ConfigurationEvent.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.configuration2.event;
/**
* <p>
* An event class for reporting updates on a configuration object.
* </p>
* <p>
* Event objects of this type are used for "raw" events, i.e. unfiltered modifications of any kind. A level
* with semantically higher events (e.g. for property changes) may be built on top of this fundamental event mechanism.
* </p>
* <p>
* Each event can contain the following data:
* </p>
* <ul>
* <li>A source object, which is usually the configuration object that was modified.</li>
* <li>The event's type. This is an object that corresponds to constant declarations in specific event classes. It
* describes what exactly has happened.</li>
* <li>If available, the name of the property whose modification caused the event.</li>
* <li>If available, the value of the property that caused this event.</li>
* <li>A flag whether this event was generated before or after the update of the source configuration. A modification of
* a configuration typically causes two events: one event before and one event after the modification is performed. This
* allows event listeners to react at the correct point of time.</li>
* </ul>
* <p>
* The following standard events are generated by typical configuration implementations (the constants for the event
* types are defined in this class:
* </p>
* <dl>
* <dt>ADD_PROPERTY</dt>
* <dd>This event is triggered for each call of the {@code addProperty()} method of a configuration object. It contains
* the name of the property, to which new data is added, and the value object that is added to this property (this may
* be an array or a list if multiple values are added).</dd>
* <dt>SET_PROPERTY</dt>
* <dd>Calling the {@code setProperty()} method triggers this event. The event object stores the name of the affected
* property and its new value.</dd>
* <dt>CLEAR_PROPERTY</dt>
* <dd>If a property is removed from a configuration (by calling the {@code clearProperty()} method), an event of this
* type is fired. In this case the event object only stores the name of the removed property, the value is
* <b>null</b>.</dd>
* <dt>CLEAR</dt>
* <dd>This event is fired when the whole configuration is cleared. The corresponding event object contains no
* additional data.</dd>
* </dl>
*
* @since 1.3
*/
public class ConfigurationEvent extends Event {
/**
* Constant for the common super type of all configuration update events.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> ANY = new EventType<>(Event.ANY, "CONFIGURATION_UPDATE");
/**
* Constant for the event type for an add property operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> ADD_PROPERTY = new EventType<>(ANY, "ADD_PROPERTY");
/**
* Constant for the event type for a set property operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> SET_PROPERTY = new EventType<>(ANY, "SET_PROPERTY");
/**
* Constant for the event type for a clear property operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> CLEAR_PROPERTY = new EventType<>(ANY, "CLEAR_PROPERTY");
/**
* Constant for the event type for a clear operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> CLEAR = new EventType<>(ANY, "CLEAR");
/**
* Constant for the common base event type for all hierarchical update events. Events derived from this type are
* generated by some specific methods of hierarchical configurations.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> ANY_HIERARCHICAL = new EventType<>(ANY, "HIERARCHICAL");
/**
* Constant for the event type for an add nodes operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> ADD_NODES = new EventType<>(ANY_HIERARCHICAL, "ADD_NODES");
/**
* Constant for the event type for a clear tree operation.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> CLEAR_TREE = new EventType<>(ANY_HIERARCHICAL, "CLEAR_TREE");
/**
* Constant for the event type indicating a change on a sub configuration.
*
* @since 2.0
*/
public static final EventType<ConfigurationEvent> SUBNODE_CHANGED = new EventType<>(ANY_HIERARCHICAL, "SUBNODE_CHANGED");
/**
* The serial version UID.
*/
private static final long serialVersionUID = 20140703L;
/** Stores the property name. */
private final String propertyName;
/** Stores the property value. */
private final Object propertyValue;
/** Stores the before update flag. */
private final boolean beforeUpdate;
/**
* Creates a new instance of {@code ConfigurationEvent} and initializes it.
*
* @param source the event source
* @param type the event's type
* @param propertyName the name of the affected property
* @param propertyValue the value of the affected property
* @param beforeUpdate the before update flag
*/
public ConfigurationEvent(final Object source, final EventType<? extends ConfigurationEvent> type, final String propertyName, final Object propertyValue,
final boolean beforeUpdate) {
super(source, type);
this.propertyName = propertyName;
this.propertyValue = propertyValue;
this.beforeUpdate = beforeUpdate;
}
/**
* Gets the name of the affected property. This can be <b>null</b> if no property change has lead to this event.
*
* @return the name of the property
*/
public String getPropertyName() {
return propertyName;
}
/**
* Gets the value of the affected property if available.
*
* @return the value of the property; can be <b>null</b>
*/
public Object getPropertyValue() {
return propertyValue;
}
/**
* Returns a flag if this event was generated before or after an update.
*
* @return <b>true</b> if this event was generated before an update; <b>false</b> otherwise
*/
public boolean isBeforeUpdate() {
return beforeUpdate;
}
}