HQL / 嵌套预加载
我想知道加载延迟加载对象的嵌套值的最佳方法是什么。我提供一个例子来帮助更好地解释这一点。
public class A{
private B b; //Lazy loaded
private C c; //Lazy loaded
private D d; //Lazy loaded
}
public class B{
private E e; //Lazy loaded
private F f; //Lazy loaded
}
public class C{
}
public class D{
}
作为一个例子，我想做：
System.out.println(a.getB().getE());
如果我运行上面的语句，我会得到一个延迟加载异常。
我总是可以执行以下操作：
for (A a : somePossiblyLargeList) {
org.hibernate.Hibernate.initialize(a.getB().getE());
}
但显然性能会很糟糕。
有没有一种方法可以编写自定义 HQL 查询，该查询返回预先填充了这些特定嵌套字段的 A 对象？
谢谢！
I am wondering what the best way is to load nested values for lazy loaded objects. I'm providing an example to help explain this better.
public class A{
private B b; //Lazy loaded
private C c; //Lazy loaded
private D d; //Lazy loaded
}
public class B{
private E e; //Lazy loaded
private F f; //Lazy loaded
}
public class C{
}
public class D{
}
As an example I want to do:
System.out.println(a.getB().getE());
If I ran the above statement I'd get a lazy load exception.
I can always do the following:
for (A a : somePossiblyLargeList) {
org.hibernate.Hibernate.initialize(a.getB().getE());
}
but obviously performance would suck.
Is there a way I can write a custom HQL query which returns A objects that are pre-populated with those specific nested fields?
Thanks!
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当然。
在 HQL 查询中使用
join fetch，如 Hibernate 参考文档（您应该阅读）：Of course.
Use
join fetchin your HQL query, as explained in the Hibernate reference documentation (that you should read):