| /******************************************************************************* |
| * 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.iterators.EmptyIterator; |
| import org.eclipse.jpt.utility.internal.iterators.SingleElementIterator; |
| 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.PropertyChangeEvent; |
| import org.eclipse.jpt.utility.model.listener.CollectionChangeListener; |
| import org.eclipse.jpt.utility.model.listener.PropertyChangeListener; |
| import org.eclipse.jpt.utility.model.value.CollectionValueModel; |
| import org.eclipse.jpt.utility.model.value.PropertyValueModel; |
| |
| /** |
| * 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<E> |
| extends AbstractModel |
| 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 ********** |
| |
| /** |
| * Wrap the specified ListValueModel. |
| */ |
| public PropertyCollectionValueModelAdapter(PropertyValueModel<? extends E> valueHolder) { |
| super(); |
| if (valueHolder == null) { |
| throw new NullPointerException(); |
| } |
| this.valueHolder = valueHolder; |
| this.propertyChangeListener = this.buildPropertyChangeListener(); |
| // postpone building the value and listening to the underlying value |
| // until we have listeners ourselves... |
| } |
| |
| @Override |
| protected ChangeSupport buildChangeSupport() { |
| return new SingleAspectChangeSupport(this, CollectionChangeListener.class, VALUES); |
| } |
| |
| /** |
| * The wrapped value has changed, forward an equivalent |
| * collection change event to our listeners. |
| */ |
| protected PropertyChangeListener buildPropertyChangeListener() { |
| return new PropertyChangeListener() { |
| @SuppressWarnings("unchecked") |
| public void propertyChanged(PropertyChangeEvent event) { |
| PropertyCollectionValueModelAdapter.this.valueChanged((E) event.getNewValue()); |
| } |
| @Override |
| public String toString() { |
| return "property change listener"; |
| } |
| }; |
| } |
| |
| |
| // ********** CollectionValueModel implementation ********** |
| |
| public Iterator<E> iterator() { |
| return (this.value == null) ? |
| EmptyIterator.<E>instance() |
| : |
| new SingleElementIterator<E>(this.value); |
| } |
| |
| public int size() { |
| return (this.value == null) ? 0 : 1; |
| } |
| |
| |
| // ********** extend change support ********** |
| |
| /** |
| * Override to start listening to the value holder if necessary. |
| */ |
| @Override |
| public void addCollectionChangeListener(CollectionChangeListener listener) { |
| if (this.hasNoListeners()) { |
| this.engageModel(); |
| } |
| super.addCollectionChangeListener(listener); |
| } |
| |
| /** |
| * Override to start listening to the value holder if necessary. |
| */ |
| @Override |
| public void addCollectionChangeListener(String collectionName, CollectionChangeListener listener) { |
| if (collectionName == VALUES && this.hasNoListeners()) { |
| this.engageModel(); |
| } |
| super.addCollectionChangeListener(collectionName, listener); |
| } |
| |
| /** |
| * Override to stop listening to the value holder if appropriate. |
| */ |
| @Override |
| public void removeCollectionChangeListener(CollectionChangeListener listener) { |
| super.removeCollectionChangeListener(listener); |
| if (this.hasNoListeners()) { |
| this.disengageModel(); |
| } |
| } |
| |
| /** |
| * Override to stop listening to the value holder if appropriate. |
| */ |
| @Override |
| public void removeCollectionChangeListener(String collectionName, CollectionChangeListener listener) { |
| super.removeCollectionChangeListener(collectionName, listener); |
| if (collectionName == VALUES && this.hasNoListeners()) { |
| this.disengageModel(); |
| } |
| } |
| |
| |
| // ********** queries ********** |
| |
| protected boolean hasListeners() { |
| return this.hasAnyCollectionChangeListeners(VALUES); |
| } |
| |
| protected boolean hasNoListeners() { |
| return ! this.hasListeners(); |
| } |
| |
| |
| // ********** behavior ********** |
| |
| protected void engageModel() { |
| this.valueHolder.addPropertyChangeListener(PropertyValueModel.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(PropertyValueModel.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(E newValue) { |
| // put in "empty" check so we don't fire events unnecessarily |
| if (this.value != null) { |
| E oldValue = this.value; |
| this.value = null; |
| this.fireItemRemoved(VALUES, oldValue); |
| } |
| this.value = newValue; |
| // put in "empty" check so we don't fire events unnecessarily |
| if (this.value != null) { |
| this.fireItemAdded(VALUES, this.value); |
| } |
| } |
| |
| @Override |
| public void toString(StringBuilder sb) { |
| sb.append(this.valueHolder); |
| } |
| |
| } |