事务入门

1、MySQL：每一条语句都属于独立事务,默认自动管理的。
2、开启事务：start transaction; 日后的语句都会处于同一个事务之中。
提交事务：commit;
回滚事务：rollback;
例子1（数据库中事务的操作命令）：

create table account (
    id int primary key auto_increment,
    name varchar(40),
    money float
)character set utf8 collate utf8_general_ci;

insert int account(name,money)values(‘aaa’,1000);
insert int account(name,money)values(‘bbb’,1000);
insert int account(name,money)values(‘ccc’,1000);

start transaction;
update account set money=money-100 where name=’aaa’;
update account set money=money+100 where name=’bbb’;
commit;

事务的常见的命令：
start transaction;
commit;
rollback;

3、JDBC如何控制事务
TxDemo.java文件：

import java.sql.Connection;
import java.sql.PreparedStatement;
import org.junit.Test;

//事务控制案例
/*


create table account(
    id int primary key auto_increment,
    name varchar(40),
    money float
)character set utf8 collate utf8_general_ci;

insert into account(name,money) values('aaa',1000);
insert into account(name,money) values('bbb',1000);
insert into account(name,money) values('ccc',1000);

 */
public class Txdemo {
    @Test
    public void test1(){
        Connection conn = null;
        PreparedStatement stmt = null;
        try{
            conn = JdbcUtil.getConnection();
            conn.setAutoCommit(false);//相当于start transaction

            stmt = conn.prepareStatement("update account set money=money-100 where name='bbb'");
            stmt.executeUpdate();

//          int i=1/0;

            stmt = conn.prepareStatement("update account set money=money+100 where name='aaa'");
            stmt.executeUpdate();

            conn.commit();// 提交事务
        }catch(Exception e){
            throw new RuntimeException(e);
        }finally{
            JdbcUtil.release(null, stmt, conn);
        }
    }
}

JdbcUtil.java文件：

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

//工具类
public class JdbcUtil {

    private static String driverClass;
    private static String url;
    private static String user;
    private static String password;

    static{
        try {
            ClassLoader cl = JdbcUtil.class.getClassLoader();
            InputStream in = cl.getResourceAsStream("dbcfg.properties");
            Properties props = new Properties();
            props.load(in);
            driverClass = props.getProperty("driverClass");
            url = props.getProperty("url");
            user = props.getProperty("user");
            password = props.getProperty("password");

            Class.forName(driverClass);
        } catch (Exception e) {
            throw new ExceptionInInitializerError(e);
        }
    }


    public static Connection getConnection() throws Exception{
        Connection conn = DriverManager.getConnection(url,user, password);
        return conn;
    }
    public static void release(ResultSet rs,Statement stmt,Connection conn){
        if(rs!=null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            rs = null;
        }
        if(stmt!=null){
            try {
                stmt.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            stmt = null;
        }
        if(conn!=null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            conn = null;
        }
    }
}

dbcnfg.properties文件：

driverClass=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/day16
user=root
password=admin