Apache OJB

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Apache ObJectRelationalBridge
Developer(s)Apache Software Foundation
Stable release
1.0.55 / December 31, 2005 (2005-12-31)
Written inJava
Operating systemCross-platform
TypeObject-relational mapping
LicenseApache License 2.0

Apache ObJectRelationalBridge (OJB) is an Object/Relational mapping tool that allows transparent persistence for Java Objects against relational databases. It was released on April 6, 2005.[1]

As of January 16, 2011 Apache ObJectRelationalBridge has been retired.[2]


OJB is an open source project. It is lightweight and easy to use requiring simply configure two files to implement a persistence layer. It is easy to integrate into an existing application because it does not generate code. It allows the use of different patterns of persistence: owner (PersistenceBroker API), JDO and Object Data Management Group (ODMG).


OJB uses an XML based Object/Relational mapping. The mapping resides in a dynamic MetaData layer, which can be manipulated at runtime through a simple Meta-Object-Protocol (MOP) to change the behaviour of the persistence kernel.


At least two files are required to configure OJB: OJB.properties and repository.xml


For mapping a 1-1 relationship, for example, you have two tables: person and account. In this case, a person has an account and vice versa.

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