Class ResourceSubscriber<T>

java.lang.Object
io.reactivex.rxjava4.subscribers.ResourceSubscriber<T>
Type Parameters:
T - the value type
All Implemented Interfaces:
FlowableSubscriber<T>, Disposable, Flow.Subscriber<T>
public abstract class ResourceSubscriber<T> extends Object implements FlowableSubscriber<T>, Disposable
An abstract Subscriber that allows asynchronous cancellation of its subscription and associated resources.

All pre-implemented final methods are thread-safe.

To release the associated resources, one has to call dispose() in onError() and onComplete() explicitly.

Use add(Disposable) to associate resources (as Disposables) with this ResourceSubscriber that will be cleaned up when dispose() is called. Removing previously associated resources is not possible but one can create a CompositeDisposable, associate it with this ResourceSubscriber and then add/remove resources to/from the CompositeDisposable freely.

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 dispose() 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 Flow.Subscriber.onNext(Object). Make sure all initialization happens before the call to request() in onStart(). Calling request(long) inside Flow.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, ResourceSubscriber 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(), Flow.Subscriber.onNext(Object), Flow.Subscriber.onError(Throwable) and Flow.Subscriber.onComplete() are not allowed to throw any unchecked exceptions. If for some reason this can't be avoided, use Flowable.safeSubscribe(org.reactivestreams.Subscriber) instead of the standard subscribe() method.

Example

Disposable d =
    Flowable.range(1, 5)
    .subscribeWith(new ResourceSubscriber<Integer>() {
        @Override public void onStart() {
            add(Schedulers.single()
                .scheduleDirect(() -> System.out.println("Time!"),
                    2, TimeUnit.SECONDS));
            request(1);
        }
        @Override public void onNext(Integer t) {
            if (t == 3) {
                dispose();
            }
            System.out.println(t);
            request(1);
        }
        @Override public void onError(Throwable t) {
            t.printStackTrace();
            dispose();
        }
        @Override public void onComplete() {
            System.out.println("Done!");
            dispose();
        }
    });
// ...
d.dispose();

  • Constructor Details

    • ResourceSubscriber

      public ResourceSubscriber()

  • Method Details

    • add

      public final void add(Disposable resource)
      Adds a resource to this ResourceSubscriber.
      Parameters:
      resource - the resource to add
      Throws:
      NullPointerException - if resource is null

    • onSubscribe

      public final void onSubscribe(Flow.Subscription s)
      Description copied from interface: FlowableSubscriber
      Implementors of this method should make sure everything that needs to be visible in Flow.Subscriber.onNext(Object) is established before calling Flow.Subscription.request(long). In practice this means no initialization should happen after the request() call and additional behavior is thread safe in respect to onNext.
      Specified by:
      onSubscribe in interface Flow.Subscriber<T>
      Specified by:
      onSubscribe in interface FlowableSubscriber<T>

    • onStart

      protected void onStart()
      Called once the upstream sets a Flow.Subscription on this ResourceSubscriber.

      You can perform initialization at this moment. The default implementation requests Long.MAX_VALUE from upstream.

    • request

      protected final void request(long n)
      Request the specified amount of elements from upstream.

      This method can be called before the upstream calls onSubscribe(Subscription). When the subscription happens, all missed requests are requested.

      Parameters:
      n - the request amount, must be positive

    • dispose

      public final void dispose()
      Cancels the subscription (if any) and disposes the resources associated with this ResourceSubscriber (if any).

      This method can be called before the upstream calls onSubscribe(Subscription) at which case the Flow.Subscription will be immediately cancelled.

      Specified by:
      dispose in interface Disposable

    • isDisposed

      public final boolean isDisposed()
      Returns true if this ResourceSubscriber has been disposed/cancelled.
      Specified by:
      isDisposed in interface Disposable
      Returns:
      true if this ResourceSubscriber has been disposed/cancelled