java 使用 Hibernate 持久化接口集合
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Persist collection of interface using Hibernate
提问by Olvagor
I want to persist my litte zoo with Hibernate:
我想用 Hibernate 坚持我的小动物园：
@Entity
@Table(name = "zoo")
public class Zoo {
@OneToMany
private Set<Animal> animals = new HashSet<Animal>();
}
// Just a marker interface
public interface Animal {
}
@Entity
@Table(name = "dog")
public class Dog implements Animal {
// ID and other properties
}
@Entity
@Table(name = "cat")
public class Cat implements Animal {
// ID and other properties
}
When I try to persist the zoo, Hibernate complains:
当我尝试坚持动物园时，Hibernate 抱怨：
Use of @OneToMany or @ManyToMany targeting an unmapped class: blubb.Zoo.animals[blubb.Animal]
I know about the targetEntity-property of @OneToManybut that would mean, only Dogs OR Cats can live in my zoo.
我知道targetEntity- 属性，@OneToMany但这意味着，只有狗或猫可以住在我的动物园里。
Is there any way to persist a collection of an interface, which has several implementations, with Hibernate?
有什么方法可以使用 Hibernate 持久化具有多个实现的接口集合？
采纳答案by Pascal Thivent
JPA annotations are not supported on interfaces. From Java Persistence with Hibernate(p.210):
接口不支持 JPA 注释。来自Java Persistence with Hibernate(p.210)：
Note that the JPA specification doesn't support any mapping annotation on an interface! This will be resolved in a future version of the specification; when you read this book, it will probably be possible with Hibernate Annotations.
请注意，JPA 规范不支持接口上的任何映射注释！这将在规范的未来版本中解决；当您阅读本书时，可能会使用 Hibernate Annotations。
A possible solution would be to use an abstract Entity with a TABLE_PER_CLASSinheritance strategy (because you can't use a mapped superclass - which is not an entity - in associations). Something like this:
一个可能的解决方案是使用具有TABLE_PER_CLASS继承策略的抽象实体（因为您不能在关联中使用映射的超类——它不是实体——）。像这样的东西：
@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public abstract class AbstractAnimal {
@Id @GeneratedValue(strategy = GenerationType.TABLE)
private Long id;
...
}
@Entity
public class Lion extends AbstractAnimal implements Animal {
...
}
@Entity
public class Tiger extends AbstractAnimal implements Animal {
...
}
@Entity
public class Zoo {
@Id @GeneratedValue
private Long id;
@OneToMany(targetEntity = AbstractAnimal.class)
private Set<Animal> animals = new HashSet<Animal>();
...
}
But there is not much advantages in keeping the interface IMO (and actually, I think persistent classes should be concrete).
但是保持接口 IMO 并没有太多优势（实际上，我认为持久类应该是具体的）。
References
参考
回答by yatskevich
I can guess that what you want is mapping of inheritance tree. @Inheritance annotation is the way to go. I don't know if it will work with interfaces, but it will definitely work with abstract classes.
我可以猜到你想要的是继承树的映射。@Inheritance 注释是要走的路。我不知道它是否适用于接口，但它肯定适用于抽象类。
回答by sammy
I think you have to annotate the interface too with @Entityand we have to annotate @Transienton all getters and setters of interface.
我认为您也必须对接口进行注释@Entity，我们必须对@Transient接口的所有 getter 和 setter进行注释。
