{"id":16424,"date":"2024-10-10T09:59:59","date_gmt":"2024-10-10T01:59:59","guid":{"rendered":"https:\/\/92it.top\/?p=16424"},"modified":"2024-10-10T09:59:59","modified_gmt":"2024-10-10T01:59:59","slug":"threadlocal%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=16424","title":{"rendered":"ThreadLocal\u8be6\u89e3"},"content":{"rendered":"\n

\u4f5c\u8005\uff1a\u82cf\u4e09\u8bf4\u6280\u672f
\u94fe\u63a5\uff1ahttps:\/\/www.zhihu.com\/question\/657130561\/answer\/3578606797
\u6765\u6e90\uff1a\u77e5\u4e4e<\/p>\n\n\n\n

\u524d\u8a00<\/strong><\/p>\n\n\n\n

\n\n\n\n

\u524d\u4e00\u6bb5\u65f6\u95f4\uff0c\u6709\u540c\u4e8b\u4f7f\u7528ThreadLocal\u8e29\u5751\u4e86\uff0c\u6b63\u597d\u5f15\u8d77\u4e86\u6211\u7684\u5174\u8da3\u3002<\/p>\n\n\n\n

\u6240\u4ee5\u8fd1\u671f\uff0c\u6211\u62bd\u7a7a\u628aThreadLocal\u7684\u6e90\u7801\u518d\u7814\u7a76\u4e86\u4e00\u4e0b\uff0c\u8d8a\u770b\u8d8a\u6709\u610f\u601d\uff0c\u53d1\u73b0\u91cc\u9762\u7684\u4e1c\u897f\u8fd8\u771f\u4e0d\u5c11\u3002<\/p>\n\n\n\n

\u6211\u628a\u7cbe\u534e\u6d53\u7f29\u4e86\u4e00\u4e0b\uff0c\u6c47\u96c6\u6210\u4e86\u4e0b\u976211\u4e2a\u95ee\u9898\uff0c\u770b\u770b\u4f60\u80fd\u9876\u4f4f\u7b2c\u51e0\u4e2a\uff1f<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

1. \u4e3a\u4ec0\u4e48\u8981\u7528ThreadLocal?<\/strong><\/p>\n\n\n\n

\n\n\n\n

\u5e76\u53d1\u7f16\u7a0b\u662f\u4e00\u9879\u975e\u5e38\u91cd\u8981\u7684\u6280\u672f\uff0c\u5b83\u8ba9\u6211\u4eec\u7684\u7a0b\u5e8f\u53d8\u5f97\u66f4\u52a0\u9ad8\u6548\u3002<\/p>\n\n\n\n

\u4f46\u5728\u5e76\u53d1\u7684\u573a\u666f\u4e2d\uff0c\u5982\u679c\u6709\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u4fee\u6539\u516c\u5171\u53d8\u91cf\uff0c\u53ef\u80fd\u4f1a\u51fa\u73b0\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898\uff0c\u5373\u8be5\u53d8\u91cf\u6700\u7ec8\u7ed3\u679c\u53ef\u80fd\u51fa\u73b0\u5f02\u5e38\u3002<\/p>\n\n\n\n

\u4e3a\u4e86\u89e3\u51b3\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898\uff0cJDK\u51fa\u73b0\u4e86\u5f88\u591a\u6280\u672f\u624b\u6bb5\uff0c\u6bd4\u5982\uff1a\u4f7f\u7528synchronized\u6216Lock\uff0c\u7ed9\u8bbf\u95ee\u516c\u5171\u8d44\u6e90\u7684\u4ee3\u7801\u4e0a\u9501\uff0c\u4fdd\u8bc1\u4e86\u4ee3\u7801\u7684\u539f\u5b50\u6027\u3002<\/p>\n\n\n\n

\u4f46\u5728\u9ad8\u5e76\u53d1\u7684\u573a\u666f\u4e2d\uff0c\u5982\u679c\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u7ade\u4e89\u4e00\u628a\u9501\uff0c\u8fd9\u65f6\u4f1a\u5b58\u5728\u5927\u91cf\u7684\u9501\u7b49\u5f85\uff0c\u53ef\u80fd\u4f1a\u6d6a\u8d39\u5f88\u591a\u65f6\u95f4\uff0c\u8ba9\u7cfb\u7edf\u7684\u54cd\u5e94\u65f6\u95f4\u4e00\u4e0b\u5b50\u53d8\u6162\u3002<\/p>\n\n\n\n

\u56e0\u6b64\uff0cJDK\u8fd8\u63d0\u4f9b\u4e86\u53e6\u5916\u4e00\u79cd\u7528\u7a7a\u95f4\u6362\u65f6\u95f4\u7684\u65b0\u601d\u8def\uff1aThreadLocal\u3002<\/p>\n\n\n\n

\u5b83\u7684\u6838\u5fc3\u601d\u60f3\u662f\uff1a\u5171\u4eab\u53d8\u91cf\u5728\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6709\u4e00\u4e2a\u526f\u672c\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u64cd\u4f5c\u7684\u90fd\u662f\u81ea\u5df1\u7684\u526f\u672c\uff0c\u5bf9\u53e6\u5916\u7684\u7ebf\u7a0b\u6ca1\u6709\u5f71\u54cd\u3002<\/p>\n\n\n\n

\u4f8b\u5982\uff1a<\/p>\n\n\n\n

@Service\npublic class ThreadLocalService {\n    private static final ThreadLocal<Integer> threadLocal = new ThreadLocal<>();\n\n    public void add() {\n        threadLocal.set(1);\n        doSamething();\n        Integer integer = threadLocal.get();\n    }\n<\/pre>\n\n\n\n
2. ThreadLocal\u7684\u539f\u7406\u662f\u4ec0\u4e48\uff1f<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u4e3a\u4e86\u641e\u6e05\u695aThreadLocal\u7684\u5e95\u5c42\u5b9e\u73b0\u539f\u7406\uff0c\u6211\u4eec\u4e0d\u5f97\u4e0d\u6252\u4e00\u4e0b\u6e90\u7801\u3002<\/p>\n\n\n\n
ThreadLocal\u7684\u5185\u90e8\u6709\u4e00\u4e2a\u9759\u6001\u7684\u5185\u90e8\u7c7b\u53eb\uff1aThreadLocalMap\u3002<\/p>\n\n\n\n
\npublic class ThreadLocal<T> {\n     ...\n     public T get() {\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\n        Thread t = Thread.currentThread();\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\u7684\u6210\u5458\u53d8\u91cfThreadLocalMap\u5bf9\u8c61\n        ThreadLocalMap map = getMap(t);\n        if (map != null) {\n            \/\/\u6839\u636ethreadLocal\u5bf9\u8c61\u4ecemap\u4e2d\u83b7\u53d6Entry\u5bf9\u8c61\n            ThreadLocalMap.Entry e = map.getEntry(this);\n            if (e != null) {\n                @SuppressWarnings(\"unchecked\")\n                \/\/\u83b7\u53d6\u4fdd\u5b58\u7684\u6570\u636e\n                T result = (T)e.value;\n                return result;\n            }\n        }\n        \/\/\u521d\u59cb\u5316\u6570\u636e\n        return setInitialValue();\n    }\n    \n    private T setInitialValue() {\n        \/\/\u83b7\u53d6\u8981\u521d\u59cb\u5316\u7684\u6570\u636e\n        T value = initialValue();\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\n        Thread t = Thread.currentThread();\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\u7684\u6210\u5458\u53d8\u91cfThreadLocalMap\u5bf9\u8c61\n        ThreadLocalMap map = getMap(t);\n        \/\/\u5982\u679cmap\u4e0d\u4e3a\u7a7a\n        if (map != null)\n            \/\/\u5c06\u521d\u59cb\u503c\u8bbe\u7f6e\u5230map\u4e2d\uff0ckey\u662fthis\uff0c\u5373threadLocal\u5bf9\u8c61\uff0cvalue\u662f\u521d\u59cb\u503c\n            map.set(this, value);\n        else\n           \/\/\u5982\u679cmap\u4e3a\u7a7a\uff0c\u5219\u9700\u8981\u521b\u5efa\u65b0\u7684map\u5bf9\u8c61\n            createMap(t, value);\n        return value;\n    }\n    \n    public void set(T value) {\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\n        Thread t = Thread.currentThread();\n        \/\/\u83b7\u53d6\u5f53\u524d\u7ebf\u7a0b\u7684\u6210\u5458\u53d8\u91cfThreadLocalMap\u5bf9\u8c61\n        ThreadLocalMap map = getMap(t);\n        \/\/\u5982\u679cmap\u4e0d\u4e3a\u7a7a\n        if (map != null)\n            \/\/\u5c06\u503c\u8bbe\u7f6e\u5230map\u4e2d\uff0ckey\u662fthis\uff0c\u5373threadLocal\u5bf9\u8c61\uff0cvalue\u662f\u4f20\u5165\u7684value\u503c\n            map.set(this, value);\n        else\n           \/\/\u5982\u679cmap\u4e3a\u7a7a\uff0c\u5219\u9700\u8981\u521b\u5efa\u65b0\u7684map\u5bf9\u8c61\n            createMap(t, value);\n    }\n    \n     static class ThreadLocalMap {\n        ...\n     }\n     ...\n}<\/pre>\n\n\n\n
ThreadLocal\u7684get\u65b9\u6cd5\u3001set\u65b9\u6cd5\u548csetInitialValue\u65b9\u6cd5\uff0c\u5176\u5b9e\u6700\u7ec8\u64cd\u4f5c\u7684\u90fd\u662fThreadLocalMap\u7c7b\u4e2d\u7684\u6570\u636e\u3002<\/p>\n\n\n\n
\u5176\u4e2dThreadLocalMap\u7c7b\u7684\u5185\u90e8\u5982\u4e0b\uff1a<\/p>\n\n\n\n
static class ThreadLocalMap {\n    static class Entry extends WeakReference<ThreadLocal<?>> {\n        Object value;\n\n        Entry(ThreadLocal<?> k, Object v) {\n            super(k);\n            value = v;\n        }\n   }\n   ...\n   private Entry[] table;\n   ...\n}\n<\/pre>\n\n\n\n
ThreadLocalMap\u91cc\u9762\u5305\u542b\u4e00\u4e2a\u9759\u6001\u7684\u5185\u90e8\u7c7bEntry\uff0c\u8be5\u7c7b\u7ee7\u627f\u4e8eWeakReference\u7c7b\uff0c\u8bf4\u660eEntry\u662f\u4e00\u4e2a\u5f31\u5f15\u7528\u3002<\/p>\n\n\n\n
ThreadLocalMap\u5185\u90e8\u8fd8\u5305\u542b\u4e86\u4e00\u4e2aEntry\u6570\u7ec4\uff0c\u5176\u4e2d\uff1aEntry = ThreadLocal + value\u3002<\/p>\n\n\n\n
\u800cThreadLocalMap\u88ab\u5b9a\u4e49\u6210\u4e86Thread\u7c7b\u7684\u6210\u5458\u53d8\u91cf\u3002<\/p>\n\n\n\n
public class Thread implements Runnable {\n    ...\n    ThreadLocal.ThreadLocalMap threadLocals = null;\n}\n<\/pre>\n\n\n\n
\u4e0b\u9762\u7528\u4e00\u5f20\u56fe\u4ece\u5b8f\u89c2\u4e0a\uff0c\u8ba4\u8bc6\u4e00\u4e0bThreadLocal\u7684\u6574\u4f53\u7ed3\u6784\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u4ece\u4e0a\u56fe\u4e2d\u770b\u51fa\uff0c\u5728\u6bcf\u4e2aThread\u7c7b\u4e2d\uff0c\u90fd\u6709\u4e00\u4e2aThreadLocalMap\u7684\u6210\u5458\u53d8\u91cf\uff0c\u8be5\u53d8\u91cf\u5305\u542b\u4e86\u4e00\u4e2aEntry\u6570\u7ec4\uff0c\u8be5\u6570\u7ec4\u771f\u6b63\u4fdd\u5b58\u4e86ThreadLocal\u7c7bset\u7684\u6570\u636e\u3002<\/p>\n\n\n\n
Entry\u662f\u7531threadLocal\u548cvalue\u7ec4\u6210\uff0c\u5176\u4e2dthreadLocal\u5bf9\u8c61\u662f\u5f31\u5f15\u7528\uff0c\u5728GC\u7684\u65f6\u5019\uff0c\u4f1a\u88ab\u81ea\u52a8\u56de\u6536\u3002\u800cvalue\u5c31\u662fThreadLocal\u7c7bset\u7684\u6570\u636e\u3002<\/p>\n\n\n\n
\u4e0b\u9762\u7528\u4e00\u5f20\u56fe\u603b\u7ed3\u4e00\u4e0b\u5f15\u7528\u5173\u7cfb\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u4e0a\u56fe\u4e2d\u9664\u4e86Entry\u7684key\u5bf9ThreadLocal\u5bf9\u8c61\u662f\u5f31\u5f15\u7528\uff0c\u5176\u4ed6\u7684\u5f15\u7528\u90fd\u662f\u5f3a\u5f15\u7528\u3002<\/p>\n\n\n\n
\u9700\u8981\u7279\u522b\u8bf4\u660e\u7684\u662f\uff0c\u4e0a\u56fe\u4e2dThreadLocal\u5bf9\u8c61\u6211\u753b\u5230\u4e86\u5806\u4e0a\uff0c\u5176\u5b9e\u5728\u5b9e\u9645\u7684\u4e1a\u52a1\u573a\u666f\u4e2d\u4e0d\u4e00\u5b9a\u5728\u5806\u4e0a\u3002\u56e0\u4e3a\u5982\u679cThreadLocal\u88ab\u5b9a\u4e49\u6210\u4e86static\u7684\uff0cThreadLocal\u7684\u5bf9\u8c61\u662f\u7c7b\u5171\u7528\u7684\uff0c\u53ef\u80fd\u51fa\u73b0\u5728\u65b9\u6cd5\u533a\u3002<\/p>\n\n\n\n
3. \u4e3a\u4ec0\u4e48\u7528ThreadLocal\u505akey\uff1f<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u4e0d\u77e5\u9053\u4f60\u6709\u6ca1\u6709\u601d\u8003\u8fc7\u8fd9\u6837\u4e00\u4e2a\u95ee\u9898\uff1aThreadLocalMap\u4e3a\u4ec0\u4e48\u8981\u7528ThreadLocal\u505akey\uff0c\u800c\u4e0d\u662f\u7528Thread\u505akey\uff1f<\/p>\n\n\n\n
\u5982\u679c\u5728\u4f60\u7684\u5e94\u7528\u4e2d\uff0c\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u53ea\u4f7f\u7528\u4e86\u4e00\u4e2aThreadLocal\u5bf9\u8c61\uff0c\u90a3\u4e48\u4f7f\u7528Thread\u505akey\u4e5f\u672a\u5c1d\u4e0d\u53ef\u3002<\/p>\n\n\n\n
@Service\npublic class ThreadLocalService {\n    private static final ThreadLocal<Integer> threadLocal = new ThreadLocal<>();\n}    \n\n<\/pre>\n\n\n\n
\u4f46\u5b9e\u9645\u60c5\u51b5\u4e2d\uff0c\u4f60\u7684\u5e94\u7528\uff0c\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u5f88\u6709\u53ef\u80fd\u4e0d\u53ea\u4f7f\u7528\u4e86\u4e00\u4e2aThreadLocal\u5bf9\u8c61\u3002\u8fd9\u65f6\u4f7f\u7528Thread\u505akey\u4e0d\u5c31\u51fa\u6709\u95ee\u9898\uff1f<\/p>\n\n\n\n
@Service\npublic class ThreadLocalService {\n    private static final ThreadLocal<Integer> threadLocal1 = new ThreadLocal<>();\n    private static final ThreadLocal<Integer> threadLocal2 = new ThreadLocal<>();\n    private static final ThreadLocal<Integer> threadLocal3 = new ThreadLocal<>();\n}\n\n<\/pre>\n\n\n\n
\u5047\u5982\u4f7f\u7528Thread\u505akey\u65f6\uff0c\u4f60\u7684\u4ee3\u7801\u4e2d\u5b9a\u4e49\u4e863\u4e2aThreadLocal\u5bf9\u8c61\uff0c\u90a3\u4e48\uff0c\u901a\u8fc7Thread\u5bf9\u8c61\uff0c\u5b83\u600e\u4e48\u77e5\u9053\u8981\u83b7\u53d6\u54ea\u4e2aThreadLocal\u5bf9\u8c61\u5462\uff1f<\/p>\n\n\n\n
\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u56e0\u6b64\uff0c\u4e0d\u80fd\u4f7f\u7528Thread\u505akey\uff0c\u800c\u5e94\u8be5\u6539\u6210\u7528ThreadLocal\u5bf9\u8c61\u505akey\uff0c\u8fd9\u6837\u624d\u80fd\u901a\u8fc7\u5177\u4f53ThreadLocal\u5bf9\u8c61\u7684get\u65b9\u6cd5\uff0c\u8f7b\u677e\u83b7\u53d6\u5230\u4f60\u60f3\u8981\u7684ThreadLocal\u5bf9\u8c61\u3002<\/p>\n\n\n\n
\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
4. Entry\u7684key\u4e3a\u4ec0\u4e48\u8bbe\u8ba1\u6210\u5f31\u5f15\u7528\uff1f<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u524d\u9762\u8bf4\u8fc7\uff0cEntry\u7684key\uff0c\u4f20\u5165\u7684\u662fThreadLocal\u5bf9\u8c61\uff0c\u4f7f\u7528\u4e86WeakReference\u5bf9\u8c61\uff0c\u5373\u88ab\u8bbe\u8ba1\u6210\u4e86\u5f31\u5f15\u7528\u3002<\/p>\n\n\n\n
\u90a3\u4e48\uff0c\u4e3a\u4ec0\u4e48\u8981\u8fd9\u6837\u8bbe\u8ba1\u5462\uff1f<\/p>\n\n\n\n
\u5047\u5982key\u5bf9ThreadLocal\u5bf9\u8c61\u7684\u5f31\u5f15\u7528\uff0c\u6539\u4e3a\u5f3a\u5f15\u7528\u3002<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u6211\u4eec\u90fd\u77e5\u9053ThreadLocal\u53d8\u91cf\u5bf9ThreadLocal\u5bf9\u8c61\u662f\u6709\u5f3a\u5f15\u7528\u5b58\u5728\u7684\u3002<\/p>\n\n\n\n
\u5373\u4f7fThreadLocal\u53d8\u91cf\u751f\u547d\u5468\u671f\u5b8c\u4e86\uff0c\u8bbe\u7f6e\u6210null\u4e86\uff0c\u4f46\u7531\u4e8ekey\u5bf9ThreadLocal\u8fd8\u662f\u5f3a\u5f15\u7528\u3002<\/p>\n\n\n\n
\u6b64\u65f6\uff0c\u5982\u679c\u6267\u884c\u8be5\u4ee3\u7801\u7684\u7ebf\u7a0b\u4f7f\u7528\u4e86\u7ebf\u7a0b\u6c60\uff0c\u4e00\u76f4\u957f\u671f\u5b58\u5728\uff0c\u4e0d\u4f1a\u88ab\u9500\u6bc1\u3002<\/p>\n\n\n\n
\u5c31\u4f1a\u5b58\u5728\u8fd9\u6837\u7684\u5f3a\u5f15\u7528\u94fe\uff1aThread\u53d8\u91cf-> Thread\u5bf9\u8c61 -> ThreadLocalMap -> Entry -> key -> ThreadLocal\u5bf9\u8c61\u3002<\/p>\n\n\n\n
\u90a3\u4e48\uff0cThreadLocal\u5bf9\u8c61\u548cThreadLocalMap\u90fd\u5c06\u4e0d\u4f1a\u88abGC\u56de\u6536\uff0c\u4e8e\u662f\u4ea7\u751f\u4e86\u5185\u5b58\u6cc4\u9732\u95ee\u9898\u3002<\/p>\n\n\n\n
\u4e3a\u4e86\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff0cJDK\u7684\u5f00\u53d1\u8005\u4eec\u628aEntry\u7684key\u8bbe\u8ba1\u6210\u4e86\u5f31\u5f15\u7528\u3002<\/p>\n\n\n\n
\u5f31\u5f15\u7528\u7684\u5bf9\u8c61\uff0c\u5728GC\u505a\u5783\u573e\u6e05\u7406\u7684\u65f6\u5019\uff0c\u5c31\u4f1a\u88ab\u81ea\u52a8\u56de\u6536\u4e86\u3002<\/p>\n\n\n\n
\u5982\u679ckey\u662f\u5f31\u5f15\u7528\uff0c\u5f53ThreadLocal\u53d8\u91cf\u6307\u5411null\u4e4b\u540e\uff0c\u5728GC\u505a\u5783\u573e\u6e05\u7406\u7684\u65f6\u5019\uff0ckey\u4f1a\u88ab\u81ea\u52a8\u56de\u6536\uff0c\u5176\u503c\u4e5f\u88ab\u8bbe\u7f6e\u6210null\u3002<\/p>\n\n\n\n
\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
\n
\"\"<\/figure><\/div>\n\n\n
\u63a5\u4e0b\u6765\uff0c\u6700\u5173\u952e\u7684\u5730\u65b9\u6765\u4e86\u3002<\/strong><\/p>\n\n\n\n
\u7531\u4e8e\u5f53\u524d\u7684ThreadLocal\u53d8\u91cf\u5df2\u7ecf\u88ab\u6307\u5411null\u4e86\uff0c\u4f46\u5982\u679c\u76f4\u63a5\u8c03\u7528\u5b83\u7684get\u3001set\u6216remove\u65b9\u6cd5\uff0c\u5f88\u663e\u7136\u4f1a\u51fa\u73b0\u7a7a\u6307\u9488\u5f02\u5e38\u3002\u56e0\u4e3a\u5b83\u7684\u751f\u547d\u5df2\u7ecf\u7ed3\u675f\u4e86\uff0c\u518d\u8c03\u7528\u5b83\u7684\u65b9\u6cd5\u4e5f\u6ca1\u5565\u610f\u4e49\u3002<\/p>\n\n\n\n
\u6b64\u65f6\uff0c\u5982\u679c\u7cfb\u7edf\u4e2d\u8fd8\u5b9a\u4e49\u4e86\u53e6\u5916\u4e00\u4e2aThreadLocal\u53d8\u91cfb\uff0c\u8c03\u7528\u4e86\u5b83\u7684get\u3001set\u6216remove\uff0c\u4e09\u4e2a\u65b9\u6cd5\u4e2d\u7684\u4efb\u4f55\u4e00\u4e2a\u65b9\u6cd5\uff0c\u90fd\u4f1a\u81ea\u52a8\u89e6\u53d1\u6e05\u7406\u673a\u5236\uff0c\u5c06key\u4e3anull\u7684value\u503c\u6e05\u7a7a\u3002<\/p>\n\n\n\n
\u5982\u679ckey\u548cvalue\u90fd\u662fnull\uff0c\u90a3\u4e48Entry\u5bf9\u8c61\u4f1a\u88abGC\u56de\u6536\u3002\u5982\u679c\u6240\u6709\u7684Entry\u5bf9\u8c61\u90fd\u88ab\u56de\u6536\u4e86\uff0cThreadLocalMap\u4e5f\u4f1a\u88ab\u56de\u6536\u4e86\u3002<\/p>\n\n\n\n
\u8fd9\u6837\u5c31\u80fd\u6700\u5927\u7a0b\u5ea6\u7684\u89e3\u51b3\u5185\u5b58\u6cc4\u9732\u95ee\u9898\u3002<\/p>\n\n\n\n
\u9700\u8981\u7279\u522b\u6ce8\u610f\u7684\u5730\u65b9\u662f\uff1a<\/p>\n\n\n\n
    \n
  • key\u4e3anull\u7684\u6761\u4ef6\u662f\uff0cThreadLocal\u53d8\u91cf\u6307\u5411null\uff0c\u5e76\u4e14key\u662f\u5f31\u5f15\u7528\u3002\u5982\u679cThreadLocal\u53d8\u91cf\u6ca1\u6709\u65ad\u5f00\u5bf9ThreadLocal\u7684\u5f3a\u5f15\u7528\uff0c\u5373ThreadLocal\u53d8\u91cf\u6ca1\u6709\u6307\u5411null\uff0cGC\u5c31\u8d38\u7136\u7684\u628a\u5f31\u5f15\u7528\u7684key\u56de\u6536\u4e86\uff0c\u4e0d\u5c31\u4f1a\u5f71\u54cd\u6b63\u5e38\u7528\u6237\u7684\u4f7f\u7528\uff1f<\/li>\n\n\n\n
  • \u5982\u679c\u5f53\u524dThreadLocal\u53d8\u91cf\u6307\u5411null\u4e86\uff0c\u5e76\u4e14key\u4e5f\u4e3anull\u4e86\uff0c\u4f46\u5982\u679c\u6ca1\u6709\u5176\u4ed6ThreadLocal\u53d8\u91cf\u89e6\u53d1get\u3001set\u6216remove\u65b9\u6cd5\uff0c\u4e5f\u4f1a\u9020\u6210\u5185\u5b58\u6cc4\u9732\u3002<\/li>\n<\/ul>\n\n\n\n
    \u4e0b\u9762\u770b\u770b\u5f31\u5f15\u7528\u7684\u4f8b\u5b50\uff1a<\/p>\n\n\n\n
    public static void main(String[] args) {\n    WeakReference<Object> weakReference0 = new WeakReference<>(new Object());\n    System.out.println(weakReference0.get());\n    System.gc();\n    System.out.println(weakReference0.get());\n}<\/pre>\n\n\n\n
    \u6253\u5370\u7ed3\u679c\uff1a<\/p>\n\n\n\n
    java.lang.Object@1ef7fe8e\nnull\n<\/pre>\n\n\n\n
    \u4f20\u5165WeakReference\u6784\u9020\u65b9\u6cd5\u7684\u662f\u76f4\u63a5new\u5904\u7406\u7684\u5bf9\u8c61\uff0c\u6ca1\u6709\u5176\u4ed6\u5f15\u7528\uff0c\u5728\u8c03\u7528gc\u65b9\u6cd5\u540e\uff0c\u5f31\u5f15\u7528\u5bf9\u8c61\u4f1a\u88ab\u81ea\u52a8\u56de\u6536\u3002<\/p>\n\n\n\n
    \u4f46\u5982\u679c\u51fa\u73b0\u4e0b\u9762\u8fd9\u79cd\u60c5\u51b5\uff1a<\/p>\n\n\n\n
    public static void main(String[] args) {\n    Object object = new Object();\n    WeakReference<Object> weakReference1 = new WeakReference<>(object);\n    System.out.println(weakReference1.get());\n    System.gc();\n    System.out.println(weakReference1.get());\n}\n\n<\/pre>\n\n\n\n
    \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
    java.lang.Object@1ef7fe8e\njava.lang.Object@1ef7fe8e<\/pre>\n\n\n\n
    \u5148\u5b9a\u4e49\u4e86\u4e00\u4e2a\u5f3a\u5f15\u7528object\u5bf9\u8c61\uff0c\u5728WeakReference\u6784\u9020\u65b9\u6cd5\u4e2d\u5c06object\u5bf9\u8c61\u7684\u5f15\u7528\u4f5c\u4e3a\u53c2\u6570\u4f20\u5165\u3002\u8fd9\u65f6\uff0c\u8c03\u7528gc\u540e\uff0c\u5f31\u5f15\u7528\u5bf9\u8c61\u4e0d\u4f1a\u88ab\u81ea\u52a8\u56de\u6536\u3002<\/p>\n\n\n\n
    \u6211\u4eec\u7684Entry\u5bf9\u8c61\u4e2d\u7684key\u4e0d\u5c31\u662f\u7b2c\u4e8c\u79cd\u60c5\u51b5\u5417\uff1f\u5728Entry\u6784\u9020\u65b9\u6cd5\u4e2d\u4f20\u5165\u7684\u662fThreadLocal\u5bf9\u8c61\u7684\u5f15\u7528\u3002<\/p>\n\n\n\n
    \u5982\u679c\u5c06object\u5f3a\u5f15\u7528\u8bbe\u7f6e\u4e3anull\uff1a<\/p>\n\n\n\n
    public static void main(String[] args) {\n    Object object = new Object();\n    WeakReference<Object> weakReference1 = new WeakReference<>(object);\n    System.out.println(weakReference1.get());\n    System.gc();\n    System.out.println(weakReference1.get());\n\n    object=null;\n    System.gc();\n    System.out.println(weakReference1.get());\n}\n<\/pre>\n\n\n\n
    \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
    java.lang.Object@6f496d9f\njava.lang.Object@6f496d9f\nnull<\/pre>\n\n\n\n
    \u7b2c\u4e8c\u6b21gc\u4e4b\u540e\uff0c\u5f31\u5f15\u7528\u80fd\u591f\u88ab\u6b63\u5e38\u56de\u6536\u3002<\/p>\n\n\n\n
    \u7531\u6b64\u53ef\u89c1\uff0c\u5982\u679c\u5f3a\u5f15\u7528\u548c\u5f31\u5f15\u7528\u540c\u65f6\u5173\u8054\u4e00\u4e2a\u5bf9\u8c61\uff0c\u90a3\u4e48\u8fd9\u4e2a\u5bf9\u8c61\u662f\u4e0d\u4f1a\u88abGC\u56de\u6536\u3002\u4e5f\u5c31\u662f\u8bf4\u8fd9\u79cd\u60c5\u51b5\u4e0bEntry\u7684key\uff0c\u4e00\u76f4\u90fd\u4e0d\u4f1a\u4e3anull\uff0c\u9664\u975e\u5f3a\u5f15\u7528\u4e3b\u52a8\u65ad\u5f00\u5173\u8054\u3002<\/p>\n\n\n\n
    \u6b64\u5916\uff0c\u4f60\u53ef\u80fd\u8fd8\u4f1a\u95ee\u8fd9\u6837\u4e00\u4e2a\u95ee\u9898\uff1aEntry\u7684value\u4e3a\u4ec0\u4e48\u4e0d\u8bbe\u8ba1\u6210\u5f31\u5f15\u7528\uff1f<\/strong><\/p>\n\n\n\n
    \u7b54\uff1aEntry\u7684value\u5047\u5982\u53ea\u662f\u88abEntry\u5f15\u7528\uff0c\u6709\u53ef\u80fd\u6ca1\u88ab\u4e1a\u52a1\u7cfb\u7edf\u4e2d\u7684\u5176\u4ed6\u5730\u65b9\u5f15\u7528\u3002\u5982\u679c\u5c06value\u6539\u6210\u4e86\u5f31\u5f15\u7528\uff0c\u88abGC\u8d38\u7136\u56de\u6536\u4e86\uff08\u6570\u636e\u7a81\u7136\u6ca1\u4e86\uff09\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u4e1a\u52a1\u7cfb\u7edf\u51fa\u73b0\u5f02\u5e38\u3002<\/p>\n\n\n\n
    \u800c\u76f8\u6bd4\u4e4b\u4e0b\uff0cEntry\u7684key\uff0c\u7ba1\u7406\u7684\u5730\u65b9\u5c31\u975e\u5e38\u660e\u786e\u4e86\u3002<\/p>\n\n\n\n
    \u8fd9\u5c31\u662fEntry\u7684key\u88ab\u8bbe\u8ba1\u6210\u5f31\u5f15\u7528\uff0c\u800cvalue\u6ca1\u88ab\u8bbe\u8ba1\u6210\u5f31\u5f15\u7528\u7684\u539f\u56e0\u3002<\/p>\n\n\n\n
    5. ThreadLocal\u771f\u7684\u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u9732\uff1f<\/strong><\/p>\n\n\n\n
    \n\n\n\n
    \u901a\u8fc7\u4e0a\u9762\u7684Entry\u5bf9\u8c61\u4e2d\u7684key\u8bbe\u7f6e\u6210\u5f31\u5f15\u7528\uff0c\u5e76\u4e14\u4f7f\u7528get\u3001set\u6216remove\u65b9\u6cd5\u6e05\u7406key\u4e3anull\u7684value\u503c\uff0c\u5c31\u80fd\u5f7b\u5e95\u89e3\u51b3\u5185\u5b58\u6cc4\u9732\u95ee\u9898\uff1f<\/p>\n\n\n\n
    \u7b54\u6848\u662f\u5426\u5b9a\u7684\u3002<\/p>\n\n\n\n
    \u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
    \n
    \"\"<\/figure><\/div>\n\n\n
    \u5047\u5982ThreadLocalMap\u4e2d\u5b58\u5728\u5f88\u591akey\u4e3anull\u7684Entry\uff0c\u4f46\u540e\u9762\u7684\u7a0b\u5e8f\uff0c\u4e00\u76f4\u90fd\u6ca1\u6709\u8c03\u7528\u8fc7\u6709\u6548\u7684ThreadLocal\u7684get\u3001set\u6216remove\u65b9\u6cd5\u3002<\/p>\n\n\n\n
    \u90a3\u4e48\uff0cEntry\u7684value\u503c\u4e00\u76f4\u90fd\u6ca1\u88ab\u6e05\u7a7a\u3002<\/p>\n\n\n\n
    \u6240\u4ee5\u4f1a\u5b58\u5728\u8fd9\u6837\u4e00\u6761\u5f3a\u5f15\u7528\u94fe\uff1aThread\u53d8\u91cf -> Thread\u5bf9\u8c61 -> ThreadLocalMap -> Entry -> value -> Object\u3002<\/p>\n\n\n\n
    \u5176\u7ed3\u679c\u5c31\u662f\uff1aEntry\u548cThreadLocalMap\u5c06\u4f1a\u957f\u671f\u5b58\u5728\u4e0b\u53bb\uff0c\u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u9732\u3002<\/p>\n\n\n\n
    6. \u5982\u4f55\u89e3\u51b3\u5185\u5b58\u6cc4\u9732\u95ee\u9898\uff1f<\/strong><\/p>\n\n\n\n
    \n\n\n\n
    \u524d\u9762\u8bf4\u8fc7\u7684ThreadLocal\u8fd8\u662f\u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u9732\u7684\u95ee\u9898\uff0c\u6211\u4eec\u6709\u6ca1\u6709\u89e3\u51b3\u529e\u6cd5\u5462\uff1f<\/p>\n\n\n\n
    \u7b54\uff1a\u6709\u529e\u6cd5\uff0c\u8c03\u7528ThreadLocal\u5bf9\u8c61\u7684remove\u65b9\u6cd5\u3002<\/p>\n\n\n\n
    \u4e0d\u662f\u5728\u4e00\u5f00\u59cb\u5c31\u8c03\u7528remove\u65b9\u6cd5\uff0c\u800c\u662f\u5728\u4f7f\u7528\u5b8cThreadLocal\u5bf9\u8c61\u4e4b\u540e\u3002\u5217\u5982\uff1a<\/p>\n\n\n\n
    \u5148\u521b\u5efa\u4e00\u4e2aCurrentUser\u7c7b\uff0c\u5176\u4e2d\u5305\u542b\u4e86ThreadLocal\u7684\u903b\u8f91\u3002<\/p>\n\n\n\n
    public class CurrentUser {\n    private static final ThreadLocal<UserInfo> THREA_LOCAL = new ThreadLocal();\n    \n    public static void set(UserInfo userInfo) {\n        THREA_LOCAL.set(userInfo);\n    }\n    \n    public static UserInfo get() {\n       THREA_LOCAL.get();\n    }\n    \n    public static void remove() {\n       THREA_LOCAL.remove();\n    }\n}\n\n<\/pre>\n\n\n\n
    \u7136\u540e\u5728\u4e1a\u52a1\u4ee3\u7801\u4e2d\u8c03\u7528\u76f8\u5173\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
    public void doSamething(UserDto userDto) {\n   UserInfo userInfo = convert(userDto);\n   \n   try{\n     CurrentUser.set(userInfo);\n     ...\n     \n     \/\/\u4e1a\u52a1\u4ee3\u7801\n     UserInfo userInfo = CurrentUser.get();\n     ...\n   } finally {\n      CurrentUser.remove();\n   }\n}\n\n<\/pre>\n\n\n\n
    \u9700\u8981\u6211\u4eec\u7279\u522b\u6ce8\u610f\u7684\u5730\u65b9\u662f\uff1a\u4e00\u5b9a\u8981\u5728finally\u4ee3\u7801\u5757\u4e2d\uff0c\u8c03\u7528remove\u65b9\u6cd5\u6e05\u7406\u6ca1\u7528\u7684\u6570\u636e\u3002\u5982\u679c\u4e1a\u52a1\u4ee3\u7801\u51fa\u73b0\u5f02\u5e38\uff0c\u4e5f\u80fd\u53ca\u65f6\u6e05\u7406\u6ca1\u7528\u7684\u6570\u636e\u3002<\/p>\n\n\n\n
    remove\u65b9\u6cd5\u4e2d\u4f1a\u628aEntry\u4e2d\u7684key\u548cvalue\u90fd\u8bbe\u7f6e\u6210null\uff0c\u8fd9\u6837\u5c31\u80fd\u88abGC\u53ca\u65f6\u56de\u6536\uff0c\u65e0\u9700\u89e6\u53d1\u989d\u5916\u7684\u6e05\u7406\u673a\u5236\uff0c\u6240\u4ee5\u5b83\u80fd\u89e3\u51b3\u5185\u5b58\u6cc4\u9732\u95ee\u9898\u3002<\/p>\n\n\n\n
    7. ThreadLocal\u662f\u5982\u4f55\u5b9a\u4f4d\u6570\u636e\u7684\uff1f<\/strong><\/p>\n\n\n\n
    \n\n\n\n
    \u524d\u9762\u8bf4\u8fc7ThreadLocalMap\u5bf9\u8c61\u5e95\u5c42\u662f\u7528Entry\u6570\u7ec4\u4fdd\u5b58\u6570\u636e\u7684\u3002<\/p>\n\n\n\n
    \u90a3\u4e48\u95ee\u9898\u6765\u4e86\uff0cThreadLocal\u662f\u5982\u4f55\u5b9a\u4f4dEntry\u6570\u7ec4\u6570\u636e\u7684\uff1f<\/p>\n\n\n\n
    \u5728ThreadLocal\u7684get\u3001set\u3001remove\u65b9\u6cd5\u4e2d\u90fd\u6709\u8fd9\u6837\u4e00\u884c\u4ee3\u7801\uff1a<\/p>\n\n\n\n
    int i = key.threadLocalHashCode & (len-1);\n<\/pre>\n\n\n\n
    \u901a\u8fc7key\u7684hashCode\u503c\uff0c\u4e0e\u6570\u7ec4\u7684\u957f\u5ea6\u51cf1\u3002\u5176\u4e2dkey\u5c31\u662fThreadLocal\u5bf9\u8c61\uff0c\u4e0e\u6570\u7ec4\u7684\u957f\u5ea6\u51cf1\uff0c\u76f8\u5f53\u4e8e\u9664\u4ee5\u6570\u7ec4\u7684\u957f\u5ea6\u51cf1\uff0c\u7136\u540e\u53d6\u6a21\u3002<\/p>\n\n\n\n
    \u8fd9\u662f\u4e00\u79cdhash\u7b97\u6cd5\u3002<\/p>\n\n\n\n
    \u63a5\u4e0b\u6765\u7ed9\u5927\u5bb6\u4e3e\u4e2a\u4f8b\u5b50\uff1a\u5047\u8bbelen=16\uff0ckey.threadLocalHashCode=31\uff0c<\/p>\n\n\n\n
    \u4e8e\u662f\uff1a int i = 31 & 15 = 15<\/p>\n\n\n\n
    \u76f8\u5f53\u4e8e\uff1aint i = 31 % 16 = 15<\/p>\n\n\n\n
    \u8ba1\u7b97\u7684\u7ed3\u679c\u662f\u4e00\u6837\u7684\uff0c\u4f46\u662f\u4f7f\u7528\u4e0e\u8fd0\u7b97\u6548\u7387\u8ddf\u9ad8\u4e00\u4e9b\u3002<\/p>\n\n\n\n
    \u4e3a\u4ec0\u4e48\u4e0e\u8fd0\u7b97\u6548\u7387\u66f4\u9ad8\uff1f<\/p>\n\n\n\n
    \u7b54\uff1a\u56e0\u4e3aThreadLocal\u7684\u521d\u59cb\u5927\u5c0f\u662f16\uff0c\u6bcf\u6b21\u90fd\u662f\u63092\u500d\u6269\u5bb9\uff0c\u6570\u7ec4\u7684\u5927\u5c0f\u5176\u5b9e\u4e00\u76f4\u90fd\u662f2\u7684n\u6b21\u65b9\u3002\u8fd9\u79cd\u6570\u636e\u6709\u4e2a\u89c4\u5f8b\u5c31\u662f\u9ad8\u4f4d\u662f0\uff0c\u4f4e\u4f4d\u90fd\u662f1\u3002\u5728\u505a\u4e0e\u8fd0\u7b97\u65f6\uff0c\u53ef\u4ee5\u4e0d\u7528\u8003\u8651\u9ad8\u4f4d\uff0c\u56e0\u4e3a\u4e0e\u8fd0\u7b97\u7684\u7ed3\u679c\u5fc5\u5b9a\u662f0\u3002\u53ea\u9700\u8003\u8651\u4f4e\u4f4d\u7684\u4e0e\u8fd0\u7b97\uff0c\u6240\u4ee5\u6548\u7387\u66f4\u9ad8\u3002<\/p>\n\n\n\n
    \u5982\u679c\u4f7f\u7528hash\u7b97\u6cd5\u5b9a\u4f4d\u5177\u4f53\u4f4d\u7f6e\u7684\u8bdd\uff0c\u5c31\u53ef\u80fd\u4f1a\u51fa\u73b0hash\u51b2\u7a81\u7684\u60c5\u51b5\uff0c\u5373\u4e24\u4e2a\u4e0d\u540c\u7684hashCode\u53d6\u6a21\u540e\u7684\u503c\u76f8\u540c\u3002<\/p>\n\n\n\n
    ThreadLocal\u662f\u5982\u4f55\u89e3\u51b3hash\u51b2\u7a81\u7684\u5462\uff1f<\/p>\n\n\n\n
    \u6211\u4eec\u770b\u770bgetEntry\u662f\u600e\u4e48\u505a\u7684\uff1a<\/p>\n\n\n\n
    private Entry getEntry(ThreadLocal<?> key) {\n    \/\/\u901a\u8fc7hash\u7b97\u6cd5\u83b7\u53d6\u4e0b\u6807\u503c\n    int i = key.threadLocalHashCode & (table.length - 1);\n    Entry e = table[i];\n    \/\/\u5982\u679c\u4e0b\u6807\u4f4d\u7f6e\u4e0a\u7684key\u6b63\u597d\u662f\u6211\u4eec\u6240\u9700\u8981\u5bfb\u627e\u7684key\n    if (e != null && e.get() == key)\n        \/\/\u8bf4\u660e\u627e\u5230\u6570\u636e\u4e86\uff0c\u76f4\u63a5\u8fd4\u56de\n        return e;\n    else\n        \/\/\u8bf4\u660e\u51fa\u73b0hash\u51b2\u7a81\u4e86\uff0c\u7ee7\u7eed\u5f80\u540e\u627e\n        return getEntryAfterMiss(key, i, e);\n}\n\n<\/pre>\n\n\n\n
    \u518d\u770b\u770bgetEntryAfterMiss\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
    \nprivate Entry getEntryAfterMiss(ThreadLocal<?> key, int i, Entry e) {\n    Entry[] tab = table;\n    int len = tab.length;\n\n    \/\/\u5224\u65adEntry\u5bf9\u8c61\u5982\u679c\u4e0d\u4e3a\u7a7a\uff0c\u5219\u4e00\u76f4\u5faa\u73af\n    while (e != null) {\n        ThreadLocal<?> k = e.get();\n        \/\/\u5982\u679c\u5f53\u524dEntry\u7684key\u6b63\u597d\u662f\u6211\u4eec\u6240\u9700\u8981\u5bfb\u627e\u7684key\n        if (k == key)\n            \/\/\u8bf4\u660e\u8fd9\u6b21\u771f\u7684\u627e\u5230\u6570\u636e\u4e86\n            return e;\n        if (k == null)\n            \/\/\u5982\u679ckey\u4e3a\u7a7a\uff0c\u5219\u6e05\u7406\u810f\u6570\u636e\n            expungeStaleEntry(i);\n        else\n            \/\/\u5982\u679c\u8fd8\u662f\u6ca1\u627e\u5230\u6570\u636e\uff0c\u5219\u7ee7\u7eed\u5f80\u540e\u627e\n            i = nextIndex(i, len);\n        e = tab[i];\n    }\n    return null;\n}<\/pre>\n\n\n\n
    \u5173\u952e\u770b\u770bnextIndex\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
    private static int nextIndex(int i, int len) {\n    return ((i + 1 < len) ? i + 1 : 0);\n}\n<\/pre>\n\n\n\n
    \u5f53\u901a\u8fc7hash\u7b97\u6cd5\u8ba1\u7b97\u51fa\u7684\u4e0b\u6807\u5c0f\u4e8e\u6570\u7ec4\u5927\u5c0f\uff0c\u5219\u5c06\u4e0b\u6807\u503c\u52a01\u3002\u5426\u5219\uff0c\u5373\u4e0b\u6807\u5927\u4e8e\u7b49\u4e8e\u6570\u7ec4\u5927\u5c0f\uff0c\u4e0b\u6807\u53d8\u62100\u4e86\u3002\u4e0b\u6807\u53d8\u62100\u4e4b\u540e\uff0c\u5219\u5faa\u73af\u4e00\u6b21\uff0c\u4e0b\u6807\u53c8\u53d8\u62101\u3002\u3002\u3002<\/p>\n\n\n\n
    \u5bfb\u627e\u7684\u5927\u81f4\u8fc7\u7a0b\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
    \n
    \"\"<\/figure><\/div>\n\n\n
    \u5982\u679c\u627e\u5230\u6700\u540e\u4e00\u4e2a\uff0c\u8fd8\u662f\u6ca1\u6709\u627e\u5230\uff0c\u5219\u518d\u4ece\u5934\u5f00\u59cb\u627e\u3002<\/p>\n\n\n
    \n
    \"\"<\/figure><\/div>\n\n\n
    \u4e0d\u77e5\u9053\u4f60\u6709\u6ca1\u6709\u53d1\u73b0\uff0c\u5b83\u6784\u6210\u4e86\u4e00\u4e2a\uff1a\u73af\u5f62\u3002<\/p>\n\n\n\n
    ThreadLocal\u4ece\u6570\u7ec4\u4e2d\u627e\u6570\u636e\u7684\u8fc7\u7a0b\u5927\u81f4\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n\n\n\n
      \n
    1. \u901a\u8fc7key\u7684hashCode\u53d6\u4f59\u8ba1\u7b97\u51fa\u4e00\u4e2a\u4e0b\u6807\u3002<\/li>\n\n\n\n
    2. \u901a\u8fc7\u4e0b\u6807\uff0c\u5728\u6570\u7ec4\u4e2d\u5b9a\u4f4d\u5177\u4f53Entry\uff0c\u5982\u679ckey\u6b63\u597d\u662f\u6211\u4eec\u6240\u9700\u8981\u7684key\uff0c\u8bf4\u660e\u627e\u5230\u4e86\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\u6570\u636e\u3002<\/li>\n\n\n\n
    3. \u5982\u679c\u7b2c2\u6b65\u6ca1\u6709\u627e\u5230\u6211\u4eec\u60f3\u8981\u7684\u6570\u636e\uff0c\u5219\u4ece\u6570\u7ec4\u7684\u4e0b\u6807\u4f4d\u7f6e\uff0c\u7ee7\u7eed\u5f80\u540e\u9762\u627e\u3002<\/li>\n\n\n\n
    4. \u5982\u679c\u7b2c3\u6b65\u4e2d\u627ekey\u7684\u6b63\u597d\u662f\u6211\u4eec\u6240\u9700\u8981\u7684key\uff0c\u8bf4\u660e\u627e\u5230\u4e86\uff0c\u5219\u76f4\u63a5\u8fd4\u56de\u6570\u636e\u3002<\/li>\n\n\n\n
    5. \u5982\u679c\u8fd8\u662f\u6ca1\u6709\u627e\u5230\u6570\u636e\uff0c\u518d\u7ee7\u7eed\u5f80\u540e\u9762\u627e\u3002\u5982\u679c\u627e\u5230\u6700\u540e\u4e00\u4e2a\u4f4d\u7f6e\uff0c\u8fd8\u662f\u6ca1\u6709\u627e\u5230\u6570\u636e\uff0c\u5219\u518d\u4ece\u5934\uff0c\u5373\u4e0b\u6807\u4e3a0\u7684\u4f4d\u7f6e\uff0c\u7ee7\u7eed\u4ece\u524d\u5f80\u540e\u627e\u6570\u636e\u3002<\/li>\n\n\n\n
    6. \u76f4\u5230\u627e\u5230\u7b2c\u4e00\u4e2aEntry\u4e3a\u7a7a\u4e3a\u6b62\u3002<\/li>\n<\/ol>\n\n\n\n
      8. ThreadLocal\u662f\u5982\u4f55\u6269\u5bb9\u7684\uff1f<\/strong><\/p>\n\n\n\n
      \n\n\n\n
      \u4ece\u4e0a\u9762\u5f97\u77e5\uff0cThreadLocal\u7684\u521d\u59cb\u5927\u5c0f\u662f16\u3002\u90a3\u4e48\u95ee\u9898\u6765\u4e86\uff0cThreadLocal\u662f\u5982\u4f55\u6269\u5bb9\u7684\uff1f<\/p>\n\n\n\n
      \u5728set\u65b9\u6cd5\u4e2d\u4f1a\u8c03\u7528rehash\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
      \n\nprivate void set(ThreadLocal<?> key, Object value) {\n    Entry[] tab = table;\n    int len = tab.length;\n    int i = key.threadLocalHashCode & (len-1);\n\n    for (Entry e = tab[i];\n         e != null;\n         e = tab[i = nextIndex(i, len)]) {\n        ThreadLocal<?> k = e.get();\n\n        if (k == key) {\n            e.value = value;\n            return;\n        }\n\n        if (k == null) {\n            replaceStaleEntry(key, value, i);\n            return;\n        }\n    }\n\n    tab[i] = new Entry(key, value);\n    int sz = ++size;\n    if (!cleanSomeSlots(i, sz) && sz >= threshold)\n        rehash();\n}<\/pre>\n\n\n\n
      \u6ce8\u610f\u4e00\u4e0b\uff0c\u5176\u4e2d\u6709\u4e2a\u5224\u65ad\u6761\u4ef6\u662f\uff1asz(\u4e4b\u524d\u7684size+1)\u5982\u679c\u5927\u4e8e\u6216\u7b49\u4e8ethreshold\u7684\u8bdd\uff0c\u5219\u8c03\u7528rehash\u65b9\u6cd5\u3002<\/p>\n\n\n\n
      threshold\u9ed8\u8ba4\u662f0\uff0c\u5728\u521b\u5efaThreadLocalMap\u65f6\uff0c\u8c03\u7528\u5b83\u7684\u6784\u9020\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
      ThreadLocalMap(ThreadLocal<?> firstKey, Object firstValue) {\n    table = new Entry[INITIAL_CAPACITY];\n    int i = firstKey.threadLocalHashCode & (INITIAL_CAPACITY - 1);\n    table[i] = new Entry(firstKey, firstValue);\n    size = 1;\n    setThreshold(INITIAL_CAPACITY);\n}\n<\/pre>\n\n\n\n
      \u8c03\u7528setThreshold\u65b9\u6cd5\u7ed9threshold\u8bbe\u7f6e\u4e00\u4e2a\u503c\uff0c\u800c\u8fd9\u4e2a\u503cINITIAL_CAPACITY\u662f\u9ed8\u8ba4\u7684\u5927\u5c0f16\u3002<\/p>\n\n\n\n
      private void setThreshold(int len) {\n    threshold = len * 2 \/ 3;\n}\n<\/pre>\n\n\n\n
      \u4e5f\u5c31\u662f\u7b2c\u4e00\u6b21\u8bbe\u7f6e\u7684threshold = 16 * 2 \/ 3\uff0c \u53d6\u6574\u540e\u7684\u503c\u662f\uff1a10\u3002<\/p>\n\n\n\n
      \u6362\u53e5\u8bdd\u8bf4\u5f53sz\u5927\u4e8e\u7b49\u4e8e10\u65f6\uff0c\u5c31\u53ef\u4ee5\u8003\u8651\u6269\u5bb9\u4e86\u3002<\/p>\n\n\n\n
      rehash\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n
      private void rehash() {\n    \/\/\u5148\u5c1d\u8bd5\u56de\u6536\u4e00\u6b21key\u4e3anull\u7684\u503c\uff0c\u817e\u51fa\u4e00\u4e9b\u7a7a\u95f4\n    expungeStaleEntries();\n\n    if (size >= threshold - threshold \/ 4)\n        resize();\n}\n<\/pre>\n\n\n\n
      \u5728\u771f\u6b63\u6269\u5bb9\u4e4b\u524d\uff0c\u5148\u5c1d\u8bd5\u56de\u6536\u4e00\u6b21key\u4e3anull\u7684\u503c\uff0c\u817e\u51fa\u4e00\u4e9b\u7a7a\u95f4\u3002<\/p>\n\n\n\n
      \u5982\u679c\u56de\u6536\u4e4b\u540e\u7684size\u5927\u4e8e\u7b49\u4e8ethreshold\u76843\/4\u65f6\uff0c\u624d\u9700\u8981\u771f\u6b63\u7684\u6269\u5bb9\u3002<\/p>\n\n\n\n
      \u8ba1\u7b97\u516c\u5f0f\u5982\u4e0b\uff1a<\/p>\n\n\n\n
      16 * 2 * 4 \/ 3 * 4 - 16 * 2 \/ 3 * 4 = 8\n<\/pre>\n\n\n\n
      \u4e5f\u5c31\u662f\u8bf4\u6dfb\u52a0\u6570\u636e\u540e\uff0c\u65b0\u7684size\u5927\u4e8e\u7b49\u4e8e\u8001size\u76841\/2\u65f6\uff0c\u624d\u9700\u8981\u6269\u5bb9\u3002<\/p>\n\n\n\n
      \nprivate void resize() {\n    Entry[] oldTab = table;\n    int oldLen = oldTab.length;\n    \/\/\u63092\u500d\u7684\u5927\u5c0f\u6269\u5bb9\n    int newLen = oldLen * 2;\n    Entry[] newTab = new Entry[newLen];\n    int count = 0;\n\n    for (int j = 0; j < oldLen; ++j) {\n        Entry e = oldTab[j];\n        if (e != null) {\n            ThreadLocal<?> k = e.get();\n            if (k == null) {\n                e.value = null; \/\/ Help the GC\n            } else {\n                int h = k.threadLocalHashCode & (newLen - 1);\n                while (newTab[h] != null)\n                    h = nextIndex(h, newLen);\n                newTab[h] = e;\n                count++;\n            }\n        }\n    }\n\n    setThreshold(newLen);\n    size = count;\n    table = newTab;\n}<\/pre>\n\n\n\n
      resize\u4e2d\u6bcf\u6b21\u90fd\u662f\u63092\u500d\u7684\u5927\u5c0f\u6269\u5bb9\u3002<\/p>\n\n\n\n
      \u6269\u5bb9\u7684\u8fc7\u7a0b\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n\n\n
      \n
      \"\"<\/figure><\/div>\n\n\n
      \u6269\u5bb9\u7684\u5173\u952e\u6b65\u9aa4\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        \n
      1. \u8001size + 1 = \u65b0size<\/li>\n\n\n\n
      2. \u5982\u679c\u65b0size\u5927\u4e8e\u7b49\u4e8e\u8001size\u76842\/3\u65f6\uff0c\u9700\u8981\u8003\u8651\u6269\u5bb9\u3002<\/li>\n\n\n\n
      3. \u6269\u5bb9\u524d\u5148\u5c1d\u8bd5\u56de\u6536\u4e00\u6b21key\u4e3anull\u7684\u503c\uff0c\u817e\u51fa\u4e00\u4e9b\u7a7a\u95f4\u3002<\/li>\n\n\n\n
      4. \u5982\u679c\u56de\u6536\u4e4b\u540e\u53d1\u73b0size\u8fd8\u662f\u5927\u4e8e\u7b49\u4e8e\u8001size\u76841\/2\u65f6\uff0c\u624d\u9700\u8981\u771f\u6b63\u7684\u6269\u5bb9\u3002<\/li>\n\n\n\n
      5. \u6bcf\u6b21\u90fd\u662f\u63092\u500d\u7684\u5927\u5c0f\u6269\u5bb9\u3002<\/li>\n<\/ol>\n\n\n\n
        9. \u7236\u5b50\u7ebf\u7a0b\u5982\u4f55\u5171\u4eab\u6570\u636e\uff1f<\/strong><\/p>\n\n\n\n
        \n\n\n\n
        \u524d\u9762\u4ecb\u7ecd\u7684ThreadLocal\u90fd\u662f\u5728\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u4fdd\u5b58\u548c\u83b7\u53d6\u6570\u636e\u7684\u3002<\/p>\n\n\n\n
        \u4f46\u5728\u5b9e\u9645\u5de5\u4f5c\u4e2d\uff0c\u6709\u53ef\u80fd\u662f\u5728\u7236\u5b50\u7ebf\u7a0b\u4e2d\u5171\u4eab\u6570\u636e\u7684\u3002\u5373\u5728\u7236\u7ebf\u7a0b\u4e2d\u5f80ThreadLocal\u8bbe\u7f6e\u4e86\u503c\uff0c\u5728\u5b50\u7ebf\u7a0b\u4e2d\u80fd\u591f\u83b7\u53d6\u5230\u3002<\/p>\n\n\n\n
        \u4f8b\u5982\uff1a<\/p>\n\n\n\n
        public class ThreadLocalTest {\n\n    public static void main(String[] args) {\n        ThreadLocal<Integer> threadLocal = new ThreadLocal<>();\n        threadLocal.set(6);\n        System.out.println(\"\u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n\n        new Thread(() -> {\n            System.out.println(\"\u5b50\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n        }).start();\n    }\n}\n<\/pre>\n\n\n\n
        \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
        \u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a6\n\u5b50\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1anull<\/pre>\n\n\n\n
        \u4f60\u4f1a\u53d1\u73b0\uff0c\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u4f7f\u7528ThreadLocal\u662f\u884c\u4e0d\u901a\u7684\u3002main\u65b9\u6cd5\u662f\u5728\u4e3b\u7ebf\u7a0b\u4e2d\u6267\u884c\u7684\uff0c\u76f8\u5f53\u4e8e\u7236\u7ebf\u7a0b\u3002\u5728main\u65b9\u6cd5\u4e2d\u5f00\u542f\u4e86\u53e6\u5916\u4e00\u4e2a\u7ebf\u7a0b\uff0c\u76f8\u5f53\u4e8e\u5b50\u7ebf\u7a0b\u3002<\/p>\n\n\n\n
        \u663e\u7136\u901a\u8fc7ThreadLocal\uff0c\u65e0\u6cd5\u5728\u7236\u5b50\u7ebf\u7a0b\u4e2d\u5171\u4eab\u6570\u636e\u3002<\/p>\n\n\n\n
        \u90a3\u4e48\uff0c\u8be5\u600e\u4e48\u529e\u5462\uff1f<\/p>\n\n\n\n
        \u7b54\uff1a\u4f7f\u7528InheritableThreadLocal\uff0c\u5b83\u662fJDK\u81ea\u5e26\u7684\u7c7b\uff0c\u7ee7\u627f\u4e86ThreadLocal\u7c7b\u3002<\/p>\n\n\n\n
        \u4fee\u6539\u4ee3\u7801\u4e4b\u540e\uff1a<\/p>\n\n\n\n
        public class ThreadLocalTest {\n\n    public static void main(String[] args) {\n        InheritableThreadLocal<Integer> threadLocal = new InheritableThreadLocal<>();\n        threadLocal.set(6);\n        System.out.println(\"\u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n\n        new Thread(() -> {\n            System.out.println(\"\u5b50\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n        }).start();\n    }\n}\n<\/pre>\n\n\n\n
        \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
        \u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a6\n\u5b50\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a6\n<\/pre>\n\n\n\n
        \u679c\u7136\uff0c\u5728\u6362\u6210InheritableThreadLocal\u4e4b\u540e\uff0c\u5728\u5b50\u7ebf\u7a0b\u4e2d\u80fd\u591f\u6b63\u5e38\u83b7\u53d6\u7236\u7ebf\u7a0b\u4e2d\u8bbe\u7f6e\u7684\u503c\u3002<\/p>\n\n\n\n
        \u5176\u5b9e\uff0c\u5728Thread\u7c7b\u4e2d\u9664\u4e86\u6210\u5458\u53d8\u91cfthreadLocals\u4e4b\u5916\uff0c\u8fd8\u6709\u53e6\u4e00\u4e2a\u6210\u5458\u53d8\u91cf\uff1ainheritableThreadLocals\u3002<\/p>\n\n\n\n
        Thread\u7c7b\u7684\u90e8\u5206\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        ThreadLocal.ThreadLocalMap threadLocals = null;\nThreadLocal.ThreadLocalMap inheritableThreadLocals = null;\n<\/pre>\n\n\n\n
        \u6700\u5173\u952e\u7684\u4e00\u70b9\u662f\uff0c\u5728\u5b83\u7684init\u65b9\u6cd5\u4e2d\u4f1a\u5c06\u7236\u7ebf\u7a0b\u4e2d\u5f80ThreadLocal\u8bbe\u7f6e\u7684\u503c\uff0c\u62f7\u8d1d\u4e00\u4efd\u5230\u5b50\u7ebf\u7a0b\u4e2d\u3002<\/p>\n\n\n\n
        10. \u7ebf\u7a0b\u6c60\u4e2d\u5982\u4f55\u5171\u4eab\u6570\u636e\uff1f<\/strong><\/p>\n\n\n\n
        \n\n\n\n
        \u5728\u771f\u5b9e\u7684\u4e1a\u52a1\u573a\u666f\u4e2d\uff0c\u4e00\u822c\u5f88\u5c11\u7528\u5355\u72ec\u7684\u7ebf\u7a0b\uff0c\u7edd\u5927\u591a\u6570\uff0c\u90fd\u662f\u7528\u7684\u7ebf\u7a0b\u6c60\u3002<\/p>\n\n\n\n
        \u90a3\u4e48\uff0c\u5728\u7ebf\u7a0b\u6c60\u4e2d\u5982\u4f55\u5171\u4eabThreadLocal\u5bf9\u8c61\u751f\u6210\u7684\u6570\u636e\u5462\uff1f<\/p>\n\n\n\n
        \u56e0\u4e3a\u6d89\u53ca\u5230\u4e0d\u540c\u7684\u7ebf\u7a0b\uff0c\u5982\u679c\u76f4\u63a5\u4f7f\u7528ThreadLocal\uff0c\u663e\u7136\u662f\u4e0d\u5408\u9002\u7684\u3002<\/p>\n\n\n\n
        \u6211\u4eec\u5e94\u8be5\u4f7f\u7528InheritableThreadLocal\uff0c\u5177\u4f53\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        \nprivate static void fun1() {\n    InheritableThreadLocal<Integer> threadLocal = new InheritableThreadLocal<>();\n    threadLocal.set(6);\n    System.out.println(\"\u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n\n    ExecutorService executorService = Executors.newSingleThreadExecutor();\n\n    threadLocal.set(6);\n    executorService.submit(() -> {\n        System.out.println(\"\u7b2c\u4e00\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n    });\n\n    threadLocal.set(7);\n    executorService.submit(() -> {\n        System.out.println(\"\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n    });\n}<\/pre>\n\n\n\n
        \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
        \u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a6\n\u7b2c\u4e00\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a6\n\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a6\n<\/pre>\n\n\n\n
        \u7531\u4e8e\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\u4f7f\u7528\u4e86\u5355\u4f8b\u7ebf\u7a0b\u6c60\uff0c\u56fa\u5b9a\u7ebf\u7a0b\u6570\u662f1\u3002<\/p>\n\n\n\n
        \u7b2c\u4e00\u6b21submit\u4efb\u52a1\u7684\u65f6\u5019\uff0c\u8be5\u7ebf\u7a0b\u6c60\u4f1a\u81ea\u52a8\u521b\u5efa\u4e00\u4e2a\u7ebf\u7a0b\u3002\u56e0\u4e3a\u4f7f\u7528\u4e86InheritableThreadLocal\uff0c\u6240\u4ee5\u521b\u5efa\u7ebf\u7a0b\u65f6\uff0c\u4f1a\u8c03\u7528\u5b83\u7684init\u65b9\u6cd5\uff0c\u5c06\u7236\u7ebf\u7a0b\u4e2d\u7684inheritableThreadLocals\u6570\u636e\u590d\u5236\u5230\u5b50\u7ebf\u7a0b\u4e2d\u3002\u6240\u4ee5\u6211\u4eec\u770b\u5230\uff0c\u5728\u4e3b\u7ebf\u7a0b\u4e2d\u5c06\u6570\u636e\u8bbe\u7f6e\u62106\uff0c\u7b2c\u4e00\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u4e86\u6b63\u786e\u7684\u6570\u636e6\u3002<\/p>\n\n\n\n
        \u4e4b\u540e\uff0c\u5728\u4e3b\u7ebf\u7a0b\u4e2d\u53c8\u5c06\u6570\u636e\u6539\u62107\uff0c\u4f46\u5728\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\u5374\u4f9d\u7136\u662f6\u3002<\/p>\n\n\n\n
        \u56e0\u4e3a\u7b2c\u4e8c\u6b21submit\u4efb\u52a1\u7684\u65f6\u5019\uff0c\u7ebf\u7a0b\u6c60\u4e2d\u5df2\u7ecf\u6709\u4e00\u4e2a\u7ebf\u7a0b\u4e86\uff0c\u5c31\u76f4\u63a5\u62ff\u8fc7\u6765\u590d\u7528\uff0c\u4e0d\u4f1a\u518d\u91cd\u65b0\u521b\u5efa\u7ebf\u7a0b\u4e86\u3002\u6240\u4ee5\u4e0d\u4f1a\u518d\u8c03\u7528\u7ebf\u7a0b\u7684init\u65b9\u6cd5\uff0c\u6240\u4ee5\u7b2c\u4e8c\u6b21\u5176\u5b9e\u6ca1\u6709\u83b7\u53d6\u5230\u6700\u65b0\u7684\u6570\u636e7\uff0c\u8fd8\u662f\u83b7\u53d6\u7684\u8001\u6570\u636e6\u3002<\/p>\n\n\n\n
        \u90a3\u4e48\uff0c\u8fd9\u8be5\u600e\u4e48\u529e\u5462\uff1f<\/p>\n\n\n\n
        \u7b54\uff1a\u4f7f\u7528TransmittableThreadLocal\uff0c\u5b83\u5e76\u975eJDK\u81ea\u5e26\u7684\u7c7b\uff0c\u800c\u662f\u963f\u91cc\u5df4\u5df4\u5f00\u6e90jar\u5305\u4e2d\u7684\u7c7b\u3002<\/p>\n\n\n\n
        \u53ef\u4ee5\u901a\u8fc7\u5982\u4e0bpom\u6587\u4ef6\u5f15\u5165\u8be5jar\u5305\uff1a<\/p>\n\n\n\n
        <dependency>\n   <groupId>com.alibaba<\/groupId>\n   <artifactId>transmittable-thread-local<\/artifactId>\n   <version>2.11.0<\/version>\n   <scope>compile<\/scope>\n<\/dependency>\n<\/pre>\n\n\n\n
        \u4ee3\u7801\u8c03\u6574\u5982\u4e0b\uff1a<\/p>\n\n\n\n
        \nprivate static void fun2() throws Exception {\n    TransmittableThreadLocal<Integer> threadLocal = new TransmittableThreadLocal<>();\n    threadLocal.set(6);\n    System.out.println(\"\u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n\n    ExecutorService ttlExecutorService = TtlExecutors.getTtlExecutorService(Executors.newFixedThreadPool(1));\n\n    threadLocal.set(6);\n    ttlExecutorService.submit(() -> {\n        System.out.println(\"\u7b2c\u4e00\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n    });\n\n    threadLocal.set(7);\n    ttlExecutorService.submit(() -> {\n        System.out.println(\"\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a\" + threadLocal.get());\n    });\n\n}<\/pre>\n\n\n\n
        \u6267\u884c\u7ed3\u679c\uff1a<\/p>\n\n\n\n
        \u7236\u7ebf\u7a0b\u83b7\u53d6\u6570\u636e\uff1a6\n\u7b2c\u4e00\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a6\n\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u6c60\u4e2d\u83b7\u53d6\u6570\u636e\uff1a7\n\n<\/pre>\n\n\n\n
        \u6211\u4eec\u770b\u5230\uff0c\u4f7f\u7528\u4e86TransmittableThreadLocal\u4e4b\u540e\uff0c\u7b2c\u4e8c\u6b21\u4ece\u7ebf\u7a0b\u4e2d\u4e5f\u80fd\u6b63\u786e\u83b7\u53d6\u6700\u65b0\u7684\u6570\u636e7\u4e86\u3002<\/p>\n\n\n\n
        nice\u3002<\/p>\n\n\n\n
        \u5982\u679c\u4f60\u4ed4\u7ec6\u89c2\u5bdf\u8fd9\u4e2a\u4f8b\u5b50\uff0c\u4f60\u53ef\u80fd\u4f1a\u53d1\u73b0\uff0c\u4ee3\u7801\u4e2d\u9664\u4e86\u4f7f\u7528TransmittableThreadLocal\u7c7b\u4e4b\u5916\uff0c\u8fd8\u4f7f\u7528\u4e86TtlExecutors.getTtlExecutorService\u65b9\u6cd5\uff0c\u53bb\u521b\u5efaExecutorService\u5bf9\u8c61\u3002<\/p>\n\n\n\n
        \u8fd9\u662f\u975e\u5e38\u91cd\u8981\u7684\u5730\u65b9\uff0c\u5982\u679c\u6ca1\u6709\u8fd9\u4e00\u6b65\uff0cTransmittableThreadLocal\u5728\u7ebf\u7a0b\u6c60\u4e2d\u5171\u4eab\u6570\u636e\u5c06\u4e0d\u4f1a\u8d77\u4f5c\u7528\u3002<\/p>\n\n\n\n
        \u521b\u5efaExecutorService\u5bf9\u8c61\uff0c\u5e95\u5c42\u7684submit\u65b9\u6cd5\u4f1aTtlRunnable\u6216TtlCallable\u5bf9\u8c61\u3002<\/p>\n\n\n\n
        \u4ee5TtlRunnable\u7c7b\u4e3a\u4f8b\uff0c\u5b83\u5b9e\u73b0\u4e86Runnable\u63a5\u53e3\uff0c\u540c\u65f6\u8fd8\u5b9e\u73b0\u4e86\u5b83\u7684run\u65b9\u6cd5\uff1a<\/p>\n\n\n\n
        \npublic void run() {\n    Map<TransmittableThreadLocal<?>, Object> copied = (Map)this.copiedRef.get();\n    if (copied != null && (!this.releaseTtlValueReferenceAfterRun || this.copiedRef.compareAndSet(copied, (Object)null))) {\n        Map backup = TransmittableThreadLocal.backupAndSetToCopied(copied);\n\n        try {\n            this.runnable.run();\n        } finally {\n            TransmittableThreadLocal.restoreBackup(backup);\n        }\n    } else {\n        throw new IllegalStateException(\"TTL value reference is released after run!\");\n    }\n}<\/pre>\n\n\n\n
        \u8fd9\u6bb5\u4ee3\u7801\u7684\u4e3b\u8981\u903b\u8f91\u5982\u4e0b\uff1a<\/p>\n\n\n\n
          \n
        1. \u628a\u5f53\u65f6\u7684ThreadLocal\u505a\u4e2a\u5907\u4efd\uff0c\u7136\u540e\u5c06\u7236\u7c7b\u7684ThreadLocal\u62f7\u8d1d\u8fc7\u6765\u3002<\/li>\n\n\n\n
        2. \u6267\u884c\u771f\u6b63\u7684run\u65b9\u6cd5\uff0c\u53ef\u4ee5\u83b7\u53d6\u5230\u7236\u7c7b\u6700\u65b0\u7684ThreadLocal\u6570\u636e\u3002<\/li>\n\n\n\n
        3. \u4ece\u5907\u4efd\u7684\u6570\u636e\u4e2d\uff0c\u6062\u590d\u5f53\u65f6\u7684ThreadLocal\u6570\u636e\u3002<\/li>\n<\/ol>\n\n\n\n
          11. ThreadLocal\u6709\u54ea\u4e9b\u7528\u9014\uff1f<\/strong><\/p>\n\n\n\n
          \n\n\n\n
          \u6700\u540e\uff0c\u4e00\u8d77\u804a\u804aThreadLocal\u6709\u54ea\u4e9b\u7528\u9014\uff1f<\/p>\n\n\n\n
          \u8001\u5b9e\u8bf4\uff0c\u4f7f\u7528ThreadLocal\u7684\u573a\u666f\u633a\u591a\u7684\u3002<\/p>\n\n\n\n
          \u4e0b\u9762\u5217\u4e3e\u51e0\u4e2a\u5e38\u89c1\u7684\u573a\u666f\uff1a<\/p>\n\n\n\n
            \n
          1. \u5728spring\u4e8b\u52a1\u4e2d\uff0c\u4fdd\u8bc1\u4e00\u4e2a\u7ebf\u7a0b\u4e0b\uff0c\u4e00\u4e2a\u4e8b\u52a1\u7684\u591a\u4e2a\u64cd\u4f5c\u62ff\u5230\u7684\u662f\u4e00\u4e2aConnection\u3002<\/li>\n\n\n\n
          2. \u5728hiberate\u4e2d\u7ba1\u7406session\u3002<\/li>\n\n\n\n
          3. \u5728JDK8\u4e4b\u524d\uff0c\u4e3a\u4e86\u89e3\u51b3SimpleDateFormat\u7684\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898\u3002<\/li>\n\n\n\n
          4. \u83b7\u53d6\u5f53\u524d\u767b\u5f55\u7528\u6237\u4e0a\u4e0b\u6587\u3002<\/li>\n\n\n\n
          5. \u4e34\u65f6\u4fdd\u5b58\u6743\u9650\u6570\u636e\u3002<\/li>\n\n\n\n
          6. \u4f7f\u7528MDC\u4fdd\u5b58\u65e5\u5fd7\u4fe1\u606f\u3002<\/li>\n<\/ol>\n\n\n\n
            \u7b49\u7b49\uff0c\u8fd8\u6709\u5f88\u591a\u4e1a\u52a1\u573a\u666f\uff0c\u8fd9\u91cc\u5c31\u4e0d\u4e00\u4e00\u5217\u4e3e\u4e86\u3002<\/p>\n\n\n\n
            \u7531\u4e8e\u7bc7\u5e45\u6709\u9650\uff0c\u4eca\u5929\u7684\u5185\u5bb9\u5148\u5206\u4eab\u5230\u8fd9\u91cc\u3002\u5e0c\u671b\u4f60\u770b\u4e86\u8fd9\u7bc7\u6587\u7ae0\uff0c\u4f1a\u6709\u6240\u6536\u83b7\u3002<\/p>\n\n\n\n
            \u63a5\u4e0b\u6765\u7559\u51e0\u4e2a\u95ee\u9898\u7ed9\u5927\u5bb6\u601d\u8003\u4e00\u4e0b\uff1a<\/p>\n\n\n\n
              \n
            1. ThreadLocal\u53d8\u91cf\u4e3a\u4ec0\u4e48\u5efa\u8bae\u8981\u5b9a\u4e49\u6210static\u7684\uff1f<\/li>\n\n\n\n
            2. Entry\u6570\u7ec4\u4e3a\u4ec0\u4e48\u8981\u901a\u8fc7hash\u7b97\u6cd5\u8ba1\u7b97\u4e0b\u6807\uff0c\u5373\u76f4\u7ebf\u5bfb\u5740\u6cd5\uff0c\u800c\u4e0d\u76f4\u63a5\u4f7f\u7528\u4e0b\u6807\u503c\uff1f<\/li>\n\n\n\n
            3. \u5f3a\u5f15\u7528\u548c\u5f31\u5f15\u7528\u6709\u4ec0\u4e48\u533a\u522b\uff1f<\/li>\n\n\n\n
            4. Entry\u6570\u7ec4\u5927\u5c0f\uff0c\u4e3a\u4ec0\u4e48\u662f2\u7684N\u6b21\u65b9\uff1f<\/li>\n\n\n\n
            5. \u4f7f\u7528InheritableThreadLocal\u65f6\uff0c\u5982\u679c\u7236\u7ebf\u7a0b\u4e2d\u91cd\u65b0set\u503c\uff0c\u5728\u5b50\u7ebf\u7a0b\u4e2d\u80fd\u591f\u6b63\u786e\u7684\u83b7\u53d6\u4fee\u6539\u540e\u7684\u65b0\u503c\u5417\uff1f<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"
              \u4f5c\u8005\uff1a\u82cf\u4e09\u8bf4\u6280\u672f\u94fe\u63a5\uff1ahttps:\/\/www.zhihu.com\/question\/657130561\/ans […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"_links":{"self":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/16424"}],"collection":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=16424"}],"version-history":[{"count":1,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/16424\/revisions"}],"predecessor-version":[{"id":16439,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/16424\/revisions\/16439"}],"wp:attachment":[{"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16424"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16424"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16424"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}