I maintain an application in which AspectJ is used with the @Entity classes. They don't have an @Id field in their class, but instead get it weaved into with AspectJ.
The Metamodel Generator misses @OneToOne and @OneToMany in this situation while Collection based Associations like @OneToMany work.
The attached project showes the problem with 4 entities:
AddressWithId and PersonWithId have an @Id field and everything works.
Address and Person don't have an @Id field. The @OneToMany field Address_.person and @OneToOne field Address_.person2 are missing.