01: /**
02: * ===========================================
03: * JFreeReport : a free Java reporting library
04: * ===========================================
05: *
06: * Project Info: http://reporting.pentaho.org/
07: *
08: * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
09: *
10: * This library is free software; you can redistribute it and/or modify it under the terms
11: * of the GNU Lesser General Public License as published by the Free Software Foundation;
12: * either version 2.1 of the License, or (at your option) any later version.
13: *
14: * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
15: * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
16: * See the GNU Lesser General Public License for more details.
17: *
18: * You should have received a copy of the GNU Lesser General Public License along with this
19: * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
20: * Boston, MA 02111-1307, USA.
21: *
22: * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
23: * in the United States and other countries.]
24: *
25: * ------------
26: * EmptyDataSource.java
27: * ------------
28: * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
29: */package org.jfree.report.filter;
30:
31: import org.jfree.report.function.ExpressionRuntime;
32:
33: /**
34: * A data source that always returns null.
35: *
36: * @author Thomas Morgner
37: */
38: public final class EmptyDataSource implements DataSource {
39: /**
40: * Default-Constructor.
41: */
42: public EmptyDataSource() {
43: }
44:
45: /**
46: * Returns the value for the data source (always null in this case).
47: *
48: * @param runtime the expression runtime that is used to evaluate formulas and expressions when computing the value of
49: * this filter.
50: * @return always null.
51: */
52: public Object getValue(final ExpressionRuntime runtime) {
53: return null;
54: }
55:
56: /**
57: * Clones the data source.
58: *
59: * @return a clone.
60: * @noinspection CloneDoesntCallSuperClone
61: */
62: public Object clone() {
63: return this;
64: }
65:
66: }
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