用Java EE 5实现的网上书店实例

......
@Entity
@Table(name = "PRODUCT")
@NamedQueries( ...{
@NamedQuery(name = "Product.findByProductId", 
query = "SELECT p FROM Product p WHERE p.productId = :productId"),
@NamedQuery(name = "Product.findByProductName", 
query = "SELECT p FROM Product p WHERE p.productName = :productName"),
@NamedQuery(name = "Product.findByPurchaseCost", 
query = "SELECT p FROM Product p WHERE p.purchaseCost = :purchaseCost")
})
public class Product implements Serializable ...{
@Id
@Column(name = "PRODUCT_ID", nullable = false)
private Integer productId;
@Column(name = "PRODUCT_NAME")
private String productName;
@Column(name = "PURCHASE_COST")
private Long purchaseCost;
......

package bookshop.ejb;
import bookshop.entities.Product;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
/** *//**
*
* @author Sun
*/
@Stateless
public class ProductFacade implements ProductFacadeLocal ...{
@PersistenceContext
private EntityManager em;

/** *//** Creates a new instance of ProductFacade */
public ProductFacade() ...{
}
public void create(Product product) ...{
em.persist(product);
}
public void edit(Product product) ...{
em.merge(product);
}
public void destroy(Product product) ...{
em.merge(product);
em.remove(product);
}
public Product find(Object pk) ...{
return (Product) em.find(Product.class, pk);
}
public List findAll() ...{
return em.createQuery("select object(o) from Product as o").getResultList();
}    
}