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/*******************************************************************************
* Copyright (c) 2009 Oracle. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0, which accompanies this distribution
* and is available at http://www.eclipse.org/legal/epl-v10.html.
*
* Contributors:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.common.utility.internal.model.value;
import org.eclipse.jpt.common.utility.internal.model.AbstractModel;
import org.eclipse.jpt.common.utility.internal.model.ChangeSupport;
import org.eclipse.jpt.common.utility.internal.model.SingleAspectChangeSupport;
import org.eclipse.jpt.common.utility.model.listener.ChangeListener;
import org.eclipse.jpt.common.utility.model.listener.CollectionChangeListener;
import org.eclipse.jpt.common.utility.model.value.CollectionValueModel;
/**
* This abstract class provides the infrastructure for "lazily" adding listeners
* to an underlying model as necessary. Subclasses will need to engage and
* disegage the underlying model and fire the appropriate collection change
* events. Subclasses must implement the appropriate {@link CollectionValueModel}.
* <p>
* Subclasses must implement the following methods:<ul>
* <li>{@link #engageModel()}<p>
* implement this method to add the appropriate listener to the underlying model
* <li>{@link #disengageModel()}<p>
* implement this method to remove the appropriate listener from the underlying model
* </ul>
*/
public abstract class AbstractCollectionValueModel
extends AbstractModel
{
// ********** constructor/initialization **********
protected AbstractCollectionValueModel() {
super();
}
@Override
protected ChangeSupport buildChangeSupport() {
return new SingleAspectChangeSupport(this, CollectionChangeListener.class, CollectionValueModel.VALUES);
}
// ********** extend change support **********
/**
* Extend to start listening to the underlying model if necessary.
*/
@Override
public synchronized void addChangeListener(ChangeListener listener) {
if (this.hasNoListeners()) {
this.engageModel();
}
super.addChangeListener(listener);
}
/**
* Extend to start listening to the underlying model if necessary.
*/
@Override
public synchronized void addCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
if (collectionName.equals(CollectionValueModel.VALUES) && this.hasNoListeners()) {
this.engageModel();
}
super.addCollectionChangeListener(collectionName, listener);
}
/**
* Extend to stop listening to the underlying model if necessary.
*/
@Override
public synchronized void removeChangeListener(ChangeListener listener) {
super.removeChangeListener(listener);
if (this.hasNoListeners()) {
this.disengageModel();
}
}
/**
* Extend to stop listening to the underlying model if necessary.
*/
@Override
public synchronized void removeCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
super.removeCollectionChangeListener(collectionName, listener);
if (collectionName.equals(CollectionValueModel.VALUES) && this.hasNoListeners()) {
this.disengageModel();
}
}
// ********** queries **********
/**
* Return whether the model has no collection value listeners.
*/
protected boolean hasNoListeners() {
return ! this.hasListeners();
}
/**
* Return whether the model has any collection value listeners.
*/
protected boolean hasListeners() {
return this.hasAnyCollectionChangeListeners(CollectionValueModel.VALUES);
}
// ********** behavior **********
/**
* Engage the underlying model.
*/
protected abstract void engageModel();
/**
* Stop listening to the underlying model.
*/
protected abstract void disengageModel();
}
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