream.get().request(n);
}
Cancels the Subscription set via onSubscribe or makes sure a
Subscription set asynchronously (later) is cancelled immediately.
This method is thread-safe and can be exposed as a public API.
/**
* Cancels the Subscription set via onSubscribe or makes sure a
* Subscription set asynchronously (later) is cancelled immediately.
* <p>This method is thread-safe and can be exposed as a public API.
*/
protected final void cancel() {
dispose();
}
@Override
public final boolean isDisposed() {
return upstream.get() == SubscriptionHelper.CANCELLED;
}
@Override
public final void dispose() {
SubscriptionHelper.cancel(upstream);
}
}