Java Persistence API (JPA)

JPA defines an interface to persist normal Java objects (or POJO's in some peoples terminology) to a datastore. JPA is tightly coupled to RDBMS datastores and so is currently of no use when you require an alternative type of datastore (such as XML, OODBMS, etc). JPA is a standard approved in June 2006 as part of "EJB3" though can be used outside of the J2EE container. A later version (JPA2) was approved in December 2009. JPA defines the interface that an implementation has to implement. The whole point of having a standard interface is that users can, in principle, swap between implementations of JPA without changing their code.

JPA has the following principal areas.

• The first thing you do with any JPA-enabled application is provide the Persistence Definition or Mapping
• Since JPA is oriented to RDBMS datastores only you now need to define the Object-Relational Mapping (ORM)
• Now you are ready to utilise the JPA API for persisting and retrieving your objects. This is performed using a EntityManagerFactory/ EntityManager. The persistence of Java objects results in changes to the lifecycle state of the objects.
• Querying your objects in the datastore.

This release of DataNucleus AccessPlatform requires JPA2. There is currently no official version however there is an Apache 2 licensed version from Geronimo that included with AccessPlatform