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JSefa (Java Simple exchange format api) is a simple library for stream-based serialization of java objects to XML, CSV, FLR or any other format and back again using an iterator-style interface independent of the serialization format. The mapping between java object types and types of the serialization format (e. g. xml complex element types) can be defined either by annotating the java classes or programmatically using a simple API. The current implementation supports XML, CSV and FLR - for XML it is based on JSR 173.

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/*
 * Copyright 2007 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.sf.jsefa.common.converter;

import java.math.BigDecimal;
import java.text.DecimalFormat;
import java.text.DecimalFormatSymbols;
import java.text.FieldPosition;
import java.text.ParseException;
import java.util.Locale;

/**
 * Converter for BigDecimal objects.

 * The format consists of two Strings. The first denotes the {@link Locale} and the second is a
 * pattern as used by {@link DecimalFormat}.

 * 
 * It is thread-safe (the access to the non-thread-safe {@link DecimalFormat} is synchronized).
 * 
 * @author Norman Lahme-Huetig
 */
public class BigDecimalConverter implements SimpleTypeConverter {
    /**
     * The default format which is used when no format is explicitly given.
     */
    private static final String[] DEFAULT_FORMAT = {"en", "#0.00"};

    private static final FieldPosition FIELD_POSITION = new FieldPosition(0);

    private final DecimalFormat decimalFormat;

    /**
     * Creates a BigDecimalConverter.

     * If no format is given, the default format (see {@link #getDefaultFormat()}) is used.
     * 
     * @param configuration the configuration
     * @return a big decimal converter
     * @throws ConversionException if the given format is not valid.
     */
    public static BigDecimalConverter create(SimpleTypeConverterConfiguration configuration) {
        return new BigDecimalConverter(configuration);
    }

    /**
     * Constructs a new BigDecimalConverter.

     * If no format is given, the default format (see {@link #getDefaultFormat()}) is used.
     * 
     * @param configuration the configuration
     * @throws ConversionException if the given format is not valid.
     */
    protected BigDecimalConverter(SimpleTypeConverterConfiguration configuration) {
        String[] format = getFormat(configuration);
        try {
            Locale locale = new Locale(format[0]);
            String pattern = format[1];
            this.decimalFormat = new DecimalFormat(pattern, new DecimalFormatSymbols(locale));
            this.decimalFormat.setParseBigDecimal(true);
        } catch (Exception e) {
            throw new ConversionException("Could not create a " + this.getClass().getName() + " with format "
                    + format[0] + ", " + format[1], e);
        }
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized BigDecimal fromString(String value) {
        if (value == null || value.length() == 0) {
            return null;
        }
        try {
            Object result = this.decimalFormat.parseObject(value);
            if (result instanceof BigDecimal) {
                return (BigDecimal) result;
            } else {
                return new BigDecimal(((Double) result).doubleValue()).setScale(this.decimalFormat
                        .getMaximumFractionDigits(), BigDecimal.ROUND_HALF_UP);
            }
        } catch (ParseException e) {
            throw new ConversionException("Wrong BigDecimal format " + value);
        }
    }

    /**
     * {@inheritDoc}
     */
    public final synchronized String toString(Object value) {
        if (value == null) {
            return null;
        }
        return this.decimalFormat.format(value, new StringBuffer(), FIELD_POSITION).toString();
    }

    /**
     * Returns the default format which is used when no format is given.
     * 
     * @return the default format.
     */
    protected String[] getDefaultFormat() {
        return BigDecimalConverter.DEFAULT_FORMAT;
    }

    private String[] getFormat(SimpleTypeConverterConfiguration configuration) {
        if (configuration.getFormat() == null) {
            return getDefaultFormat();
        }
        if (configuration.getFormat().length != 2) {
            throw new ConversionException("The format for a BigDecimalConverter must be an array with 2 entries");
        }
        return configuration.getFormat();
    }

}