幻影参考对象 [英] Phantom Referenced Objects

问题描述

Phantom References用于验尸操作。
Java规范规定，在清除幻像引用本身之前，不会释放幻像引用对象。

Phantom References serve for post-mortem operations. The Java specification states that a phantom referenced object will not be deallocated until the phantom-reference itself is cleaned.

我的问题是：这个功能（对象未解除分配）的目的是什么？

My question is: What purpose does this feature (object not deallocated) serve?

（我想出的唯一想法是允许本机代码进行事后清理对象，但它并不太令人信服。）

(The only idea i came up with, is to allow native code to do post-mortem cleanup on the object, but it isn't much convincing).

推荐答案

我能想到的唯一好的用例，那就是防止重新分配，是某种JNI实现的异步数据源写入引用对象的一种方式，必须告诉它要停下来 - 停止写入对象 - 在内存被回收之前。如果允许先前的释放，一个简单的忘记处置（）错误可能导致内存损坏。

The only good use-case I can think of, that would prevent deallocation, is one where some kind of JNI-implemented asynchronous data source is writing into the referenced object, and must be told to stand down - to stop writing into the object - before the memory is recycled. If prior deallocation were allowed, a simple forgot-to-dispose() bug could result in memory corruption.

这是过去使用finalize（）的情况之一，可能会引发一些怪癖。

This is one of the cases where finalize() would have been used in the past, and probably drove some of its quirks.

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