com.ovea.tajin.framework.async.guava.AsyncEventBus.groovy Maven / Gradle / Ivy

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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 com.ovea.tajin.framework.async.guava

import com.google.common.annotations.Beta

import java.util.concurrent.ConcurrentLinkedQueue
import java.util.concurrent.Executor

import static com.google.common.base.Preconditions.checkNotNull

/**
 * 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.
     */
    public AsyncEventBus(Executor executor) {
        this.executor = checkNotNull(executor);
    }

    @Override
    void enqueueEvent(Object event, EventHandler handler) {
        eventsToDispatch.offer(new EventWithHandler(event, handler));
    }

    /**
     * Dispatch {@code events} in the order they were posted, regardless of
     * the posting thread.
     */
    @SuppressWarnings("deprecation") // only deprecated for external subclasses
    @Override
    void dispatchQueuedEvents() {
        while (true) {
            EventWithHandler eventWithHandler = eventsToDispatch.poll();
            if (eventWithHandler == null) {
                break;
            }

            dispatch(eventWithHandler.event, eventWithHandler.handler);
        }
    }

    /**
     * Calls the {@link #executor} to dispatch {@code event} to {@code handler}.
     */
    @Override
    void dispatch(final Object event, final EventHandler handler) {
        checkNotNull(event);
        checkNotNull(handler);
        executor.execute(
            new Runnable() {
                @Override
                public void run() {
                    handler.handleEvent(event);
                }
            });
    }
}