控制 Hibernate 生成的子选择
考虑以下三个 Hibernate 实体：
public class Car {
@OneToMany(fetch = FetchType.LAZY)
@Fetch(FetchMode.SUBSELECT)
private List<Wheel> wheels;
}
public class Wheel {
@OneToOne(fetch = FetchType.LAZY)
private Hubcap hubcap;
}
public class Hubcap {
}
考虑以下标准：
Criteria criteria = getSession().createCriteria(Car.class);
List<Car> cars = criteria.list();
for (Car car : cars) {
Hibernate.initialize(car.getWheels());
}
是否有任何方法可以控制将生成的子选择查询？具体来说，我想加入子选择，以便在获取车轮时也获取轮毂盖。这当然可以通过将 FetchType 更改为 EAGER 来完成，但我需要一些更特别的东西 - 在逐个查询的基础上。
由于代码当前，我需要生成另一个选择来获取轮毂盖。
Consider the following three Hibernate entities:
public class Car {
@OneToMany(fetch = FetchType.LAZY)
@Fetch(FetchMode.SUBSELECT)
private List<Wheel> wheels;
}
public class Wheel {
@OneToOne(fetch = FetchType.LAZY)
private Hubcap hubcap;
}
public class Hubcap {
}
Consider the following Criteria:
Criteria criteria = getSession().createCriteria(Car.class);
List<Car> cars = criteria.list();
for (Car car : cars) {
Hibernate.initialize(car.getWheels());
}
Is there any way to control the subselect query that will be generated? Specifically I'd like to join in the subselect so that the hubcaps are also fetched when the wheels are fetched. This can of course be accomplished by changing the FetchType to EAGER, but I need something more ad hoc - on a query by query basis.
As the code is currently I'd need to generate another select to fetch the Hubcaps.
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是的，你可以使用标准来做到这一点，但我不记得它是如何完成的，只需寻找标准中的联接，但是我建议使用 HQL 而不是 Criteria 更具可读性：
Yes you can do it using criteria but I don't remember how its done, just look for joins in criteria, however I would suggest using HQL rather Criteria is far more readable:
您可以使用 setFetchMode 方法更改条件查询中的获取类型。
http://docs.jboss.org/hibernate/ core/3.3/reference/en/html/querycriteria.html
You can change the fetch type in a criteria query with the setFetchMode method.
http://docs.jboss.org/hibernate/core/3.3/reference/en/html/querycriteria.html
经过大量研究后发现，在现阶段这是不可能的，至少在不扩展 Hibernate 的情况下是不可能的。
After lots of research it appears that this is impossible at this stage, at least without extending Hibernate.