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 2725 2007-04-01 18:49:29Z taqua $
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    }