mysql工具类

package com.qr.util;

import java.lang.reflect.Field;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @author 安然的尾巴
 * @version 1.0
 */
public class mysqlUtil{
    //数据库连接参数
    //数据库地址
    private static final String URL = "jdbc:mysql://mysql.lldwb.top:33366/register?serverTimezone=Asia/Shanghai";
    //账号
    private static final String USER_NAME = "root";
    //密码
    private static final String PASSWORD = "@dwb123456";

    //加载驱动，导入数据到数据库连接对象
    private static Connection conn;
    {
        try {
            //加载驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //导入数据到数据库连接对象
            conn = DriverManager.getConnection(URL, USER_NAME, PASSWORD);
        } catch (Exception e) {
            System.out.println("异常" + e.getMessage());
        }
    }

    //关闭数据库连接
    private static void close(PreparedStatement pstm){
        try {
            if(pstm != null){
                pstm.close();//关闭预编译对象
            }
            if (conn != null){
                conn.close();//关闭结果集对象
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
    private static void close(ResultSet rs,PreparedStatement pstm){
        try {
            if (rs != null){
                rs.close();
            }
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        close(pstm);
    }

    //通用的增删改数据，传入SQL语句，可变参数
    public static int update(String sql,Object... objs){
        try {
            //传入SQL语句
            PreparedStatement pstm = conn.prepareStatement(sql);
            //数据参数索引
            int i = 1;
            //传入可变参数
            for (Object obj:objs){
                pstm.setObject(i++,obj);
            }
            //执行并返回影响的行数
            int count = pstm.executeUpdate();
            close(pstm);
            //返回影响的行数
            return count;
        } catch (SQLException throwables) {
            throwables.printStackTrace();
            return 0;
        }
    }

    //查询注意 记得关闭到ResultSet
    public static ResultSet queryResultSet(String sql,Object...agrs) {
        ResultSet rs =null;
        try {
            //创建预编译语句
            PreparedStatement pstm = conn.prepareStatement(sql);
            //添加参数
            if (agrs!=null) {
                 for(int i=1;i<=agrs.length;i++) {
                     pstm.setObject(i, agrs[i-1]);
                    }
            }
             rs = pstm.executeQuery();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return rs;
    }

    //通用的查询 返回 List<实体类> 集合
    public static <T> List<T> queryList(Class<T> class1,String sql,Object...args) {
        List<T> list = new ArrayList<T>();
        PreparedStatement pstm =null;
        ResultSet rs =null;
        try {
            pstm = conn.prepareStatement(sql);
            //设置参数
            if (args!=null) {
                for (int i = 1; i <= args.length; i++) {
                    pstm.setObject(i, args[i-1]);
                }
            }
            //查询
            rs =  pstm.executeQuery();
            //获取元数据
            ResultSetMetaData metaData =  rs.getMetaData();
            //拿到有多少列
            int count = metaData.getColumnCount();
            while(rs.next()) {
                T t = class1.newInstance();
                for (int i = 1; i <=count; i++) {
                    //getColumnLabel(i) 拿到别名  没有别名就是列名
                    Field field = class1.getDeclaredField(metaData.getColumnLabel(i));
                    field.setAccessible(true);
                    field.set(t, rs.getObject(i));
                }
                list.add(t);
            }
        } catch (InstantiationException | IllegalAccessException | NoSuchFieldException | SecurityException
                | IllegalArgumentException | SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }finally {
            close(rs,pstm);
        }
        return list;
    }

}

    private final String URL="jdbc:mysql://127.0.0.1:3306/dubo?serverTimezone=Asia/Shanghai";
    private final String USER_NAME="root";
    private final String PASSWORD="";
    Connection conn;
    {
        try{
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(URL,USER_NAME,PASSWORD);
        }catch(Exception e){
            System.out.println("异常"+e.getMessage());
        }
    }

    private boolean operateSql(String sql,Object... obj){
        try{

            PreparedStatement pstm = conn.prepareStatement(sql);
            for(int i = 0;i < obj.length;i++){
                pstm.setObject(i + 1,obj[i]);
            }
            pstm.executeUpdate();
            return true;
        }catch(Exception e){
            System.out.println("异常" + e.getMessage());
            return false;
        }
    }

//sql语句 args参数(可加可不加)
public static <T> List<T> queryList(Class<T> class1,String sql,Object...args) {
    List<T> list = new ArrayList<T>();
    Connection connection =null;
    PreparedStatement preparedStatement =null;
    ResultSet rs =null;
    try {
        connection = getConnection();
        preparedStatement = connection.prepareStatement(sql);
        //设置参数
        if (args!=null) {
            for (int i = 1; i <= args.length; i++) {
                preparedStatement.setObject(i, args[i-1]);
            }
        }
        //查询
        rs =  preparedStatement.executeQuery();
        //获取元数据
        ResultSetMetaData metaData =  rs.getMetaData();
        //拿到有多少列
        int count = metaData.getColumnCount();
        while(rs.next()) {
            T t = class1.newInstance();
            for (int i = 1; i <=count; i++) {
                //getColumnLabel(i) 拿到别名  没有别名就是列名
                Field field = class1.getDeclaredField(metaData.getColumnLabel(i));
                field.setAccessible(true);
                field.set(t, rs.getObject(i));
            }
            list.add(t);
        }
    } catch (InstantiationException | IllegalAccessException | NoSuchFieldException | SecurityException
             | IllegalArgumentException | SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }finally {
        close(rs,preparedStatement,connection);
    }
    return list;

}