https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
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;

import io.reactivex.annotations.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Cancellable;


Abstraction over a Reactive Streams Subscriber that allows associating a resource with it and exposes the current number of downstream requested amount. 
 The Emitter.onNext(Object), Emitter.onError(Throwable), tryOnError(Throwable) and Emitter.onComplete() methods should be called in a sequential manner, just like the Subscriber's methods. Use the FlowableEmitter the serialize() method returns instead of the original FlowableEmitter instance provided by the generator routine if you want to ensure this. The other methods are thread-safe. 
 The emitter allows the registration of a single resource, in the form of a Disposable or Cancellable via setDisposable(Disposable) or setCancellable(Cancellable) respectively. The emitter implementations will dispose/cancel this instance when the downstream cancels the flow or after the event generator logic calls Emitter.onError(Throwable), Emitter.onComplete() or when tryOnError(Throwable) succeeds. 
 Only one Disposable or Cancellable object can be associated with the emitter at a time. Calling either set method will dispose/cancel any previous object. If there is a need for handling multiple resources, one can create a CompositeDisposable and associate that with the emitter instead. 
 The Cancellable is logically equivalent to Disposable but allows using cleanup logic that can throw a checked exception (such as many close() methods on Java IO components). Since the release of resources happens after the terminal events have been delivered or the sequence gets cancelled, exceptions throw within Cancellable are routed to the global error handler via RxJavaPlugins.onError(Throwable). 
Type parameters:
  • <T> – the value type to emit
/**
 * Abstraction over a Reactive Streams {@link org.reactivestreams.Subscriber} that allows associating
 * a resource with it and exposes the current number of downstream
 * requested amount.
 * <p>
 * The {@link #onNext(Object)}, {@link #onError(Throwable)}, {@link #tryOnError(Throwable)}
 * and {@link #onComplete()} methods should be called in a sequential manner, just like
 * the {@link org.reactivestreams.Subscriber Subscriber}'s methods.
 * Use the {@code FlowableEmitter} the {@link #serialize()} method returns instead of the original
 * {@code FlowableEmitter} instance provided by the generator routine if you want to ensure this.
 * The other methods are thread-safe.
 * <p>
 * The emitter allows the registration of a single resource, in the form of a {@link Disposable}
 * or {@link Cancellable} via {@link #setDisposable(Disposable)} or {@link #setCancellable(Cancellable)}
 * respectively. The emitter implementations will dispose/cancel this instance when the
 * downstream cancels the flow or after the event generator logic calls {@link #onError(Throwable)},
 * {@link #onComplete()} or when {@link #tryOnError(Throwable)} succeeds.
 * <p>
 * Only one {@code Disposable} or {@code Cancellable} object can be associated with the emitter at
 * a time. Calling either {@code set} method will dispose/cancel any previous object. If there
 * is a need for handling multiple resources, one can create a {@link io.reactivex.disposables.CompositeDisposable}
 * and associate that with the emitter instead.
 * <p>
 * The {@link Cancellable} is logically equivalent to {@code Disposable} but allows using cleanup logic that can
 * throw a checked exception (such as many {@code close()} methods on Java IO components). Since
 * the release of resources happens after the terminal events have been delivered or the sequence gets
 * cancelled, exceptions throw within {@code Cancellable} are routed to the global error handler via
 * {@link io.reactivex.plugins.RxJavaPlugins#onError(Throwable)}.
 *
 * @param <T> the value type to emit
 */
public interface FlowableEmitter<T> extends Emitter<T> {

    
Sets a Disposable on this emitter; any previous Disposable or Cancellable will be disposed/cancelled. 
Params:
  • d – the disposable, null is allowed
/**
     * Sets a Disposable on this emitter; any previous {@link Disposable}
     * or {@link Cancellable} will be disposed/cancelled.
     * @param d the disposable, null is allowed
     */
    void setDisposable(@Nullable Disposable d);

    
Sets a Cancellable on this emitter; any previous Disposable or Cancellable will be disposed/cancelled. 
Params:
  • c – the cancellable resource, null is allowed
/**
     * Sets a Cancellable on this emitter; any previous {@link Disposable}
     * or {@link Cancellable} will be disposed/cancelled.
     * @param c the cancellable resource, null is allowed
     */
    void setCancellable(@Nullable Cancellable c);

    
The current outstanding request amount.

This method is thread-safe.

Returns:the current outstanding request amount
/**
     * The current outstanding request amount.
     * <p>This method is thread-safe.
     * @return the current outstanding request amount
     */
    long requested();

    
Returns true if the downstream cancelled the sequence or the emitter was terminated via Emitter.onError(Throwable), Emitter.onComplete or a successful tryOnError(Throwable). 
This method is thread-safe.

Returns:true if the downstream cancelled the sequence or the emitter was terminated
/**
     * Returns true if the downstream cancelled the sequence or the
     * emitter was terminated via {@link #onError(Throwable)}, {@link #onComplete} or a
     * successful {@link #tryOnError(Throwable)}.
     * <p>This method is thread-safe.
     * @return true if the downstream cancelled the sequence or the emitter was terminated
     */
    boolean isCancelled();

    
Ensures that calls to onNext, onError and onComplete are properly serialized.

Returns:the serialized FlowableEmitter
/**
     * Ensures that calls to onNext, onError and onComplete are properly serialized.
     * @return the serialized FlowableEmitter
     */
    @NonNull
    FlowableEmitter<T> serialize();

    
Attempts to emit the specified Throwable error if the downstream hasn't cancelled the sequence or is otherwise terminated, returning false if the emission is not allowed to happen due to lifecycle restrictions. 
 Unlike Emitter.onError(Throwable), the RxJavaPlugins.onError is not called if the error could not be delivered. 
History: 2.1.1 - experimental

Params:
  • t – the throwable error to signal if possible
Returns:true if successful, false if the downstream is not able to accept further
events
Since:2.2
/**
     * Attempts to emit the specified {@code Throwable} error if the downstream
     * hasn't cancelled the sequence or is otherwise terminated, returning false
     * if the emission is not allowed to happen due to lifecycle restrictions.
     * <p>
     * Unlike {@link #onError(Throwable)}, the {@code RxJavaPlugins.onError} is not called
     * if the error could not be delivered.
     * <p>History: 2.1.1 - experimental
     * @param t the throwable error to signal if possible
     * @return true if successful, false if the downstream is not able to accept further
     * events
     * @since 2.2
     */
    boolean tryOnError(@NonNull Throwable t);
}