多session下的事务隔离级别

来源：互联网发布：房产php源码编辑：程序博客网时间：2024/05/21 11:23

//事务的隔离级配置为repeatable read

package com.test;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.model.Account;

public class TestHql2 extends Thread{
   public static Session s=HibernateSessionFactory.getSession();
   public static void main(String args[]){
       //s = ;
       test0();

   }
   public static void test0(){
       Thread t = new ReadDatabase2();
       t.start();

       s = HibernateSessionFactory.getSession();//Session
       Transaction t0 = s.beginTransaction();
       try{
       System.out.println("取款事务：开始事务 ");
       delay(2);
       Account get = (Account)s.load(Account.class, new Integer(1));
       System.out.println("取款事务：查询账户的余额为： "+get.getBalance());
       delay(2);
       get.setBalance(get.getBalance().intValue()-100);//取出100元
       System.out.println("取款事务:准备提交");
       t0.commit();
       System.out.println("取款事务：结束事务");
       delay(10);
       }catch(Exception e){
           System.out.println("取款事务: 出错");
           if(null !=t0)
           t0.rollback();
       }
   //   s.close();
   }
   public static void test2(){

   }

   public static void delay(int seconds){
       try {
           Thread.currentThread().sleep(1000 * seconds);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
   }

}
class ReadDatabase2 extends Thread {

   @Override
   public void run() {
           Session s = HibernateSessionFactory.getSession();
           Transaction t2=null;
           try {
               Thread.currentThread().sleep(1000 * 1);

           System.out.println("存款事务:开始事务");
           t2 = s.beginTransaction();

           TestHql2.delay(2);

           Account save = (Account)s.load(Account.class, new Integer(1));
           System.out.println("存款事务:查询账户的余额为 "+save.getBalance());
           TestHql2.delay(4);

           save.setBalance(save.getBalance()+100);
           System.out.println("存款事务：提交事务");
           t2.commit();

           //TestHql2.s.close();
           } catch (Exception e) {
               System.out.println("have an error");
               e.printStackTrace();
               if(null !=t2)
                   t2.rollback();
           }finally {

               //TestHql2.s.close();
           }
   }

}

执行结果为：

15:47:31,820 WARN Configurator:126 - No configuration found. Configuring ehcache from ehcache-failsafe.xml found in the classpath: jar:file:/D:/jar/all/ehcache-1.1.jar!/ehcache-failsafe.xml
取款事务：开始事务
存款事务:开始事务
Hibernate: select account0_.ID as ID2_0_, account0_.USERNAME as USERNAME2_0_, account0_.BALANCE as BALANCE2_0_ from accounts account0_ where account0_.ID=?
取款事务：查询账户的余额为： 1000
Hibernate: select account0_.ID as ID2_0_, account0_.USERNAME as USERNAME2_0_, account0_.BALANCE as BALANCE2_0_ from accounts account0_ where account0_.ID=?
存款事务:查询账户的余额为 1000
取款事务:准备提交
Hibernate: update accounts set USERNAME=?, BALANCE=? where ID=?
取款事务：结束事务
存款事务：提交事务
Hibernate: update accounts set USERNAME=?, BALANCE=? where ID=?

个人看法：

执行前mysql表中：admin的balance为1000，执行后balance为1100，出现第二类丢失更新。

当把事务隔离级别定为serializable时，最后就不会产生第二类丢失更新了

从结果可以看出在多session下的repeatable read 并没有添加版本控制，不然的换存款事务该报异常才是。