com.google.common.eventbus.DeadEvent.java Source code

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Here is the source code for com.google.common.eventbus.DeadEvent.java

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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.google.common.eventbus;

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

import com.google.common.annotations.Beta;
import com.google.common.base.MoreObjects;

/**
 * Wraps an event that was posted, but which had no subscribers and thus could
 * not be delivered.
 *
 * <p>Registering a DeadEvent subscriber is useful for debugging or logging, as
 * it can detect misconfigurations in a system's event distribution.
 *
 * @author Cliff Biffle
 * @since 10.0
 */
@Beta
public class DeadEvent {

    private final Object source;
    private final Object event;

    /**
     * Creates a new DeadEvent.
     *
     * @param source  object broadcasting the DeadEvent (generally the
     *                {@link EventBus}).
     * @param event   the event that could not be delivered.
     */
    public DeadEvent(Object source, Object event) {
        this.source = checkNotNull(source);
        this.event = checkNotNull(event);
    }

    /**
     * Returns the object that originated this event (<em>not</em> the object that
     * originated the wrapped event).  This is generally an {@link EventBus}.
     *
     * @return the source of this event.
     */
    public Object getSource() {
        return source;
    }

    /**
     * Returns the wrapped, 'dead' event, which the system was unable to deliver
     * to any registered subscriber.
     *
     * @return the 'dead' event that could not be delivered.
     */
    public Object getEvent() {
        return event;
    }

    @Override
    public String toString() {
        return MoreObjects.toStringHelper(this).add("source", source).add("event", event).toString();
    }
}