9 Using Multiple Databases with a Composite Persistence Unit

With EclipseLink, you can expose multiple persistence units (each with unique sets of entity types) as a single persistence context by using a composite persistence unit. Individual persistence units that are part of this composite persistence unit are called composite member persistence units.

This chapter includes the following sections:

• Introduction to the Solution

• Implementing the Solution

• Additional Resources

Use Case

Users need to map expose multiple persistence units as a single persistence context within an application.

Solution

EclipseLink supports a "composite" persistence unit which can include multiple member persistence units.

Components

• EclipseLink 2.4.2 or later.

• Multiple databases.

Sample

See the following EclipseLink examples for related information:

• http://wiki.eclipse.org/EclipseLink/Examples/JPA/Composite