开启事务
在执行SQL语句之前开启事务

提交事务
当所有SQL都执行完提交事务

回滚事务
在catch()中回滚事务

转账代码示例：张三向李四转账500元

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public static void main(String[] args) {
        Connection conn = null;
        PreparedStatement pstmt1 = null;
        PreparedStatement pstmt2 = null;
        try {
            //1、获取连接
            conn = JDBCUtils2.getConnection();

            //开启事务
            conn.setAutoCommit(false);

            //2、定义sql
            //张三 - 500
            String sql1 = "update account1 set balance = balance - ? where id = ?";
            //李四 + 500
            String sql2 = "update account1 set balance = balance + ? where id = ?";
            //获取执行SQL对象
            pstmt1 = conn.prepareStatement(sql1);
            pstmt2 = conn.prepareStatement(sql2);
            //4、设置参数
            pstmt1.setDouble(1,500);
            pstmt1.setInt(2,3);
            pstmt2.setDouble(1,500);
            pstmt2.setInt(2,4);
            //执行SQL语句：修改事update
            pstmt1.executeUpdate();
            pstmt2.executeUpdate();

            //提交事务
            conn.commit();

        } catch (SQLException e) {
            //事务回滚
            try {
                if (conn!=null){
                    conn.rollback();
                }

            } catch (Exception ex) {
                ex.printStackTrace();
            }
            e.printStackTrace();
        }finally {
            //释放资源
            JDBCUtils2.close(pstmt1,conn);
            JDBCUtils2.close(pstmt2,null);
        }

    }