001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.commons.configuration2.event; 018 019/** 020 * <p> 021 * A data class holding information about an event listener registration. 022 * </p> 023 * <p> 024 * An instance of this class stores all information required to determine 025 * whether a specific event listener is to be invoked for a given event. The 026 * class is used internally by {@link EventListenerList}, but is also useful in 027 * general when information about event listeners is to be stored. 028 * </p> 029 * <p> 030 * Implementation note: Instances of this class are immutable and can safely be 031 * shared between multiple threads or components. 032 * </p> 033 * 034 * @since 2.0 035 * @param <T> the type of events processed by the listener 036 */ 037public final class EventListenerRegistrationData<T extends Event> 038{ 039 /** Constant for the factor used by the calculation of the hash code. */ 040 private static final int HASH_FACTOR = 31; 041 042 /** The event type. */ 043 private final EventType<T> eventType; 044 045 /** The event listener. */ 046 private final EventListener<? super T> listener; 047 048 /** 049 * Creates a new instance of {@code EventListenerRegistrationData}. 050 * 051 * @param type the event type (must not be <b>null</b>) 052 * @param lstnr the event listener (must not be <b>null</b>) 053 * @throws IllegalArgumentException if a required parameter is <b>null</b> 054 */ 055 public EventListenerRegistrationData(final EventType<T> type, 056 final EventListener<? super T> lstnr) 057 { 058 if (type == null) 059 { 060 throw new IllegalArgumentException("Event type must not be null!"); 061 } 062 if (lstnr == null) 063 { 064 throw new IllegalArgumentException( 065 "Listener to be registered must not be null!"); 066 } 067 068 eventType = type; 069 listener = lstnr; 070 } 071 072 /** 073 * Returns the event type for this listener registration. 074 * 075 * @return the event type 076 */ 077 public EventType<T> getEventType() 078 { 079 return eventType; 080 } 081 082 /** 083 * Returns the listener this registration is about. 084 * 085 * @return the event listener 086 */ 087 public EventListener<? super T> getListener() 088 { 089 return listener; 090 } 091 092 @Override 093 public int hashCode() 094 { 095 int result = eventType.hashCode(); 096 result = HASH_FACTOR * result + listener.hashCode(); 097 return result; 098 } 099 100 /** 101 * Compares this object with another one. Two instances of 102 * {@code EventListenerRegistrationData} are considered equal if they 103 * reference the same listener and event type. 104 * 105 * @param obj the object to be compared to 106 * @return a flag whether these objects are equal 107 */ 108 @Override 109 public boolean equals(final Object obj) 110 { 111 if (this == obj) 112 { 113 return true; 114 } 115 if (!(obj instanceof EventListenerRegistrationData)) 116 { 117 return false; 118 } 119 120 final EventListenerRegistrationData<?> c = 121 (EventListenerRegistrationData<?>) obj; 122 return getListener() == c.getListener() 123 && getEventType().equals(c.getEventType()); 124 } 125}