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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 org.eclipse.jpt.utility.internal.model.event.CollectionChangeEvent;
import org.eclipse.jpt.utility.internal.model.listener.CollectionChangeListener;
/**
* This abstract class provides the infrastructure needed to wrap
* a collection value model, "lazily" listen to it, and convert
* its change notifications into property value model change
* notifications.
*
* Subclasses must override:
* - #buildValue()
* to return the current property value, as derived from the
* current collection value
*
* Subclasses might want to override:
* - #itemsAdded(CollectionChangeEvent e)
* - #itemsRemoved(CollectionChangeEvent e)
* - #collectionCleared(CollectionChangeEvent e)
* - #collectionChanged(CollectionChangeEvent e)
* to improve performance (by not recalculating the value, if possible)
*/
public abstract class CollectionPropertyValueModelAdapter<T>
extends AspectPropertyValueModelAdapter<T>
{
/** The wrapped collection value model. */
protected final CollectionValueModel<?> collectionHolder;
/** A listener that allows us to synch with changes to the wrapped collection holder. */
protected final CollectionChangeListener collectionChangeListener;
// ********** constructor/initialization **********
/**
* Construct a property value model with the specified wrapped
* collection value model.
*/
protected CollectionPropertyValueModelAdapter(CollectionValueModel<?> collectionHolder) {
super();
this.collectionHolder = collectionHolder;
this.collectionChangeListener = this.buildCollectionChangeListener();
}
protected CollectionChangeListener buildCollectionChangeListener() {
return new CollectionChangeListener() {
public void itemsAdded(CollectionChangeEvent e) {
CollectionPropertyValueModelAdapter.this.itemsAdded(e);
}
public void itemsRemoved(CollectionChangeEvent e) {
CollectionPropertyValueModelAdapter.this.itemsRemoved(e);
}
public void collectionCleared(CollectionChangeEvent e) {
CollectionPropertyValueModelAdapter.this.collectionCleared(e);
}
public void collectionChanged(CollectionChangeEvent e) {
CollectionPropertyValueModelAdapter.this.collectionChanged(e);
}
@Override
public String toString() {
return "collection change listener";
}
};
}
// ********** behavior **********
/**
* Start listening to the collection holder.
*/
@Override
protected void engageModel_() {
this.collectionHolder.addCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
}
/**
* Stop listening to the collection holder.
*/
@Override
protected void disengageModel_() {
this.collectionHolder.removeCollectionChangeListener(CollectionValueModel.VALUES, this.collectionChangeListener);
}
@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 void itemsAdded(CollectionChangeEvent e) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
/**
* Items were removed from the wrapped collection holder;
* propagate the change notification appropriately.
*/
protected void itemsRemoved(CollectionChangeEvent e) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
/**
* The wrapped collection holder was cleared;
* propagate the change notification appropriately.
*/
protected void collectionCleared(CollectionChangeEvent e) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
/**
* The value of the wrapped collection holder has changed;
* propagate the change notification appropriately.
*/
protected void collectionChanged(CollectionChangeEvent e) {
// by default, simply recalculate the value and fire an event
this.propertyChanged();
}
}
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