Java Data Objects: Difference between revisions

Revision as of 20:01, 10 May 2011

Revision as of 08:31, 18 June 2011

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JDO is integrated with [[Java Platform, Enterprise Edition|Java EE]] in several ways. First of all, the vendor implementation may be provided as a JEE Connector. Secondly, JDO may work in the context of JEE [[Java transaction service|transaction services]].

== JDO vs. EJB3 vs. JPA ==

[[Enterprise Java Beans]] 3.0 (EJB3) specification also covered persistence, as had EJB v2 with Entity Beans. There has been standards conflict between the two standards bodies in terms of pre-eminence. JDO has several commercial implementations.

In the end, persistence has been "broken out" of "EJB3 Core", and a new standard formed, the [[Java Persistence API]] (JPA). JPA uses the <code>javax.persistence</code> package, and iswas first specified in a separate document within the EJB3 spec [http://www.jcp.org/en/jsr/detail?id=220 JSR 220], but was later moved to its own spec [http://www.jcp.org/en/jsr/detail?id=317 JSR 317]. Significantly, <code>javax.persistence</code> will '''not''' require an EJB container, and thus will work within a Java SE environment as well, as JDO always has. JPA, however, is an [[Object-relational mapping]] (ORM) standard, while JDO is both an [[Object-relational mapping]] standard and a transparent object persistence standard. JDO, from an API point of view, is agnostic to the technology of the underlying datastore, whereas JPA is targeted to RDBMS datastores (although there are several JPA providers that support access to non-relational datastores through the JPA API, such as EclipseLink, DataNucleus and ObjectDB).

Leading JDO commercial implementations and open source projects also offer a JPA API implementation as an alternative access to their underlying persistence engines, formerly exposed solely via JDO in the original products. There are many open source implementations of JDO.