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001    /*
002     * Copyright (C) 2007 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.eventbus;
018    
019    import com.google.common.annotations.Beta;
020    
021    /**
022     * Wraps an event that was posted, but which had no subscribers and thus could
023     * not be delivered.
024     *
025     * <p>Subscribing a DeadEvent handler is useful for debugging or logging, as it
026     * can detect misconfigurations in a system's event distribution.
027     *
028     * @author Cliff Biffle
029     * @since 10.0
030     */
031    @Beta
032    public class DeadEvent {
033    
034      private final Object source;
035      private final Object event;
036    
037      /**
038       * Creates a new DeadEvent.
039       *
040       * @param source  object broadcasting the DeadEvent (generally the
041       *                {@link EventBus}).
042       * @param event   the event that could not be delivered.
043       */
044      public DeadEvent(Object source, Object event) {
045        this.source = source;
046        this.event = event;
047      }
048    
049      /**
050       * Returns the object that originated this event (<em>not</em> the object that
051       * originated the wrapped event).  This is generally an {@link EventBus}.
052       *
053       * @return the source of this event.
054       */
055      public Object getSource() {
056        return source;
057      }
058    
059      /**
060       * Returns the wrapped, 'dead' event, which the system was unable to deliver
061       * to any registered handler.
062       *
063       * @return the 'dead' event that could not be delivered.
064       */
065      public Object getEvent() {
066        return event;
067      }
068    
069    }