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 whether a specific event listener is to be 025 * invoked for a given event. The class is used internally by {@link EventListenerList}, but is also useful in general 026 * when information about event listeners is to be stored. 027 * </p> 028 * <p> 029 * Implementation note: Instances of this class are immutable and can safely be shared between multiple threads or 030 * components. 031 * </p> 032 * 033 * @since 2.0 034 * @param <T> the type of events processed by the listener 035 */ 036public final class EventListenerRegistrationData<T extends Event> { 037 /** Constant for the factor used by the calculation of the hash code. */ 038 private static final int HASH_FACTOR = 31; 039 040 /** The event type. */ 041 private final EventType<T> eventType; 042 043 /** The event listener. */ 044 private final EventListener<? super T> listener; 045 046 /** 047 * Creates a new instance of {@code EventListenerRegistrationData}. 048 * 049 * @param type the event type (must not be <b>null</b>) 050 * @param lstnr the event listener (must not be <b>null</b>) 051 * @throws IllegalArgumentException if a required parameter is <b>null</b> 052 */ 053 public EventListenerRegistrationData(final EventType<T> type, final EventListener<? super T> lstnr) { 054 if (type == null) { 055 throw new IllegalArgumentException("Event type must not be null!"); 056 } 057 if (lstnr == null) { 058 throw new IllegalArgumentException("Listener to be registered must not be null!"); 059 } 060 061 eventType = type; 062 listener = lstnr; 063 } 064 065 /** 066 * Gets the event type for this listener registration. 067 * 068 * @return the event type 069 */ 070 public EventType<T> getEventType() { 071 return eventType; 072 } 073 074 /** 075 * Gets the listener this registration is about. 076 * 077 * @return the event listener 078 */ 079 public EventListener<? super T> getListener() { 080 return listener; 081 } 082 083 @Override 084 public int hashCode() { 085 final int result = eventType.hashCode(); 086 return HASH_FACTOR * result + listener.hashCode(); 087 } 088 089 /** 090 * Compares this object with another one. Two instances of {@code EventListenerRegistrationData} are considered equal if 091 * they reference the same listener and event type. 092 * 093 * @param obj the object to be compared to 094 * @return a flag whether these objects are equal 095 */ 096 @Override 097 public boolean equals(final Object obj) { 098 if (this == obj) { 099 return true; 100 } 101 if (!(obj instanceof EventListenerRegistrationData)) { 102 return false; 103 } 104 105 final EventListenerRegistrationData<?> c = (EventListenerRegistrationData<?>) obj; 106 return getListener() == c.getListener() && getEventType().equals(c.getEventType()); 107 } 108}