使用Spring Boot，Spring Data（MongoDB）。假设我有两个具有一些共同超类的类，因此它们位于同一个集合中：
@Document(collection = "automobiles")
public class Automobile {
private String maker;
}
儿童班：
@Document(collection = "automobiles") //not sure if this is needed, but put it in anyway
public class Truck extends Automobile {
}
@Document(collection = "automobiles") //not sure if this is needed, but put it in anyway
public class Van extends Automobile {
}
每种类型的相应MongoRepository：
public interface TruckRepository extends MongoRepository<Truck,String> {
}
public interface VanRepository extends MongoRepository<Van,String> {
}
问题
@Autowired private TruckRepository truckRepository
@Autowired private VanRepository vanRepository
// save 1 of each in a fresh collection
truckRepository.save(new Truck(...));
vanRepository.save(new Van(...));
// try to get all vans
int size = vanRepository.findAll().size() // expect this to be 1, but is 2!
事实上，findAll发现所有的汽车，包括卡车，并下载到范（!!）。如何在不引入类型字段的情况下使Repository类对类型更严格？
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