Getting Entity Class in JPA and Repository Interface

I am applying repository similar to Spring Data JPA where I would only create an interface of an entity repository:

public interface AuthorRepository extends Repository<Author, Long> {
}

I have this also Repository interface:

public interface Repository <T, ID extends Serializable> {
    List<T> findAll() throws Exception;
}

And its implementation, which I find it difficult to get the class name passed in as parameterized (T) to Repository :

public class RepositoryImpl implements Repository {
    @Inject
    private EntityManager em;

    @Override
    public List<Object> findAll() throws Exception {
        try {
            String namedQuery = "SELECT a FROM " + <How do I get the entity here as Author?> + " a";
            TypedQuery<Object> query = em.createNamedQuery(namedQuery, <How do I get the entity class as Author.class?>);

            return query.getResultList();
        } catch (Exception e) {
            System.out.println(e.getMessage());
            throw new ApplicationException();
        }
    }

}

I can't find way how to dynamically generate the entity class (ex. Author) to be created as part of NamedQuery string and an argument for em.createNamequery().

Thanks for any help.

Searching world wide web gave me similar approach and codes but none worked but TypeTools works like a charm.