jdbc查询

import java.sql.*;import connectionsql.*;public class SearchData {    String sql;    String url;    ConnectionSql connectionSql;    Connection conn;    org.mariadb.jdbc.Driver driver;    void search(){        sql="select * from person";        url="";        connectionSql=new ConnectionSql(url);        //Connection conn=connectionSql.connectSql();        try {            Statement stmt = connectionSql.connectSql().createStatement();            ResultSet rs = stmt.executeQuery(sql);            int col = rs.getMetaData().getColumnCount();            System.out.println("============================");            while (rs.next()) {                for (int i = 1; i <= col; i++) {                    System.out.print(rs.getString(i) + "\t");                    if ((i == 2) && (rs.getString(i).length() < 8)) {                        System.out.print("\t");                    }                }                System.out.println("");            }            System.out.println("============================");        } catch (SQLException e) {            e.printStackTrace();        }    }}