hibernate初印象
1，ddl，
create会重写创建表
update不会
2, one to many
https://www.cnblogs.com/bella-fly/articles/5114182.html
3, cache
first level cache, session scope
second-level cache, shading,
@Cacheable, @Cache(usage=CacheConcurrencyStrategy.readonly
eh cached, 要下载jar,注意和hibernate版本一样
query cache
在property指出，在语句指出，q1.setCachealbe(true)
4，lifecycle
transient:刚刚创建出来的状态
persistent：
- 调用了session的save/ saveOrUpdate/ get/ load/ list方法
- 数据库对应， known as dirty checking in hibernate.
- 受session管理
detach：session关闭后
5，get and load
when we don't use data, get method still hit the database
load give you a proxy, with throw a exception
6, 4步
1，语句
2，createQuery
3, setParameter
4, getResult
自增主键
use-new-id-generator-mappings: false, 这个没用
面试答题：https://www.javatpoint.com/hibernate-interview-questions
