Copyright 2014 Netflix, Inc.
Licensed 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.
/**
 * Copyright 2014 Netflix, Inc.
 *
 * Licensed 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 com.netflix.config;

Listener that handles property event notifications. It handles events to add a property, set property,
remove property, load and clear of the configuration source. 
 DynamicPropertySupport registers this type listener with a DynamicPropertySupport to receive callbacks on changes so that it can dynamically change a value of a DynamicProperty. 
Author:
awang
See Also:
DynamicPropertySupport.addConfigurationListener(PropertyListener)/**
 * Listener that handles property event notifications. It handles events to add a property, set property,
 * remove property, load and clear of the configuration source. 
 * <p>
 * {@link DynamicPropertySupport} registers this type listener with a {@link DynamicPropertySupport} to receive 
 * callbacks on changes so that it can dynamically change a value of a DynamicProperty.
 * 
 * @see DynamicPropertySupport#addConfigurationListener(PropertyListener)
 * @author awang
 *
 */
public interface PropertyListener {
    
    
    
Notifies this listener about a new source of configuration being invalidated and/or added
Params:
source – the event source./**
     * <p>Notifies this listener about a new source of configuration being invalidated and/or added</p>
     * 
     * 
     * @param source the event source.
     * 
     */
    public void configSourceLoaded(Object source);
    
    
Notifies this listener about a new value for the given property.
Params:
source – the event source.
name – the property name.
value – the property value (current value if
       beforeUpdate is true, otherwise the new value).
beforeUpdate – true if this callback is occuring before the
       property has changed./**
     * <p>Notifies this listener about a new value for the given property.</p>
     * 
     * @param source the event source.
     * @param name the property name.
     * @param value the property value (current value if
     *        <code>beforeUpdate</code> is true, otherwise the new value).
     * @param beforeUpdate true if this callback is occuring before the
     *        property has changed.
     */
    public void addProperty(Object source, String name, Object value, boolean beforeUpdate);
    
    
Notifies this listener about a changed value for the given
property.
Params:
source – the event source.
name – the property name.
value – the property value (current value if
       beforeUpdate is true, otherwise the replacement
       value).
beforeUpdate – true if this callback is occuring before the
       property has changed./**
     * <p>Notifies this listener about a changed value for the given
     * property.</p>
     * 
     * @param source the event source.
     * @param name the property name.
     * @param value the property value (current value if
     *        <code>beforeUpdate</code> is true, otherwise the replacement
     *        value).
     * @param beforeUpdate true if this callback is occuring before the
     *        property has changed.
     */
    public void setProperty(Object source, String name, Object value, boolean beforeUpdate);
    
    
Notifies this listener about a cleared property, which now has no
value.
Params:
source – the event source.
name – the property name.
value – the property value (current value if
       beforeUpdate is true, otherwise the new value which
       should be null).
beforeUpdate – true if this callback is occuring before the
       property has changed./**
     * <p>Notifies this listener about a cleared property, which now has no
     * value.</p>
     * 
     * @param source the event source.
     * @param name the property name.
     * @param value the property value (current value if
     *        <code>beforeUpdate</code> is true, otherwise the new value which
     *        should be <code>null</code>).
     * @param beforeUpdate true if this callback is occuring before the
     *        property has changed.
     */
    public void clearProperty(Object source, String name, Object value, boolean beforeUpdate);
    
    
Notifies this listener that all properties have been cleared.
Params:
source – the event source.
beforeUpdate – true if this callback is occuring before the
       properties have been cleared./**
     * <p>Notifies this listener that all properties have been cleared.</p>
     * 
     * @param source the event source.
     * @param beforeUpdate true if this callback is occuring before the
     *        properties have been cleared.
     */
    public void clear(Object source, boolean beforeUpdate);
}