| /******************************************************************************* |
| * 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.Arrays; |
| import java.util.Collection; |
| |
| import org.eclipse.jpt.utility.internal.model.Model; |
| import org.eclipse.jpt.utility.internal.model.event.PropertyChangeEvent; |
| import org.eclipse.jpt.utility.internal.model.listener.ChangeListener; |
| import org.eclipse.jpt.utility.internal.model.listener.PropertyChangeListener; |
| |
| /** |
| * This AspectAdapter provides basic PropertyChange support. |
| * This allows us to convert a set of one or more properties into |
| * a single property, VALUE. |
| * |
| * The typical subclass will override the following methods: |
| * #buildValue_() |
| * at the very minimum, override this method to return the value of the |
| * subject's property (or "virtual" property); it does not need to be |
| * overridden if #buildValue() is overridden and its behavior changed |
| * #setValue_(Object) |
| * override this method if the client code needs to *set* the value of |
| * the subject's property; oftentimes, though, the client code (e.g. UI) |
| * will need only to *get* the value; it does not need to be |
| * overridden if #setValue(Object) is overridden and its behavior changed |
| * #buildValue() |
| * override this method only if returning a null value when the subject is null |
| * is unacceptable |
| * #setValue(Object) |
| * override this method only if something must be done when the subject |
| * is null (e.g. throw an exception) |
| */ |
| public abstract class PropertyAspectAdapter<S extends Model, T> |
| extends AspectAdapter<S> |
| implements WritablePropertyValueModel<T> |
| { |
| /** |
| * Cache the current value of the aspect so we |
| * can pass an "old value" when we fire a property change event. |
| * We need this because the value may be calculated and may |
| * not be in the property change event fired by the subject, |
| * especially when dealing with multiple aspects. |
| */ |
| protected T value; |
| |
| /** The name of the subject's properties that we use for the value. */ |
| protected final String[] propertyNames; |
| protected static final String[] EMPTY_PROPERTY_NAMES = new String[0]; |
| |
| /** A listener that listens to the appropriate properties of the subject. */ |
| protected final PropertyChangeListener propertyChangeListener; |
| |
| |
| // ********** constructors ********** |
| |
| /** |
| * Construct a PropertyAspectAdapter for the specified subject |
| * and property. |
| */ |
| protected PropertyAspectAdapter(String propertyName, S subject) { |
| this(new String[] {propertyName}, subject); |
| } |
| |
| /** |
| * Construct a PropertyAspectAdapter for the specified subject |
| * and properties. |
| */ |
| protected PropertyAspectAdapter(String[] propertyNames, S subject) { |
| this(new StaticPropertyValueModel<S>(subject), propertyNames); |
| } |
| |
| /** |
| * Construct a PropertyAspectAdapter for the specified subject holder |
| * and properties. |
| */ |
| protected PropertyAspectAdapter(PropertyValueModel<? extends S> subjectHolder, String... propertyNames) { |
| super(subjectHolder); |
| this.propertyNames = propertyNames; |
| this.propertyChangeListener = this.buildPropertyChangeListener(); |
| // our value is null when we are not listening to the subject |
| this.value = null; |
| } |
| |
| /** |
| * Construct a PropertyAspectAdapter for the specified subject holder |
| * and properties. |
| */ |
| protected PropertyAspectAdapter(PropertyValueModel<? extends S> subjectHolder, Collection<String> propertyNames) { |
| this(subjectHolder, propertyNames.toArray(new String[propertyNames.size()])); |
| } |
| |
| /** |
| * Construct a PropertyAspectAdapter for an "unchanging" property in |
| * the specified subject. This is useful for a property aspect that does not |
| * change for a particular subject; but the subject will change, resulting in |
| * a new property. (A TransformationPropertyValueModel could also be |
| * used in this situation.) |
| */ |
| protected PropertyAspectAdapter(PropertyValueModel<? extends S> subjectHolder) { |
| this(subjectHolder, EMPTY_PROPERTY_NAMES); |
| } |
| |
| |
| // ********** initialization ********** |
| |
| /** |
| * The subject's property has changed, notify the listeners. |
| */ |
| protected PropertyChangeListener buildPropertyChangeListener() { |
| // transform the subject's property change events into VALUE property change events |
| return new PropertyChangeListener() { |
| public void propertyChanged(PropertyChangeEvent event) { |
| PropertyAspectAdapter.this.propertyChanged(); |
| } |
| @Override |
| public String toString() { |
| return "property change listener: " + Arrays.asList(PropertyAspectAdapter.this.propertyNames); |
| } |
| }; |
| } |
| |
| |
| // ********** PropertyValueModel implementation ********** |
| |
| /** |
| * Return the value of the subject's property. |
| */ |
| @Override |
| public final T value() { |
| return this.value; |
| } |
| |
| |
| // ********** WritablePropertyValueModel implementation ********** |
| |
| /** |
| * Set the value of the subject's property. |
| */ |
| public void setValue(T value) { |
| if (this.subject != null) { |
| this.setValue_(value); |
| } |
| } |
| |
| /** |
| * Set the value of the subject's property. |
| * At this point we can be sure that the subject is not null. |
| * @see #setValue(Object) |
| */ |
| protected void setValue_(T value) { |
| throw new UnsupportedOperationException(); |
| } |
| |
| |
| // ********** AspectAdapter implementation ********** |
| |
| @Override |
| protected Class<? extends ChangeListener> listenerClass() { |
| return PropertyChangeListener.class; |
| } |
| |
| @Override |
| protected String listenerAspectName() { |
| return VALUE; |
| } |
| |
| @Override |
| protected boolean hasListeners() { |
| return this.hasAnyPropertyChangeListeners(VALUE); |
| } |
| |
| @Override |
| protected void fireAspectChange(Object oldValue, Object newValue) { |
| this.firePropertyChanged(VALUE, oldValue, newValue); |
| } |
| |
| @Override |
| protected void engageSubject() { |
| super.engageSubject(); |
| // synch our value *after* we start listening to the subject, |
| // since its value might change when a listener is added |
| this.value = this.buildValue(); |
| } |
| |
| @Override |
| protected void engageSubject_() { |
| for (String propertyName : this.propertyNames) { |
| ((Model) this.subject).addPropertyChangeListener(propertyName, this.propertyChangeListener); |
| } |
| } |
| |
| @Override |
| protected void disengageSubject() { |
| super.disengageSubject(); |
| // clear out our value when we are not listening to the subject |
| this.value = null; |
| } |
| |
| @Override |
| protected void disengageSubject_() { |
| for (String propertyName : this.propertyNames) { |
| ((Model) this.subject).removePropertyChangeListener(propertyName, this.propertyChangeListener); |
| } |
| } |
| |
| |
| // ********** AbstractModel implementation ********** |
| |
| @Override |
| public void toString(StringBuilder sb) { |
| for (int i = 0; i < this.propertyNames.length; i++) { |
| if (i != 0) { |
| sb.append(", "); |
| } |
| sb.append(this.propertyNames[i]); |
| } |
| } |
| |
| |
| // ********** behavior ********** |
| |
| /** |
| * Return the aspect's value. |
| * At this point the subject may be null. |
| */ |
| protected T buildValue() { |
| return (this.subject == null) ? null : this.buildValue_(); |
| } |
| |
| /** |
| * Return the value of the subject's property. |
| * At this point we can be sure that the subject is not null. |
| * @see #buildValue() |
| */ |
| protected T buildValue_() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| protected void propertyChanged() { |
| T old = this.value; |
| this.value = this.buildValue(); |
| this.fireAspectChange(old, this.value); |
| } |
| |
| } |