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我正在努力探索JPA 2.1的新功能， EntityGraph功能通过使用产品，采购订单和订单项目之间的样本关系进行样本CRUD操作。带有提示和命名查询的Jpa实体图形
下面我主做豆腐的代码，我定义了一个命名查询检索所有数据，以及实体图形
@Entity
@Table(name = "purchase_order")
@NamedQueries({
@NamedQuery(name = "Order.findAll", query = "SELECT o FROM Order o")})
@NamedEntityGraph(name = "graph.Order.items", attributeNodes = @NamedAttributeNode(value = "items", subgraph = "items"),
subgraphs = @NamedSubgraph(name = "items", attributeNodes = @NamedAttributeNode("product")))
public class Order implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
@Column(name = "id", updatable = false, nullable = false)
private Long id = null;
@Version
@Column(name = "version")
private int version = 0;
@Column
private String orderNumber;
@OneToMany(mappedBy = "order", fetch = FetchType.LAZY)
private Set<OrderItem> items = new HashSet<OrderItem>();
... getter and setter methods
我想打电话给命名查询和图形从DAO方法我已经为下
public List<Order> getOrderDetails() {
return (List<Order>) entityManager.createNamedQuery("Order.findAll").setHint("javax.persistence.loadgraph",
entityManager.getEntityGraph("graph.Order.items")).getResultList();
}
虽然数据库包含许多行，虽然我试图改变提示调用DAO方法的结果返回零指数在“javax.persistence.fetchgraph”和“javax.persistence.loadgraph”之间请指教。