Package io.reactivex.rxjava3.subscribers

Class ResourceSubscriber<T>

  • Type Parameters:
    T - the value type
    All Implemented Interfaces:
    FlowableSubscriber<T>, Disposable, org.reactivestreams.Subscriber<T>
    public abstract class ResourceSubscriber<T>
extends java.lang.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 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, 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(), 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(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();

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private java.util.concurrent.atomic.AtomicLong missedRequested
      Remembers the request(n) counts until a subscription arrives.
      private ListCompositeDisposable resources
      The resource composite, can never be null.
      private java.util.concurrent.atomic.AtomicReference<org.reactivestreams.Subscription> upstream
      The active subscription.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      void add​(Disposable resource)
      Adds a resource to this ResourceSubscriber.
      void dispose()
      Cancels the subscription (if any) and disposes the resources associated with this ResourceSubscriber (if any).
      boolean isDisposed()
      Returns true if this ResourceSubscriber has been disposed/cancelled.
      protected void onStart()
      Called once the upstream sets a Subscription on this ResourceSubscriber.
      void onSubscribe​(org.reactivestreams.Subscription s)
      Implementors of this method should make sure everything that needs to be visible in Subscriber.onNext(Object) is established before calling Subscription.request(long).
      protected void request​(long n)
      Request the specified amount of elements from upstream.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

      • Methods inherited from interface org.reactivestreams.Subscriber

        onComplete, onError, onNext

    • Field Detail

      • upstream

        private final java.util.concurrent.atomic.AtomicReference<org.reactivestreams.Subscription> upstream
        The active subscription.

      • missedRequested

        private final java.util.concurrent.atomic.AtomicLong missedRequested
        Remembers the request(n) counts until a subscription arrives.

    • Constructor Detail

      • ResourceSubscriber

        public ResourceSubscriber()

    • Method Detail

      • add

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

      • onSubscribe

        public final void onSubscribe​(org.reactivestreams.Subscription s)
        Description copied from interface: FlowableSubscriber
        Implementors of this method should make sure everything that needs to be visible in Subscriber.onNext(Object) is established before calling 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 FlowableSubscriber<T>
        Specified by:
        onSubscribe in interface org.reactivestreams.Subscriber<T>

      • onStart

        protected void onStart()
        Called once the upstream sets a 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 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