我正在寻找一种有效的方法来保留一周中的某几天。换句话说,用户将从工作日列表中选择任意天数。特定日期无关紧要,仅是星期几。我需要将这几天存储在休眠实体中。

我可以存储其中之一:

Set<DayOfWeek>
Set<Integer>

但是我认为这可能会更简单。如果我只使用一个int来存储数据并使用按位运算该怎么办。例如:
Sun = 1
Mon = 2
Tue = 4
Wed = 8
Thu = 16
Fri = 32
Sat = 64

因此,为了表示星期日,星期一,星期三和星期六的集合,我将保留整数75。这是因为1 + 2 + 8 + 64 = 75。

我关心的是在这样的字段上执行查询。我能找到所有已选择周三的实体吗?

这似乎是个好方法吗?有谁有更好的主意吗?

谢谢!

最佳答案

您可以使用Enum设置星期几

public enum DAYS_OF_THE_WEEK {
    SUN,
    MON,
    TUE,
    WED,
    THU,
    FRI,
    SAT;
}

由于Hibernate支持,因此现在可以使用值类型的集合。
@CollectionOfElements
@Enumerated(EnumType.STRING)
@JoinTable(
    name="SELECTED_DAYS_OF_THE_WEEK",
    joinColumns=@JoinColumn(name="<OWNING_ENTITY_ID_GOES_HERE>")
)
public Set<DAYS_OF_THE_WEEK> getSelectedDays() {
    return this.selectedDays;
}

不要忘记复合元素的寿命,或者值类型实例的寿命受所属实体实例的寿命的限制。

如前所述:

我能找到所有已选择周三的实体吗?


select distinc OwningEntity _owningEntity inner join fetch _owningEntity.selectedDays selectedDay where selectedDay = :selectedDay

query.setParameter("selectedDay", DAYS_OF_THE_WEEK.WED);

query.list();

已添加到原始答案:如何实现FetchingStrategy

假设以下模型
@Entity
public class Customer {

    private List<Order> orderList = new ArrayList<Order>();

    // getter's and setter's

}

现在我们的界面CustomerRepository
public interface CustomerRepository {

    Customer getById(Integer id, CustomerFetchingStrategy fetchingStrategy);
    List<Customer> getAll(CustomerFetchingStrategy fetchingStrategy);

    public static enum CustomerFetchingStrategy {
        PROXY,
        CUSTOMER,
        CUSTOMER_WITH_ORDERS;
    }

}

我们的实施
import static br.com.app.CustomerRepository.CustomerFetchingStrategy;

public class CustomerRepositoryImpl implements CustomerRepository {

    // Usually Spring IoC or Seam @In-jection or something else
    private SessionFactory sessionFactory;

    public Customer getById(Integer id, CustomerFetchingStrategy fetchingStrategy) {
        switch(fetchingStrategy) {
            case PROXY:
                return (Customer) sessionFactory.getCurrentSession().load(Customer.class, id);
            case CUSTOMER:
                return (Customer) sessionFactory.getCurrentSession().get(Customer.class, id);
            case CUSTOMER_WITH_ORDERS:
                return (Customer) sessionFactory.getCurrentSession().createQuery("from Customer c left join fetch c.orderList where c.id = :id")
                                  .setParameter("id", id)
                                  .list().get(0);
        }
    }

    public List<Customer> getAll(CustomerFetchingStrategy fetchingStrategy) {
        // Same strategy as shown above
    }

}

因此,是否某些用例需要CUSTOMER,我打电话
import static br.com.app.CustomerRepository.CustomerFetchingStrategy;

public class SomeController {

    // Again Spring Ioc or Seam @In-jection
    private CustomerRepository customerRepository;

    public void proccessForm(HttpServletRequest request, HttpServletResponse response) {
        request.setParameter("customer", customerRepository.getById(Integer.valueOf(request.getParameter("customerId"))), CUSTOMER);
    }
}

希望对您有用

问候,

09-15 15:12