jdk、第三方jar中WeaReference的应用

原创于 2017-04-15 14:02:46 发布 · 270 阅读

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#jdk #java #弱引用

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本文探讨了Java中弱引用的应用实例，包括ThreadLocal中Entry类的实现方式以及ResourceBundle中LoaderReference类的设计，展示了如何利用弱引用来避免内存泄漏并有效管理资源。

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1 ThreadLocal.ThreadLocalMap的Entry继承了WeakReference< ThreadLocal > ，即ThreadLocal对象为弱引用，Entry以ThreadLocal对象的弱引用为key：

static class Entry extends WeakReference<ThreadLocal> {
    /** The value associated with this ThreadLocal. */
    Object value;

    Entry(ThreadLocal k, Object v) {
        super(k);
        value = v;
    }
}

2 ResourceBundle的LoaderReference继承了WeakReference< ClassLoader > ，持有一个ClassLoader对象的弱引用：

/**
 * References to class loaders are weak references, so that they can be
 * garbage collected when nobody else is using them. The ResourceBundle
 * class has no reason to keep class loaders alive.
 */
private static class LoaderReference extends WeakReference<ClassLoader>
                                     implements CacheKeyReference {
    private CacheKey cacheKey;

    LoaderReference(ClassLoader referent, ReferenceQueue<Object> q, CacheKey key) {
        super(referent, q);
        cacheKey = key;
    }

    public CacheKey getCacheKey() {
        return cacheKey;
    }
}