EclipseLink/UserGuide/JPA/Basic JPA Development/Mapping/Relationship Mappings
EclipseLink persistence provider requires that you map relationships explicitly.
Additional advanced mapping and mapping options are available through EclipseLink's descriptor and mapping API through using a DescriptorCustomizer.
For more information, see Relational Mapping Types.
You can access additional advanced mappings and mapping options through EclipseLink descriptor and mapping API using a DescriptorCustomizer Class.