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The TwelveMonkeys Core library. Contains common utility classes.
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/*
 * Copyright (c) 2008, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name "TwelveMonkeys" nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.twelvemonkeys.util.convert;

import com.twelvemonkeys.lang.*;

import java.util.*;
import java.text.*;
import java.lang.reflect.InvocationTargetException;

/**
 * Converts strings to dates and back.
 * 
 * This class has a static cache of {@code DateFormats}, to avoid
 * creation and  parsing of dateformats every time one is used.
 *
 * @author Harald Kuhr
 * @author last modified by $Author: haku $
 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/convert/DateConverter.java#2 $
 */
public class DateConverter extends NumberConverter  {

    /** Creates a {@code DateConverter} */
    public DateConverter() {
    }
    
    /**
     * Converts the string to a date, using the given format for parsing.
     *
     * @param pString the string to convert.
     * @param pType the type to convert to. {@code java.util.Date} and
     * subclasses allowed.
     * @param pFormat the format used for parsing. Must be a legal
     * {@code SimpleDateFormat} format, or {@code null} which will use the
     * default format.
     *
     * @return the object created from the given string. May safely be typecast
     * to {@code java.util.Date}
     *
     * @see Date
     * @see java.text.DateFormat
     *
     * @throws ConversionException
     */
    public Object toObject(String pString, Class pType, String pFormat)
        throws ConversionException {
        if (StringUtil.isEmpty(pString))
            return null;

        try {
            DateFormat format;
	    
            if (pFormat == null) {
                // Use system default format, using default locale
                format = DateFormat.getDateTimeInstance();
            }
            else {
                // Get format from cache
                format = getDateFormat(pFormat);
            }
            
            Date date =  StringUtil.toDate(pString, format);

            // Allow for conversion to Date subclasses (ie. java.sql.*)
            if (pType != Date.class) {
                try {
                    date = (Date) BeanUtil.createInstance(pType, new Long(date.getTime()));
                }
                catch (ClassCastException e) {
                    throw new TypeMismathException(pType);
                }
                catch (InvocationTargetException e) {
                    throw new ConversionException(e);
                }
            }

            return date;
        }
        catch (RuntimeException rte) {
            throw new ConversionException(rte);
        }
    }

    /**
     * Converts the object to a string, using the given format
     *
     * @param pObject the object to convert.
     * @param pFormat the format used for conversion. Must be a legal
     * {@code SimpleDateFormat} format, or {@code null} which will use the
     * default format.
     *
     * @return the string representation of the object, on the correct format.
     *
     * @throws ConversionException if the object is not a subclass of
     * {@code java.util.Date}
     *
     * @see Date
     * @see java.text.DateFormat
     */
    public String toString(Object pObject, String pFormat)
        throws ConversionException {
        if (pObject == null)
            return null;

        if (!(pObject instanceof Date))
            throw new TypeMismathException(pObject.getClass());

        try {
            // Convert to string, default way
            if (StringUtil.isEmpty(pFormat)) {
                return DateFormat.getDateTimeInstance().format(pObject);
            }
	    
            // Convert to string, using format
            DateFormat format = getDateFormat(pFormat);
            return format.format(pObject);
        }
        catch (RuntimeException rte) {
            throw new ConversionException(rte);
        }
    }

    private DateFormat getDateFormat(String pFormat) {
        return (DateFormat) getFormat(SimpleDateFormat.class, pFormat);
    }
}