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 * @version $Id: EventListenerRegistrationData.java 1842194 2018-09-27 22:24:23Z ggregory $ 035 * @since 2.0 036 * @param <T> the type of events processed by the listener 037 */ 038public final class EventListenerRegistrationData<T extends Event> 039{ 040 /** Constant for the factor used by the calculation of the hash code. */ 041 private static final int HASH_FACTOR = 31; 042 043 /** The event type. */ 044 private final EventType<T> eventType; 045 046 /** The event listener. */ 047 private final EventListener<? super T> listener; 048 049 /** 050 * Creates a new instance of {@code EventListenerRegistrationData}. 051 * 052 * @param type the event type (must not be <b>null</b>) 053 * @param lstnr the event listener (must not be <b>null</b>) 054 * @throws IllegalArgumentException if a required parameter is <b>null</b> 055 */ 056 public EventListenerRegistrationData(final EventType<T> type, 057 final EventListener<? super T> lstnr) 058 { 059 if (type == null) 060 { 061 throw new IllegalArgumentException("Event type must not be null!"); 062 } 063 if (lstnr == null) 064 { 065 throw new IllegalArgumentException( 066 "Listener to be registered must not be null!"); 067 } 068 069 eventType = type; 070 listener = lstnr; 071 } 072 073 /** 074 * Returns the event type for this listener registration. 075 * 076 * @return the event type 077 */ 078 public EventType<T> getEventType() 079 { 080 return eventType; 081 } 082 083 /** 084 * Returns the listener this registration is about. 085 * 086 * @return the event listener 087 */ 088 public EventListener<? super T> getListener() 089 { 090 return listener; 091 } 092 093 @Override 094 public int hashCode() 095 { 096 int result = eventType.hashCode(); 097 result = HASH_FACTOR * result + listener.hashCode(); 098 return result; 099 } 100 101 /** 102 * Compares this object with another one. Two instances of 103 * {@code EventListenerRegistrationData} are considered equal if they 104 * reference the same listener and event type. 105 * 106 * @param obj the object to be compared to 107 * @return a flag whether these objects are equal 108 */ 109 @Override 110 public boolean equals(final Object obj) 111 { 112 if (this == obj) 113 { 114 return true; 115 } 116 if (!(obj instanceof EventListenerRegistrationData)) 117 { 118 return false; 119 } 120 121 final EventListenerRegistrationData<?> c = 122 (EventListenerRegistrationData<?>) obj; 123 return getListener() == c.getListener() 124 && getEventType().equals(c.getEventType()); 125 } 126}