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 org.reactivestreams.Subscription;
import io.reactivex.FlowableSubscriber;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.internal.util.EndConsumerHelper;
Abstract base implementation of a Subscriber with support for requesting via request(long), cancelling via via cancel() (both synchronously) and calls onStart() when the subscription happens. 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.
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.
Use the protected cancel() to cancel the sequence from within an onNext implementation.
Like all other consumers, DefaultSubscriber 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.
Type parameters: - <T> – the value type
Example
Flowable.range(1, 5)
.subscribe(new DefaultSubscriber<Integer>() {
@Override public void onStart() {
System.out.println("Start!");
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!");
}
});
/**
* Abstract base implementation of a {@link org.reactivestreams.Subscriber Subscriber} with
* support for requesting via {@link #request(long)}, cancelling via
* via {@link #cancel()} (both synchronously) and calls {@link #onStart()}
* when the subscription happens.
*
* <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.
*
* <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>Use the protected {@link #cancel()} to cancel the sequence from within an
* {@code onNext} implementation.
*
* <p>Like all other consumers, {@code DefaultSubscriber} 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.
* @param <T> the value type
*
* <p>Example<pre><code>
* Flowable.range(1, 5)
* .subscribe(new DefaultSubscriber<Integer>() {
* @Override public void onStart() {
* System.out.println("Start!");
* 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!");
* }
* });
* </code></pre>
*/
public abstract class DefaultSubscriber<T> implements FlowableSubscriber<T> {
Subscription upstream;
@Override
public final void onSubscribe(Subscription s) {
if (EndConsumerHelper.validate(this.upstream, s, getClass())) {
this.upstream = s;
onStart();
}
}
Requests from the upstream Subscription.
Params: - n – the request amount, positive
/**
* Requests from the upstream Subscription.
* @param n the request amount, positive
*/
protected final void request(long n) {
Subscription s = this.upstream;
if (s != null) {
s.request(n);
}
}
Cancels the upstream's Subscription.
/**
* Cancels the upstream's Subscription.
*/
protected final void cancel() {
Subscription s = this.upstream;
this.upstream = SubscriptionHelper.CANCELLED;
s.cancel();
}
Called once the subscription has been set on this observer; override this
to perform initialization or issue an initial request.
The default implementation requests Long.MAX_VALUE.
/**
* Called once the subscription has been set on this observer; override this
* to perform initialization or issue an initial request.
* <p>
* The default implementation requests {@link Long#MAX_VALUE}.
*/
protected void onStart() {
request(Long.MAX_VALUE);
}
}