Convierta float/int a Calendar en jpa hibernate SQL Server

Here is my solution! Hope is useful for someone!

As suggested by Vikdor I've implemented UserType interface:

public class MyDate implements UserType{

    private final static int SECONDS_IN_A_DAY = 86400;

    @Override
    public Object assemble(Serializable cached, Object owner) throws HibernateException {
        return cached;
    }

    @Override
    public Object deepCopy(Object value) throws HibernateException {
        if (value == null)
            return null;

        return value;
    }

    @Override
    public Serializable disassemble(Object value) throws HibernateException {
        return (Serializable)value;
    }

    @Override
    public boolean equals(Object x, Object y) throws HibernateException {
        return ObjectUtils.equals(x, y);
    }

    @Override
    public int hashCode(Object x) throws HibernateException {
         assert (x != null);
         return x.hashCode();
    }

    @Override
    public boolean isMutable() {
        return false;
    }

    @Override
    public Object nullSafeGet(ResultSet resultSet, String[] names, Object owner) throws HibernateException, SQLException {
        assert names.length == 1;

        final String value = (String) StringType.INSTANCE.get(resultSet, names[0]);
        if (value == null) return null;     
        try{
        final String daysValue = value.substring(0, value.indexOf("."));
            final String secondsValue = value.substring(value.indexOf("."));

            final Calendar calendar = Calendar.getInstance();
            calendar.set(Calendar.YEAR, 1900);
            calendar.setTime(DateUtils.truncate(calendar, Calendar.YEAR).getTime());

            calendar.add(Calendar.DATE, Integer.valueOf(daysValue));
            calendar.add(Calendar.SECOND, (int)(SECONDS_IN_A_DAY * Float.valueOf(secondsValue)));
            return calendar;
        }catch(Exception e){
            throw new HibernateException("Cannot convert DB value " +value);
        }
    }

    @Override
    /**
     * Convert from date to float
     */
    public void nullSafeSet(PreparedStatement preparedStatement, Object value, int index) throws HibernateException, SQLException {     
        final Calendar currentDate = (Calendar) value;
        final Calendar zeroDate = Calendar.getInstance();

        zeroDate.set(Calendar.YEAR, 1900);
        zeroDate.setTime(DateUtils.truncate(zeroDate, Calendar.YEAR).getTime());

        final Days days = Days.daysBetween(new DateTime(zeroDate), new DateTime(currentDate) );

        final Seconds seconds = Seconds.secondsBetween(new DateTime(DateUtils.truncate(currentDate, Calendar.DAY_OF_MONTH).getTime()), new DateTime(currentDate) );
        float finalValue = days.getDays() + ((float)seconds.getSeconds()/SECONDS_IN_A_DAY);

        preparedStatement.setFloat(index, finalValue);      
    }

    @Override
    public Object replace(Object original, Object target, Object owner) throws HibernateException {
        return original;
    }

    @Override
    public Class<Calendar> returnedClass() {
        return Calendar.class;
    }

    @Override
    public int[] sqlTypes() {
        return new int[]{
                FloatType.INSTANCE.sqlType()
        };
    }

}

Lo haría de la siguiente manera:

1. Two classes, MyDate & MyDateTime each implementing the Hibernate UserType de la interfaz del.
2. MyDate will read the integer date as String, assuming the integer is of the format 20120828. In the nullSafeGet() implementation, it will convert this string to a Joda DateTime or Java.util.Date usando el SimpleDateFormat class with format as "yyyyMMdd".
3. MyDateTime will read the float as String, asumiendo el float is of the format 20120828.190800. In the nullSafeGet() implementation, it too will convert this string to a Joda Datetime or java.util.Date usando el SimpleDateFormat class with format as "yyyyMMdd.HHmmss".
4. Programas de nullSafeSet() will format back the data using the same SimpleDateFormat in the respective classes.

Espero que esto ayude.