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/*******************************************************************************
* Copyright (c) 2007, 2008 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.utility.internal.model.value;
import java.util.Iterator;
import org.eclipse.jpt.utility.internal.model.AbstractModel;
import org.eclipse.jpt.utility.internal.model.ChangeSupport;
import org.eclipse.jpt.utility.internal.model.SingleAspectChangeSupport;
import org.eclipse.jpt.utility.model.event.CollectionChangeEvent;
import org.eclipse.jpt.utility.model.listener.CollectionChangeListener;
import org.eclipse.jpt.utility.model.value.CollectionValueModel;
/**
* This abstract class provides the infrastructure needed to wrap
* another collection value model, "lazily" listen to it, and propagate
* its change notifications.
*/
public abstract class CollectionValueModelWrapper<E>
extends AbstractModel
{
/** The wrapped collection value model. */
protected final CollectionValueModel<? extends E> collectionHolder;
/** A listener that allows us to synch with changes to the wrapped collection holder. */
protected final CollectionChangeListener collectionChangeListener;
// ********** constructors **********
/**
* Construct a collection value model with the specified wrapped
* collection value model.
*/
protected CollectionValueModelWrapper(CollectionValueModel<? extends E> collectionHolder) {
super();
this.collectionHolder = collectionHolder;
this.collectionChangeListener = this.buildCollectionChangeListener();
}
// ********** initialization **********
@Override
protected ChangeSupport buildChangeSupport() {
return new SingleAspectChangeSupport(this, CollectionChangeListener.class, CollectionValueModel.VALUES);
}
protected CollectionChangeListener buildCollectionChangeListener() {
return new CollectionChangeListener() {
public void itemsAdded(CollectionChangeEvent event) {
CollectionValueModelWrapper.this.itemsAdded(event);
}
public void itemsRemoved(CollectionChangeEvent event) {
CollectionValueModelWrapper.this.itemsRemoved(event);
}
public void collectionCleared(CollectionChangeEvent event) {
CollectionValueModelWrapper.this.collectionCleared(event);
}
public void collectionChanged(CollectionChangeEvent event) {
CollectionValueModelWrapper.this.collectionChanged(event);
}
@Override
public String toString() {
return "collection change listener";
}
};
}
// ********** extend change support **********
/**
* Extend to start listening to the nested model if necessary.
*/
@Override
public synchronized void addCollectionChangeListener(CollectionChangeListener listener) {
if (this.hasNoCollectionChangeListeners(CollectionValueModel.VALUES)) {
this.engageModel();
}
super.addCollectionChangeListener(listener);
}
/**
* Extend to start listening to the nested model if necessary.
*/
@Override
public synchronized void addCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
if (collectionName == CollectionValueModel.VALUES && this.hasNoCollectionChangeListeners(CollectionValueModel.VALUES)) {
this.engageModel();
}
super.addCollectionChangeListener(collectionName, listener);
}
/**
* Extend to stop listening to the nested model if necessary.
*/
@Override
public synchronized void removeCollectionChangeListener(CollectionChangeListener listener) {
super.removeCollectionChangeListener(listener);
if (this.hasNoCollectionChangeListeners(CollectionValueModel.VALUES)) {
this.disengageModel();
}
}
/**
* Extend to stop listening to the nested model if necessary.
*/
@Override
public synchronized void removeCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
super.removeCollectionChangeListener(collectionName, listener);
if (collectionName == CollectionValueModel.VALUES && this.hasNoCollectionChangeListeners(CollectionValueModel.VALUES)) {
this.disengageModel();
}
}
// ********** behavior **********
/**
* Start listening to the collection holder.
*/
protected void engageModel() {
this.collectionHolder.addCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
}
/**
* Stop listening to the collection holder.
*/
protected void disengageModel() {
this.collectionHolder.removeCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
}
// minimize scope of suppressed warnings
@SuppressWarnings("unchecked")
protected Iterator<E> items(CollectionChangeEvent event) {
return (Iterator<E>) event.items();
}
@Override
public void toString(StringBuilder sb) {
sb.append(this.collectionHolder);
}
// ********** collection change support **********
/**
* Items were added to the wrapped collection holder;
* propagate the change notification appropriately.
*/
protected abstract void itemsAdded(CollectionChangeEvent event);
/**
* Items were removed from the wrapped collection holder;
* propagate the change notification appropriately.
*/
protected abstract void itemsRemoved(CollectionChangeEvent event);
/**
* The wrapped collection holder was cleared;
* propagate the change notification appropriately.
*/
protected abstract void collectionCleared(CollectionChangeEvent event);
/**
* The value of the wrapped collection holder has changed;
* propagate the change notification appropriately.
*/
protected abstract void collectionChanged(CollectionChangeEvent event);
}
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