001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
006 *
007 * Project Info:  http://www.jfree.org/jfreechart/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it 
010 * under the terms of the GNU Lesser General Public License as published by 
011 * the Free Software Foundation; either version 2.1 of the License, or 
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but 
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
022 * USA.  
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
025 * in the United States and other countries.]
026 *
027 * --------------------
028 * AbstractDataset.java
029 * --------------------
030 * (C)opyright 2000-2007, by Object Refinery Limited.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   Nicolas Brodu (for Astrium and EADS Corporate Research 
034 *                   Center);
035 *
036 * Changes (from 21-Aug-2001)
037 * --------------------------
038 * 21-Aug-2001 : Added standard header. Fixed DOS encoding problem (DG);
039 * 18-Sep-2001 : Updated e-mail address in header (DG);
040 * 15-Oct-2001 : Moved to new package (com.jrefinery.data.*) (DG);
041 * 22-Oct-2001 : Renamed DataSource.java --> Dataset.java etc. (DG);
042 * 17-Nov-2001 : Changed constructor from public to protected, created new 
043 *               AbstractSeriesDataset class and transferred series-related 
044 *               methods, updated Javadoc comments (DG);
045 * 04-Mar-2002 : Updated import statements (DG);
046 * 11-Jun-2002 : Updated for change in the event constructor (DG);
047 * 07-Aug-2002 : Changed listener list to use  
048 *               javax.swing.event.EventListenerList (DG);
049 * 04-Oct-2002 : Fixed errors reported by Checkstyle (DG);
050 * 27-Mar-2003 : Implemented Serializable (DG);
051 * 18-Aug-2003 : Implemented Cloneable (DG);
052 * 08-Sep-2003 : Serialization fixes (NB);
053 * 11-Sep-2003 : Cloning Fixes (NB);
054 * 01-Jun-2005 : Added hasListener() method for unit testing (DG);
055 * 
056 */
057
058package org.jfree.data.general;
059
060import java.io.IOException;
061import java.io.InvalidObjectException;
062import java.io.ObjectInputStream;
063import java.io.ObjectInputValidation;
064import java.io.ObjectOutputStream;
065import java.io.Serializable;
066import java.util.Arrays;
067import java.util.EventListener;
068import java.util.List;
069
070import javax.swing.event.EventListenerList;
071
072/**
073 * An abstract implementation of the {@link Dataset} interface, containing a 
074 * mechanism for registering change listeners.
075 */
076public abstract class AbstractDataset implements Dataset, 
077                                                 Cloneable, 
078                                                 Serializable,
079                                                 ObjectInputValidation {
080
081    /** For serialization. */
082    private static final long serialVersionUID = 1918768939869230744L;
083    
084    /** The group that the dataset belongs to. */
085    private DatasetGroup group;
086
087    /** Storage for registered change listeners. */
088    private transient EventListenerList listenerList;
089
090    /**
091     * Constructs a dataset. By default, the dataset is assigned to its own 
092     * group.
093     */
094    protected AbstractDataset() {
095        this.group = new DatasetGroup();
096        this.listenerList = new EventListenerList();
097    }
098
099    /**
100     * Returns the dataset group for the dataset.
101     *
102     * @return The group.
103     */
104    public DatasetGroup getGroup() {
105        return this.group;
106    }
107
108    /**
109     * Sets the dataset group for the dataset.
110     *
111     * @param group  the group (<code>null</code> not permitted).
112     */
113    public void setGroup(DatasetGroup group) {
114        if (group == null) {
115            throw new IllegalArgumentException("Null 'group' argument.");
116        }
117        this.group = group;
118    }
119
120    /**
121     * Registers an object to receive notification of changes to the dataset.
122     *
123     * @param listener  the object to register.
124     */
125    public void addChangeListener(DatasetChangeListener listener) {
126        this.listenerList.add(DatasetChangeListener.class, listener);
127    }
128
129    /**
130     * Deregisters an object so that it no longer receives notification of 
131     * changes to the dataset.
132     *
133     * @param listener  the object to deregister.
134     */
135    public void removeChangeListener(DatasetChangeListener listener) {
136        this.listenerList.remove(DatasetChangeListener.class, listener);
137    }
138
139    /**
140     * Returns <code>true</code> if the specified object is registered with
141     * the dataset as a listener.  Most applications won't need to call this 
142     * method, it exists mainly for use by unit testing code.
143     * 
144     * @param listener  the listener.
145     * 
146     * @return A boolean.
147     */
148    public boolean hasListener(EventListener listener) {
149        List list = Arrays.asList(this.listenerList.getListenerList());
150        return list.contains(listener);
151    }
152    
153    /**
154     * Notifies all registered listeners that the dataset has changed.
155     */
156    protected void fireDatasetChanged() {
157        notifyListeners(new DatasetChangeEvent(this, this));
158    }
159
160    /**
161     * Notifies all registered listeners that the dataset has changed.
162     *
163     * @param event  contains information about the event that triggered the 
164     *               notification.
165     */
166    protected void notifyListeners(DatasetChangeEvent event) {
167
168        Object[] listeners = this.listenerList.getListenerList();
169        for (int i = listeners.length - 2; i >= 0; i -= 2) {
170            if (listeners[i] == DatasetChangeListener.class) {
171                ((DatasetChangeListener) listeners[i + 1]).datasetChanged(
172                    event
173                );
174            }
175        }
176
177    }
178
179    /**
180     * Returns a clone of the dataset. The cloned dataset will NOT include the 
181     * {@link DatasetChangeListener} references that have been registered with 
182     * this dataset.
183     * 
184     * @return A clone.
185     * 
186     * @throws CloneNotSupportedException  if the dataset does not support 
187     *                                     cloning.
188     */
189    public Object clone() throws CloneNotSupportedException {
190        AbstractDataset clone = (AbstractDataset) super.clone();
191        clone.listenerList = new EventListenerList();
192        return clone;    
193    }
194    
195    /**
196     * Handles serialization.
197     *
198     * @param stream  the output stream.
199     *
200     * @throws IOException if there is an I/O problem.
201     */
202    private void writeObject(ObjectOutputStream stream) throws IOException {
203        stream.defaultWriteObject();
204    }
205
206    /**
207     * Restores a serialized object.
208     *
209     * @param stream  the input stream.
210     *
211     * @throws IOException if there is an I/O problem.
212     * @throws ClassNotFoundException if there is a problem loading a class.
213     */
214    private void readObject(ObjectInputStream stream) 
215        throws IOException, ClassNotFoundException {
216        stream.defaultReadObject();
217        this.listenerList = new EventListenerList();
218        stream.registerValidation(this, 10);  // see comments about priority of
219                                              // 10 in validateObject() 
220    }
221 
222    /**
223     * Validates the object. We use this opportunity to call listeners who have 
224     * registered during the deserialization process, as listeners are not 
225     * serialized. This method is called by the serialization system after the 
226     * entire graph is read.
227     *  
228     * This object has registered itself to the system with a priority of 10. 
229     * Other callbacks may register with a higher priority number to be called 
230     * before this object, or with a lower priority number to be called after 
231     * the listeners were notified.
232     * 
233     * All listeners are supposed to have register by now, either in their 
234     * readObject or validateObject methods. Notify them that this dataset has 
235     * changed.  
236     *
237     * @exception InvalidObjectException If the object cannot validate itself.
238     */
239    public void validateObject() throws InvalidObjectException {
240       fireDatasetChanged();
241    }
242   
243}