{"id":3891,"date":"2025-07-13T11:44:48","date_gmt":"2025-07-13T03:44:48","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3891"},"modified":"2025-07-13T11:44:48","modified_gmt":"2025-07-13T03:44:48","slug":"threadlocal%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f%e5%ae%83%e7%9a%84%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e5%91%a2%ef%bc%9f","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/07\/13\/threadlocal%e6%98%af%e4%bb%80%e4%b9%88%ef%bc%9f%e5%ae%83%e7%9a%84%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e5%91%a2%ef%bc%9f\/","title":{"rendered":"ThreadLocal\u662f\u4ec0\u4e48\uff1f\u5b83\u7684\u5b9e\u73b0\u539f\u7406\u5462\uff1f"},"content":{"rendered":"\n<p><code>ThreadLocal<\/code> \u662f Java \u4e2d\u7684\u4e00\u4e2a\u975e\u5e38\u91cd\u8981\u7684\u7c7b\uff0c\u7528\u4e8e\u5b9e\u73b0<strong>\u7ebf\u7a0b\u672c\u5730\u53d8\u91cf\uff08Thread-local variable\uff09<\/strong>\uff0c\u5373\uff1a<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6709\u81ea\u5df1\u72ec\u7acb\u7684\u53d8\u91cf\u526f\u672c\uff0c\u4e92\u4e0d\u5f71\u54cd<\/strong>\u3002<\/p>\n<\/blockquote>\n\n\n\n<p>\u8fd9\u5728\u5f00\u53d1\u4e2d\u975e\u5e38\u6709\u7528\uff0c\u5c24\u5176\u9002\u5408\u89e3\u51b3<strong>\u591a\u7ebf\u7a0b\u5171\u4eab\u53d8\u91cf\u5bfc\u81f4\u7684\u6570\u636e\u51b2\u7a81\u95ee\u9898<\/strong>\uff0c\u6bd4\u5982\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6570\u636e\u5e93\u8fde\u63a5\uff08\u5982\u6bcf\u4e2a\u7ebf\u7a0b\u72ec\u4eab\u4e00\u4e2a <code>Connection<\/code>\uff09\uff1b<\/li>\n\n\n\n<li>\u7528\u6237\u4f1a\u8bdd\u4fe1\u606f\uff1b<\/li>\n\n\n\n<li>\u683c\u5f0f\u5316\u5bf9\u8c61\uff08\u5982 <code>SimpleDateFormat<\/code> \u7ebf\u7a0b\u4e0d\u5b89\u5168\uff09\uff1b<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001ThreadLocal \u662f\u4ec0\u4e48\uff1f<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u5b9a\u4e49\uff1a<\/h3>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><code>ThreadLocal<\/code> \u63d0\u4f9b\u4e86\u7ebf\u7a0b\u5c40\u90e8\u53d8\u91cf\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u901a\u8fc7 <code>ThreadLocal.get()<\/code> \u548c <code>ThreadLocal.set()<\/code> \u8bbf\u95ee\u5c5e\u4e8e\u5b83\u81ea\u5df1\u7684\u53d8\u91cf\u526f\u672c\u3002<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001\u5178\u578b\u4f7f\u7528\u793a\u4f8b<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>public class ThreadLocalExample {\n    private static final ThreadLocal&lt;Integer&gt; threadLocal = ThreadLocal.withInitial(() -&gt; 0);\n\n    public static void main(String&#91;] args) {\n        Runnable task = () -&gt; {\n            int value = threadLocal.get();\n            threadLocal.set(value + 1);\n            System.out.println(Thread.currentThread().getName() + \" value: \" + threadLocal.get());\n        };\n\n        Thread t1 = new Thread(task);\n        Thread t2 = new Thread(task);\n\n        t1.start();\n        t2.start();\n    }\n}<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\">\u8f93\u51fa\u7c7b\u4f3c\uff1a<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>Thread-0 value: 1\nThread-1 value: 1<\/code><\/pre>\n\n\n\n<p>\u6bcf\u4e2a\u7ebf\u7a0b\u7ef4\u62a4\u4e00\u4efd\u72ec\u7acb\u7684\u503c\uff0c\u4e92\u4e0d\u5e72\u6270\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u5e95\u5c42\u5b9e\u73b0\u539f\u7406\uff08\u8be6\u7ec6\u5206\u6790\uff09<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u5173\u952e\u70b9\uff1a<\/h3>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u7ec4\u6210<\/th><th>\u4f5c\u7528<\/th><\/tr><\/thead><tbody><tr><td><code>ThreadLocal<\/code><\/td><td>\u63d0\u4f9b\u8bbf\u95ee\u63a5\u53e3\uff1a<code>set()<\/code>\u3001<code>get()<\/code>\u3001<code>remove()<\/code><\/td><\/tr><tr><td><code>Thread<\/code> \u7c7b<\/td><td>\u6bcf\u4e2a\u7ebf\u7a0b\u7ef4\u62a4\u4e00\u4e2a <code>ThreadLocalMap<\/code> \u6210\u5458\u53d8\u91cf<\/td><\/tr><tr><td><code>ThreadLocalMap<\/code><\/td><td>\u5b9e\u9645\u662f\u4e00\u4e2a\u5b9a\u5236\u7248\u7684 HashMap\uff0ckey \u662f <code>ThreadLocal<\/code> \u5bf9\u8c61<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">1. \u6bcf\u4e2a\u7ebf\u7a0b\u7ef4\u62a4\u4e00\u4e2a <code>ThreadLocalMap<\/code><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/ java.lang.Thread \u6e90\u7801\nThreadLocal.ThreadLocalMap threadLocals = null;<\/code><\/pre>\n\n\n\n<p>\u8fd9\u662f\u7ebf\u7a0b\u79c1\u6709\u7684\u53d8\u91cf\u5bb9\u5668\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. <code>set()<\/code> \u7684\u5e95\u5c42\u903b\u8f91<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public void set(T value) {\n    Thread t = Thread.currentThread();\n    ThreadLocalMap map = getMap(t);\n    if (map != null)\n        map.set(this, value);\n    else\n        createMap(t, value);\n}<\/code><\/pre>\n\n\n\n<p>\u8fd9\u91cc\u5173\u952e\u70b9\u662f\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6301\u6709\u4e00\u4e2a <code>ThreadLocalMap<\/code>\uff1b<\/li>\n\n\n\n<li><code>ThreadLocalMap<\/code> \u7684 key \u662f\u5f53\u524d\u7684 <code>ThreadLocal<\/code> \u5b9e\u4f8b\u672c\u8eab\uff1b<\/li>\n\n\n\n<li><code>value<\/code> \u662f\u7528\u6237\u5b58\u50a8\u7684\u503c\u3002<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. <code>get()<\/code> \u7684\u5e95\u5c42\u903b\u8f91<\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>public T get() {\n    Thread t = Thread.currentThread();\n    ThreadLocalMap map = getMap(t);\n    if (map != null) {\n        ThreadLocalMap.Entry e = map.getEntry(this);\n        if (e != null) {\n            @SuppressWarnings(\"unchecked\")\n            T result = (T)e.value;\n            return result;\n        }\n    }\n    return setInitialValue();\n}<\/code><\/pre>\n\n\n\n<p>\u6bcf\u4e2a\u7ebf\u7a0b\u53ea\u80fd\u83b7\u53d6\u81ea\u5df1\u7684\u526f\u672c\uff0c\u4e0d\u4f1a\u5f71\u54cd\u5176\u4ed6\u7ebf\u7a0b\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">4. ThreadLocalMap \u7684\u5b9e\u73b0\u7279\u70b9<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u672c\u8d28\u662f\u6570\u7ec4\uff08\u7c7b\u4f3c HashMap\uff09\uff1b<\/li>\n\n\n\n<li>key \u662f <code>ThreadLocal<\/code> \u5b9e\u4f8b\uff1b<\/li>\n\n\n\n<li>\u4f7f\u7528**\u5f31\u5f15\u7528\uff08WeakReference\uff09**\u4f5c\u4e3a key\uff1b<\/li>\n\n\n\n<li>\u5982\u679c <code>ThreadLocal<\/code> \u88ab GC \u56de\u6536\u800c\u7ebf\u7a0b\u8fd8\u5728\uff0c\u53ef\u80fd\u51fa\u73b0 <strong>\u5185\u5b58\u6cc4\u6f0f<\/strong>\uff08value \u65e0\u6cd5\u8bbf\u95ee\u4f46\u8fd8\u672a\u91ca\u653e\uff09\uff1b<\/li>\n<\/ul>\n\n\n\n<h4 class=\"wp-block-heading\">\u5b98\u65b9\u5efa\u8bae\uff08\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\uff09\uff1a<\/h4>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u7528\u5b8c\u540e\u624b\u52a8\u8c03\u7528 <code>remove()<\/code> \u6e05\u7406<\/strong><\/li>\n<\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>threadLocal.remove();<\/code><\/pre>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u56db\u3001\u56fe\u89e3\u539f\u7406<\/h2>\n\n\n\n<pre class=\"wp-block-code\"><code>Thread A:\n  ThreadLocalMap:\n    Key: ThreadLocal1  \u2192 Value: 100\n    Key: ThreadLocal2  \u2192 Value: \"abc\"\n\nThread B:\n  ThreadLocalMap:\n    Key: ThreadLocal1  \u2192 Value: 200\n    Key: ThreadLocal2  \u2192 Value: \"xyz\"<\/code><\/pre>\n\n\n\n<p>\u6bcf\u4e2a\u7ebf\u7a0b\u5404\u81ea\u7ef4\u62a4\u81ea\u5df1\u7684 <code>ThreadLocalMap<\/code>\uff0c\u4e92\u76f8\u72ec\u7acb\u3002<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e94\u3001\u5e94\u7528\u573a\u666f\u603b\u7ed3<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u573a\u666f<\/th><th>\u4f7f\u7528 ThreadLocal \u7684\u597d\u5904<\/th><\/tr><\/thead><tbody><tr><td>\u591a\u7ebf\u7a0b\u7528\u6237\u767b\u5f55\u4e0a\u4e0b\u6587<\/td><td>\u6bcf\u4e2a\u7ebf\u7a0b\u72ec\u7acb\u5b58\u50a8\u7528\u6237 session\uff0c\u4e0d\u5f71\u54cd\u5176\u4ed6\u7ebf\u7a0b<\/td><\/tr><tr><td>\u6570\u636e\u5e93\u8fde\u63a5<\/td><td>\u6bcf\u4e2a\u7ebf\u7a0b\u4e00\u4e2a <code>Connection<\/code>\uff0c\u907f\u514d\u8fde\u63a5\u5171\u4eab\u5bfc\u81f4\u5e76\u53d1\u95ee\u9898<\/td><\/tr><tr><td>\u65e5\u671f\u683c\u5f0f\u5316\uff08SimpleDateFormat\uff09<\/td><td>\u7ebf\u7a0b\u4e0d\u5b89\u5168\u7684\u7c7b\uff0c\u53ef\u4ee5\u901a\u8fc7 ThreadLocal \u4e3a\u6bcf\u7ebf\u7a0b\u63d0\u4f9b\u72ec\u7acb\u5b9e\u4f8b<\/td><\/tr><tr><td>Spring AOP\u4e8b\u52a1\u7ba1\u7406\u5e95\u5c42<\/td><td>\u4f7f\u7528 ThreadLocal \u4fdd\u5b58\u5f53\u524d\u4e8b\u52a1\u72b6\u6001<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516d\u3001\u66ff\u4ee3\u65b9\u6848\u4e0e\u6846\u67b6\u5c01\u88c5<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">\u2714 JDK 8+\uff1a<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ThreadLocal.withInitial(Supplier)<\/code> \u63d0\u4f9b\u9ed8\u8ba4\u521d\u59cb\u5316\u65b9\u5f0f<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u2714 Spring \u5c01\u88c5\uff1a<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>RequestContextHolder<\/code>\u3001<code>TransactionSynchronizationManager<\/code> \u7b49\u90fd\u662f\u57fa\u4e8e <code>ThreadLocal<\/code> \u5b9e\u73b0\u7684<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e03\u3001\u5916\u90e8\u6587\u732e\u4e0e\u94fe\u63a5<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\ud83d\udcd8 \u5b98\u65b9 Java API \u6587\u6863\uff1a<\/li>\n\n\n\n<li><a href=\"https:\/\/docs.oracle.com\/javase\/8\/docs\/api\/java\/lang\/ThreadLocal.html\"><code>ThreadLocal<\/code><\/a><\/li>\n\n\n\n<li>\ud83d\udcd8 JDK \u6e90\u7801\uff08OpenJDK\uff09\uff1a<\/li>\n\n\n\n<li><a href=\"https:\/\/github.com\/openjdk\/jdk\/blob\/master\/src\/java.base\/share\/classes\/java\/lang\/ThreadLocal.java\"><code>ThreadLocal.java<\/code><\/a><\/li>\n\n\n\n<li>\ud83d\udcd8 Java \u5e76\u53d1\u5b9e\u6218\u4e66\u7c4d\uff1a<\/li>\n\n\n\n<li>\u300aJava Concurrency in Practice\u300b\uff1aBrian Goetz\uff08\u7b2c3\u7ae0\uff09<\/li>\n\n\n\n<li>\ud83d\udcc4 Martin Fowler \u76f8\u5173\u6587\u7ae0\uff1a<\/li>\n\n\n\n<li><a href=\"https:\/\/martinfowler.com\/bliki\/ThreadLocal.html\">Using ThreadLocal for Web Context<\/a><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u516b\u3001\u603b\u7ed3\u7b54\u9898\u7ed3\u6784\uff08\u9762\u8bd5\/\u5b9e\u6218\uff09<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>\u95ee\u9898<\/th><th>\u56de\u7b54\u8981\u70b9<\/th><\/tr><\/thead><tbody><tr><td>\u4ec0\u4e48\u662f ThreadLocal\uff1f<\/td><td>\u6bcf\u4e2a\u7ebf\u7a0b\u72ec\u4eab\u7684\u53d8\u91cf\u526f\u672c\uff0c\u89e3\u51b3\u7ebf\u7a0b\u95f4\u5171\u4eab\u53d8\u91cf\u51b2\u7a81<\/td><\/tr><tr><td>\u5e95\u5c42\u539f\u7406\uff1f<\/td><td>\u6bcf\u4e2a\u7ebf\u7a0b\u6301\u6709\u4e00\u4e2a ThreadLocalMap\uff0ckey \u662f ThreadLocal\uff0cvalue \u662f\u526f\u672c\u503c<\/td><\/tr><tr><td>\u6709\u4ec0\u4e48\u4f7f\u7528\u98ce\u9669\uff1f<\/td><td>\u4f7f\u7528\u5f31\u5f15\u7528\u5bb9\u6613\u5185\u5b58\u6cc4\u6f0f\uff0c\u9700\u624b\u52a8\u8c03\u7528 remove()<\/td><\/tr><tr><td>\u5b9e\u9645\u5e94\u7528\u573a\u666f\uff1f<\/td><td>\u6570\u636e\u5e93\u8fde\u63a5\u3001\u7528\u6237\u4e0a\u4e0b\u6587\u3001\u7ebf\u7a0b\u5c01\u88c5\u72b6\u6001\u3001\u683c\u5f0f\u5316\u5668\u7b49<\/td><\/tr><tr><td>\u6846\u67b6\u662f\u5426\u4f7f\u7528\uff1f<\/td><td>Spring\u3001MyBatis \u7b49\u5e95\u5c42\u5927\u91cf\u4f7f\u7528 ThreadLocal \u7ba1\u7406\u4e0a\u4e0b\u6587<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<p>\u66f4\u591a\u8be6\u7ec6\u5185\u5bb9\u8bf7\u5173\u6ce8\u5176\u4ed6\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>ThreadLocal \u662f Java \u4e2d\u7684\u4e00\u4e2a\u975e\u5e38\u91cd\u8981\u7684\u7c7b\uff0c\u7528\u4e8e\u5b9e\u73b0\u7ebf\u7a0b\u672c\u5730\u53d8\u91cf\uff08Thread-local v [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3892,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[86],"tags":[],"class_list":["post-3891","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3891","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=3891"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3891\/revisions"}],"predecessor-version":[{"id":3893,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3891\/revisions\/3893"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/3892"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=3891"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=3891"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=3891"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}