求问 Mybatis 的缓存

This topic created in 1618 days ago, the information mentioned may be changed or developed.

已经将一级缓存设置为了 statement ，关闭了二级缓存

mybatis:
  configuration:
    cache-enabled: false
    local-cache-scope: statement

测试

    @GetMapping("/test")
    @Transactional
    public User test() throws InterruptedException {
        User user = userMapper.selectById(1);
        System.out.println(user);
        TimeUnit.SECONDS.sleep(5);
        User user2 = userMapper.selectById(1);
        System.out.println(user2);
        return user2;
    }

疑问

2022-01-01 19:33:18.320 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : ==>  Preparing: SELECT * FROM `user` WHERE id = ? 
2022-01-01 19:33:18.321 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : ==> Parameters: 1(Integer)
2022-01-01 19:33:18.322 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : <==      Total: 1
User(id=1, username=test, password=222, phone=)
2022-01-01 19:33:23.327 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : ==>  Preparing: SELECT * FROM `user` WHERE id = ? 
2022-01-01 19:33:23.327 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : ==> Parameters: 1(Integer)
2022-01-01 19:33:23.328 DEBUG 49182 --- [nio-8000-exec-4] com.ding.mapper.UserMapper.selectById    : <==      Total: 0
User(id=1, username=test, password=222, phone=)

日志是打印了两遍 sql ，在休眠的 5 秒前我已经在数据库把这条数据清空了，但是第二次执行的结果返回的还是和第一次一样

Supplement 1 · Jan 1, 2022

总结：
Spring 中
1. mybatis 的一级缓存默认为 session ，但是只有在事务中缓存才会生效，也就是相同的两次查询只会执行一次
2. 如果碰到这种情况则是隔离级别导致的。修改为 read committed 即可。Spring 的隔离级别默认是和数据库一致的
如果不想修改数据库的隔离级别，则要在指定 Transactional 中指定 isolation

5 replies • 2022-01-02 09:57:12 +08:00