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*** THIS VERSION UPLOADED FOR USE WITH CEDAR-COMMON, TO AVOID DEPENDENCIES ON GOOGLE CODE-BASED MAVEN REPOSITORIES. *** The simplest convenient interface to the Google App Engine datastore

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package com.googlecode.objectify.impl.conv;

import java.math.BigDecimal;

/**
 * This a simple strategy for storing BigDecimal in the datastore.  BigDecimalLongConverter multiplies
 * by a fixed factor and stores the result as a Long.  This is appropriate for monetary and other (relatively)
 * small values with fixed decimal precision.
 *  
 * This is one possible strategy and not appropriate for all uses of BigDecimal - especially very large
 * values which cannot fit in a Long.  For this reason, the converter is not installed by default.  You can
 * Install this converter at the same time you perform registration:
 * 
 * ObjectifyService.factory().getConversions().add(new BigDecimalLongConverter());
 * 
 * The default factor of 1,000 is good for currency, which usually has 0-3 digits of precision past
 * the decimal point.  But you can pick any other factor appropriate to your application.
 */
public class BigDecimalLongConverter implements Converter
{
	/** Default factor is 1000, which gives you three digits of precision past the decimal point */
	public static final long DEFAULT_FACTOR = 1000;
	
	/** */
	BigDecimal factor;
	
	/**
	 * Construct this converter with the default factor (1000), which can store three points of
	 * precision past the decimal point.
	 */
	public BigDecimalLongConverter()
	{
		this(DEFAULT_FACTOR);
	}
	
	/**
	 * Construct this with an arbitrary factor.  Powers of ten are highly recommended if you want to
	 * be able to interpret the numbers in the datastore viewer.
	 * 
	 * @param factor number multiplied by before storage and divided by on retrieval.
	 */
	public BigDecimalLongConverter(long factor)
	{
		this.factor = new BigDecimal(factor);
	}
	
	@Override
	public Object forDatastore(Object value, ConverterSaveContext ctx)
	{
		if (value instanceof BigDecimal)
			return ((BigDecimal)value).multiply(this.factor).longValueExact();
		else
			return null;
	}

	@Override
	public Object forPojo(Object value, Class fieldType, ConverterLoadContext ctx, Object onPojo)
	{
		if (value instanceof Long && fieldType == BigDecimal.class)
			return new BigDecimal((Long)value).divide(this.factor);
		else
			return null;
	}
}