Open Source Persistence Project

TopLink is an object-relational mapping (ORM) package for Java developers. It was originally developed by The Object People, later acquired by Oracle Corporation. TopLink provides a flexible framework for storing Java objects in a relational database or for converting Java objects into XML documents.

In 2007, Oracle gave its Java persistence framework, TopLink, to the open source community. The software offers object-to-relational, object-to-XML, and Enterprise Information System data access through the major standards, including the Java Persistence API, Java API for XML Binding, Service Data Objects, and the Java Connector Architecture. Oracle TopLink works with any database, any application server, any development toolset and process and any Java application architecture. In addition to its code contribution, Oracle proposes to lead a new Eclipse run-time project to provide a set of persistence services that can be utilized in Java and OSGi environments. Oracle will use the existing code base as the starting point for this project. Oracle will help create a set of blueprints that define how OSGi applications can access standardized persistence technologies.

1. Object-Relational Mapping (ORM): At its core, TopLink allows developers to map Java objects to relational database tables. It provides a rich selection of mapping options and a robust query framework, including support for stored procedures and database functions.
2. Java Persistence API (JPA): TopLink includes a full implementation of the JPA specification, a standard API for object-relational mapping in Java EE and Java SE environments. This means that developers can use standard JPA annotations and APIs in their code and can use TopLink as the underlying ORM provider.
3. Object-XML Mapping (OXM): In addition to ORM, TopLink also provides object-XML mapping capabilities, which can be used for marshalling (writing) and unmarshalling (reading) XML to and from Java objects.
4. Database Web Services: TopLink can also expose database stored procedures and functions as web services.
5. EclipseLink: After Oracle donated the source code of TopLink to the Eclipse Foundation, it continues to be developed as the EclipseLink project. EclipseLink is the reference implementation of the JPA 2.0 and JPA 2.1 specification and has evolved to include additional features like NoSQL database support, multi-tenancy, and more.

TopLink's focus is on providing a highly customizable, performance-oriented framework that simplifies the task of dealing with relational data in a Java application.