| /******************************************************************************* |
| * Copyright (c) 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 java.util.ListIterator; |
| |
| import org.eclipse.jpt.utility.internal.iterators.EmptyListIterator; |
| import org.eclipse.jpt.utility.internal.iterators.SingleElementListIterator; |
| 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.internal.model.event.PropertyChangeEvent; |
| import org.eclipse.jpt.utility.internal.model.listener.ListChangeListener; |
| import org.eclipse.jpt.utility.internal.model.listener.PropertyChangeListener; |
| |
| /** |
| * An adapter that allows us to make a PropertyValueModel behave like |
| * a read-only, single-element ListValueModel, sorta. |
| * |
| * If the property's value is null, an empty iterator is returned |
| * (i.e. you can't have a list with a null element). |
| */ |
| public class PropertyListValueModelAdapter<E> |
| extends AbstractModel |
| implements ListValueModel<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 property value model. |
| */ |
| public PropertyListValueModelAdapter(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, ListChangeListener.class, LIST_VALUES); |
| } |
| |
| /** |
| * The wrapped value has changed, forward an equivalent |
| * list change event to our listeners. |
| */ |
| protected PropertyChangeListener buildPropertyChangeListener() { |
| return new PropertyChangeListener() { |
| @SuppressWarnings("unchecked") |
| public void propertyChanged(PropertyChangeEvent event) { |
| PropertyListValueModelAdapter.this.valueChanged((E) event.newValue()); |
| } |
| @Override |
| public String toString() { |
| return "property change listener"; |
| } |
| }; |
| } |
| |
| |
| // ********** ListValueModel implementation ********** |
| |
| public Iterator<E> iterator() { |
| return this.listIterator(); |
| } |
| |
| public ListIterator<E> listIterator() { |
| return (this.value == null) ? |
| EmptyListIterator.<E>instance() |
| : |
| new SingleElementListIterator<E>(this.value); |
| } |
| |
| public int size() { |
| return (this.value == null) ? 0 : 1; |
| } |
| |
| public E get(int index) { |
| if (this.value == null) { |
| throw this.ioobe(index, 0); |
| } |
| if (index > 0) { |
| throw this.ioobe(index, 1); |
| } |
| return this.value; |
| } |
| |
| protected static final Object[] EMPTY_OBJECT_ARRAY = new Object[0]; |
| public Object[] toArray() { |
| return (this.value == null) ? EMPTY_OBJECT_ARRAY : new Object[] {this.value}; |
| } |
| |
| |
| // ********** extend change support ********** |
| |
| /** |
| * Override to start listening to the value holder if necessary. |
| */ |
| @Override |
| public void addListChangeListener(ListChangeListener listener) { |
| if (this.hasNoListeners()) { |
| this.engageModel(); |
| } |
| super.addListChangeListener(listener); |
| } |
| |
| /** |
| * Override to start listening to the value holder if necessary. |
| */ |
| @Override |
| public void addListChangeListener(String listName, ListChangeListener listener) { |
| if (listName == LIST_VALUES && this.hasNoListeners()) { |
| this.engageModel(); |
| } |
| super.addListChangeListener(listName, listener); |
| } |
| |
| /** |
| * Override to stop listening to the value holder if appropriate. |
| */ |
| @Override |
| public void removeListChangeListener(ListChangeListener listener) { |
| super.removeListChangeListener(listener); |
| if (this.hasNoListeners()) { |
| this.disengageModel(); |
| } |
| } |
| |
| /** |
| * Override to stop listening to the value holder if appropriate. |
| */ |
| @Override |
| public void removeListChangeListener(String listName, ListChangeListener listener) { |
| super.removeListChangeListener(listName, listener); |
| if (listName == LIST_VALUES && this.hasNoListeners()) { |
| this.disengageModel(); |
| } |
| } |
| |
| |
| // ********** queries ********** |
| |
| protected boolean hasListeners() { |
| return this.hasAnyListChangeListeners(LIST_VALUES); |
| } |
| |
| protected boolean hasNoListeners() { |
| return ! this.hasListeners(); |
| } |
| |
| |
| // ********** behavior ********** |
| |
| protected IndexOutOfBoundsException ioobe(int index, int size) { |
| return new IndexOutOfBoundsException("Index: " + index + ", Size: " + size); |
| } |
| |
| 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.value(); |
| } |
| |
| 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) { |
| E oldValue = this.value; |
| this.value = newValue; |
| if (oldValue == null) { |
| this.fireItemAdded(LIST_VALUES, 0, newValue); |
| } else { |
| if (newValue == null) { |
| this.fireItemRemoved(LIST_VALUES, 0, oldValue); |
| } else { |
| this.fireItemReplaced(LIST_VALUES, 0, newValue, oldValue); |
| } |
| } |
| } |
| |
| @Override |
| public void toString(StringBuilder sb) { |
| sb.append(this.valueHolder); |
| } |
| |
| } |