jboss处理管理的Entity Manager并发问题吗？ [英] Does jboss handle managed Entity Manager concurrency issues for me?

问题描述

似乎实体管理器实例jboss管理和提供是绑定到持久化上下文的实际实现的代理。

It seems that the Entity Manager instance jboss manages and provides is a proxy to the actual implementation bound to a persistence context.

这个实际实现收集提供的隔离JTA事务（每个事务上下文）。

This actual implementation gathers the isolation provided by JTA transactions (per transaction contexts).

这让我认为我不需要担心处理代理实例时的并发问题。

That makes me think I don't need to worry about concurrency issues when dealing with the proxy instance.

也许我甚至可以缓存这个代理实例，如果我决定从JNDI查找而不是容器注入？

Maybe I can even cache this proxy instance if I decide to bring it from JNDI lookups instead of container injection?

这是合理吗？

推荐答案

容器负责扫描 @PersistenceContext 注释和注入 EntityManagers 。 可以代理 EntityManager 的实例。

The container is responsible for scanning for @PersistenceContext annotations and injection of EntityManagers. It can proxy the instances of EntityManager.

在EJB中，容器负责依赖注入，你可以肯定你是线程安全的。

In EJB, where the container is responsible for dependency injection, you can be sure that you're thread-safe. The persistence context will be shared between multiple components within the same transaction.

但是，如果你注入这个 EntityManager 使用 @PersistenceContext 在Servlets环境（其中并发是一个问题），你不线程安全。您应该使用 @PersistenceUnit 。您可以参考 JBoss 7 JPA参考指南的这一部分：

However, if you inject this EntityManager using @PersistenceContext in Servlets environment (where the concurrency is a concern), you're not thread-safe. You should use @PersistenceUnit instead. You can refer to this part of the JBoss 7 JPA Reference Guide:

请记住，实体管理器不应该是线程安全的
into a servlet class variable which is visible to
multiple threads）。

总结了我所知道的关于持久化上下文共享的JTA事务和代理 EntityManager 由容器，并发布这里。我希望你会发现它有用。

Some time ago I've summed up what I know about Persistence Context sharing between JTA transactions and proxying of EntityManagers by the container and published it here. I hope you'll find it useful.

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