如何在 EJB 中设置事务隔离？

发布于 2024-08-29 10:30:38 字数 1131 浏览 3 评论 0原文

我无法找到在 ejb 中设置 TransactionIsolation 的方法。有人能告诉我如何设置吗？我正在用坚持。

我看过以下课程： EntityManager、EntityManagerFactory、用户事务。他们似乎都没有像 setTransactionIsolation 之类的方法。我们需要更改 persistence.xml 吗？

我刚刚读了一本名为 Mastering EJB 3.0 第四版的书。他们给出了一个完整的 10 页关于隔离级别的理论，这个问题发生了，发生了，诸如此类的事情，但最后他们给出了这一段：-

"As we now know, the EJB standard does not deal with isolation levels directly,
and rightly so. EJB is a component specification. It defines the behavior and
contracts of a business component with clients and middleware infrastructure
(containers) such that the component can be rendered as various middleware
services properly. EJBs therefore are transactional components that interact
with resource managers, such as the JDBC resource manager or JMS resource
manager, via JTS, as part of a transaction. They are not, hence, resource
components in themselves. Since isolation levels are very specific to the
behavior and capabilities of the underlying resources, they should therefore be
specified at the resource API levels. "

它到底是什么意思？资源级 API 是什么意思？请帮我。如果持久性无法设置隔离级别，那么为什么他们在 EJB 书中给出如此庞大的理论并不必要地加重它的分量:(

原文

I am not able to find a way to set TransactionIsolation in ejb. Can anybody tell me how do i set it? I am using persistence.

I have looked the following classes :
EntityManager , EntityManagerFactory, UserTransaction. None of them seems to have any method like setTransactionIsolation or such. Do we need to change persistence.xml?

I just read a book named Mastering EJB 3.0 4th edition. They gave a full 10 page theory about Isolation level that this problems occur and that occurs and such things but at the end they gave this paragraph :-

"As we now know, the EJB standard does not deal with isolation levels directly,
and rightly so. EJB is a component specification. It defines the behavior and
contracts of a business component with clients and middleware infrastructure
(containers) such that the component can be rendered as various middleware
services properly. EJBs therefore are transactional components that interact
with resource managers, such as the JDBC resource manager or JMS resource
manager, via JTS, as part of a transaction. They are not, hence, resource
components in themselves. Since isolation levels are very specific to the
behavior and capabilities of the underlying resources, they should therefore be
specified at the resource API levels. "

What exactly does it mean? What is meant by resource level APIs? Please help me. If persistence has no way to set Isolation Level then why do they give such huge theory in an EJB book and make it heavy in weight unnecessarily :(

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乖乖兔^ω^ 2024-09-05 10:30:38

正如 EJB 规范所述

事务不仅使工作单元的完成成为原子的，而且还使工作单元彼此隔离，前提是系统允许多个工作单元并发执行。

用于管理隔离级别的 API特定于资源管理器。（因此，EJB 体系结构没有定义用于管理隔离级别的 API。）
Bean 提供程序在设置隔离级别时必须小心。大多数资源管理器
要求事务中对资源管理器的所有访问都使用相同的隔离级别完成。
对于会话 bean 和消息驱动 bean 具有 bean 管理的事务划分，Bean 提供者可以在企业 bean 的方法中以编程方式指定所需的隔离级别，使用资源管理器特定的 API强>。例如，java.sql.Connection.setTransactionIsolation
容器提供者应该确保提供合适的隔离级别来保证实体bean 的数据一致性
如果多个企业bean 访问同一个资源管理器，则必须格外小心。同一笔交易。 必须避免所请求的隔离级别发生冲突。

希望它能够满足您的需求