有一个客户Customer,里面有一下属性:

@Entity
@Table(name="t_customer")
public class Customer {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)
    private Integer id;
    private String cusName;
    private String cusTel;  
    private String cusImgsrc;
    @OneToMany(mappedBy="customer",targetEntity=Order.class)
    @Cascade(CascadeType.DELETE)
    private Set<Order> orders =new HashSet<Order>();

还有一个订单类:

@Entity
@Table(name="t_order")
public class Order {
    @Id
    @GenericGenerator(name="myuuid",strategy="uuid")
    @GeneratedValue(generator="myuuid")
    private String id;
    private String orderNum;
    private String receiverInfo;
    @Column(precision=23,scale=2)
    private BigDecimal price; 
    @ManyToOne(targetEntity=Customer.class)
    @JoinColumn(name="customer_id")
    private Customer customer;

怎么根据客户id去查询到这个客户的所有订单的数量

((Long) this.getHibernateTemplate().find("select count(*) from Order").iterator().next()).intValue();

我写的这个只能查出所有订单.后面不知道怎么写