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.builder; 018 019import java.util.Collections; 020import java.util.Map; 021 022import org.apache.commons.configuration2.event.Event; 023import org.apache.commons.configuration2.event.EventListener; 024import org.apache.commons.configuration2.event.EventListenerList; 025import org.apache.commons.configuration2.event.EventListenerRegistrationData; 026import org.apache.commons.configuration2.event.EventType; 027 028/** 029 * <p> 030 * A specialized parameters implementation for {@link BasicConfigurationBuilder} 031 * which allows for a convenient event listener initialization. 032 * </p> 033 * <p> 034 * This class offers a fluent interface for registering event listeners. A fully 035 * initialized instance can be passed to the 036 * {@link BasicConfigurationBuilder#configure(BuilderParameters...)} method. All 037 * event listeners which have been registered at the instance are then copied 038 * over to the configuration builder. 039 * </p> 040 * <p> 041 * The code fragment below shows a typical usage scenario: 042 * </p> 043 * 044 * <pre> 045 * BasicConfigurationBuilder<Configuration> builder = 046 * new BasicConfigurationBuilder<Configuration>( 047 * PropertiesConfiguration.class) 048 * .configure(new EventListenerParameters().addEventListener( 049 * ConfigurationEvent.ANY, myListener)); 050 * </pre> 051 * 052 * <p> 053 * In order to support a configuration builder's {@code configure()} method, 054 * this class implements the {@code BuilderParameters} interface. However, this 055 * is just a dummy implementation; no parameters are propagated to the builder. 056 * </p> 057 * 058 * @version $Id: EventListenerParameters.java 1679772 2015-05-16 17:41:17Z oheger $ 059 * @since 2.0 060 */ 061public class EventListenerParameters implements BuilderParameters, 062 EventListenerProvider 063{ 064 /** Stores the event listener registrations added to this object. */ 065 private final EventListenerList eventListeners; 066 067 /** 068 * Creates a new instance of {@code EventListenerParameters}. 069 */ 070 public EventListenerParameters() 071 { 072 eventListeners = new EventListenerList(); 073 } 074 075 /** 076 * Adds an event listener of the specified event type to this object. 077 * 078 * @param eventType the event type object 079 * @param listener the event listener 080 * @param <T> the event type 081 * @return a reference to this object for method chaining 082 */ 083 public <T extends Event> EventListenerParameters addEventListener( 084 EventType<T> eventType, EventListener<? super T> listener) 085 { 086 eventListeners.addEventListener(eventType, listener); 087 return this; 088 } 089 090 /** 091 * Adds the specified {@code EventListenerRegistrationData} instance to this 092 * object. 093 * 094 * @param registrationData the registration object to be added 095 * @param <T> the event type of the contained event listener 096 * @return a reference to this object for method chaining 097 */ 098 public <T extends Event> EventListenerParameters addEventListener( 099 EventListenerRegistrationData<T> registrationData) 100 { 101 eventListeners.addEventListener(registrationData); 102 return this; 103 } 104 105 /** 106 * {@inheritDoc} This implementation returns an empty map. 107 */ 108 @Override 109 public Map<String, Object> getParameters() 110 { 111 return Collections.emptyMap(); 112 } 113 114 @Override 115 public EventListenerList getListeners() 116 { 117 return eventListeners; 118 } 119}