question: public static < T > T selectOne ( Connection connection , String rawSqlQuery , RowProcessor < T > rowProcessor , Object ... parameters ) throws IOException , SQLException { List < T > resultList = JdbcUtils . select ( connection , rawSqlQuery , rowProcessor , parameters ) ; if ( resultList . isEmpty ( ) ) { return null ; } else if ( resultList . size ( ) == 1 ) { return resultList . get ( 0 ) ; } else { throw new SQLException ( String . format ( "Too many rows returned: %d" , resultList . size ( ) ) ) ; } }
target:  A convenience method when only one row is expected from the returned result set. When there are no rows satisfying the criteria, null is returned; when there are more than one row satisfying the criteria, DataservicesRuntimeException is thrown.