Product.java

@Entity
public class Product implements Serializable {
	@Id
	private Long id;

	@Transient
	private String translation;

	public String getTranslation() {
		return translation;
	}

	public void setTranslation(String translation) {
		this.translation = translation;
	}

	...
}

ProductDescription.java

@Entity
public class ProductDescription implements Serializable {
	@EmbeddedId
    ProductDescriptionPK id;

	private String translation;	
}

ProductDescriptionPK.java

@Embeddable
public class ProductDescriptionPK implements Serializable {
    @Column(nullable=false)
    private String locale;

    @ManyToOne(optional = false)
    private Product product;
}

ProductService.java

@Stateless
public class ProductDescriptionPK implements Serializable {
	@PersistenceContext
	private EntityManager em;

	public String findProductTranslation(Product product, Locale locale) {
		return em.createQuery("SELECT pd.translation FROM ProductDescription pd WHERE pd.id.locale = :locale AND pd.id.product = :product", String.class).setParameter("locale", locale.toString()).setParameter("product", product).getSingleResult();
	}

	public List<Product> findAllProducts(Locale locale) {
		Query q = em.createQuery("SELECT p, pd.translation FROM ProductDescription pd JOIN pd.id.product p WHERE pd.id.locale = :locale ORDER BY pd.translation ASC", Object[].class);
		q.setParameter("locale", locale.toString());
		List<Object[]> results = q.getResultList();
		List<Product> products = new ArrayList<Product>();

		for(Object[] result : results) {
			Product product = (Product) result[0];
			String translation = (String) result[1];
			
			product.setTranslation(translation);
			products.add(product);
		}
		
		return products;
	}
}