JPA的commit()方法会使实体分离吗?

本文介绍了JPA的commit()方法会使实体分离吗?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

如今，我一直在搜索JPA实体的生命周期. 但是现在，关于实体生命周期还有一些遗漏之处.我在stackoverflow帖子之一中找到了以下图形，请记住该图已被修改.

I have been searching JPA entity life cycle nowadays. But now , there are some missing points about entity life cyle. I have found following graphic in one of stackoverflow posts and keep in mind this diagram had been upvoted.

根据此图，当我们持久化实体时，该实体将变为托管对象. 好的 .没问题 . 当我们提交时，数据进入数据库.好的 . 没问题. 但是图向我们展示了该提交操作使实体脱离了！ 让我们看下面的伪代码.

According to this diagram , when we persist entity it becomes managed . OK . No problem . When we commit , data goes to database. OK . No problem. But diagram shows us this commit operation made entity detached ! Let's look at below psuedo code.

entityManager.persist(entity); transactionmit(); // action completed and entity has become detached.(According to the diagram.) entityManager.remove(entity); //Attention this step please .

在上一步(提交步骤)中.那么如何去除分离的对象呢? 如果该实体分离，我们都知道不可能管理分离实体，因为它不再具有与持久性上下文的关联.

in previous step(commit step). So how is it possible to remove a detached object? If this entity becomes detached , we all know it is not possible to manage a detached entity since it has no assocaiton with persistence context anymore.

那么如何删除分离的对象呢?在这一点上，你能请我澄清一下吗? 预先感谢！

So how is it possible to remove a detached object? Could you please clarify me at this point ? Thanks in advance !

推荐答案

实体可以通过以下方式之一分离(可能有更多方式):

Entity can become detached in one of the following ways (there could be more ways):

在事务(在事务范围内的持久性上下文中)提交时，由持久性上下文管理的实体将分离.

When the transaction (in transaction-scoped persistence context) commits, entities managed by the persistence context become detached.

如果关闭了应用程序管理的持久性上下文，则所有托管实体都将分离.

If an application-managed persistence context is closed, all managed entities become detached.

使用清除方法

使用分离方法

回滚

在扩展的持久性上下文中，当删除有状态的Bean时，所有受管实体都将被分离.

In extended persistence context when a stateful bean is removed, all managed entities become detached.

我认为问题可能出在应用程序管理的，用户管理的，扩展的持久性上下文之间.

I think the problem could be the difference between application managed, user managed, extended persistence contexts.