persistence.xml不同的事务类型属性

问题描述

在persistence.xml JPA配置文件中，您可以使用以下行：

In the persistence.xml JPA configuration file, you can have a line like:

<persistence-unit name="com.nz_war_1.0-SNAPSHOTPU" transaction-type="JTA">

或有时：

<persistence-unit name="com.nz_war_1.0-SNAPSHOTPU" transaction-type="RESOURCE_LOCAL">

我的问题是：

transaction-type =JTA和 transaction-type =RESOURCE_LOCAL？

我还注意到一些缺少事务类型的persistence.xml文件。这是正确的吗？

I also noticed some persistence.xml files with the transaction-type missing. Is it correct?

推荐答案

默认值

默认为 JavaEE环境中的JTA 和JavaSE环境中的 RESOURCE_LOCAL 。

Defaults

Default to JTA in a JavaEE environment and to RESOURCE_LOCAL in a JavaSE environment.

使用< persistence-unit transaction-type =RESOURCE_LOCAL> 您负责 EntityManager （ PersistenceContext / Cache ）创建和跟踪

With <persistence-unit transaction-type="RESOURCE_LOCAL"> you are responsible for EntityManager (PersistenceContext/Cache) creating and tracking

• 您必须使用 EntityManagerFactory 获取 EntityManager


• 生成的 EntityManager 实例是 PersistenceContext / Cache
可以通过 EntityManagerFactory code> @PersistenceUnit 仅限注释（不是 @PersistenceContext ）


• 您不被允许使用 @PersistenceContext 来引用类型的单位RESOURCE_LOCAL


• 你必须使用 EntityTransaction 用于开始/提交每次调用 EntityManger的API


• 调用 entityManagerFactory.createEntityManager（）两次导致两个单独的 EntityManager 实例，因此有两个单独的 PersistenceContexts / Caches 。


• 使用多个 EntityManager 的实例几乎绝不是一个好主意（不要创建）第二个，除非你已经销毁了第一个）

• You must use the EntityManagerFactory to get an EntityManager
• The resulting EntityManager instance is a PersistenceContext/CacheAn EntityManagerFactory can be injected via the @PersistenceUnit annotation only (not @PersistenceContext)
• You are not allowed to use @PersistenceContext to refer to a unit of type RESOURCE_LOCAL
• You must use the EntityTransaction API to begin/commit around every call to your EntityManger
• Calling entityManagerFactory.createEntityManager() twice results in two separate EntityManager instances and therefor two separate PersistenceContexts/Caches.
• It is almost never a good idea to have more than one instance of an EntityManager in use (don't create a second one unless you've destroyed the first)

使用< persistence-unit transaction-type =JTA> 容器将执行 EntityManager （ PersistenceContext / Cache ）创建和跟踪。

With <persistence-unit transaction-type="JTA"> the container will do EntityManager (PersistenceContext/Cache) creating and tracking.

• 你不能使用 EntityManagerFactory 获取 EntityManager


• 您只能获得 EntityManager 由容器提供


• 可以通过<$ c注入 EntityManager $ c> @PersistenceContext 仅注释（不是 @PersistenceUnit ）


• 您不能使用 @PersistenceUnit 引用JTA类型的单位


• EntityManager 由容器是对与JTA事务关联的 PersistenceContext / Cache 的引用。


• 如果没有正在进行的JTA事务， EntityManager 无法使用，因为没有 PersistenceContext / Cache 。


• 每个人都有 EntityManager 对同一事务中同一单元的引用将自动引用相同的 PersistenceContext / Cache


• PersistenceContext / Cache 在JTA提交时刷新并清除

• You cannot use the EntityManagerFactory to get an EntityManager
• You can only get an EntityManager supplied by the container
• An EntityManager can be injected via the @PersistenceContext annotation only (not @PersistenceUnit)
• You are not allowed to use @PersistenceUnit to refer to a unit of type JTA
• The EntityManager given by the container is a reference to the PersistenceContext/Cache associated with a JTA Transaction.
• If no JTA transaction is in progress, the EntityManager cannot be used because there is no PersistenceContext/Cache.
• Everyone with an EntityManager reference to the same unit in the same transaction will automatically have a reference to the same PersistenceContext/Cache
• The PersistenceContext/Cache is flushed and cleared at JTA commit time

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