code: public JdbcMapperFactory addCustomFieldMapper(String key, FieldMapper<ResultSet, ?> fieldMapper) {
  		return addColumnDefinition(key, FieldMapperColumnDefinition.<JdbcColumnKey>customFieldMapperDefinition(fieldMapper));
  	}
docs: Associate the specified FieldMapper for the specified property.
  @param key the property
  @param fieldMapper the fieldMapper
  @return the current factory