什么是持久性语境？ [英] What is Persistence Context?

问题描述

我是Java世界和JPA的新手。我正在研究JPA，并遇到了许多新的术语，如实体，持久性。在阅读时，我无法理解持久性上下文的确切定义。

任何人都可以用简单的非专业术语来解释它吗？它与 @Entity 中使用的数据有什么关系？

例如，我也发现了这个定义难以理解：

持久化上下文是一组实体，对于任何持久性身份，都有一个唯一的实体实例。

解决方案

持久化上下文处理一组实体，这些实体将数据保存在某个持久性存储中（例如一个数据库）。特别是，上下文知道实体与上下文和底层持久性存储相关的不同状态（例如托管，分离）。

尽管Hibernate相关（JPA提供商），我认为这些链接很有用：

http://docs.jboss.org/hibernate/core/4.0/devguide/en-US/html/ch03.html

http://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/architecture.html

在Java EE中，持久化上下文通常通过EntityManager访问。

http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html

<各种各样的一个实体可以拥有的状态，以及它们之间的转换如下所述：

http://docs.jboss.org/hibernate/entitymanager/3.6/reference/en/html/objectstate.html

http：/ /gerrydevstory.com/wp-content/uploads/2012/05/jpa-state-transtition.png

I am new to the Java world and JPA. I was studying JPA and came across many new terms like Entity, persistence. While reading, I could not understand the exact definition for Persistence Context.

Can anyone explain it in simple laymen terms? What is it to do with the data used in the @Entity?

For example, I find this definition too complicated to understand:

A persistence context is a set of entities such that for any persistent identity there is a unique entity instance.

解决方案

A persistence context handles a set of entities which hold data to be persisted in some persistence store (e.g. a database). In particular, the context is aware of the different states an entity can have (e.g. managed, detached) in relation to both the context and the underlying persistence store.

Although Hibernate-related (a JPA provider), I think these links are useful:

http://docs.jboss.org/hibernate/core/4.0/devguide/en-US/html/ch03.html

http://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/architecture.html

In Java EE, a persistence context is normally accessed via an EntityManager.

http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html

The various states an entity can have and the transitions between these are described below:

http://docs.jboss.org/hibernate/entitymanager/3.6/reference/en/html/objectstate.html

http://gerrydevstory.com/wp-content/uploads/2012/05/jpa-state-transtition.png

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