JPA 8.2.1.6.1 Annotated Classes in the Root of the Persistence Unit

All classes contained in the root of the persistence unit are searched for annotated managed persistence classes—classes with the Entity, Embeddable, or MappedSuperclass annotation—and any mapping metadata annotations found on these classes will be processed, or they will be mapped using the mapping annotation defaults. If it is not intended that the annotated persistence classes contained in the root of the persistence unit be included in the persistence unit, the exclude-unlisted-classes element must be specified as true.
The exclude-unlisted-classes element is not intended for use in Java SE environments.