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PublishSubject.java
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/**
* Copyright 2014 Netflix, Inc.
*
* 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 rx.subjects;
import java.util.*;
import rx.Observer;
import rx.annotations.Experimental;
import rx.exceptions.Exceptions;
import rx.functions.Action1;
import rx.internal.operators.NotificationLite;
import rx.subjects.SubjectSubscriptionManager.SubjectObserver;
/**
* Subject that, once an {@link Observer} has subscribed, emits all subsequently observed items to the
* subscriber.
* <p>
* <img width="640" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/S.PublishSubject.png" alt="">
* <p>
* Example usage:
* <p>
* <pre> {@code
PublishSubject<Object> subject = PublishSubject.create();
// observer1 will receive all onNext and onCompleted events
subject.subscribe(observer1);
subject.onNext("one");
subject.onNext("two");
// observer2 will only receive "three" and onCompleted
subject.subscribe(observer2);
subject.onNext("three");
subject.onCompleted();
} </pre>
*
* @param <T>
* the type of items observed and emitted by the Subject
*/
public final class PublishSubject<T> extends Subject<T, T> {
/**
* Creates and returns a new {@code PublishSubject}.
*
* @param <T> the value type
* @return the new {@code PublishSubject}
*/
public static <T> PublishSubject<T> create() {
final SubjectSubscriptionManager<T> state = new SubjectSubscriptionManager<T>();
state.onTerminated = new Action1<SubjectObserver<T>>() {
@Override
public void call(SubjectObserver<T> o) {
o.emitFirst(state.get(), state.nl);
}
};
return new PublishSubject<T>(state, state);
}
final SubjectSubscriptionManager<T> state;
private final NotificationLite<T> nl = NotificationLite.instance();
protected PublishSubject(OnSubscribe<T> onSubscribe, SubjectSubscriptionManager<T> state) {
super(onSubscribe);
this.state = state;
}
@Override
public void onCompleted() {
if (state.active) {
Object n = nl.completed();
for (SubjectObserver<T> bo : state.terminate(n)) {
bo.emitNext(n, state.nl);
}
}
}
@Override
public void onError(final Throwable e) {
if (state.active) {
Object n = nl.error(e);
List<Throwable> errors = null;
for (SubjectObserver<T> bo : state.terminate(n)) {
try {
bo.emitNext(n, state.nl);
} catch (Throwable e2) {
if (errors == null) {
errors = new ArrayList<Throwable>();
}
errors.add(e2);
}
}
Exceptions.throwIfAny(errors);
}
}
@Override
public void onNext(T v) {
for (SubjectObserver<T> bo : state.observers()) {
bo.onNext(v);
}
}
@Override
public boolean hasObservers() {
return state.observers().length > 0;
}
/**
* Check if the Subject has terminated with an exception.
* @return true if the subject has received a throwable through {@code onError}.
*/
@Experimental
@Override
public boolean hasThrowable() {
Object o = state.get();
return nl.isError(o);
}
/**
* Check if the Subject has terminated normally.
* @return true if the subject completed normally via {@code onCompleted}
*/
@Experimental
@Override
public boolean hasCompleted() {
Object o = state.get();
return o != null && !nl.isError(o);
}
/**
* Returns the Throwable that terminated the Subject.
* @return the Throwable that terminated the Subject or {@code null} if the
* subject hasn't terminated yet or it terminated normally.
*/
@Experimental
@Override
public Throwable getThrowable() {
Object o = state.get();
if (nl.isError(o)) {
return nl.getError(o);
}
return null;
}
/**
* {@inheritDoc}
* @deprecated this method is scheduled to be removed in the next release
*/
@Override
@Experimental
@Deprecated
public boolean hasValue() {
return false;
}
/**
* {@inheritDoc}
* @deprecated this method is scheduled to be removed in the next release
*/
@Override
@Experimental
@Deprecated
public T getValue() {
return null;
}
/**
* {@inheritDoc}
* @deprecated this method is scheduled to be removed in the next release
*/
@Override
@Experimental
@Deprecated
public Object[] getValues() {
return new Object[0];
}
/**
* {@inheritDoc}
* @deprecated this method is scheduled to be removed in the next release
*/
@Override
@Experimental
@Deprecated
public T[] getValues(T[] a) {
if (a.length > 0) {
a[0] = null;
}
return a;
}
}