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