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 * An event class for reporting updates on a configuration object. 022 * </p> 023 * <p> 024 * Event objects of this type are used for "raw" events, i.e. 025 * unfiltered modifications of any kind. A level with semantically higher events 026 * (e.g. for property changes) may be built on top of this fundamental event 027 * mechanism. 028 * </p> 029 * <p> 030 * Each event can contain the following data: 031 * </p> 032 * <ul> 033 * <li>A source object, which is usually the configuration object that was 034 * modified.</li> 035 * <li>The event's type. This is an object that corresponds to constant 036 * declarations in specific event classes. It describes what exactly has 037 * happened.</li> 038 * <li>If available, the name of the property whose modification caused the 039 * event.</li> 040 * <li>If available, the value of the property that caused this event.</li> 041 * <li>A flag whether this event was generated before or after the update of 042 * the source configuration. A modification of a configuration typically causes 043 * two events: one event before and one event after the modification is 044 * performed. This allows event listeners to react at the correct point of time.</li> 045 * </ul> 046 * <p> 047 * The following standard events are generated by typical configuration 048 * implementations (the constants for the event types are defined in 049 * this class: 050 * </p> 051 * <dl> 052 * <dt>ADD_PROPERTY</dt> 053 * <dd>This event is triggered for each call of the {@code addProperty()} 054 * method of a configuration object. It contains the name of the property, to 055 * which new data is added, and the value object that is added to this property 056 * (this may be an array or a list if multiple values are added).</dd> 057 * <dt>SET_PROPERTY</dt> 058 * <dd>Calling the {@code setProperty()} method triggers this event. The 059 * event object stores the name of the affected property and its new value.</dd> 060 * <dt>CLEAR_PROPERTY</dt> 061 * <dd>If a property is removed from a configuration (by calling the 062 * {@code clearProperty()} method), an event of this type is fired. In 063 * this case the event object only stores the name of the removed property, the 064 * value is <b>null</b>.</dd> 065 * <dt>CLEAR</dt> 066 * <dd>This event is fired when the whole configuration is cleared. The 067 * corresponding event object contains no additional data.</dd> 068 * </dl> 069 * 070 * @since 1.3 071 */ 072public class ConfigurationEvent extends Event 073{ 074 /** 075 * Constant for the common super type of all configuration update events. 076 * 077 * @since 2.0 078 */ 079 public static final EventType<ConfigurationEvent> ANY = 080 new EventType<>(Event.ANY, "CONFIGURATION_UPDATE"); 081 082 /** 083 * Constant for the event type for an add property operation. 084 * 085 * @since 2.0 086 */ 087 public static final EventType<ConfigurationEvent> ADD_PROPERTY = 088 new EventType<>(ANY, "ADD_PROPERTY"); 089 090 /** 091 * Constant for the event type for a set property operation. 092 * 093 * @since 2.0 094 */ 095 public static final EventType<ConfigurationEvent> SET_PROPERTY = 096 new EventType<>(ANY, "SET_PROPERTY"); 097 098 /** 099 * Constant for the event type for a clear property operation. 100 * 101 * @since 2.0 102 */ 103 public static final EventType<ConfigurationEvent> CLEAR_PROPERTY = 104 new EventType<>(ANY, "CLEAR_PROPERTY"); 105 106 /** 107 * Constant for the event type for a clear operation. 108 * 109 * @since 2.0 110 */ 111 public static final EventType<ConfigurationEvent> CLEAR = 112 new EventType<>(ANY, "CLEAR"); 113 114 /** 115 * Constant for the common base event type for all hierarchical update 116 * events. Events derived from this type are generated by some specific 117 * methods of hierarchical configurations. 118 * 119 * @since 2.0 120 */ 121 public static final EventType<ConfigurationEvent> ANY_HIERARCHICAL = 122 new EventType<>(ANY, "HIERARCHICAL"); 123 124 /** 125 * Constant for the event type for an add nodes operation. 126 * 127 * @since 2.0 128 */ 129 public static final EventType<ConfigurationEvent> ADD_NODES = 130 new EventType<>(ANY_HIERARCHICAL, "ADD_NODES"); 131 132 /** 133 * Constant for the event type for a clear tree operation. 134 * 135 * @since 2.0 136 */ 137 public static final EventType<ConfigurationEvent> CLEAR_TREE = 138 new EventType<>(ANY_HIERARCHICAL, "CLEAR_TREE"); 139 140 /** 141 * Constant for the event type indicating a change on a sub configuration. 142 * 143 * @since 2.0 144 */ 145 public static final EventType<ConfigurationEvent> SUBNODE_CHANGED = 146 new EventType<>(ANY_HIERARCHICAL, 147 "SUBNODE_CHANGED"); 148 149 /** 150 * The serial version UID. 151 */ 152 private static final long serialVersionUID = 20140703L; 153 154 /** Stores the property name. */ 155 private final String propertyName; 156 157 /** Stores the property value. */ 158 private final Object propertyValue; 159 160 /** Stores the before update flag. */ 161 private final boolean beforeUpdate; 162 163 /** 164 * Creates a new instance of {@code ConfigurationEvent} and 165 * initializes it. 166 * 167 * @param source the event source 168 * @param type the event's type 169 * @param propertyName the name of the affected property 170 * @param propertyValue the value of the affected property 171 * @param beforeUpdate the before update flag 172 */ 173 public ConfigurationEvent(final Object source, 174 final EventType<? extends ConfigurationEvent> type, final String propertyName, 175 final Object propertyValue, final boolean beforeUpdate) 176 { 177 super(source, type); 178 this.propertyName = propertyName; 179 this.propertyValue = propertyValue; 180 this.beforeUpdate = beforeUpdate; 181 } 182 183 /** 184 * Returns the name of the affected property. This can be <b>null</b> if no 185 * property change has lead to this event. 186 * 187 * @return the name of the property 188 */ 189 public String getPropertyName() 190 { 191 return propertyName; 192 } 193 194 /** 195 * Returns the value of the affected property if available. 196 * 197 * @return the value of the property; can be <b>null</b> 198 */ 199 public Object getPropertyValue() 200 { 201 return propertyValue; 202 } 203 204 /** 205 * Returns a flag if this event was generated before or after an update. 206 * 207 * @return <b>true</b> if this event was generated before an update; 208 * <b>false</b> otherwise 209 */ 210 public boolean isBeforeUpdate() 211 { 212 return beforeUpdate; 213 } 214}