If you have a strange requirement in the rowMapper to check if a column exists or not, you could try to catch a SQLException of invalid column name or you could try:

public static boolean doesColumnExist(String columnName, ResultSet rs) throws SQLException{
	ResultSetMetaData meta = rs.getMetaData();
	int numCol = meta.getColumnCount();
	for (int i = 1; i <= numCol; i++) {
		if(meta.getColumnName(i).equalsIgnoreCase(columnName)) {
			return true;

		}

	}
	return false;
}