Question

我有两个表由以下实体对象层次结构表示：

 @Entity
 @Table(name = Transport.TABLE_NAME)
 @DiscriminatorColumn(name="transport_type", discriminatorType = DiscriminatorType.INTEGER)
 @Inheritance(strategy=InheritanceType.SINGLE_TABLE)
 public abstract class Transport {
     ...
     private Date departure;
 }
 @Entity
 @DiscriminatorValue("1")
 public class Bicycle extends Transport {
     ...
     @OneToOne(mappedBy = "transport", fetch = FetchType.LAZY)
     private BikePassenger passenger;
 }
 @Entity
 @DiscriminatorValue("2")
 public class Car extends Transport {
     ...
     @OneToMany(mappedBy = "transport", fetch = FetchType.EAGER)
     private List<CarPassanger> passengers;
 }

 @Entity
 @Table(name = Passenger.TABLE_NAME)
 @DiscriminatorColumn(name="passenger_type", discriminatorType = DiscriminatorType.INTEGER)
 @Inheritance(strategy=InheritanceType.SINGLE_TABLE)
 public abstract class Passenger {
     ...
     private int passengerGUID;
 }
 @Entity
 @DiscriminatorValue("1")
 public class BicyclePassenger extends Passenger {
     ...
     @OneToOne(fetch = FetchType.EAGER)
     @JoinColumn(name = "transportid")
     private Bicycle transport;
 }
 @Entity
 @DiscriminatorValue("2")
 public class CarPassenger extends Passenger {
     ...
     @ManyToOne(fetch = FetchType.EAGER)
     @JoinColumn(name = "transportid")
     private Car transport;
 }

现在使用JPA Criteria API（或至少JPA），我该怎么做：

获取具有特定乘客GUID的乘客的所有交通工具？
按出发日期分组运输（连同乘客）？

我认为＃1应该有很好的解决方案，但我只能为每个子类型提供2个子选择。这看起来很难看。

最后第三个问题 - 它是一个好模型吗？从OOP的角度来看，它看起来还不错，但从ORM的角度来看，查询的容易程度看起来不太好......

P.S。我正在使用hibernate JPA 2.1

用于查询子对象层次结构的JPA Criteria

0 个答案: