如何检查OSGi包中的类是否已正确卸载？ [英] How to check if a class in an OSGi bundle has been correctly unloaded?

问题描述

我有一个应用程序，我怀疑它泄露了一些类的引用。

为了暴露这种错误的行为，我们写了一个测试： BundleUnloadIT

在这个测试中，我使用

  Assertions.assertThat（weakReference.isEnqueued（） ）
 .as（弱引用应该被排入队列，但不是）isTrue（）; 
  

测试我的引用是否正确。
但是无论我尝试做什么，参考都不会排队。
所以我怀疑这个类的某些引用正在泄漏某处。

所以...我用正确的方法来测试我的类是否被卸载了？

如果不是的话，我该如何正确地做这个测试？ 如果是，那里有一个参考泄漏某处。我怎么才能找到它？

解决方案

如果类的类加载器不强烈引用（也就是说，类的类加载器也可以被垃圾收集）。如果所有加载的类都没有强引用，则类加载器只能被垃圾回收。所以这是一个全有或全无的主张。每个类都对其类加载器有强烈的参考，每个类加载器都强烈地引用了它所加载的所有类。所以如果任何类加载的类被强引用，那么就不可能收集垃圾。

I have an application which I suspect to leak some class references.

To expose that buggy behaviour, we wrote a test : BundleUnloadIT

In that test, I use

    Assertions.assertThat(weakReference.isEnqueued())
        .as("weak reference should have been enqueued, but is not").isTrue();

To test if my reference is correctly gc'ed. But whatever I try to do, the reference is never enqueued. So I suspect some reference to that class is leaking somewhere.

So ... am I using the right method to test my class is unloaded ?

And if not, how can I properly do that test ?

And if it is, there is a reference leaked somewhere. how can I find it ?

解决方案

A class can only be unloaded (garbage collected) if the class' class loader is not strongly referenced (that is, the class' class loader can also be garbage collected). And a class loader can only be garbage collected if all of the classes it loaded are not strongly referenced. So it is an all-or-nothing proposition. Each class has a strong reference to its class loader and each class loader has strong references to all the classes it has loaded. So it is not possible for a class to be garbage collected if any class loaded by the class loader is strongly referenced.

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