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Java > Open Source Codes > org > jfree > data > general > AbstractDataset


1 /* ===========================================================
2  * JFreeChart : a free chart library for the Java(tm) platform
3  * ===========================================================
4  *
5  * (C) Copyright 2000-2006, by Object Refinery Limited and Contributors.
6  *
7  * Project Info: http://www.jfree.org/jfreechart/index.html
8  *
9  * This library is free software; you can redistribute it and/or modify it
10  * under the terms of the GNU Lesser General Public License as published by
11  * the Free Software Foundation; either version 2.1 of the License, or
12  * (at your option) any later version.
13  *
14  * This library is distributed in the hope that it will be useful, but
15  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
17  * License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with this library; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
22  * USA.
23  *
24  * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
25  * in the United States and other countries.]
26  *
27  * --------------------
28  * AbstractDataset.java
29  * --------------------
30  * (C)opyright 2000-2006, by Object Refinery Limited.
31  *
32  * Original Author: David Gilbert (for Object Refinery Limited);
33  * Contributor(s): Nicolas Brodu (for Astrium and EADS Corporate Research
34  * Center);
35  *
36  * $Id: AbstractDataset.java,v 1.5.2.2 2006/07/26 12:14:20 mungady Exp $
37  *
38  * Changes (from 21-Aug-2001)
39  * --------------------------
40  * 21-Aug-2001 : Added standard header. Fixed DOS encoding problem (DG);
41  * 18-Sep-2001 : Updated e-mail address in header (DG);
42  * 15-Oct-2001 : Moved to new package (com.jrefinery.data.*) (DG);
43  * 22-Oct-2001 : Renamed DataSource.java --> Dataset.java etc. (DG);
44  * 17-Nov-2001 : Changed constructor from public to protected, created new
45  * AbstractSeriesDataset class and transferred series-related
46  * methods, updated Javadoc comments (DG);
47  * 04-Mar-2002 : Updated import statements (DG);
48  * 11-Jun-2002 : Updated for change in the event constructor (DG);
49  * 07-Aug-2002 : Changed listener list to use
50  * javax.swing.event.EventListenerList (DG);
51  * 04-Oct-2002 : Fixed errors reported by Checkstyle (DG);
52  * 27-Mar-2003 : Implemented Serializable (DG);
53  * 18-Aug-2003 : Implemented Cloneable (DG);
54  * 08-Sep-2003 : Serialization fixes (NB);
55  * 11-Sep-2003 : Cloning Fixes (NB);
56  * 01-Jun-2005 : Added hasListener() method for unit testing (DG);
57  *
58  */
59
60 package org.jfree.data.general;
61
62 import java.io.IOException JavaDoc;
63 import java.io.InvalidObjectException JavaDoc;
64 import java.io.ObjectInputStream JavaDoc;
65 import java.io.ObjectInputValidation JavaDoc;
66 import java.io.ObjectOutputStream JavaDoc;
67 import java.io.Serializable JavaDoc;
68 import java.util.Arrays JavaDoc;
69 import java.util.EventListener JavaDoc;
70 import java.util.List JavaDoc;
71
72 import javax.swing.event.EventListenerList JavaDoc;
73
74 /**
75  * An abstract implementation of the {@link Dataset} interface, containing a
76  * mechanism for registering change listeners.
77  */
78 public abstract class AbstractDataset implements Dataset,
79                                                  Cloneable JavaDoc,
80                                                  Serializable JavaDoc,
81                                                  ObjectInputValidation JavaDoc {
82
83     /** For serialization. */
84     private static final long serialVersionUID = 1918768939869230744L;
85     
86     /** The group that the dataset belongs to. */
87     private DatasetGroup group;
88
89     /** Storage for registered change listeners. */
90     private transient EventListenerList JavaDoc listenerList;
91
92     /**
93      * Constructs a dataset. By default, the dataset is assigned to its own
94      * group.
95      */
96     protected AbstractDataset() {
97         this.group = new DatasetGroup();
98         this.listenerList = new EventListenerList JavaDoc();
99     }
100
101     /**
102      * Returns the dataset group for the dataset.
103      *
104      * @return The group.
105      */
106     public DatasetGroup getGroup() {
107         return this.group;
108     }
109
110     /**
111      * Sets the dataset group for the dataset.
112      *
113      * @param group the group (<code>null</code> not permitted).
114      */
115     public void setGroup(DatasetGroup group) {
116         if (group == null) {
117             throw new IllegalArgumentException JavaDoc("Null 'group' argument.");
118         }
119         this.group = group;
120     }
121
122     /**
123      * Registers an object to receive notification of changes to the dataset.
124      *
125      * @param listener the object to register.
126      */
127     public void addChangeListener(DatasetChangeListener listener) {
128         this.listenerList.add(DatasetChangeListener.class, listener);
129     }
130
131     /**
132      * Deregisters an object so that it no longer receives notification of
133      * changes to the dataset.
134      *
135      * @param listener the object to deregister.
136      */
137     public void removeChangeListener(DatasetChangeListener listener) {
138         this.listenerList.remove(DatasetChangeListener.class, listener);
139     }
140
141     /**
142      * Returns <code>true</code> if the specified object is registered with
143      * the dataset as a listener. Most applications won't need to call this
144      * method, it exists mainly for use by unit testing code.
145      *
146      * @param listener the listener.
147      *
148      * @return A boolean.
149      */
150     public boolean hasListener(EventListener JavaDoc listener) {
151         List JavaDoc list = Arrays.asList(this.listenerList.getListenerList());
152         return list.contains(listener);
153     }
154     
155     /**
156      * Notifies all registered listeners that the dataset has changed.
157      */
158     protected void fireDatasetChanged() {
159         notifyListeners(new DatasetChangeEvent(this, this));
160     }
161
162     /**
163      * Notifies all registered listeners that the dataset has changed.
164      *
165      * @param event contains information about the event that triggered the
166      * notification.
167      */
168     protected void notifyListeners(DatasetChangeEvent event) {
169
170         Object JavaDoc[] listeners = this.listenerList.getListenerList();
171         for (int i = listeners.length - 2; i >= 0; i -= 2) {
172             if (listeners[i] == DatasetChangeListener.class) {
173                 ((DatasetChangeListener) listeners[i + 1]).datasetChanged(
174                     event
175                 );
176             }
177         }
178
179     }
180
181     /**
182      * Returns a clone of the dataset. The cloned dataset will NOT include the
183      * {@link DatasetChangeListener} references that have been registered with
184      * this dataset.
185      *
186      * @return A clone.
187      *
188      * @throws CloneNotSupportedException if the dataset does not support
189      * cloning.
190      */
191     public Object JavaDoc clone() throws CloneNotSupportedException JavaDoc {
192         AbstractDataset clone = (AbstractDataset) super.clone();
193         clone.listenerList = new EventListenerList JavaDoc();
194         return clone;
195     }
196     
197     /**
198      * Handles serialization.
199      *
200      * @param stream the output stream.
201      *
202      * @throws IOException if there is an I/O problem.
203      */
204     private void writeObject(ObjectOutputStream JavaDoc stream) throws IOException JavaDoc {
205         stream.defaultWriteObject();
206     }
207
208     /**
209      * Restores a serialized object.
210      *
211      * @param stream the input stream.
212      *
213      * @throws IOException if there is an I/O problem.
214      * @throws ClassNotFoundException if there is a problem loading a class.
215      */
216     private void readObject(ObjectInputStream JavaDoc stream)
217         throws IOException JavaDoc, ClassNotFoundException JavaDoc {
218         stream.defaultReadObject();
219         this.listenerList = new EventListenerList JavaDoc();
220         stream.registerValidation(this, 10); // see comments about priority of
221 // 10 in validateObject()
222 }
223  
224     /**
225      * Validates the object. We use this opportunity to call listeners who have
226      * registered during the deserialization process, as listeners are not
227      * serialized. This method is called by the serialization system after the
228      * entire graph is read.
229      *
230      * This object has registered itself to the system with a priority of 10.
231      * Other callbacks may register with a higher priority number to be called
232      * before this object, or with a lower priority number to be called after
233      * the listeners were notified.
234      *
235      * All listeners are supposed to have register by now, either in their
236      * readObject or validateObject methods. Notify them that this dataset has
237      * changed.
238      *
239      * @exception InvalidObjectException If the object cannot validate itself.
240      */
241     public void validateObject() throws InvalidObjectException JavaDoc {
242        fireDatasetChanged();
243     }
244    
245 }
246
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