Spring Transaction属性之Isolation

上一篇博客《Spring Transaction属性之Propagation》讲解了Propagation相关的知识，这篇博客主要关注于Isolation这个属性。

一、Isolation基础

请先移步Wikipedia：isolation.

Isolation Level VS Phenomena

上图来自wikipeida。

因为我们在申明Isolation Level时，我们仅仅关心什么Phenomena不会出现。所以，在SQL标准中，仅仅规定了Isolation Level会保证哪种读现象不会出现，而不会规定某种读现象一定会出现。

例如，在Isolation设置为Repeatable Read时，不会出现Dirty Read。但是可能< http://www.2cto.com/kf/ware/vc/" target="_blank" class="keylink">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"insert into User (id, username, age) values (123, 'xxx', 19)");
doSleep(20000);
}


@Transactional(isolation = Isolation.READ_COMMITTED)
public void readRange() {
System.out.println(jdbcTemplate.queryForList("select * from User where uses > 18").size());
doSleep(40000);
System.out.println(jdbcTemplate.queryForList("select * from User where uses > 18").size());
}