persistence.xml 不同的事务类型属性 [英] persistence.xml different transaction-type attributes

问题描述

在persistence.xml JPA配置文件中，你可以有这样一行:

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">

或者有时:

<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" 有什么区别?

我还注意到一些缺少事务类型的 persistence.xml 文件.正确吗?

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

推荐答案

Defaults

在 JavaEE 环境中默认为 JTA，在 JavaSE 环境中默认为 RESOURCE_LOCAL.

Defaults

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

使用 你负责 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 来获取 EntityManager
• 生成的 EntityManager 实例是一个 PersistenceContext/CacheEntityManagerFactory 只能通过 @PersistenceUnit 注释注入(不是 @PersistenceContext)
• 不允许使用 @PersistenceContext 来引用类型为 RESOURCE_LOCAL
的单元
• 您必须使用 EntityTransaction API 来开始/提交对您的 EntityManger
的每次调用
• 调用 entityManagerFactory.createEntityManager() 两次会导致两个单独的 EntityManager 实例，并因此产生两个单独的 PersistenceContexts/Caches.
• 使用多个 EntityManager 的实例几乎从来都不是一个好主意(不要创建第二个，除非您已经销毁了第一个)

• You must use the EntityManagerFactory to get an EntityManager
• The resulting EntityManager instance is a PersistenceContext/Cache An 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 容器将做 EntityManager (PersistenceContext/Cache) 创建和跟踪.

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

• 您不能使用 EntityManagerFactory 来获取 EntityManager
• 你只能得到一个容器提供的EntityManager
• EntityManager 只能通过 @PersistenceContext 注释注入(不是 @PersistenceUnit)
• 不允许使用 @PersistenceUnit 来引用类型为 JTA 的单元
• 容器提供的 EntityManager 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，则无法使用 EntityManager，因为没有 PersistenceContext/Cache.
• 在同一事务中对同一单元具有 EntityManager 引用的每个人都将自动拥有对同一 PersistenceContext/Cache
的引用
• PersistenceContext/Cache 在 JTA 提交时被刷新和清除

• 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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