java – 为什么Hibernate Open Session in View被认为是一种不好的做法？

您使用什么样的替代策略来避免LazyLoadExceptions？

我确实理解在视图中打开会话有以下问题：

>分层应用程序在不同的jvm中运行
>事务只在最后提交,很可能你以前想要结果.

但是,如果您知道您的应用程序在单个虚拟机上运行,​​为什么不通过在视图策略中使用开放会话来减轻您的痛苦？

解决方法:

因为在视图层中发送可能未初始化的代理(尤其是集合)并从中触发休眠加载可能会从性能和理解的角度来解决问题.

理解：

使用OSIV“污染”视图层,其中涉及与数据访问层相关的问题.

视图层不准备处理延迟加载时可能发生的HibernateException,但可能是数据访问层.

性能：

OSIV倾向于在地毯下拖拽适当的实体加载 – 您往往没有注意到您的集合或实体被懒惰地初始化(可能是N 1).更方便,更少控制.

更新：有关此主题的更多讨论,请参阅The OpenSessionInView antipattern.作者列出了三个要点：

1. each lazy initialization will get you a query meaning each entity will need N + 1 queries, where N is the number of lazy associations. If your screen presents tabular data, reading Hibernate’s log is a big hint that you do not do as you should
2. this completely defeats layered architecture, since you sully your nails with DB in the presentation layer. This is a conceptual con, so I could live with it but there is a corollary
3. last but not least, if an exception occurs while fetching the session, it will occur during the writing of the page: you cannot present a clean error page to the user and the only thing you can do is write an error message in the body

标签：java,jpa,hibernate,lazy-loading,open-session-in-view
来源： https://codeday.me/bug/20190911/1804433.html