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Java Data Objects (JDO) is a specification of Java object persistence.

One of its features is a transparency of the persistence services to the

domain model. JDO persistent objects are ordinary

Java programming language classes (POJOs); there is no requirement for

them to implement certain interfaces or extend from special classes. JDO

1.0 was developed under the Java Community Process as JSR 12. JDO 2.0

was developed under JSR 243 and was released on May 10, 2006. JDO 2.1

was completed in Feb 2008, developed by the Apache JDO project. JDO 2.2

was released in October 2008. JDO 3.0 was released in April 2010.

Object persistence is defined in the external XML metafiles, which may

have vendor-specific extensions. JDO vendors provide developers with

enhancers, which modify compiled Java class files so they can be

transparently persisted. (Note that byte-code enhancement is not

mandated by the JDO specification, although it is the commonly used

mechanism for implementing the JDO specification's requirements.)

Currently, JDO vendors offer several options for persistence, e.g. to

RDBMS, to OODB, or to files.

JDO enhanced classes are portable across different vendors'

implementation. Once enhanced, a Java class can be used with any

vendor's JDO product.

JDO is integrated with 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 transaction services.

• JDO vs. EJB3 vs. JPA

• New Features in JDO Version 2 Not Found In Version 1

• JDO Reference Implementations

• See also

• Bibliography

• External links

Enterprise JavaBeans 3.0 (EJB3) specification also covered persistence,

as had EJB v2 with Entity Beans. There have been standards conflicts

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

javax.persistence package, and was first specified in a separate

document within the EJB3 spec JSR 220, but was later moved to its own

spec JSR 317. Significantly, javax.persistence 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 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.

• Disconnected object graphs concept

• Standardized ORM mapping descriptors (for ORM-based JDO

implementations)

• JDOQL Enhancements (Single String Form; more String, Map & Math

methods support mandated)

• Get e.g. a Connection from javax.jdo.PersistenceManager

• More: Named Queries (pm.newNamedQuery), FetchPlan, Sequence, Delete by

Query, multiple User Objects on PM

• JDO 1.0 : FOStore

• JDO 2.0 : JPOX 1.1

• JDO 2.1 : JPOX 1.2

• JDO 2.2 : DataNucleus AccessPlatform 1.0.1

• JDO 3.0 : DataNucleus AccessPlatform 2.1.0

• JDO 3.1 : DataNucleus AccessPlatform 3.2.0

• JDO 3.2 : DataNucleus AccessPlatform 5.2.0

• Object-relational mapping

• Object database

• Java Persistence API (JPA)

• DataNucleus

• ObjectDB

• ActiveJPA

• citerefjordanrussell2003Jordan, David; Russell, Craig (April 22, 2003). Java Data Objects (1st

ed.). O'Reilly Media. p. 384. ISBN 0-596-00276-9.

• citereftyagivorburgermccammonbobzin2003Tyagi, Sameer; Vorburger, Michael; McCammon, Keiron; Bobzin, Heiko

(September 21, 2003). Core Java Data Objects (1st ed.). Prentice Hall.

p. 576. ISBN 0-13-140731-7.

• citerefezzio2003Ezzio, David (June 6, 2003). Using and Understanding Java Data Objects

(1st ed.). Apress. p. 456. ISBN 1-59059-043-0. Archived from the

original on December 23, 2010. Retrieved February 8, 2010.

• JDO 1.0 specification

• JDO 2.0 specification

• JDO 2.1 specification

• JDO 2.2 specification

• JDO 3.0 specification