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/*******************************************************************************
* Copyright (c) 2007, 2012 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 java.util.Collections;
import java.util.Iterator;
import org.eclipse.jpt.common.utility.internal.StringTools;
import org.eclipse.jpt.common.utility.internal.iterators.EmptyIterator;
import org.eclipse.jpt.common.utility.internal.iterators.SingleElementIterator;
import org.eclipse.jpt.common.utility.model.event.PropertyChangeEvent;
import org.eclipse.jpt.common.utility.model.listener.PropertyChangeListener;
import org.eclipse.jpt.common.utility.model.value.CollectionValueModel;
import org.eclipse.jpt.common.utility.model.value.PropertyValueModel;
/**
* An adapter that allows us to make a {@link PropertyValueModel} behave like
* a read-only, single-element {@link CollectionValueModel}, sorta.
* <p>
* If the property's value is null, an empty iterator is returned
* (i.e. you can't have a collection with a <code>null</code> element).
*/
public class PropertyCollectionValueModelAdapter<E>
extends AbstractCollectionValueModel
implements CollectionValueModel<E>
{
/** The wrapped property value model. */
protected final PropertyValueModel<? extends E> valueHolder;
/** A listener that forwards any events fired by the value holder. */
protected final PropertyChangeListener propertyChangeListener;
/** Cache the value. */
protected E value;
// ********** constructors/initialization **********
/**
* Convert the specified property value model to a collection
* value model.
*/
public PropertyCollectionValueModelAdapter(PropertyValueModel<? extends E> valueHolder) {
super();
if (valueHolder == null) {
throw new NullPointerException();
}
this.valueHolder = valueHolder;
this.propertyChangeListener = this.buildPropertyChangeListener();
this.value = null;
// postpone building the value and listening to the underlying value
// until we have listeners ourselves...
}
/**
* The wrapped value has changed, forward an equivalent
* collection change event to our listeners.
*/
protected PropertyChangeListener buildPropertyChangeListener() {
return new PropertyChangeListener() {
public void propertyChanged(PropertyChangeEvent event) {
@SuppressWarnings("unchecked")
E eventNewValue = (E) event.getNewValue();
PropertyCollectionValueModelAdapter.this.valueChanged(eventNewValue);
}
@Override
public String toString() {
return "property change listener"; //$NON-NLS-1$
}
};
}
// ********** CollectionValueModel implementation **********
public Iterator<E> iterator() {
return (this.value == null) ? EmptyIterator.<E>instance() : this.iterator_();
}
protected Iterator<E> iterator_() {
return new SingleElementIterator<E>(this.value);
}
public int size() {
return (this.value == null) ? 0 : 1;
}
// ********** AbstractCollectionValueModel implementation **********
@Override
protected void engageModel() {
this.valueHolder.addPropertyChangeListener(PropertyValueModel.VALUE, this.propertyChangeListener);
// sync our value *after* we start listening to the value model,
// since its value might change when a listener is added
this.value = this.valueHolder.getValue();
}
@Override
protected void disengageModel() {
this.valueHolder.removePropertyChangeListener(PropertyValueModel.VALUE, this.propertyChangeListener);
// clear out the value when we are not listening to the value holder
this.value = null;
}
// ********** behavior **********
/**
* synchronize our internal value with the wrapped value
* and fire the appropriate events
*/
protected void valueChanged(E newValue) {
E oldValue = this.value;
this.value = newValue;
if (oldValue == null) {
// we wouldn't get the event if the new value were null too
this.fireItemAdded(VALUES, newValue);
} else {
if (newValue == null) {
this.fireItemRemoved(VALUES, oldValue);
} else {
// we wouldn't get the event if the new value was the same as the old
this.fireCollectionChanged(VALUES, Collections.singleton(newValue));
}
}
}
@Override
public void toString(StringBuilder sb) {
StringTools.append(sb, this);
}
}
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