AbstractAuditable.java

@MappedSuperclass
public abstract class AbstractAuditable<U, PK extends Serializable> extends AbstractPersistable<PK> implements
  	Auditable<U, PK> {
  // …
}

AbstractPersistable.java

@MappedSuperclass
public abstract class AbstractPersistable<PK extends Serializable> implements Persistable<PK> {
	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private PK id;
  
  // …
}

AuditableUser.java

@Entity
public class AuditableUser extends AbstractAuditable<AuditableUser, Long> {
  // …
}

Persistable.java

interface Persistable<ID extends Serializable> extends Serializable {

	ID getId();

  boolean isNew();
}