/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.uitools.app;
import java.beans.PropertyChangeListener;
import org.eclipse.persistence.tools.workbench.utility.AbstractModel;
import org.eclipse.persistence.tools.workbench.utility.events.ChangeSupport;
import org.eclipse.persistence.tools.workbench.utility.events.CollectionChangeEvent;
import org.eclipse.persistence.tools.workbench.utility.events.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:
* - #setValue(Object)
* to manipulate the collection in some appropriate fashion
* - #itemsAdded(CollectionChangeEvent e)
* - #itemsRemoved(CollectionChangeEvent e)
* - #collectionChanged(CollectionChangeEvent e)
* to improve performance (by not recalculating the value, if possible)
*/
public abstract class CollectionPropertyValueModelAdapter
extends AbstractModel
implements PropertyValueModel
{
/**
* Cache the current value so we can pass an "old value" when
* we fire a property change event.
* We need this because the value may be calculated and we may
* not able to derive the "old value" from the collection
* change event fired by the collection value model.
*/
protected Object value;
/** The wrapped collection value model. */
protected CollectionValueModel collectionHolder;
/** A listener that allows us to synch with changes to the wrapped collection holder. */
protected CollectionChangeListener collectionChangeListener;
// ********** constructor/initialization **********
/**
* Construct a property value model with the specified wrapped
* collection value model.
*/
protected CollectionPropertyValueModelAdapter(CollectionValueModel collectionHolder) {
super();
this.collectionHolder = collectionHolder;
}
protected void initialize() {
super.initialize();
// our value is null when we are not listening to the collection holder
this.value = null;
this.collectionChangeListener = this.buildCollectionChangeListener();
}
/**
* @see org.eclipse.persistence.tools.workbench.utility.AbstractModel#buildDefaultChangeSupport()
*/
protected ChangeSupport buildDefaultChangeSupport() {
return new ValueModelChangeSupport(this);
}
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 collectionChanged(CollectionChangeEvent e) {
CollectionPropertyValueModelAdapter.this.collectionChanged(e);
}
public String toString() {
return "collection change listener";
}
};
}
// ********** ValueModel implementation **********
/**
* Return the cached value.
* @see ValueModel#getValue()
*/
public Object getValue() {
return this.value;
}
// ********** PropertyValueModel implementation **********
/**
* @see PropertyValueModel#setValue(Object)
*/
public void setValue(Object value) {
throw new UnsupportedOperationException();
}
// ********** extend change support **********
/**
* Extend to start listening to the wrapped collection if necessary.
* @see Model#addPropertyChangeListener(PropertyChangeListener)
*/
public synchronized void addPropertyChangeListener(PropertyChangeListener listener) {
if (this.hasNoListeners()) {
this.engageModel();
}
super.addPropertyChangeListener(listener);
}
/**
* Extend to start listening to the wrapped collection if necessary.
* @see Model#addPropertyChangeListener(String, PropertyChangeListener)
*/
public synchronized void addPropertyChangeListener(String propertyName, PropertyChangeListener listener) {
if (propertyName == VALUE && this.hasNoListeners()) {
this.engageModel();
}
super.addPropertyChangeListener(propertyName, listener);
}
/**
* Extend to stop listening to the wrapped collection if necessary.
* @see Model#removePropertyChangeListener(PropertyChangeListener)
*/
public synchronized void removePropertyChangeListener(PropertyChangeListener listener) {
super.removePropertyChangeListener(listener);
if (this.hasNoListeners()) {
this.disengageModel();
}
}
/**
* Extend to stop listening to the wrapped collection if necessary.
* @see Model#removePropertyChangeListener(String, PropertyChangeListener)
*/
public synchronized void removePropertyChangeListener(String propertyName, PropertyChangeListener listener) {
super.removePropertyChangeListener(propertyName, listener);
if (propertyName == VALUE && this.hasNoListeners()) {
this.disengageModel();
}
}
// ********** queries **********
/**
* Return whether there are any listeners for the aspect.
*/
protected boolean hasListeners() {
return this.hasAnyPropertyChangeListeners(VALUE);
}
/**
* Return whether there are any listeners for the aspect.
*/
protected boolean hasNoListeners() {
return ! this.hasListeners();
}
// ********** behavior **********
/**
* Start listening to the collection holder.
*/
protected void engageModel() {
this.collectionHolder.addCollectionChangeListener(VALUE, this.collectionChangeListener);
// synch our value *after* we start listening to the collection,
// since the collection's value might change when a listener is added
this.value = this.buildValue();
}
/**
* Build and return the current value, as derived from the
* current state of the wrapped collection.
*/
protected abstract Object buildValue();
/**
* Stop listening to the collection holder.
*/
protected void disengageModel() {
this.collectionHolder.removeCollectionChangeListener(VALUE, this.collectionChangeListener);
// clear out our value when we are not listening to the collection
this.value = null;
}
/**
* @see org.eclipse.persistence.tools.workbench.utility.AbstractModel#toString(StringBuffer)
*/
public void toString(StringBuffer 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 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();
}
/**
* The wrapped collection changed in some fashion.
* Recalculate the value and notify any listeners.
*/
protected void propertyChanged() {
Object old = this.value;
this.value = this.buildValue();
this.firePropertyChanged(VALUE, old, this.value);
}
}