http://commons.apache.org/configuration/: Tools to assist in the reading of configuration/preferences files in various formats. (The Apache Software Foundation)
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/*
 * 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.configuration.event;

import java.util.EventObject;



An event class for reporting updates on a configuration object.




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.




Each event can contain the following data:

    

  • A source object, which is usually the configuration object that was
modified.
    • 

  • The event's type. This is a numeric value that corresponds to constant
declarations in concrete configuration classes. It describes what exactly has
happended.
    • 

  • If available, the name of the property whose modification caused the
event.
    • 

  • If available, the value of the property that caused this event.
    • 

  • 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.
    • 





 The following standard events are generated by typical configuration implementations (the constants for the event types are defined in AbstractConfiguration): 


EVENT_ADD_PROPERTY


This event is triggered for each call of the 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).


EVENT_SET_PROPERTY


Calling the setProperty() method triggers this event. The event object stores the name of the affected property and its new value.


EVENT_CLEAR_PROPERTY


If a property is removed from a configuration (by calling the 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 null.


EVENT_CLEAR


This event is fired when the whole configuration is cleared. The
corresponding event object contains no additional data.






Author:Commons
Configuration team
Version:$Id: ConfigurationEvent.java 1207610 2011-11-28 21:06:22Z oheger $
Since:1.3
/**
 * <p>
 * An event class for reporting updates on a configuration object.
 * </p>
 * <p>
 * Event objects of this type are used for &quot;raw&quot; 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:
 * <ul>
 * <li>A source object, which is usually the configuration object that was
 * modified.</li>
 * <li>The event's type. This is a numeric value that corresponds to constant
 * declarations in concrete configuration classes. It describes what exactly has
 * happended.</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>
 * <p>
 * The following standard events are generated by typical configuration
 * implementations (the constants for the event types are defined in
 * {@link org.apache.commons.configuration.AbstractConfiguration}):
 * <dl>
 * <dt>EVENT_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>EVENT_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>EVENT_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>EVENT_CLEAR</dt>
 * <dd>This event is fired when the whole configuration is cleared. The
 * corresponding event object contains no additional data.</dd>
 * </dl>
 * </p>
 *
 * @author <a
 * href="http://commons.apache.org/configuration/team-list.html">Commons
 * Configuration team</a>
 * @version $Id: ConfigurationEvent.java 1207610 2011-11-28 21:06:22Z oheger $
 * @since 1.3
 */
public class ConfigurationEvent extends EventObject
{
    
The serial version UID.

/**
     * The serial version UID.
     */
    private static final long serialVersionUID = 3277238219073504136L;

    
Stores the event type. 
/** Stores the event type. */
    private int type;

    
Stores the property name. 
/** Stores the property name. */
    private String propertyName;

    
Stores the property value. 
/** Stores the property value. */
    private Object propertyValue;

    
Stores the before update flag. 
/** Stores the before update flag. */
    private boolean beforeUpdate;

    
Creates a new instance of ConfigurationEvent and initializes it. 
Params:
  • source – the event source
  • type – the event's type
  • propertyName – the name of the affected property
  • propertyValue – the value of the affected property
  • beforeUpdate – the before update flag
/**
     * 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(Object source, int type, String propertyName,
            Object propertyValue, boolean beforeUpdate)
    {
        super(source);
        this.type = type;
        this.propertyName = propertyName;
        this.propertyValue = propertyValue;
        this.beforeUpdate = beforeUpdate;
    }

    
Returns the name of the affected property. This can be null if no
property change has lead to this event.

Returns:the name of the property
/**
     * Returns 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;
    }

    
Returns the value of the affected property if available.

Returns:the value of the property; can be null
/**
     * Returns 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 the type of this event. This describes the update process that
caused this event.

Returns:the event's type
/**
     * Returns the type of this event. This describes the update process that
     * caused this event.
     *
     * @return the event's type
     */
    public int getType()
    {
        return type;
    }

    
Returns a flag if this event was generated before or after an update.

Returns:true if this event was generated before an update;
false otherwise
/**
     * 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;
    }
}