001    /**
002     * =========================================
003     * LibFormula : a free Java formula library
004     * =========================================
005     *
006     * Project Info:  http://reporting.pentaho.org/libformula/
007     *
008     * (C) Copyright 2006-2007, by 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     * ------------
027     * $Id: MonthFunction.java 2822 2007-05-20 21:47:52Z mimil $
028     * ------------
029     * (C) Copyright 2006-2007, by Pentaho Corporation.
030     */
031    package org.jfree.formula.function.datetime;
032    
033    import java.util.Calendar;
034    import java.util.Date;
035    
036    import org.jfree.formula.EvaluationException;
037    import org.jfree.formula.FormulaContext;
038    import org.jfree.formula.LibFormulaErrorValue;
039    import org.jfree.formula.function.Function;
040    import org.jfree.formula.function.ParameterCallback;
041    import org.jfree.formula.lvalues.TypeValuePair;
042    import org.jfree.formula.typing.TypeRegistry;
043    import org.jfree.formula.typing.coretypes.NumberType;
044    import org.jfree.formula.util.DateUtil;
045    
046    /**
047     * This function extracts the month from a date.
048     * 
049     * @author Cedric Pronzato
050     */
051    public class MonthFunction implements Function
052    {
053      public MonthFunction()
054      {
055      }
056    
057      public String getCanonicalName()
058      {
059        return "MONTH";
060      }
061    
062      public TypeValuePair evaluate(final FormulaContext context,
063          final ParameterCallback parameters) throws EvaluationException
064      {
065        if (parameters.getParameterCount() != 1)
066        {
067          throw new EvaluationException(LibFormulaErrorValue.ERROR_ARGUMENTS_VALUE);
068        }
069    
070        final TypeRegistry typeRegistry = context.getTypeRegistry();
071    
072        final Date d = typeRegistry.convertToDate(parameters.getType(0), parameters
073            .getValue(0));
074    
075        if (d == null)
076        {
077          throw new EvaluationException(
078              LibFormulaErrorValue.ERROR_INVALID_ARGUMENT_VALUE);
079        }
080    
081        final Calendar gc = DateUtil.createCalendar(d, context
082            .getLocalizationContext());
083    
084        final int month = gc.get(Calendar.MONTH) + 1;
085        return new TypeValuePair(NumberType.GENERIC_NUMBER, new Integer(month));
086      }
087    }