while(resultSet.next())循环获取每条记录
每个循环中循环获取每列
通过getMetaData获取列信息，
resultSet.getXXX(第几列)
XXX为java类型，对应数据库类型，列信息中可以获取到
所以判断第几行第几列的列数据库类型，转成java类型
从而知道XXX的具体类型
从而获取到第几行第几列的数据

import java.sql.*;
import java.util.*;

public class Pre {

    private static String url = "jdbc:mysql:///dict?useSSL=false";
    private static String user = "root";
    private static String password = "123456";
    private static String sql = "select * from products";


    private static  Connection conn = null;

    private static PreparedStatement pre = null;

    private static ResultSet resultSet = null;

    private static ResultSetMetaData metaData = null;

    private static int columnCount = 0;

    //private static Map<String,String> maplt = null; //labelName与其对应数据库类型的映射

    //private static List labell = null; //labelName集合


    static {
        try {
            //1.注册
            Class.forName("com.mysql.cj.jdbc.Driver");
            //2连接
            conn = DriverManager.getConnection(url,user,password);
            //操作对象
            pre  = conn.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);

            resultSet = pre.executeQuery();

            //获取列信息，元数据
            metaData = resultSet.getMetaData();

            //总共有多少列
            columnCount = metaData.getColumnCount();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    /*
    private static String kv(String k){
        //Map根据键找值
        for (String key : maplt.keySet()) {
            if(key == k){
                return maplt.get(key);
            }
        }
        return "1";



    }*/

    /*
    private static  void labelMapType() throws Exception{
        //label与类型的映射
        maplt = new HashMap();
        if(resultSet.next()){
            for(int i = 1; i<=columnCount; i++){
                String columnLabel = metaData.getColumnLabel(i);
                String columnTypeName = metaData.getColumnTypeName(i);
                maplt.put(columnLabel,columnTypeName);

            }
        }
        resultSet.first();
    }*/
    /*
    private static void labelList() throws Exception{
        //label集合
        labell = new ArrayList();
        if (resultSet.next()){
            for (int i = 1; i<= columnCount; i++){
                String columnLabel = metaData.getColumnLabel(i);
                labell.add(columnLabel);
            }
        }
        resultSet.first();
    }

     */

    //数据库类型与java类型对应

    /*Iterator entries = map.entrySet().iterator();
            while (entries.hasNext()) {
        Map.Entry entry = (Map.Entry) entries.next();
        System.out.println(entry.getKey() + "," +entry.getValue());
    }*/
    //数据库类型与java类型对应，根据数据库类型获得java类型

    private static String typeorm(String label){
        Map<String,String> ormap = new HashMap();
        ormap.put("VARCHAR","String");
        ormap.put("DECIMAL","int");
        ormap.put("TEXT","String");
        return ormap.get(label);

    }





    public static void main(String[] args) throws Exception {
        //labelMapType();//labelName与其对应类型映射，知道labelName就知道其数据库类型  //maplt
        //labelList();//labelName的集合 //labell

        resultSet.previous();
        while (resultSet.next()){
            for (int i = 1; i <= columnCount;i++){

                /*
                //获取其中一个labelName,找到其对应的数据库类型,再找到其对应的java类型
                if (typeorm(kv((String) labell.get(i-1)))== "String"){
                    System.out.print(resultSet.getString(i));
                    System.out.print(" ");
                } else if(typeorm(kv((String) labell.get(i-1)))== "int") {
                    System.out.print(resultSet.getInt(i));
                    System.out.print(" ");
                }*/
                if(typeorm(metaData.getColumnTypeName(i)) == "String"){
                    System.out.print(resultSet.getString(i));
                    System.out.print(" ");
                } else if(typeorm(metaData.getColumnTypeName(i)) == "int") {
                    System.out.print(resultSet.getInt(i));
                    System.out.print(" ");
                }




            }
            System.out.println();
        }
















    }
}