/*
* 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.wicket.util.watch;
import java.util.Set;
import org.apache.wicket.util.listener.IChangeListener;
import org.apache.wicket.util.time.Duration;
/**
* Monitors one or more <code>IModifiable</code> objects, calling a {@link IChangeListener
* IChangeListener} when a given object's modification time changes.
*
* @author Juergen Donnerstag
*/
public interface IModificationWatcher
{
/**
* Adds an <code>IModifiable</code> object and an <code>IChangeListener</code> object to call
* when the modifiable object is modified.
*
* @param modifiable
* an <code>IModifiable</code> object to monitor
* @param listener
* an <code>IChangeListener</code> to call if the <code>IModifiable</code> object is
* modified
* @return <code>true</code> if the set did not already contain the specified element
*/
boolean add(final IModifiable modifiable, final IChangeListener listener);
/**
* Removes all entries associated with an <code>IModifiable</code> object.
*
* @param modifiable
* an <code>IModifiable</code> object
* @return the <code>IModifiable</code> object that was removed, else <code>null</code>
*/
IModifiable remove(final IModifiable modifiable);
/**
* Starts watching at a given <code>Duration</code> polling rate.
*
* @param pollFrequency
* the polling rate <code>Duration</code>
*/
void start(final Duration pollFrequency);
/**
* Stops this <code>ModificationWatcher</code>.
*/
void destroy();
/**
* Retrieves a key set of all <code>IModifiable</code> objects currently being monitored.
*
* @return a <code>Set</code> of all <code>IModifiable</code> entries currently maintained
*/
Set<IModifiable> getEntries();
}
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