ConnectableObservable.java
/*
* 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.rxjava3.observables;
import java.util.Objects;
import java.util.concurrent.TimeUnit;
import io.reactivex.rxjava3.annotations.*;
import io.reactivex.rxjava3.core.*;
import io.reactivex.rxjava3.disposables.Disposable;
import io.reactivex.rxjava3.functions.Consumer;
import io.reactivex.rxjava3.internal.functions.*;
import io.reactivex.rxjava3.internal.operators.observable.*;
import io.reactivex.rxjava3.internal.util.ConnectConsumer;
import io.reactivex.rxjava3.plugins.RxJavaPlugins;
import io.reactivex.rxjava3.schedulers.Schedulers;
/**
* A {@code ConnectableObservable} resembles an ordinary {@link Observable}, except that it does not begin
* emitting items when it is subscribed to, but only when its {@link #connect} method is called. In this way you
* can wait for all intended {@link Observer}s to {@link Observable#subscribe} to the {@code Observable}
* before the {@code Observable} begins emitting items.
* <p>
* <img width="640" height="510" src="https://github.com/ReactiveX/RxJava/wiki/images/rx-operators/publishConnect.v3.png" alt="">
* <p>
* When the upstream terminates, the {@code ConnectableObservable} remains in this terminated state and,
* depending on the actual underlying implementation, relays cached events to late {@code Observer}s.
* In order to reuse and restart this {@code ConnectableObservable}, the {@link #reset()} method has to be called.
* When called, this {@code ConnectableObservable} will appear as fresh, unconnected source to new {@code Observer}s.
* Disposing the connection will reset the {@code ConnectableObservable} to its fresh state and there is no need to call
* {@link #reset()} in this case.
* <p>
* Note that although {@link #connect()} and {@link #reset()} are safe to call from multiple threads, it is recommended
* a dedicated thread or business logic manages the connection or resetting of a {@code ConnectableObservable} so that
* there is no unwanted signal loss due to early {@code connect()} or {@code reset()} calls while {@code Observer}s are
* still being subscribed to to this {@code ConnectableObservable} to receive signals from the get go.
*
* @see <a href="https://github.com/ReactiveX/RxJava/wiki/Connectable-Observable-Operators">RxJava Wiki: Connectable Observable Operators</a>
* @param <T>
* the type of items emitted by the {@code ConnectableObservable}
*/
public abstract class ConnectableObservable<T> extends Observable<T> {
/**
* Instructs the {@code ConnectableObservable} to begin emitting the items from its underlying
* {@link Observable} to its {@link Observer}s.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>The behavior is determined by the implementor of this abstract class.</dd>
* </dl>
*
* @param connection
* the action that receives the connection subscription before the subscription to source happens
* allowing the caller to synchronously disconnect a synchronous source
* @throws NullPointerException if {@code connection} is {@code null}
* @see <a href="http://reactivex.io/documentation/operators/connect.html">ReactiveX documentation: Connect</a>
*/
@SchedulerSupport(SchedulerSupport.NONE)
public abstract void connect(@NonNull Consumer<? super Disposable> connection);
/**
* Resets this {@code ConnectableObservable} into its fresh state if it has terminated
* or has been disposed.
* <p>
* Calling this method on a fresh or active {@code ConnectableObservable} has no effect.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>The behavior is determined by the implementor of this abstract class.</dd>
* </dl>
* @since 3.0.0
*/
@SchedulerSupport(SchedulerSupport.NONE)
public abstract void reset();
/**
* Instructs the {@code ConnectableObservable} to begin emitting the items from its underlying
* {@link Observable} to its {@link Observer}s.
* <p>
* To disconnect from a synchronous source, use the {@link #connect(Consumer)} method.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>The behavior is determined by the implementor of this abstract class.</dd>
* </dl>
*
* @return the {@link Disposable} representing the connection
* @see <a href="http://reactivex.io/documentation/operators/connect.html">ReactiveX documentation: Connect</a>
*/
@NonNull
@SchedulerSupport(SchedulerSupport.NONE)
public final Disposable connect() {
ConnectConsumer cc = new ConnectConsumer();
connect(cc);
return cc.disposable;
}
/**
* Returns an {@link Observable} that stays connected to this {@code ConnectableObservable} as long as there
* is at least one subscription to this {@code ConnectableObservable}.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload does not operate on any particular {@link Scheduler}.</dd>
* </dl>
* @return a new {@code Observable} instance
* @see <a href="http://reactivex.io/documentation/operators/refcount.html">ReactiveX documentation: RefCount</a>
* @see #refCount(int)
* @see #refCount(long, TimeUnit)
* @see #refCount(int, long, TimeUnit)
*/
@NonNull
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public Observable<T> refCount() {
return RxJavaPlugins.onAssembly(new ObservableRefCount<>(this));
}
/**
* Connects to the upstream {@code ConnectableObservable} if the number of subscribed
* observers reaches the specified count and disconnect if all {@link Observer}s have unsubscribed.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload does not operate on any particular {@link Scheduler}.</dd>
* </dl>
* <p>History: 2.1.14 - experimental
* @param observerCount the number of {@code Observer}s required to connect to the upstream
* @return the new {@link Observable} instance
* @throws IllegalArgumentException if {@code observerCount} is non-positive
* @since 2.2
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
@NonNull
public final Observable<T> refCount(int observerCount) {
return refCount(observerCount, 0, TimeUnit.NANOSECONDS, Schedulers.trampoline());
}
/**
* Connects to the upstream {@code ConnectableObservable} if the number of subscribed
* observers reaches 1 and disconnect after the specified
* timeout if all {@link Observer}s have unsubscribed.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload operates on the {@code computation} {@link Scheduler}.</dd>
* </dl>
* <p>History: 2.1.14 - experimental
* @param timeout the time to wait before disconnecting after all {@code Observer}s unsubscribed
* @param unit the time unit of the timeout
* @return the new {@link Observable} instance
* @throws NullPointerException if {@code unit} is {@code null}
* @see #refCount(long, TimeUnit, Scheduler)
* @since 2.2
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.COMPUTATION)
@NonNull
public final Observable<T> refCount(long timeout, @NonNull TimeUnit unit) {
return refCount(1, timeout, unit, Schedulers.computation());
}
/**
* Connects to the upstream {@code ConnectableObservable} if the number of subscribed
* observers reaches 1 and disconnect after the specified
* timeout if all {@link Observer}s have unsubscribed.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload operates on the specified {@link Scheduler}.</dd>
* </dl>
* <p>History: 2.1.14 - experimental
* @param timeout the time to wait before disconnecting after all {@code Observer}s unsubscribed
* @param unit the time unit of the timeout
* @param scheduler the target scheduler to wait on before disconnecting
* @return the new {@link Observable} instance
* @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null}
* @since 2.2
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
@NonNull
public final Observable<T> refCount(long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
return refCount(1, timeout, unit, scheduler);
}
/**
* Connects to the upstream {@code ConnectableObservable} if the number of subscribed
* observers reaches the specified count and disconnect after the specified
* timeout if all {@link Observer}s have unsubscribed.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload operates on the {@code computation} {@link Scheduler}.</dd>
* </dl>
* <p>History: 2.1.14 - experimental
* @param observerCount the number of {@code Observer}s required to connect to the upstream
* @param timeout the time to wait before disconnecting after all {@code Observer}s unsubscribed
* @param unit the time unit of the timeout
* @return the new {@link Observable} instance
* @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null}
* @throws IllegalArgumentException if {@code observerCount} is non-positive
* @see #refCount(int, long, TimeUnit, Scheduler)
* @since 2.2
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.COMPUTATION)
@NonNull
public final Observable<T> refCount(int observerCount, long timeout, @NonNull TimeUnit unit) {
return refCount(observerCount, timeout, unit, Schedulers.computation());
}
/**
* Connects to the upstream {@code ConnectableObservable} if the number of subscribed
* observers reaches the specified count and disconnect after the specified
* timeout if all {@link Observer}s have unsubscribed.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>This {@code refCount} overload operates on the specified {@link Scheduler}.</dd>
* </dl>
* <p>History: 2.1.14 - experimental
* @param observerCount the number of {@code Observer}s required to connect to the upstream
* @param timeout the time to wait before disconnecting after all {@code Observer}s unsubscribed
* @param unit the time unit of the timeout
* @param scheduler the target scheduler to wait on before disconnecting
* @return the new {@link Observable} instance
* @throws NullPointerException if {@code unit} or {@code scheduler} is {@code null}
* @throws IllegalArgumentException if {@code observerCount} is non-positive
* @since 2.2
*/
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.CUSTOM)
@NonNull
public final Observable<T> refCount(int observerCount, long timeout, @NonNull TimeUnit unit, @NonNull Scheduler scheduler) {
ObjectHelper.verifyPositive(observerCount, "observerCount");
Objects.requireNonNull(unit, "unit is null");
Objects.requireNonNull(scheduler, "scheduler is null");
return RxJavaPlugins.onAssembly(new ObservableRefCount<>(this, observerCount, timeout, unit, scheduler));
}
/**
* Returns an {@link Observable} that automatically connects (at most once) to this {@code ConnectableObservable}
* when the first {@link Observer} subscribes.
* <p>
* <img width="640" height="348" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/autoConnect.o.png" alt="">
* <p>
* The connection happens after the first subscription and happens at most once
* during the lifetime of the returned {@code Observable}. If this {@code ConnectableObservable}
* terminates, the connection is never renewed, no matter how {@code Observer}s come
* and go. Use {@link #refCount()} to renew a connection or dispose an active
* connection when all {@code Observer}s have disposed their {@link Disposable}s.
* <p>
* This overload does not allow disconnecting the connection established via
* {@link #connect(Consumer)}. Use the {@link #autoConnect(int, Consumer)} overload
* to gain access to the {@code Disposable} representing the only connection.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code autoConnect} overload does not operate on any particular {@link Scheduler}.</dd>
* </dl>
*
* @return a new {@code Observable} instance that automatically connects to this {@code ConnectableObservable}
* when the first {@code Observer} subscribes
*/
@NonNull
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public Observable<T> autoConnect() {
return autoConnect(1);
}
/**
* Returns an {@link Observable} that automatically connects (at most once) to this {@code ConnectableObservable}
* when the specified number of {@link Observer}s subscribe to it.
* <p>
* <img width="640" height="348" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/autoConnect.o.png" alt="">
* <p>
* The connection happens after the given number of subscriptions and happens at most once
* during the lifetime of the returned {@code Observable}. If this {@code ConnectableObservable}
* terminates, the connection is never renewed, no matter how {@code Observer}s come
* and go. Use {@link #refCount()} to renew a connection or dispose an active
* connection when all {@code Observer}s have disposed their {@link Disposable}s.
* <p>
* This overload does not allow disconnecting the connection established via
* {@link #connect(Consumer)}. Use the {@link #autoConnect(int, Consumer)} overload
* to gain access to the {@code Disposable} representing the only connection.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code autoConnect} overload does not operate on any particular {@link Scheduler}.</dd>
* </dl>
*
* @param numberOfObservers the number of subscribers to await before calling connect
* on the {@code ConnectableObservable}. A non-positive value indicates
* an immediate connection.
* @return a new {@code Observable} instance that automatically connects to this {@code ConnectableObservable}
* when the specified number of {@code Observer}s subscribe to it
*/
@NonNull
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public Observable<T> autoConnect(int numberOfObservers) {
return autoConnect(numberOfObservers, Functions.emptyConsumer());
}
/**
* Returns an {@link Observable} that automatically connects (at most once) to this {@code ConnectableObservable}
* when the specified number of {@link Observer}s subscribe to it and calls the
* specified callback with the {@link Disposable} associated with the established connection.
* <p>
* <img width="640" height="348" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/autoConnect.o.png" alt="">
* <p>
* The connection happens after the given number of subscriptions and happens at most once
* during the lifetime of the returned {@code Observable}. If this {@code ConnectableObservable}
* terminates, the connection is never renewed, no matter how {@code Observer}s come
* and go. Use {@link #refCount()} to renew a connection or dispose an active
* connection when all {@code Observer}s have disposed their {@code Disposable}s.
* <dl>
* <dt><b>Scheduler:</b></dt>
* <dd>{@code autoConnect} overload does not operate on any particular {@link Scheduler}.</dd>
* </dl>
*
* @param numberOfObservers the number of subscribers to await before calling connect
* on the {@code ConnectableObservable}. A non-positive value indicates
* an immediate connection.
* @param connection the callback {@link Consumer} that will receive the {@code Disposable} representing the
* established connection
* @return a new {@code Observable} instance that automatically connects to this {@code ConnectableObservable}
* when the specified number of {@code Observer}s subscribe to it and calls the
* specified callback with the {@code Disposable} associated with the established connection
* @throws NullPointerException if {@code connection} is {@code null}
*/
@NonNull
@CheckReturnValue
@SchedulerSupport(SchedulerSupport.NONE)
public Observable<T> autoConnect(int numberOfObservers, @NonNull Consumer<? super Disposable> connection) {
Objects.requireNonNull(connection, "connection is null");
if (numberOfObservers <= 0) {
this.connect(connection);
return RxJavaPlugins.onAssembly(this);
}
return RxJavaPlugins.onAssembly(new ObservableAutoConnect<>(this, numberOfObservers, connection));
}
}