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: * DataSource.java
27: * ------------
28: * (C) Copyright 2001-2007, by Object Refinery Ltd, Pentaho Corporation and Contributors.
29: */package org.jfree.report.filter;
30:
31: import java.io.Serializable;
32:
33: import org.jfree.report.function.ExpressionRuntime;
34:
35: /**
36: * A DataSource is a producer in the data chain. Common Sources are StaticSources (predefined data), ReportDataSources
37: * (data filled from the reports data set) or FunctionDataSource (the data is filled by querying an assigned function).
38: * <p/>
39: * All DataSources have to support the Cloneable interface so that a report can be completley cloned with all assigned
40: * filters and DataSources. Reports are cloned before they are processed to remove the side effect when having multiple
41: * report processors working on the same object.
42: *
43: * @author Thomas Morgner
44: */
45: public interface DataSource extends Serializable, Cloneable {
46: /**
47: * Returns the current value for the data source.
48: *
49: * @param runtime the expression runtime that is used to evaluate formulas and expressions when computing the value of
50: * this filter.
51: * @return the value.
52: */
53: public Object getValue(ExpressionRuntime runtime);
54:
55: /**
56: * Clones this <code>DataSource</code>.
57: *
58: * @return the clone.
59: * @throws CloneNotSupportedException this should never happen.
60: */
61: public Object clone() throws CloneNotSupportedException;
62:
63: }
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