001 /**
002 * ========================================
003 * JFreeReport : a free Java report library
004 * ========================================
005 *
006 * Project Info: http://reporting.pentaho.org/
007 *
008 * (C) Copyright 2000-2007, by Object Refinery Limited, Pentaho Corporation and Contributors.
009 *
010 * This library is free software; you can redistribute it and/or modify it under the terms
011 * of the GNU Lesser General Public License as published by the Free Software Foundation;
012 * either version 2.1 of the License, or (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
015 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
016 * See the GNU Lesser General Public License for more details.
017 *
018 * You should have received a copy of the GNU Lesser General Public License along with this
019 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
020 * Boston, MA 02111-1307, USA.
021 *
022 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
023 * in the United States and other countries.]
024 *
025 * ------------
026 * $Id: IsEmptyDataExpression.java,v 1.4 2007/04/01 18:49:25 taqua Exp $
027 * ------------
028 * (C) Copyright 2000-2005, by Object Refinery Limited.
029 * (C) Copyright 2005-2007, by Pentaho Corporation.
030 */
031 package org.jfree.report.expressions.sys;
032
033 import org.jfree.report.DataSourceException;
034 import org.jfree.report.ReportData;
035 import org.jfree.report.expressions.AbstractExpression;
036 import org.jfree.report.expressions.ExpressionRuntime;
037
038 /**
039 * Creation-Date: 31.01.2006, 18:55:09
040 *
041 * @author Thomas Morgner
042 */
043 public class IsEmptyDataExpression extends AbstractExpression
044 {
045 public IsEmptyDataExpression()
046 {
047 }
048
049 /**
050 * Return the current expression value. <P> The value depends (obviously) on
051 * the expression implementation.
052 *
053 * @return the value of the function.
054 */
055 public Object computeValue() throws DataSourceException
056 {
057
058 final ExpressionRuntime runtime = getRuntime();
059 if (runtime == null)
060 {
061 return null;
062 }
063
064 final ReportData data = runtime.getData();
065 if (data == null)
066 {
067 return null;
068 }
069 synchronized(data)
070 {
071 if (data.getCursorPosition() > 0)
072 {
073 return Boolean.FALSE;
074 }
075 if (data.isAdvanceable() == false)
076 {
077 return Boolean.TRUE;
078 }
079 return Boolean.FALSE;
080 }
081 }
082 }