Hibernate的两个配置文件的目的是什么? [英] what is the purpose of two config files for Hibernate?
问题描述
这是我目前的项目结构:
pom.xml
/ src
/ main
/ resources
hibernate.cfg.xml
/ META-INF
persistence.xml
在这两个文件中都有类似的配置参数( hibernate.cfg.xml
和 persistence.xml
),这看起来很奇怪,但这是我在许多在线示例和教程中看到的。我不明白为什么我需要有两个文件。是否有可能只与一个工作?请解释。
ps。例如,我应该在两个文件中声明 hibernate.dialect
,还是只有一个就足够了?如果是这样,哪一个使用?
如果您使用Hibernate的专有API,则需要的hibernate.cfg.xml
。如果您使用的是JPA,即Hibernate EntityManager,则需要 persistence.xml
。
但是,如果正在使用 Hibernate Proprietary API并且已经有一个 hibernate.cfg.xml
(和 hbm.xml
XML映射文件),但想要开始使用JPA,可以通过引用 hibernate.cfg.xml
来重用现有的配置文件。在 hibernate.ejb.cfgfile
属性中的 persistence.xml
中 - 并且因此具有这两个文件。重用现有的 hbm.xml
文件是IMO的一个现实场景,可以证明两者保持一致(即使我可能长期迁移到JPA注释)。
引用
- Hibernate EntityManager
This is my current project structure:
pom.xml
/src
/main
/resources
hibernate.cfg.xml
/META-INF
persistence.xml
I have very similar configuration params in both files (hibernate.cfg.xml
and persistence.xml
), which looks strange, but this is what I saw in many online examples and tutorials. I can't understand why do I need to have two files. Is it possible to work just with one? Please explain.
ps. For example, should I declare hibernate.dialect
in both files, or just one will be enough? If so, which one to use?
If you are using Hibernate's proprietary API, you'll need the hibernate.cfg.xml
. If you are using JPA i.e. Hibernate EntityManager, you'll need the persistence.xml
.
So you generally don't need both as you use either Hibernate proprietary API or JPA.
However, if you were using Hibernate Proprietary API and already have a hibernate.cfg.xml
(and hbm.xml
XML mapping files) but want to start using JPA, you can reuse the existing configuration files by referencing the hibernate.cfg.xml
in the persistence.xml
in the hibernate.ejb.cfgfile
property - and thus have both files. Reusing existing hbm.xml
files is IMO a realistic scenario that could justify keeping both (even if I'd probably migrate to JPA annotations on the long run).
References
- Hibernate EntityManager
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