/*******************************************************************************
* 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.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.Collection;
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.CollectionChangeListener;
import org.eclipse.persistence.tools.workbench.utility.iterators.NullIterator;
import org.eclipse.persistence.tools.workbench.utility.iterators.SingleElementIterator;
/**
* An adapter that allows us to make a PropertyValueModel behave like
* a read-only, single-element CollectionValueModel, sorta.
*
* If the property's value is null, an empty iterator is returned
* (i.e. you can't have a collection with a null element).
*/
public class PropertyCollectionValueModelAdapter
extends AbstractModel
implements CollectionValueModel
{
/** The wrapped property value model. */
protected PropertyValueModel valueHolder;
/** A listener that forwards any events fired by the value holder. */
protected PropertyChangeListener propertyChangeListener;
/** Cache the value. */
protected Object value;
// ********** constructors/initialization **********
/**
* Wrap the specified ListValueModel.
*/
public PropertyCollectionValueModelAdapter(PropertyValueModel valueHolder) {
super();
if (valueHolder == null) {
throw new NullPointerException();
}
this.valueHolder = valueHolder;
// postpone building the value and listening to the underlying value
// until we have listeners ourselves...
}
protected void initialize() {
super.initialize();
this.propertyChangeListener = this.buildPropertyChangeListener();
}
/**
* @see org.eclipse.persistence.tools.workbench.utility.AbstractModel#buildDefaultChangeSupport()
*/
protected ChangeSupport buildDefaultChangeSupport() {
return new ValueModelChangeSupport(this);
}
/**
* The wrapped value has changed, forward an equivalent
* collection change event to our listeners.
*/
protected PropertyChangeListener buildPropertyChangeListener() {
return new PropertyChangeListener() {
public void propertyChange(PropertyChangeEvent e) {
PropertyCollectionValueModelAdapter.this.valueChanged(e.getNewValue());
}
public String toString() {
return "property change listener";
}
};
}
// ********** ValueModel implementation **********
/**
* @see ValueModel#getValue()
*/
public Object getValue() {
if (this.value == null) {
return NullIterator.instance();
}
return new SingleElementIterator(this.value);
}
// ********** CollectionValueModel implementation **********
/**
* @see CollectionValueModel#addItem(Object)
*/
public void addItem(Object item) {
throw new UnsupportedOperationException();
}
/**
* @see CollectionValueModel#addItems(java.util.Collection)
*/
public void addItems(Collection items) {
throw new UnsupportedOperationException();
}
/**
* @see CollectionValueModel#removeItem(Object)
*/
public void removeItem(Object item) {
throw new UnsupportedOperationException();
}
/**
* @see CollectionValueModel#removeItems(java.util.Collection)
*/
public void removeItems(Collection items) {
throw new UnsupportedOperationException();
}
/**
* @see CollectionValueModel#size()
*/
public int size() {
return (this.value == null) ? 0 : 1;
}
// ********** extend change support **********
/**
* Override to start listening to the value holder if necessary.
* @see org.eclipse.persistence.tools.workbench.utility.Model#addCollectionChangeListener(CollectionChangeListener)
*/
public void addCollectionChangeListener(CollectionChangeListener listener) {
if (this.hasNoListeners()) {
this.engageModel();
}
super.addCollectionChangeListener(listener);
}
/**
* Override to start listening to the value holder if necessary.
* @see org.eclipse.persistence.tools.workbench.utility.Model#addCollectionChangeListener(String, CollectionChangeListener)
*/
public void addCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
if (collectionName == VALUE && this.hasNoListeners()) {
this.engageModel();
}
super.addCollectionChangeListener(collectionName, listener);
}
/**
* Override to stop listening to the value holder if appropriate.
* @see org.eclipse.persistence.tools.workbench.utility.Model#removeCollectionChangeListener(CollectionChangeListener)
*/
public void removeCollectionChangeListener(CollectionChangeListener listener) {
super.removeCollectionChangeListener(listener);
if (this.hasNoListeners()) {
this.disengageModel();
}
}
/**
* Override to stop listening to the value holder if appropriate.
* @see org.eclipse.persistence.tools.workbench.utility.Model#removeCollectionChangeListener(String, CollectionChangeListener)
*/
public void removeCollectionChangeListener(String collectionName, CollectionChangeListener listener) {
super.removeCollectionChangeListener(collectionName, listener);
if (collectionName == VALUE && this.hasNoListeners()) {
this.disengageModel();
}
}
// ********** queries **********
protected boolean hasListeners() {
return this.hasAnyCollectionChangeListeners(VALUE);
}
protected boolean hasNoListeners() {
return ! this.hasListeners();
}
// ********** behavior **********
protected void engageModel() {
this.valueHolder.addPropertyChangeListener(VALUE, this.propertyChangeListener);
// synch our value *after* we start listening to the value holder,
// since its value might change when a listener is added
this.value = this.valueHolder.getValue();
}
protected void disengageModel() {
this.valueHolder.removePropertyChangeListener(VALUE, this.propertyChangeListener);
// clear out the value when we are not listening to the value holder
this.value = null;
}
/**
* synchronize our internal value with the wrapped value
* and fire the appropriate events
*/
protected void valueChanged(Object newValue) {
// put in "empty" check so we don't fire events unnecessarily
if (this.value != null) {
Object oldValue = this.value;
this.value = null;
this.fireItemRemoved(VALUE, oldValue);
}
this.value = newValue;
// put in "empty" check so we don't fire events unnecessarily
if (this.value != null) {
this.fireItemAdded(VALUE, this.value);
}
}
public void toString(StringBuffer sb) {
sb.append(this.valueHolder);
}
}