Apache OJB


Apache ObJectRelationalBridge is an Object/Relational mapping tool that allows transparent persistence for Java Objects against relational databases. It was released on April 6, 2005.
As of January 16, 2011 Apache ObJectRelationalBridge has been retired.
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Features

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, JDO and Object Data Management Group .

Functionality

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 to change the behaviour of the persistence kernel.

Configuration

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

Allocation

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.