我是JPA 2.1的新手，仅开始使用最近命名的实体图。对于我的项目，我正在JPA 2.1中映射以下关系：

订单-> OrderDetail->产品-> ProductLine

问题：

我想指示JPA加入并正确获取所有需要的数据。到目前为止，这对于Order-> OrderDetail-> Product而言是完美无缺的，但是到目前为止，我还没有设法添加Sub-Sub Graph来深入到ProductLine类。如何制作子图的子图？取得产品的ProductLine吗？

这是我的实体（省略了getter和setter的方法）：

命令

@Entity
@Table(name="ORDERS")
@NamedEntityGraph(
    name = "graph.Order.details",
    attributeNodes = {
        @NamedAttributeNode(value = "details", subgraph = "graph.OrderDetail.product")
    },
    subgraphs = {
        @NamedSubgraph(name = "graph.OrderDetail.product", attributeNodes = @NamedAttributeNode("product"))
    }
)

public class Order implements Serializable{
  @Id
  @Column(name = "orderNumber")
  private Long number;

  @Column(name = "orderDate")
  private Date date;

  @OneToMany(mappedBy = "order")
  private List<OrderDetail> details;
}

订单详情

@Entity
@Table(name = "orderdetails")
public class OrderDetail implements Serializable{

   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "orderNumber")
   @Id
   private Order order;

   @ManyToOne(fetch = FetchType.LAZY)
   @JoinColumn(name = "productCode", nullable = false)
   @Id
   private Product product;

   @Column(name = "orderLineNumber")
   private int lineNumber;

   @Column(name = "quantityOrdered")
   private int quantity;

产品

@Entity
@Table(name = "products")
class Product {
    @Column(name = "productCode")
    @Id
    private String code;

    @Column(name = "quantityInStock")
    public int quantity;

    @ManyToOne
    @JoinColumn(name = "productLine")
    private ProductLine line;

生产线

@Entity
@Table(name = "productlines")
public class ProductLine {
    @Id
    @Column(name = "productLine")
    private String line;

    @Column
    private String textDescription;