JDBC 事务回滚 关闭事务自动提交

package com.mxy.jdbc;


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

/*
    sql脚本：
        drop table if exists t_act
        create table t_act(
            actno int,
            balance double(7, 2) //注意:7表示有效数字的个数，2表示小数位的个数
        );
        insert into t_act(actno, balance) values(111, 20000);
        insert into t_act(actno, balance) values(222, 0);
        commit;
        select * from t_act;

        重点三行代码：
            conn.setAutoCommit(false);
            conn.commit();
            conn.rollback();
 */
public class JDBCTest11 {
    
    
    public static void main(String[] args) {
    
    
        Connection conn = null;
        PreparedStatement ps = null;
        try {
    
    
            //1.注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取连接
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/book?useUnicode=true&characterEncoding=utf8&useSSL=false", "root", "123456");
            //将自动提交机制修改为手动提交
            conn.setAutoCommit(false);//开启事务
            //3.获取预编译的数据库操作对象
            String sql = "update t_act set balance = ? where actno = ?";
            ps = conn.prepareStatement(sql);
            //给?传值
            ps.setDouble(1, 10000);
            ps.setInt(2, 111);
            int count = ps.executeUpdate();
        //    String s = null;
        //    s.toString();
            //给?传值
            ps.setDouble(1, 10000);
            ps.setInt(2, 222);
            count += ps.executeUpdate();
            System.out.println(count == 2 ? "转账成功" : "转账失败");
            //程序能够走到这里说明以上程序没有异常，事务结束，手动提交数据
            conn.commit();//提交事务
        } catch (ClassNotFoundException | SQLException e) {
    
    
           //回滚事务
            if(conn != null){
    
    
                try {
    
    
                    conn.rollback();
                } catch (SQLException ex) {
    
    
                    ex.printStackTrace();
                }
            }
            e.printStackTrace();
        }finally {
    
    
            if(ps != null){
    
    
                try {
    
    
                    ps.close();
                } catch (SQLException e) {
    
    
                    e.printStackTrace();
                }
            }
            if(conn != null){
    
    
                try {
    
    
                    conn.close();
                } catch (SQLException e) {
    
    
                    e.printStackTrace();
                }
            }
        }
    }
}