Java Persistence Query Language

@Entity
public class Publisher {
    @Id
    private Integer id;
    private String name;
    private String address;

    @OneToMany(mappedBy = "publisher")
    private List<Book> books;
}

SELECT a FROM Author a ORDER BY a.firstName, a.lastName

SELECT DISTINCT a FROM Author a INNER JOIN a.books b WHERE b.publisher.name = 'XYZ Press'

import javax.persistence.EntityManager;
import javax.persistence.Query;
import org.apache.commons.lang.StringUtils;

...

@SuppressWarnings("unchecked")
public List<Author> getAuthorsByLastName(String lastName) {
    String queryString = "SELECT a FROM Author a " +
                         "WHERE:lastName IS NULL OR LOWER(a.lastName) =:lastName";
    Query query = getEntityManager().createQuery(queryString);
    
    query.setParameter("lastName", StringUtils.lowerCase(lastName));
    return query.getResultList();
}