/*******************************************************************************
* Copyright (c) 2004, 2005 Elias Volanakis and others.
�* 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:
�*����Elias Volanakis - initial API and implementation
�*******************************************************************************/
package org.eclipse.gef.examples.shapes.model;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeSupport;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import org.eclipse.ui.views.properties.IPropertyDescriptor;
import org.eclipse.ui.views.properties.IPropertySource;
/**
* Abstract prototype of a model element.
* <p>This class provides features necessary for all model elements, like:</p>
* <ul>
* <li>property-change support (used to notify edit parts of model changes),</li>
* <li>property-source support (used to display property values in the Property View) and</li>
* <li>serialization support (the model hierarchy must be serializable, so that the editor can
* save and restore a binary representation. You might not need this, if you store the model
* a non-binary form like XML).</li>
* </ul>
* @author Elias Volanakis
*/
public abstract class ModelElement implements IPropertySource, Serializable {
/** An empty property descriptor. */
private static final IPropertyDescriptor[] EMPTY_ARRAY = new IPropertyDescriptor[0];
private static final long serialVersionUID = 1;
/** Delegate used to implemenent property-change-support. */
private transient PropertyChangeSupport pcsDelegate = new PropertyChangeSupport(this);
/**
* Attach a non-null PropertyChangeListener to this object.
* @param l a non-null PropertyChangeListener instance
* @throws IllegalArgumentException if the parameter is null
*/
public synchronized void addPropertyChangeListener(PropertyChangeListener l) {
if (l == null) {
throw new IllegalArgumentException();
}
pcsDelegate.addPropertyChangeListener(l);
}
/**
* Report a property change to registered listeners (for example edit parts).
* @param property the programmatic name of the property that changed
* @param oldValue the old value of this property
* @param newValue the new value of this property
*/
protected void firePropertyChange(String property, Object oldValue, Object newValue) {
if (pcsDelegate.hasListeners(property)) {
pcsDelegate.firePropertyChange(property, oldValue, newValue);
}
}
/**
* Returns a value for this property source that can be edited in a property sheet.
* <p>My personal rule of thumb:</p>
* <ul>
* <li>model elements should return themselves and</li>
* <li>custom IPropertySource implementations (like DimensionPropertySource in the GEF-logic
* example) should return an editable value.</li>
* </ul>
* <p>Override only if necessary.</p>
* @return this instance
*/
public Object getEditableValue() {
return this;
}
/**
* Children should override this. The default implementation returns an empty array.
*/
public IPropertyDescriptor[] getPropertyDescriptors() {
return EMPTY_ARRAY;
}
/**
* Children should override this. The default implementation returns null.
*/
public Object getPropertyValue(Object id) {
return null;
}
/**
* Children should override this. The default implementation returns false.
*/
public boolean isPropertySet(Object id) {
return false;
}
/**
* Deserialization constructor. Initializes transient fields.
* @see java.io.Serializable
*/
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException {
in.defaultReadObject();
pcsDelegate = new PropertyChangeSupport(this);
}
/**
* Remove a PropertyChangeListener from this component.
* @param l a PropertyChangeListener instance
*/
public synchronized void removePropertyChangeListener(PropertyChangeListener l) {
if (l != null) {
pcsDelegate.removePropertyChangeListener(l);
}
}
/**
* Children should override this. The default implementation does nothing.
*/
public void resetPropertyValue(Object id) {
// do nothing
}
/**
* Children should override this. The default implementation does nothing.
*/
public void setPropertyValue(Object id, Object value) {
// do nothing
}
}