Source for org.jfree.report.expressions.sys.IsEmptyDataExpression

   1: /**
   2:  * ========================================
   3:  * JFreeReport : a free Java report library
   4:  * ========================================
   5:  *
   6:  * Project Info:  http://reporting.pentaho.org/
   7:  *
   8:  * (C) Copyright 2000-2007, by Object Refinery Limited, Pentaho Corporation and Contributors.
   9:  *
  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:  * $Id: IsEmptyDataExpression.java 2725 2007-04-01 18:49:29Z taqua $
  27:  * ------------
  28:  * (C) Copyright 2000-2005, by Object Refinery Limited.
  29:  * (C) Copyright 2005-2007, by Pentaho Corporation.
  30:  */
  31: package org.jfree.report.expressions.sys;
  32: 
  33: import org.jfree.report.DataSourceException;
  34: import org.jfree.report.ReportData;
  35: import org.jfree.report.expressions.AbstractExpression;
  36: import org.jfree.report.expressions.ExpressionRuntime;
  37: 
  38: /**
  39:  * Creation-Date: 31.01.2006, 18:55:09
  40:  *
  41:  * @author Thomas Morgner
  42:  */
  43: public class IsEmptyDataExpression extends AbstractExpression
  44: {
  45:   public IsEmptyDataExpression()
  46:   {
  47:   }
  48: 
  49:   /**
  50:    * Return the current expression value. <P> The value depends (obviously) on
  51:    * the expression implementation.
  52:    *
  53:    * @return the value of the function.
  54:    */
  55:   public Object computeValue() throws DataSourceException
  56:   {
  57: 
  58:     final ExpressionRuntime runtime = getRuntime();
  59:     if (runtime == null)
  60:     {
  61:       return null;
  62:     }
  63: 
  64:     final ReportData data = runtime.getData();
  65:     if (data == null)
  66:     {
  67:       return null;
  68:     }
  69:     synchronized(data)
  70:     {
  71:       if (data.getCursorPosition() > 0)
  72:       {
  73:         return Boolean.FALSE;
  74:       }
  75:       if (data.isAdvanceable() == false)
  76:       {
  77:         return Boolean.TRUE;
  78:       }
  79:       return Boolean.FALSE;
  80:     }
  81:   }
  82: }