读取列列缺省值时失败,请教高手！！！

code：      DatabaseMetaData dbMetaData = conn.getMetaData ();
            rs = dbMetaData.getColumns ( null ,
                                         "zhao",
                                        "O_DATATYPE_DEFAULTBASICDATA" , "%" );
            while ( rs.next () )
            {
                String colName = rs.getString ( 4 );
                int typeID = rs.getInt ( 5 );
                String defaultStr = rs.getString ( 13 ); ; //列缺省值
                .....
            }
error: 
         java.sql.SQLException: 流已被关闭 at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:169) at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:211) at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:274) at oracle.jdbc.dbaccess.DBDataSetImpl.getStreamItem(DBDataSetImpl.java:1087) at oracle.jdbc.driver.OracleStatement.getBytesInternal(OracleStatement.java:2647) at oracle.jdbc.driver.OracleStatement.getStringValue(OracleStatement.java:2701) at oracle.jdbc.driver.OracleResultSetImpl.getString(OracleResultSetImpl.java:307) at com.test.jdts.data.database.schema.table.Table.getColumnList(Table.java:453) at com.test.jdts.data.database.schema.table.Table.getColumns(Table.java:367)