Broadcaster.java
/*
* Copyright (c) 2012, 2019 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.jersey.server;
import java.io.IOException;
import java.util.Iterator;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.glassfish.jersey.server.internal.LocalizationMessages;
/**
* Used for broadcasting response chunks to multiple {@link ChunkedOutput} instances.
*
* @param <T> broadcast type.
* @author Pavel Bucek
* @author Martin Matula
*/
public class Broadcaster<T> implements BroadcasterListener<T> {
// We do not expect large amounts of broadcaster listeners additions/removals, but large amounts of traversals.
private final CopyOnWriteArrayList<BroadcasterListener<T>> listeners =
new CopyOnWriteArrayList<BroadcasterListener<T>>();
private final ConcurrentLinkedQueue<ChunkedOutput<T>> chunkedOutputs =
new ConcurrentLinkedQueue<ChunkedOutput<T>>();
/**
* Creates a new instance.
* If this constructor is called by a subclass, it assumes the the reason for the subclass to exist is to implement
* {@link #onClose(ChunkedOutput)} and {@link #onException(ChunkedOutput, Exception)} methods, so it adds
* the newly created instance as the listener. To avoid this, subclasses may call {@link #Broadcaster(Class)}
* passing their class as an argument.
*/
public Broadcaster() {
this(Broadcaster.class);
}
/**
* Can be used by subclasses to override the default functionality of adding self to the set of
* {@link BroadcasterListener listeners}. If creating a direct instance of a subclass passed in the parameter,
* the broadcaster will not register itself as a listener.
*
* @param subclass subclass of Broadcaster that should not be registered as a listener - if creating a direct instance
* of this subclass, this constructor will not register the new instance as a listener.
* @see #Broadcaster()
*/
protected Broadcaster(final Class<? extends Broadcaster> subclass) {
if (subclass != getClass()) {
listeners.add(this);
}
}
/**
* Register {@link ChunkedOutput} to this {@code Broadcaster} instance.
*
* @param chunkedOutput {@link ChunkedOutput} to register.
* @return {@code true} if the instance was successfully registered, {@code false} otherwise.
*/
public <OUT extends ChunkedOutput<T>> boolean add(final OUT chunkedOutput) {
return chunkedOutputs.offer(chunkedOutput);
}
/**
* Un-register {@link ChunkedOutput} from this {@code Broadcaster} instance.
*
* This method does not close the {@link ChunkedOutput} being unregistered.
*
* @param chunkedOutput {@link ChunkedOutput} instance to un-register from this broadcaster.
* @return {@code true} if the instance was unregistered, {@code false} otherwise.
*/
public <OUT extends ChunkedOutput<T>> boolean remove(final OUT chunkedOutput) {
return chunkedOutputs.remove(chunkedOutput);
}
/**
* Register {@link BroadcasterListener} for {@code Broadcaster} events listening.
* <p>
* This operation is potentially slow, especially if large number of listeners get registered in the broadcaster.
* The {@code Broadcaster} implementation is optimized to efficiently handle small amounts of
* concurrent listener registrations and removals and large amounts of registered listener notifications.
* </p>
*
* @param listener listener to be registered.
* @return {@code true} if registered, {@code false} otherwise.
*/
public boolean add(final BroadcasterListener<T> listener) {
return listeners.add(listener);
}
/**
* Un-register {@link BroadcasterListener}.
* <p>
* This operation is potentially slow, especially if large number of listeners get registered in the broadcaster.
* The {@code Broadcaster} implementation is optimized to efficiently handle small amounts of
* concurrent listener registrations and removals and large amounts of registered listener notifications.
* </p>
*
* @param listener listener to be unregistered.
* @return {@code true} if unregistered, {@code false} otherwise.
*/
public boolean remove(final BroadcasterListener<T> listener) {
return listeners.remove(listener);
}
/**
* Broadcast a chunk to all registered {@link ChunkedOutput} instances.
*
* @param chunk chunk to be sent.
*/
public void broadcast(final T chunk) {
forEachOutput(new Task<ChunkedOutput<T>>() {
@Override
public void run(final ChunkedOutput<T> cr) throws IOException {
cr.write(chunk);
}
});
}
/**
* Close all registered {@link ChunkedOutput} instances.
*/
public void closeAll() {
forEachOutput(new Task<ChunkedOutput<T>>() {
@Override
public void run(final ChunkedOutput<T> cr) throws IOException {
cr.close();
}
});
}
/**
* {@inheritDoc}
*
* Can be implemented by subclasses to handle the event of exception thrown from a particular {@link ChunkedOutput}
* instance when trying to write to it or close it.
*
* @param chunkedOutput instance that threw exception.
* @param exception exception that was thrown.
*/
@Override
public void onException(final ChunkedOutput<T> chunkedOutput, final Exception exception) {
}
/**
* {@inheritDoc}
*
* Can be implemented by subclasses to handle the event of {@link ChunkedOutput} being closed.
*
* @param chunkedOutput instance that was closed.
*/
@Override
public void onClose(final ChunkedOutput<T> chunkedOutput) {
}
private static interface Task<T> {
void run(T parameter) throws IOException;
}
private void forEachOutput(final Task<ChunkedOutput<T>> t) {
for (Iterator<ChunkedOutput<T>> iterator = chunkedOutputs.iterator(); iterator.hasNext(); ) {
ChunkedOutput<T> chunkedOutput = iterator.next();
if (!chunkedOutput.isClosed()) {
try {
t.run(chunkedOutput);
} catch (Exception e) {
fireOnException(chunkedOutput, e);
}
}
if (chunkedOutput.isClosed()) {
iterator.remove();
fireOnClose(chunkedOutput);
}
}
}
private void forEachListener(final Task<BroadcasterListener<T>> t) {
for (BroadcasterListener<T> listener : listeners) {
try {
t.run(listener);
} catch (Exception e) {
// log, but don't break
Logger.getLogger(Broadcaster.class.getName()).log(Level.WARNING,
LocalizationMessages.BROADCASTER_LISTENER_EXCEPTION(e.getClass().getSimpleName()), e);
}
}
}
private void fireOnException(final ChunkedOutput<T> chunkedOutput, final Exception exception) {
forEachListener(new Task<BroadcasterListener<T>>() {
@Override
public void run(BroadcasterListener<T> parameter) throws IOException {
parameter.onException(chunkedOutput, exception);
}
});
}
private void fireOnClose(final ChunkedOutput<T> chunkedOutput) {
forEachListener(new Task<BroadcasterListener<T>>() {
@Override
public void run(BroadcasterListener<T> parameter) throws IOException {
parameter.onClose(chunkedOutput);
}
});
}
}