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 017package com.google.common.eventbus; 018 019import static com.google.common.base.Preconditions.checkNotNull; 020 021import com.google.common.annotations.Beta; 022import com.google.common.base.MoreObjects; 023 024/** 025 * Wraps an event that was posted, but which had no subscribers and thus could 026 * not be delivered. 027 * 028 * <p>Registering a DeadEvent subscriber is useful for debugging or logging, as 029 * it can detect misconfigurations in a system's event distribution. 030 * 031 * @author Cliff Biffle 032 * @since 10.0 033 */ 034@Beta 035public class DeadEvent { 036 037 private final Object source; 038 private final Object event; 039 040 /** 041 * Creates a new DeadEvent. 042 * 043 * @param source object broadcasting the DeadEvent (generally the 044 * {@link EventBus}). 045 * @param event the event that could not be delivered. 046 */ 047 public DeadEvent(Object source, Object event) { 048 this.source = checkNotNull(source); 049 this.event = checkNotNull(event); 050 } 051 052 /** 053 * Returns the object that originated this event (<em>not</em> the object that 054 * originated the wrapped event). This is generally an {@link EventBus}. 055 * 056 * @return the source of this event. 057 */ 058 public Object getSource() { 059 return source; 060 } 061 062 /** 063 * Returns the wrapped, 'dead' event, which the system was unable to deliver 064 * to any registered subscriber. 065 * 066 * @return the 'dead' event that could not be delivered. 067 */ 068 public Object getEvent() { 069 return event; 070 } 071 072 @Override 073 public String toString() { 074 return MoreObjects.toStringHelper(this) 075 .add("source", source) 076 .add("event", event) 077 .toString(); 078 } 079}