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/*
* Copyright (C) 2007 The Guava Authors
*
* 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 org.glowroot.shaded.google.common.eventbus;
import static org.glowroot.shaded.google.common.base.Preconditions.checkNotNull;
import org.glowroot.shaded.google.common.annotations.Beta;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Executor;
/**
* An {@link EventBus} that takes the Executor of your choice and uses it to
* dispatch events, allowing dispatch to occur asynchronously.
*
* @author Cliff Biffle
* @since 10.0
*/
@Beta
public class AsyncEventBus extends EventBus {
private final Executor executor;
/** the queue of events is shared across all threads */
private final ConcurrentLinkedQueue eventsToDispatch =
new ConcurrentLinkedQueue();
/**
* Creates a new AsyncEventBus that will use {@code executor} to dispatch
* events. Assigns {@code identifier} as the bus's name for logging purposes.
*
* @param identifier short name for the bus, for logging purposes.
* @param executor Executor to use to dispatch events. It is the caller's
* responsibility to shut down the executor after the last event has
* been posted to this event bus.
*/
public AsyncEventBus(String identifier, Executor executor) {
super(identifier);
this.executor = checkNotNull(executor);
}
/**
* Creates a new AsyncEventBus that will use {@code executor} to dispatch
* events.
*
* @param executor Executor to use to dispatch events. It is the caller's
* responsibility to shut down the executor after the last event has
* been posted to this event bus.
* @param subscriberExceptionHandler Handler used to handle exceptions thrown from subscribers.
* See {@link SubscriberExceptionHandler} for more information.
* @since 16.0
*/
public AsyncEventBus(Executor executor, SubscriberExceptionHandler subscriberExceptionHandler) {
super(subscriberExceptionHandler);
this.executor = checkNotNull(executor);
}
/**
* Creates a new AsyncEventBus that will use {@code executor} to dispatch
* events.
*
* @param executor Executor to use to dispatch events. It is the caller's
* responsibility to shut down the executor after the last event has
* been posted to this event bus.
*/
public AsyncEventBus(Executor executor) {
super("default");
this.executor = checkNotNull(executor);
}
@Override
void enqueueEvent(Object event, EventSubscriber subscriber) {
eventsToDispatch.offer(new EventWithSubscriber(event, subscriber));
}
/**
* Dispatch {@code events} in the order they were posted, regardless of
* the posting thread.
*/
@SuppressWarnings("deprecation") // only deprecated for external subclasses
@Override
protected void dispatchQueuedEvents() {
while (true) {
EventWithSubscriber eventWithSubscriber = eventsToDispatch.poll();
if (eventWithSubscriber == null) {
break;
}
dispatch(eventWithSubscriber.event, eventWithSubscriber.subscriber);
}
}
/**
* Calls the {@link #executor} to dispatch {@code event} to {@code subscriber}.
*/
@Override
void dispatch(final Object event, final EventSubscriber subscriber) {
checkNotNull(event);
checkNotNull(subscriber);
executor.execute(
new Runnable() {
@Override
public void run() {
AsyncEventBus.super.dispatch(event, subscriber);
}
});
}
}