JPA is a specification for data persistence with Java applications. Hibernate is an implementation of this specification. The JPA specification defines two important principles - that JPA engines should be pluggable and able to run outside of an EJB container. Hibernate Core is the foundational module that other Hibernate modules like Hibernate Annotations and Hibernate EntityManager are built upon. It provides the base persistence services using its native API or XML mappings and includes features like the HQL query language.

1. Professional Open Source™
JPA Introduction
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2. What is JPA ?
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 JPA is a specification .
 Hibernate is an implementation of this specification.
 Two important principles in this specification are :
JPA engines should be pluggable, which means you should be
able to take out one product and replace it with another if you
aren’t satisfied—even if you want to stay with the same EJB 3.0
container
JPA engines should be able to run outside of an EJB
3.0 runtime environment, without a container in plain Java.
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3. Modules in Hibernate
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Hibernate Core
Hibernate Annotations
Hibernate EntityManager
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4. Hibernate Core
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 It is the base service for persistence, with its native API and its
mapping metadata stored in XML files.
 It has a query language called HQL , as well as programmatic
 query interfaces for Criteria and Example queries.
 Hibernate Core is the foundation and the platform all other
modules are built on.
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