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: PrecomputedValueRegistry.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    
032    package org.jfree.report.data;
033    
034    /**
035     * Expression precomputation processes the report in a parallel process to
036     * retrieve the final value of an function. The final value of an expression
037     * is the value the expression would return before it goes out of scope.
038     *
039     * Precomputation can be generally considered expensive, so it should be done
040     * only once. During the precomputation run, no output is generated at all.
041     * Only named data-row expressions can be precomputed.
042     *
043     * @author Thomas Morgner
044     */
045    public interface PrecomputedValueRegistry
046    {
047      public void startElement (PrecomputeNodeKey element);
048      public void finishElement (PrecomputeNodeKey element);
049      public PrecomputeNode currentNode ();
050    
051      public void addFunction(final String name, final Object value);
052    
053      public void startElementPrecomputation(final PrecomputeNodeKey element);
054    
055      public void finishElementPrecomputation(final PrecomputeNodeKey element);
056    }