{"id":82,"date":"2023-02-13T11:51:44","date_gmt":"2023-02-13T03:51:44","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=82"},"modified":"2023-02-13T11:52:05","modified_gmt":"2023-02-13T03:52:05","slug":"java-multi-threag-programming-threadlocal","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/02\/13\/java-multi-threag-programming-threadlocal\/","title":{"rendered":"Java\u591a\u7ebf\u7a0b\u7f16\u7a0b\u4e94\uff08\u7ebf\u7a0b\u95f4\u901a\u4fe1\u4e4bThreadLocal\uff09"},"content":{"rendered":"<p>\u53d8\u91cf\u503c\u7684\u5171\u4eab\u53ef\u4ee5\u4f7f\u7528<code>public static<\/code>\u53d8\u91cf\u7684\u5f62\u5f0f\uff0c\u6240\u6709\u7684\u7ebf\u7a0b\u90fd\u662f\u7528\u540c\u4e00\u4e2a<code>public static<\/code>\u53d8\u91cf\u3002\u5982\u679c\u60f3\u5b9e\u73b0\u6bcf\u4e00\u4e2a\u7ebf\u7a0b\u90fd\u6709\u81ea\u5df1\u5171\u4eab\u53d8\u91cf\u8be5\u5982\u4f55\u89e3\u51b3\u5462\uff1fJDK\u4e2d\u63d0\u4f9b\u7684\u7c7b<code>ThreadLocal<\/code>\u6b63\u662f\u4e3a\u4e86\u89e3\u51b3\u8fd9\u6837\u7684\u95ee\u9898\u3002<br \/>\n\u7c7b<code>ThreadLocal<\/code>\u4e3b\u8981\u89e3\u51b3\u7684\u5c31\u662f\u6bcf\u4e2a\u7ebf\u7a0b\u7ed1\u5b9a\u81ea\u5df1\u7684\u503c\uff0c\u53ef\u4ee5\u5c06<code>ThreadLocal<\/code>\u7c7b\u6bd4\u55bb\u6210\u5168\u5c40\u5b58\u653e\u6570\u636e\u7684\u76d2\u5b50\uff0c\u76d2\u5b50\u4e2d\u53ef\u4ee5\u5b58\u50a8\u6bcf\u4e2a\u7ebf\u7a0b\u7684\u79c1\u6709\u6570\u636e\u3002<\/p>\n<h2>\u65b9\u6cd5 get()<\/h2>\n<pre><code class=\"language-java\">public class ThreadMain {\n\n    public static ThreadLocal tl = new ThreadLocal();\n\n    public static void main (String[] args){\n        if (tl.get() == null) {\n            System.out.println(&quot;\u4ece\u672a\u653e\u8fc7\u503c&quot;);\n            tl.set(&quot;\u6211\u7684\u503c&quot;);\n        }\n        System.out.println(tl.get());\n        System.out.println(tl.get());\n\n    }\n}<\/code><\/pre>\n<p>\u4ece\u7ed3\u679c\u6765\u770b\uff0c\u7b2c\u4e00\u6b21\u8c03\u7528tl\u5bf9\u8c61\u7684<code>get()<\/code>\u65b9\u6cd5\u65f6\u8fd4\u56de\u7684\u503c\u662fnull\uff0c\u901a\u8fc7\u8c03\u7528<code>set()<\/code>\u65b9\u6cd5\u8f85\u52a9\u540e\u624d\u80fd\u53d6\u51fa\u503c\u6765\u3002<\/p>\n<pre><code>\u4ece\u672a\u653e\u8fc7\u503c\n\u6211\u7684\u503c\n\u6211\u7684\u503c<\/code><\/pre>\n<h2>\u53d8\u91cf\u9694\u79bb\u6027<\/h2>\n<p>\u7c7b<code>ThreadLocal<\/code>\u89e3\u51b3\u7684\u662f\u53d8\u91cf\u5728\u4e0d\u540c\u7ebf\u7a0b\u95f4\u7684\u9694\u79bb\u6027\uff0c\u4e5f\u5c31\u662f\u4e0d\u540c\u7ebf\u7a0b\u62e5\u6709\u81ea\u5df1\u7684\u503c\uff0c\u4e0d\u540c\u7ebf\u7a0b\u4e2d\u7684\u503c\u662f\u53ef\u4ee5\u653e\u5165<code>ThreadLocal<\/code>\u7c7b\u4e2d\u8fdb\u884c\u4fdd\u5b58\u7684\u3002<\/p>\n<p>\u5982\u4e0b\uff1a\u6bcf\u4e2a\u7ebf\u7a0b\u518dset\u548cget\u65f6\u90fd\u662f\u81ea\u5df1\u6240\u6709\u7684\u4e2a\u4eba\u503c<\/p>\n<pre><code class=\"language-java\">public class ThreadMain {\n    public static void main(String[] args) {\n        final ThreadLocal threadLocal = new ThreadLocal();\n        Thread thread1 = new Thread(new Runnable() {\n            @SuppressWarnings(&quot;all&quot;)\n            public void run() {\n                threadLocal.set(&quot;\u7ebf\u7a0b\u4e00\u7684\u503c&quot;);\n                for (int i = 0; i &lt; 5; i++) {\n                    System.out.println(Thread.currentThread().getName() + &quot;----&quot; + threadLocal.get());\n                    try {\n                        Thread.sleep(500);\n                    } catch (InterruptedException e) {\n                        e.printStackTrace();\n                    }\n                }\n            }\n        });\n        thread1.setName(&quot;\u7ebf\u7a0b\u4e00&quot;);\n        thread1.start();\n\n        Thread thread2 = new Thread(new Runnable() {\n            @SuppressWarnings(&quot;all&quot;)\n            public void run() {\n                threadLocal.set(&quot;\u7ebf\u7a0b\u4e8c\u7684\u503c&quot;);\n                for (int i = 0; i &lt; 5; i++) {\n                    System.out.println(Thread.currentThread().getName() + &quot;----&quot; + threadLocal.get());\n                    try {\n                        Thread.sleep(500);\n                    } catch (InterruptedException e) {\n                        e.printStackTrace();\n                    }\n                }\n            }\n        });\n        thread2.setName(&quot;\u7ebf\u7a0b\u4e8c&quot;);\n        thread2.start();\n    }\n}<\/code><\/pre>\n<h2>\u89e3\u51b3get()\u8fd4\u56denull<\/h2>\n<p>\u6211\u4eec\u53ef\u4ee5\u7ee7\u627f<code>ThreadLocal<\/code>\u91cd\u5199\u5176<code>initialValue()<\/code>\u65b9\u6cd5\uff0ceg\uff1a<\/p>\n<pre><code class=\"language-java\">public class MyThreadLocal extends ThreadLocal {\n    @Override\n    protected Object initialValue() {\n        return &quot;\u6211\u7684\u521d\u59cb\u503c&quot;;\n    }\n}<\/code><\/pre>\n<h2>InheritableThreadLocal\u7684\u4f7f\u7528\uff08\u503c\u7ee7\u627f\uff09<\/h2>\n<p>\u4f7f\u7528<code>InheritableThreadLocal<\/code>\u7c7b\u53ef\u4ee5\u8ba9\u5b50\u7ebf\u7a0b\u4ece\u7236\u7ebf\u7a0b\u4e2d\u53d6\u5f97\u503c\u3002<\/p>\n<pre><code class=\"language-java\">public class InheritableThreadLocalExt extends InheritableThreadLocal {\n\n    @Override\n    protected Object initialValue() {\n        return &quot;InheritableThreadLocalExt&quot;;\n    }\n}\n\npublic class ThreadMain {\n\n    static InheritableThreadLocalExt inheritableThreadLocalExt = new InheritableThreadLocalExt();\n\n    public static void main(String[] args) {\n        try {\n            for (int i = 0; i &lt; 10; i++) {\n                System.out.println(&quot;\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=&quot; + inheritableThreadLocalExt.get());\n                Thread.sleep(100);\n            }\n            Thread.sleep(2000);\n            inheritableThreadLocalExt.set(&quot;first change&quot;);\n            ThreadA threadA = new ThreadA();\n            threadA.start();\n            Thread.sleep(300);\n            inheritableThreadLocalExt.set(&quot;second change&quot;);\n            Thread.sleep(2000);\n            System.out.println(&quot;last value = &quot; + inheritableThreadLocalExt.get());\n            new ThreadA().start();\n        } catch (InterruptedException e) {\n            e.printStackTrace();\n        }\n    }\n\n    static class ThreadA extends Thread {\n\n        @Override\n        public void run() {\n            try {\n                for (int i = 0; i &lt; 10; i++) {\n                    System.out.println(&quot;\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=&quot; + inheritableThreadLocalExt.get());\n                    Thread.sleep(100);\n                }\n                inheritableThreadLocalExt.set(&quot;change&quot;);\n                System.out.println(&quot;\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=&quot; + inheritableThreadLocalExt.get());\n            } catch (InterruptedException e) {\n                e.printStackTrace();\n            }\n        }\n    }\n}<\/code><\/pre>\n<p>\u8fd0\u884c\u7ed3\u679c\uff1a<\/p>\n<pre><code>\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=first change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=change\nlast value = second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=change<\/code><\/pre>\n<p>\u7531\u7ed3\u679c\u53ef\u77e5\uff1a\u5b50\u7ebf\u7a0b\u5728\u8c03\u7528<code>get()<\/code>\u65b9\u6cd5\u65f6\uff0c\u5b50\u7ebf\u7a0b\u4e2d<code>InheritableThreadLocal<\/code>\u7684\u521d\u59cb\u503c\u4e5f\u5c31\u662f\u7ee7\u627f\u5f97\u5230\u7684\u521d\u59cb\u503c\u6c38\u8fdc\u662f<code>InheritableThreadLocal<\/code>\u5728\u7236\u7ebf\u7a0b\u4e2d\u5f53\u524d\u7684\u503c<\/p>\n<h2>\u7ee7\u627f\u503c\u518d\u4fee\u6539<\/h2>\n<p>\u4fee\u6539\u4ee5\u4e0a<code>InheritableThreadLocalExt<\/code>\u4ee3\u7801\uff0c\u91cd\u5199\u65b9\u6cd5<code>childValue<\/code>\u4e3a\uff1a<\/p>\n<pre><code class=\"language-java\">public class InheritableThreadLocalExt extends InheritableThreadLocal {\n\n    @Override\n    protected Object initialValue() {\n        return &quot;InheritableThreadLocalExt&quot;;\n    }\n\n    @Override\n    protected Object childValue(Object parentValue) {\n        return &quot;child value&quot;;\n    }\n}<\/code><\/pre>\n<p>\u5176\u4ed6\u4e0d\u53d8\u8fd0\u884c\u7ed3\u679c\u4e3a\uff1a<\/p>\n<pre><code>\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728Main\u7ebf\u7a0b\u4e2d\u53d6\u503c=InheritableThreadLocalExt\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=change\nlast value = second change\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=child value\n\u5728ThreadA\u7ebf\u7a0b\u4e2d\u53d6\u503c=change<\/code><\/pre>\n<p>\u7531\u7ed3\u679c\u53ef\u77e5\uff1a\u518d\u91cd\u5199<code>childValue<\/code>\u65b9\u6cd5\u540e\uff0c<code>InheritableThreadLocal<\/code>\u5728\u5b50\u7ebf\u7a0b\u4e2d\u7684\u521d\u59cb\u503c\u90fd\u4e3a<code>childValue<\/code>\u4e2d\u8fd4\u56de\u7684\u503c\uff0c\u548c\u7236\u7ebf\u7a0b\u4e2d<code>InheritableThreadLocal<\/code>\u7684\u503c\u65e0\u5173\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u53d8\u91cf\u503c\u7684\u5171\u4eab\u53ef\u4ee5\u4f7f\u7528public static\u53d8\u91cf\u7684\u5f62\u5f0f\uff0c\u6240\u6709\u7684\u7ebf\u7a0b\u90fd\u662f\u7528\u540c\u4e00\u4e2apublic static\u53d8\u91cf [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[43],"tags":[],"class_list":["post-82","post","type-post","status-publish","format-standard","hentry","category-java-basic"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/82","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=82"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/82\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=82"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=82"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=82"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}