{"id":10020946,"date":"2025-08-10T21:22:48","date_gmt":"2025-08-10T13:22:48","guid":{"rendered":"https:\/\/itmax.cn\/?p=10020946"},"modified":"2025-08-10T21:22:48","modified_gmt":"2025-08-10T13:22:48","slug":"java-spi-%e6%9c%ba%e5%88%b6%e5%88%9d%e6%8e%a2%ef%bd%9c%e5%be%97%e7%89%a9%e6%8a%80%e6%9c%af","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10020946","title":{"rendered":"Java SPI \u673a\u5236\u521d\u63a2\uff5c\u5f97\u7269\u6280\u672f"},"content":{"rendered":"<h2>\u4e00\uff0c\u6982\u8ff0<\/h2>\n<h4>\u4ec0\u4e48\u662f SPI<\/h4>\n<p>SPI \u5373 Service Provider Interface \uff0c\u4e5f\u5c31\u662f\u201c\u670d\u52a1\u63d0\u4f9b\u8005\u7684\u63a5\u53e3\u201d\u3002<\/p>\n<p>SPI \u5c06\u670d\u52a1\u63a5\u53e3\u548c\u5177\u4f53\u7684\u670d\u52a1\u5b9e\u73b0\u5206\u79bb\u5f00\u6765\uff0c\u5c06\u670d\u52a1\u8c03\u7528\u65b9\u548c\u670d\u52a1\u5b9e\u73b0\u8005\u89e3\u8026\uff0c\u80fd\u591f\u63d0\u5347\u7a0b\u5e8f\u7684\u6269\u5c55\u6027\u3001\u53ef\u7ef4\u62a4\u6027\u3002\u540c\u65f6\uff0c\u4fee\u6539\u6216\u8005\u66ff\u6362\u670d\u52a1\u7684\u5b9e\u73b0\u4e0d\u9700\u8981\u4fee\u6539\u8c03\u7528\u65b9\u3002<\/p>\n<p>Java \u4e2d\u6709\u8bb8\u591a\u5730\u65b9\u90fd\u4f7f\u7528\u5230\u4e86 SPI \u673a\u5236\uff0c\u6bd4\u5982\u6570\u636e\u5e93\u52a0\u8f7d\u9a71\u52a8 JDBC\u3001Spring\u3001\u4ee5\u53ca<\/p>\n<p>Dubbo \u7684\u6269\u5c55\u5b9e\u73b0\u7b49\u3002<\/p>\n<h4>\u5bf9\u6bd4 API \u6709\u4ec0\u4e48\u533a\u522b<\/h4>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"723\" height=\"381\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVdlY7a\" alt=\"image.png\" title=\"image.png\"><br \/>API\uff1a\u63a5\u53e3\u5b9e\u73b0\u65b9\u540c\u65f6\u8d1f\u8d23\u63a5\u53e3\u5b9a\u4e49\u548c\u63a5\u53e3\u5b9e\u73b0\uff0c\u63a5\u53e3\u63a7\u5236\u6743\u5728\u670d\u52a1\u63d0\u4f9b\u65b9\u3002<\/p>\n<p>SPI\uff1a\u670d\u52a1\u8c03\u7528\u65b9\u8d1f\u8d23\u63a5\u53e3\u5b9a\u4e49\uff0c\u4e0d\u540c\u7684\u63a5\u53e3\u5b9e\u73b0\u65b9\u6839\u636e\u63a5\u53e3\u5b9a\u4e49\u53ef\u4ee5\u6709\u4e0d\u540c\u7684\u5b9e\u73b0\uff0c\u80fd\u591f\u5728\u8fd0\u884c\u65f6\u52a8\u6001\u7684\u52a0\u8f7d\u4e0d\u7528\u5b9e\u73b0\u7c7b\uff0c\u63a5\u53e3\u63a7\u5236\u6743\u5728\u670d\u52a1\u8c03\u7528\u65b9\u3002<\/p>\n<h4>SPI \u6709\u4ec0\u4e48\u7528<\/h4>\n<h5>\u89e3\u8026<\/h5>\n<p>\u5728\u6846\u67b6\u5f00\u53d1\u4e2d\uff0c\u901a\u5e38\u9700\u8981\u4f9d\u8d56\u4e00\u4e9b\u53ef\u63d2\u62d4\u7684\u529f\u80fd\uff0c\u4f46\u4e0d\u5e0c\u671b\u5b9e\u73b0\u5177\u4f53\u7684\u9002\u914d\uff08\u80fd\u591f\u4fdd\u6301\u7075\u6d3b\u6027\uff09\u3002SPI \u673a\u5236\u901a\u8fc7\u5b9a\u4e49\u63a5\u53e3\u548c\u52a8\u6001\u52a0\u8f7d\u5b9e\u73b0 \uff0c\u53ef\u4ee5\u8ba9\u6846\u67b6\u4e0e\u670d\u52a1\u5b9e\u73b0\u89e3\u8026\u3002<\/p>\n<p>\u203b \u573a\u666f<\/p>\n<ul>\n<li>\u4e00\u4e2a\u6570\u636e\u5e93\u8fde\u63a5\u6c60\u5e93\u9700\u8981\u652f\u6301\u591a\u4e2a\u6570\u636e\u5e93\u5b9e\u73b0\uff08\u5982 MySQL\u3001PostgreSQL\uff09\uff0c\u53ef\u4ee5\u901a\u8fc7 SPI \u673a\u5236\u52a8\u6001\u52a0\u8f7d\u8fd9\u4e9b\u6570\u636e\u5e93\u9a71\u52a8\u3002<\/li>\n<\/ul>\n<p>\u65e5\u5fd7\u6846\u67b6\uff08\u6bd4\u5982 SLF4J\uff09\u7684\u5177\u4f53\u5b9e\u73b0\uff0c\u53ef\u4ee5\u901a\u8fc7 SPI \u673a\u5236\u52a0\u8f7d\u4e0d\u540c\u7684\u65e5\u5fd7\u5e93\uff08\u5982 Log4j\u3001Logback\uff09\u3002<\/p>\n<p><strong>\u53ef\u6269\u5c55<\/strong><\/p>\n<p>SPI \u673a\u5236\u63d0\u4f9b\u4e86\u52a8\u6001\u53d1\u73b0\u548c\u52a0\u8f7d\u670d\u52a1\u7684\u80fd\u529b\uff0c\u53ef\u4ee5\u8ba9\u5e94\u7528\u7a0b\u5e8f\u975e\u5e38\u65b9\u4fbf\u5730\u5b9e\u73b0\u6269\u5c55\uff0c\u800c\u4e0d\u9700\u8981\u4fee\u6539\u73b0\u6709\u4ee3\u7801\u3002<\/p>\n<p>\u203b \u573a\u666f<\/p>\n<p>\u4e00\u4e2a\u6587\u4ef6\u5904\u7406\u7cfb\u7edf\u9700\u8981\u652f\u6301\u4e0d\u540c\u7684\u6587\u4ef6\u683c\u5f0f\uff08\u5982 JSON \u6216 XML\uff09\u3002\u901a\u8fc7 SPI \u673a\u5236\u53ef\u4ee5\u52a8\u6001\u53d1\u73b0\u4e0d\u540c\u7684\u6587\u4ef6\u89e3\u6790\u5668\u63d2\u4ef6\uff0c\u65e0\u9700\u63d0\u524d\u786c\u7f16\u7801\u652f\u6301\u7684\u683c\u5f0f\u3002<\/p>\n<p><strong>\u52a8\u6001\u52a0\u8f7d<\/strong><\/p>\n<p>SPI \u53ef\u4ee5\u7528\u6765\u5b9e\u73b0\u63d2\u4ef6\u5316\u67b6\u6784\uff0c\u901a\u8fc7\u52a8\u6001\u52a0\u8f7d\u5177\u4f53\u7684\u670d\u52a1\u5b9e\u73b0\u589e\u51cf\u6a21\u5757\uff0c\u800c\u65e0\u9700\u91cd\u65b0\u53d1\u5e03\u6574\u4e2a\u7cfb\u7edf\u3002<\/p>\n<p>\u203b \u573a\u666f<\/p>\n<ul>\n<li>Web \u670d\u52a1\u5668\uff08\u5982 Tomcat\uff09\u53ef\u4ee5\u901a\u8fc7 SPI \u673a\u5236\u52a8\u6001\u52a0\u8f7d\u4e0d\u540c\u7684 HTTP \u5904\u7406\u5668\u6216\u8fc7\u6ee4\u5668\u3002<\/li>\n<li>\u6570\u636e\u5206\u6790\u7cfb\u7edf\u53ef\u4ee5\u901a\u8fc7 SPI \u673a\u5236\u52a8\u6001\u52a0\u8f7d\u65b0\u7684\u5206\u6790\u7b97\u6cd5\u3002<\/li>\n<\/ul>\n<h4>SPI \u5de5\u4f5c\u673a\u5236<\/h4>\n<p><img decoding=\"async\" width=\"723\" height=\"567\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/bVdlY7b\" alt=\"image.png\" title=\"image.png\" loading=\"lazy\"><\/p>\n<h2>\u4e8c\uff0cServiceLoader<\/h2>\n<p>ServiceLoader \u662f JDK \u4e2d\u63d0\u4f9b\u7684\u670d\u52a1\u52a0\u8f7d\u7c7b\uff0c\u4f4d\u4e8e java.util \u5305\u4e0b\uff0cfinal \u4fee\u9970\u4e0d\u53ef\u88ab\u7ee7\u627f\uff0c\u662f\u5b9e\u73b0 SPI \u673a\u5236\u7684\u6838\u5fc3\u3002<\/p>\n<h4>\u6e90\u7801\u89e3\u6790<\/h4>\n<pre><code>public final class ServiceLoader&lt;S&gt;\n    implements Iterable&lt;S&gt;\n{\n    \/\/ \u9ed8\u8ba4\u52a0\u8f7d\u8def\u5f84\u524d\u7f00\n    private static final String PREFIX = &quot;META-INF\/services\/&quot;;\n   \n    \/\/ The class or interface representing the service being loaded\n    \/\/ \u88ab\u52a0\u8f7d\u7684\u5b9e\u4f8b\u6216\u63a5\u53e3\n    private final Class&lt;S&gt; service;\n    \n    \/\/ The class loader used to locate, load, and instantiate providers\n    \/\/ \u7c7b\u52a0\u8f7d\u5668\n    private final ClassLoader loader;\n   \n    \/\/ The access control context taken when the ServiceLoader is created\n    private final AccessControlContext acc;\n    \n    \/\/ Cached providers, in instantiation order\n    \/\/ \u672c\u5730\u7f13\u5b58\uff0ckey: \u7c7b\u540d value\uff1b\u7c7b\n    private LinkedHashMap&lt;String,S&gt; providers = new LinkedHashMap&lt;&gt;();\n  \n    \/\/ The current lazy-lookup iterator\n    \/\/ \u8fed\u4ee3\u5668\n    private LazyIterator lookupIterator;\n}\n<\/code><\/pre>\n<p>\u203b load \u65b9\u6cd5<\/p>\n<pre><code>\/\/ \u66b4\u9732\u7ed9\u5916\u90e8\u4f7f\u7528\u7684\u52a0\u8f7d\u65b9\u6cd5\npublic static &lt;S&gt; ServiceLoader&lt;S&gt; load(Class&lt;S&gt; service,\n                                        ClassLoader loader)\n{\n    return new ServiceLoader&lt;&gt;(service, loader);\n}\npublic static &lt;S&gt; ServiceLoader&lt;S&gt; load(Class&lt;S&gt; service) {\n    ClassLoader cl = Thread.currentThread().getContextClassLoader();\n    return ServiceLoader.load(service, cl);\n}\n\n\/\/ \u6784\u9020\u65b9\u6cd5\u79c1\u6709\u5316\nprivate ServiceLoader(Class&lt;S&gt; svc, ClassLoader cl) {\n    service = Objects.requireNonNull(svc, &quot;Service interface cannot be null&quot;);\n    \/\/ \u5982\u679c\u6307\u5b9a\u4e86claseLoader\uff0c\u5219\u4f7f\u7528\u8be5classLoader\uff0c\u5982\u679c\u6ca1\u6709\u6307\u5b9a\uff0c\u5219\u4f7f\u7528\u9ed8\u8ba4classLoader\n    loader = (cl == null) ? ClassLoader.getSystemClassLoader() : cl;\n    acc = (System.getSecurityManager() != null) ? AccessController.getContext() : null;\n    reload();\n}\n<\/code><\/pre>\n<p>\u203b reload \u65b9\u6cd5<\/p>\n<pre><code>public void reload() {\n    \/\/ \u6e05\u7a7a\u7f13\u5b58\uff0c\u5c06linkedHashMap\u7684\u5934\u548c\u5c3e\u7f6e\u4e3anull\n    providers.clear();\n    lookupIterator = new LazyIterator(service, loader);\n}\n<\/code><\/pre>\n<p>ServiceLoader\u00a0\u5b9e\u73b0\u4e86\u00a0Iterable\u00a0\u63a5\u53e3\u7684\u65b9\u6cd5\u540e\uff0c\u62e5\u6709\u4e86\u8fed\u4ee3\u7684\u80fd\u529b\uff0c\u5728\u8fd9\u4e2a\u00a0iterator\u00a0\u65b9\u6cd5\u88ab\u8c03\u7528\u65f6\uff0c\u9996\u5148\u4f1a\u5728\u00a0ServiceLoader\u00a0\u7684\u00a0Provider\u00a0\u7f13\u5b58\u4e2d\u8fdb\u884c\u67e5\u627e\uff0c\u5982\u679c\u7f13\u5b58\u4e2d\u6ca1\u6709\u547d\u4e2d\uff0c\u5219\u5728\u00a0LazyIterator\u00a0\u4e2d\u8fdb\u884c\u67e5\u627e\u3002<\/p>\n<pre><code>public Iterator&lt;S&gt; iterator() {\n    return new Iterator&lt;S&gt;() {\n        \/\/ \u672c\u5730\u7f13\u5b58providers\n        Iterator&lt;Map.Entry&lt;String,S&gt;&gt; knownProviders\n            = providers.entrySet().iterator();\n       \n        public boolean hasNext() {\n            \/\/ \u4f18\u5148\u67e5\u672c\u5730\u7f13\u5b58\n            if (knownProviders.hasNext())\n                return true;\n            \/\/ \u6ca1\u6709\u5219\u5728LazyInterator\u4e2d\u8fdb\u884c\u67e5\u627e\n            return lookupIterator.hasNext();\n        }\n      \n        public S next() {\n            if (knownProviders.hasNext())\n                return knownProviders.next().getValue();\n            return lookupIterator.next();\n        }\n     \n        public void remove() {\n            throw new UnsupportedOperationException();\n        }\n    \n    };\n}\n<\/code><\/pre>\n<p>LazyIterator\u00a0\u4f7f ServiceLoader \u62e5\u6709\u4e86\u61d2\u52a0\u8f7d\u7684\u80fd\u529b\uff0c\u53ea\u6709\u8c03\u7528 iterator \u65b9\u6cd5\u6216\u904d\u5386\u7684\u65f6\u5019\u624d\u4f1a\u53bb\u52a0\u8f7d\u5bf9\u5e94\u7684\u5b9e\u73b0\u7c7b\uff0c\u6838\u5fc3\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre><code>\/\/ Private inner class implementing fully-lazy provider lookup\n\/\/\nprivate class LazyIterator\n    implements Iterator&lt;S&gt;\n{\n    \n    Class&lt;S&gt; service;\n    ClassLoader loader;\n    Enumeration&lt;URL&gt; configs = null;\n    Iterator&lt;String&gt; pending = null;\n    String nextName = null;\n    \n    private LazyIterator(Class&lt;S&gt; service, ClassLoader loader) {\n        this.service = service;\n        this.loader = loader;\n    }\n    \n    private boolean hasNextService() {\n        if (nextName != null) {\n            return true;\n        }\n        if (configs == null) {\n            try {\n            \/\/ \u914d\u7f6e\u6587\u4ef6\u8def\u5f84\uff0c\u9ed8\u8ba4 \/META-INF\/services\/ \u5f00\u5934\n                String fullName = PREFIX + service.getName();\n                if (loader == null)\n                    configs = ClassLoader.getSystemResources(fullName);\n                else \/\/ \u8bfb\u53d6\u5b9e\u73b0\u7c7b \u7c7b\u540d\n                    configs = loader.getResources(fullName);\n            } catch (IOException x) {\n                fail(service, &quot;Error locating configuration files&quot;, x);\n            }\n        }\n        while ((pending == null) || !pending.hasNext()) {\n            if (!configs.hasMoreElements()) {\n                return false;\n            }\n            \/\/ \u89e3\u6790\u914d\u7f6e\u6587\u4ef6\u4e2d\u6bcf\u884c\u7c7b\u540d\n            pending = parse(service, configs.nextElement());\n        }\n        nextName = pending.next();\n        return true;\n    }\n    \n    private S nextService() {\n        if (!hasNextService())\n            throw new NoSuchElementException();\n        String cn = nextName;\n        nextName = null;\n        Class&lt;?&gt; c = null;\n        try {\n        \/\/ \u52a0\u8f7d\u5bf9\u5e94\u7684\u5b9e\u73b0\u7c7b\n            c = Class.forName(cn, false, loader);\n        } catch (ClassNotFoundException x) {\n            fail(service,\n                 &quot;Provider &quot; + cn + &quot; not found&quot;);\n        }\n        if (!service.isAssignableFrom(c)) {\n            fail(service,\n                 &quot;Provider &quot; + cn  + &quot; not a subtype&quot;);\n        }\n        try {\n        \/\/ \u521b\u5efa\u5b9e\u73b0\u7c7b\n            S p = service.cast(c.newInstance());\n        \/\/ \u653e\u5230\u7f13\u5b58\u4e2d\n            providers.put(cn, p);\n            return p;\n        } catch (Throwable x) {\n            fail(service,\n                 &quot;Provider &quot; + cn + &quot; could not be instantiated&quot;,\n                 x);\n        }\n        throw new Error();          \/\/ This cannot happen\n    }\n    \n    public boolean hasNext() {\n        if (acc == null) {\n            return hasNextService();\n        } else {\n            PrivilegedAction&lt;Boolean&gt; action = new PrivilegedAction&lt;Boolean&gt;() {\n                public Boolean run() { return hasNextService(); }\n            };\n            return AccessController.doPrivileged(action, acc);\n        }\n    }\n    \n    public S next() {\n        if (acc == null) {\n            return nextService();\n        } else {\n            PrivilegedAction&lt;S&gt; action = new PrivilegedAction&lt;S&gt;() {\n                public S run() { return nextService(); }\n            };\n            return AccessController.doPrivileged(action, acc);\n        }\n    }\n    \n    public void remove() {\n        throw new UnsupportedOperationException();\n    }\n\n}\n<\/code><\/pre>\n<h4>\u5c0f\u7ed3<\/h4>\n<p>ServiceLoader \u672c\u8d28\u4e0a\u5c31\u662f\u8bfb\u53d6\u7ea6\u5b9a\u76ee\u5f55\uff08\/META-INF\/services\/ \uff09\u4e0b\u5bf9\u5e94\u63a5\u53e3\u5168\u9650\u5b9a\u547d\u540d\u7684\u6587\u4ef6\uff0c\u7136\u540e\u901a\u8fc7\u53cd\u5c04\u5168\u91cf\u52a0\u8f7d\u6587\u4ef6\u4e2d\u5b9a\u4e49\u7684\u6240\u6709\u63a5\u53e3\u5b9e\u73b0\u7c7b\uff0c\u4ece\u800c\u5c06\u63a5\u53e3\u4e0e\u5b9e\u73b0\u8fdb\u884c\u89e3\u8026\u3002<\/p>\n<p><strong>\u203b \u4f18\u70b9<\/strong><\/p>\n<p>\u89e3\u8026 \uff1a\u63a5\u53e3\u4e0e\u5b9e\u73b0\u5206\u79bb\uff0c\u65e0\u9700\u5728\u4ee3\u7801\u4e2d\u786c\u7f16\u7801\u5b9e\u73b0\u7c7b\u3002<\/p>\n<p>\u6269\u5c55\u6027 \uff1a\u65b0\u589e\u5b9e\u73b0\u53ea\u9700\u6dfb\u52a0\u914d\u7f6e\uff0c\u65e0\u9700\u4fee\u6539\u5df2\u6709\u4ee3\u7801\u3002<\/p>\n<p><strong>\u203b \u7f3a\u70b9<\/strong><\/p>\n<p>\u7ebf\u7a0b\u4e0d\u5b89\u5168 \uff1a ServiceLoader \u975e\u7ebf\u7a0b\u5b89\u5168\uff0c\u4e0d\u80fd\u4fdd\u8bc1\u5355\u4f8b\u3002<\/p>\n<p>\u6027\u80fd\u5f00\u9500 \uff1a\u6bcf\u6b21\u8fed\u4ee3\u90fd\u91cd\u65b0\u52a0\u8f7d\u6587\u4ef6\uff08\u53ef\u901a\u8fc7\u7f13\u5b58\u89e3\u51b3\uff09\uff0c\u5e76\u4e14\u4f1a\u5168\u91cf\u914d\u7f6e\u6587\u4ef6\u4e2d\u6307\u5b9a\u7684\u6240\u6709\u5b9e\u73b0\u7c7b\u3002<\/p>\n<p>\u65e0\u5065\u58ee\u6027 \uff1a\u914d\u7f6e\u9519\u8bef\uff08\u5982\u7c7b\u672a\u627e\u5230\uff09\u4f1a\u629b\u51fa\u5f02\u5e38\u800c\u975e\u4f18\u96c5\u964d\u7ea7\u3002<\/p>\n<h2>\u4e09\uff0cSPI \u5b9e\u9645\u5e94\u7528\u573a\u666f<\/h2>\n<h4>JDBC<\/h4>\n<p>JDK \u4e2d\u5b9a\u4e49\u4e86 Driver \u63a5\u53e3\uff0c\u7528\u4e8e\u8fde\u63a5\u6570\u636e\u5e93\u3002<\/p>\n<pre><code>package java.sql;\n\nimport java.util.logging.Logger;\n\npublic interface Driver {\n   \n    Connection connect(String url, java.util.Properties info)\n        throws SQLException;\n   \n    boolean acceptsURL(String url) throws SQLException;\n    DriverPropertyInfo[] getPropertyInfo(String url, java.util.Properties info)\n                         throws SQLException;\n    int getMajorVersion();\n    int getMinorVersion();\n    boolean jdbcCompliant();\n    public Logger getParentLogger() throws SQLFeatureNotSupportedException;\n}\n<\/code><\/pre>\n<p>\u4e0d\u540c\u7684\u6570\u636e\u5e93\u5382\u5546\u5b9e\u73b0\u8fd9\u4e2a\u63a5\u53e3\uff0c\u4ece\u800c\u5b9e\u73b0\u4e0e\u6570\u636e\u5e93\u7684\u8fde\u63a5\uff0c\u4ee5\u6211\u4eec\u6700\u719f\u6089\u7684 MySQL \u4e3a\u4f8b\uff0c\u83b7\u53d6\u6570\u636e\u5e93\u8fde\u63a5\u7684\u793a\u4f8b\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre><code>\/\/ \u83b7\u53d6\u6570\u636e\u5e93\u8fde\u63a5\nDriverManager connection = DriverManager.getConnection(&quot;jdbc:mysql:\/\/localhost:3306\/test&quot;, &quot;root&quot;, &quot;123&quot;);\n\/\/ \u521b\u5efastatement\nStatement statement = connection.createStatement();\n\/\/ \u6267\u884csql\nResultSet resultSet = statement.executeQuery(&quot;select * from student&quot;);\n<\/code><\/pre>\n<p>\u5176\u4e2d DriverManager \u52a0\u8f7d\u65f6\u4f1a\u6267\u884c\u9759\u6001\u4ee3\u7801\u5757\u53bb\u52a0\u8f7d driver\uff0c\u90e8\u5206\u6838\u5fc3\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre><code>static {\n    loadInitialDrivers();\n    println(&quot;JDBC DriverManager initialized&quot;);\n}\n\nprivate static void loadInitialDrivers() {\n    String drivers;\n    try {\n        drivers = AccessController.doPrivileged(new PrivilegedAction&lt;String&gt;() {\n            public String run() {\n                return System.getProperty(&quot;jdbc.drivers&quot;);\n            }\n        });\n    } catch (Exception ex) {\n        drivers = null;\n    }\n    \n    \/\/ \u5982\u679c\u9a71\u52a8\u7a0b\u5e8f\u88ab\u6253\u5305\u4e3a\u670d\u52a1\u63d0\u4f9b\u8005\uff08Service Provider\uff09\uff0c\u5219\u52a0\u8f7d\u5b83\u3002\n    \/\/ \u901a\u8fc7\u7c7b\u52a0\u8f7d\u5668\u83b7\u53d6\u6240\u6709\u9a71\u52a8\u7a0b\u5e8f\n    AccessController.doPrivileged(new PrivilegedAction&lt;Void&gt;() {\n        public Void run() {\n            \/\/ \u8fd9\u91cc\u5c31\u4f7f\u7528ServiceLoader\u53bb\u52a0\u8f7d\u63a5\u53e3\u5b9e\u73b0\u7c7b\n            \/\/ \u4ee5mysql-connector-java\u4e3a\u4f8b\uff0c\u52a0\u8f7d\u7684\u662f com.mysql.jdbc.Driver \u548c com.mysql.fabric.jdbc.FabricMySQLDriver\n            ServiceLoader&lt;Driver&gt; loadedDrivers = ServiceLoader.load(Driver.class);\n            Iterator&lt;Driver&gt; driversIterator = loadedDrivers.iterator();\n            try{\n                while(driversIterator.hasNext()) {\n                    driversIterator.next();\n                }\n            } catch(Throwable t) {\n            \/\/ Do nothing\n            }\n            return null;\n        }\n    });\n    \n    println(&quot;DriverManager.initialize: jdbc.drivers = &quot; + drivers);\n    \n    if (drivers == null || drivers.equals(&quot;&quot;)) {\n        return;\n    }\n    String[] driversList = drivers.split(&quot;:&quot;);\n    println(&quot;number of Drivers:&quot; + driversList.length);\n    for (String aDriver : driversList) {\n        try {\n            println(&quot;DriverManager.Initialize: loading &quot; + aDriver);\n            \/\/ \u52a0\u8f7d\u6570\u636e\u5e93\u9a71\u52a8Driver\uff0c \u4ee5mysql-connector-java\u4e3a\u4f8b\uff0c\u8fd9\u91cc\u52a0\u8f7d\u7684\u662f com.mysql.jdbc.Driver \u548c com.mysql.fabric.jdbc.FabricMySQLDrive\n            \/\/ \u5e76\u6ce8\u518c\u5230registeredDrivers\u4e2d\n            Class.forName(aDriver, true,\n                    ClassLoader.getSystemClassLoader());\n        } catch (Exception ex) {\n            println(&quot;DriverManager.Initialize: load failed: &quot; + ex);\n        }\n    }\n}\n<\/code><\/pre>\n<p>\u968f\u540e\u5728 getConnection \u65b9\u6cd5\u4e2d\u904d\u5386\u5df2\u7ecf\u52a0\u8f7d\u7684 driver\uff0c\u6267\u884c connect \u65b9\u6cd5\u8fdb\u884c\u8fde\u63a5\u3002<\/p>\n<pre><code>private final static CopyOnWriteArrayList&lt;DriverInfo&gt; registeredDrivers = new CopyOnWriteArrayList&lt;&gt;();\n\n\/\/ \u904d\u5386\u5df2\u7ecf\u6ce8\u518c\u7684driver\uff0c\u8c03\u7528connect\u65b9\u6cd5\u8fdb\u884c\u8fde\u63a5\nfor(DriverInfo aDriver : registeredDrivers) {\n \n    if(isDriverAllowed(aDriver.driver, callerCL)) {\n        try {\n            println(&quot;    trying &quot; + aDriver.driver.getClass().getName());\n            Connection con = aDriver.driver.connect(url, info);\n            if (con != null) {\n                \/\/ Success!\n                println(&quot;getConnection returning &quot; + aDriver.driver.getClass().getName());\n                return (con);\n            }\n        } catch (SQLException ex) {\n            if (reason == null) {\n                reason = ex;\n            }\n        }\n \n    } else {\n        println(&quot;    skipping: &quot; + aDriver.getClass().getName());\n    }\n\n}\n<\/code><\/pre>\n<p>&lt;!&#8212;-&gt;<\/p>\n<pre><code>public class Driver extends NonRegisteringDriver implements java.sql.Driver {\n    public Driver() throws SQLException {\n    }\n   \n    static {\n        try {\n            DriverManager.registerDriver(new Driver());\n        } catch (SQLException var1) {\n            throw new RuntimeException(&quot;Can't register driver!&quot;);\n        }\n    }\n}\n<\/code><\/pre>\n<h4>Spring<\/h4>\n<p>Spring \u4e2d\u6ca1\u6709\u76f4\u63a5\u4f7f\u7528 Java SPI \u673a\u5236\uff0c\u4e0d\u8fc7 Spring \u7684 spring.factories \u673a\u5236\u7c7b\u4f3c\u4e8e SPI \u673a\u5236\u5e76\u62e5\u6709\u66f4\u5f3a\u5927\u7684\u6269\u5c55\u673a\u5236\uff0c\u901a\u8fc7\u8bfb\u53d6 META-INF\/spring.factories \u6587\u4ef6\u5b9e\u73b0\u81ea\u52a8\u88c5\u914d\u3001\u4e0a\u4e0b\u6587\u521d\u59cb\u5316\u7b49\u529f\u80fd\u3002<\/p>\n<pre><code>\/\/ SpringFactoriesLoader \u6e90\u7801\u6838\u5fc3\u903b\u8f91\npublic final class SpringFactoriesLoader {\n    public static final String FACTORIES_RESOURCE_LOCATION = &quot;META-INF\/spring.factories&quot;;\n\n    public static List&lt;String&gt; loadFactoryNames(Class&lt;?&gt; factoryType, @Nullable ClassLoader classLoader) {\n        \/\/ \u4ece\u6240\u6709jar\u5305\u7684spring.factories\u6587\u4ef6\u52a0\u8f7d\u914d\u7f6e\n        Enumeration&lt;URL&gt; urls = (classLoader != null ?\n                 classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :\n                 ClassLoader.getSystemResources(FACTORIES_RESOURCE_LOCATION));\n\n        List&lt;String&gt; result = new ArrayList&lt;&gt;();\n        while (urls.hasMoreElements()) {\n            Properties properties = PropertiesLoaderUtils.loadProperties(\n                new UrlResource(urls.nextElement()));\n            String factoryClassNames = properties.getProperty(factoryType.getName());\n            \/\/ \u652f\u6301\u9017\u53f7\u5206\u9694\u7684\u591a\u4e2a\u5b9e\u73b0\n            result.addAll(Arrays.asList(StringUtils.commaDelimitedListToStringArray(factoryClassNames)));\n        }\n        return result;\n    }\n\n    public static &lt;T&gt; List&lt;T&gt; loadFactories(Class&lt;T&gt; factoryType, @Nullable ClassLoader classLoader) {\n        \/\/ 1. \u52a0\u8f7d\u6240\u6709\u5b9e\u73b0\u7c7b\u540d\n        List&lt;String&gt; names = loadFactoryNames(factoryType, classLoader);\n        \/\/ 2. \u5b9e\u4f8b\u5316\u6240\u6709\u5b9e\u73b0\n        List&lt;T&gt; instances = new ArrayList&lt;&gt;(names.size());\n        for (String name : names) {\n            Class&lt;?&gt; instanceClass = ClassUtils.forName(name, classLoader);\n            instances.add((T) ReflectionUtils.accessibleConstructor(instanceClass).newInstance());\n        }\n        \/\/ 3. \u6309@Order\u6392\u5e8f\n        AnnotationAwareOrderComparator.sort(instances);\n        return instances;\n    }\n\n    private static Map&lt;String, List&lt;String&gt;&gt; loadSpringFactories(@Nullable ClassLoader classLoader) {\n    MultiValueMap&lt;String, String&gt; result = (MultiValueMap)cache.get(classLoader);\n    if (result != null) {\n        return result;\n    } else {\n        try {\n            Enumeration&lt;URL&gt; urls = classLoader != null ? classLoader.getResources(&quot;META-INF\/spring.factories&quot;) : ClassLoader.getSystemResources(&quot;META-INF\/spring.factories&quot;);\n            MultiValueMap&lt;String, String&gt; result = new LinkedMultiValueMap();\n   \n            while(urls.hasMoreElements()) {\n                URL url = (URL)urls.nextElement();\n                UrlResource resource = new UrlResource(url);\n                Properties properties = PropertiesLoaderUtils.loadProperties(resource);\n                Iterator var6 = properties.entrySet().iterator();\n      \n                while(var6.hasNext()) {\n                    Map.Entry&lt;?, ?&gt; entry = (Map.Entry)var6.next();\n                    String factoryClassName = ((String)entry.getKey()).trim();\n                    String[] var9 = StringUtils.commaDelimitedListToStringArray((String)entry.getValue());\n                    int var10 = var9.length;\n \n                    for(int var11 = 0; var11 &lt; var10; ++var11) {\n                        String factoryName = var9[var11];\n                        result.add(factoryClassName, factoryName.trim());\n                    }\n                }\n            }\n            \/\/ \u8bfb\u53d6META-INF\/spring.factories\u6587\u4ef6\u5939\u4e0b\u6587\u4ef6\uff0c\u89e3\u6790\u6587\u4ef6\u5185\u5bb9\u5e76\u7f13\u5b58\u5230Map\u4e2d\n            cache.put(classLoader, result);\n            return result;\n        } catch (IOException var13) {\n            IOException ex = var13;\n            throw new IllegalArgumentException(&quot;Unable to load factories from location [META-INF\/spring.factories]&quot;, ex);\n        }\n    }\n}\n}\n<\/code><\/pre>\n<p>spring.factories \u6587\u4ef6\u7684\u683c\u5f0f\u4e3a xxx=xxxx\uff0c=\u53f7\u524d\u9762\u7684 key \u4e3a\u63a5\u53e3\u5168\u9650\u5b9a\u540d\uff0c=\u53f7\u540e\u9762\u7684 value \u4e3a\u63a5\u53e3\u5b9e\u73b0\u7c7b\u5168\u9650\u5b9a\u540d \uff0c\u591a\u4e2a\u5b9e\u73b0\u7c7b\u4e4b\u95f4\u7528\u9017\u53f7\u5206\u5272\uff0c\u4e0b\u56fe\u4e2d\u6307\u5b9a\u7684 key \u4e3a EnableAutoConfiguration\uff0c\u8fd9\u6837 spring \u5c31\u4f1a\u4e3a=\u53f7\u540e\u9762\u7684\u7c7b\u6ce8\u518c\u4e3a bean\u3002spring \u81ea\u52a8\u88c5\u914d\u539f\u7406\u8fd9\u91cc\u6682\u4e0d\u5c55\u5f00\u3002<\/p>\n<pre><code>org.springframework.boot.autoconfigure.EnableAutoConfiguration=\/\norg.apache.hadoop.hbase.client.MonitorAlicloudHBaseAutoConfiguration\n<\/code><\/pre>\n<h4>Dubbo<\/h4>\n<p>Dubbo \u7684\u53ef\u6269\u5c55\u673a\u5236\u4e5f\u4f7f\u7528\u5230\u4e86 SPI\uff0c\u4e0d\u8fc7\u4e0d\u662f\u539f\u751f\u7684 SPI\uff0c\u800c\u662f\u7ecf\u8fc7\u4f18\u5316\u7684\u3002<\/p>\n<p>\u7531\u4e0a\u6587 ServiceLoader \u6e90\u7801\u89e3\u6790\u53ef\u77e5\uff0cSPI \u4f1a\u8bfb\u53d6\u914d\u7f6e\u6587\u4ef6\uff0c\u904d\u5386\u6240\u6709\u7c7b\u5e76\u5b9e\u4f8b\u5316\uff0c\u5982\u679c\u67d0\u4e9b\u7c7b\u5e76\u4e0d\u4f1a\u4f7f\u7528\uff0c\u6b64\u65f6\u8fd8\u662f\u4f1a\u52a0\u8f7d\u8fdb\u6765\uff0c\u9020\u6210\u4e86\u8d44\u6e90\u7684\u6d6a\u8d39\uff1bJava SPI \u914d\u7f6e\u6587\u4ef6\u4e2d\u53ea\u662f\u7b80\u5355\u5217\u51fa\u4e86\u6240\u6709\u6269\u5c55\u5b9e\u73b0\uff0c\u6ca1\u6709\u7ed9\u4ed6\u4eec\u547d\u540d\uff0c\u65e0\u6cd5\u5728\u7a0b\u5e8f\u4e2d\u51c6\u786e\u5f15\u7528\uff1b\u65e0\u6cd5\u505a\u5230\u81ea\u52a8\u6ce8\u5165\u548c\u88c5\u914d\u7b49\u7b49\u2026\u2026 Dubbo \u6269\u5c55\u70b9\u673a\u5236\u4f18\u5316\u4e86\u4e0a\u8ff0\u95ee\u9898\uff0c\u63d0\u4f9b\u4e86\u52a8\u6001\u6269\u5c55\u7684\u80fd\u529b\u3002<\/p>\n<p><strong>Demo<\/strong><\/p>\n<p>\u5b9a\u4e49\u4e00\u4e2a\u63a5\u53e3\uff0c\u5e76\u4f7f\u7528 @SPI \u6ce8\u89e3\u6807\u6ce8\uff0c\u8fd9\u8868\u660e\u8fd9\u4e2a\u63a5\u53e3\u662f\u4e00\u4e2a\u6269\u5c55\u70b9\uff0c\u53ef\u88ab Dubbo \u7684 ExtensionLoader \u52a0\u8f7d\u3002<\/p>\n<pre><code>@SPI\npublic interface DemoSpi {\n    void say();\n}\n<\/code><\/pre>\n<p>\u63a5\u53e3\u5b9e\u73b0:<\/p>\n<pre><code>public class DemoSpiImpl implements DemoSpi {\n    public void say() {\n    }\n}\n<\/code><\/pre>\n<p>\u5c06\u5b9e\u73b0\u7c7b\u653e\u5728\u7279\u5b9a\u76ee\u5f55\u4e0b\uff0cDubbo \u5728\u52a0\u8f7d\u6269\u5c55\u7c7b\u7684\u65f6\u5019\uff0c\u4f1a\u4ece META-INF\/services\/ META-INF\/dubbo\/ META-INF\/dubbo\/internal\/ \u8fd9\u51e0\u4e2a\u76ee\u5f55\u4e0b\u8bfb\u53d6\u3002\u8fd9\u91cc\u5728 META-INF\/dubbo \u76ee\u5f55\u4e0b\u65b0\u5efa\u4e00\u4e2a\u4ee5 DemoSpi \u63a5\u53e3\u540d\u4e3a\u6587\u4ef6\u540d\u7684\u6587\u4ef6\uff0c\u5185\u5bb9\u5982\u4e0b\uff1a<\/p>\n<pre><code>demoSpiImpl = com.xxx.xxx.DemoSpiImpl(\u4e3a DemoSpi \u63a5\u53e3\u5b9e\u73b0\u7c7b\u7684\u5168\u7c7b\u540d)\n<\/code><\/pre>\n<p>\u63a5\u53e3\u5b9e\u73b0\u7c7b\u7684\u5168\u7c7b\u540d)\u4f7f\u7528\u5982\u4e0b\uff1a<\/p>\n<pre><code>public class DubboSPITest {\n \n    @Test    \n    public void sayHello() throws Exception {\n        ExtensionLoader&lt;DemoSpi&gt; extensionLoader = \n            ExtensionLoader.getExtensionLoader(DemoSpi.class);\n        DemoSpi dmeoSpi = extensionLoader.getExtension(&quot;demoSpiImpl&quot;);\n        dmeoSpi.sayHello();\n    }\n}\n<\/code><\/pre>\n<p><strong>\u6e90\u7801\u89e3\u6790<\/strong><\/p>\n<p>\u7531\u4e0a\u9762\u7684\u4f8b\u5b50\u53ef\u4ee5\u770b\u51fa\uff0cDubbo \u4e3b\u8981\u901a\u8fc7 ExtensionLoader \u52a0\u8f7d\u914d\u7f6e\u6587\u4ef6\u4e2d\u6307\u5b9a\u7684\u5b9e\u73b0\u7c7b\uff0c\u6574\u4f53\u6d41\u7a0b\u4e0a\u548c ServiceLoader \u52a0\u8f7d\u6d41\u7a0b\u7c7b\u4f3c\uff0c\u540c\u65f6\u505a\u4e86\u76f8\u5173\u7684\u4f18\u5316\u6269\u5c55\u3002<\/p>\n<p><strong>\u203b duboo \u52a0\u8f7d\u6269\u5c55\u4e3b\u8981\u6b65\u9aa4<\/strong><\/p>\n<ul>\n<li>\u8bfb\u53d6\u5e76\u89e3\u6790\u914d\u7f6e\u6587\u4ef6<\/li>\n<li>\u7f13\u5b58\u6240\u6709\u6269\u5c55\u5b9e\u73b0<\/li>\n<li>\u57fa\u4e8e\u7528\u6237\u6267\u884c\u7684\u6269\u5c55\u540d\uff0c\u5b9e\u4f8b\u5316\u5bf9\u5e94\u7684\u6269\u5c55\u5b9e\u73b0<\/li>\n<li>\u8fdb\u884c\u6269\u5c55\u5b9e\u4f8b\u5316\u5c5e\u6027\u7684 IOC \u6ce8\u5165\u53ca\u5b9e\u4f8b\u5316\u6269\u5c55\u7684\u5305\u88c5\u7c7b\uff0c\u5b9e\u73b0 AOP \u7279\u6027<\/li>\n<\/ul>\n<p>SPI \u52a0\u8f7d\u56fa\u5b9a\u6269\u5c55\u7c7b\u7684\u5165\u53e3\u662f ExtensionLoader \u7684 getExtension \u65b9\u6cd5\uff0c\u8be5\u65b9\u6cd5\u4e3b\u8981\u8c03\u7528 createExtession \u65b9\u6cd5\u83b7\u53d6\u6269\u5c55\u5b9e\u4f8b\uff1a<\/p>\n<pre><code>private T createExtension(String name, boolean wrap) {\n    \/\/ \u4ece\u914d\u7f6e\u6587\u4ef6\u4e2d\u52a0\u8f7d\u6240\u6709\u7684\u62d3\u5c55\u7c7b\uff0c\u53ef\u5f97\u5230\u201c\u914d\u7f6e\u9879\u540d\u79f0\u201d\u5230\u201c\u914d\u7f6e\u7c7b\u201d\u7684\u6620\u5c04\u5173\u7cfb\u8868    \n    Class&lt;?&gt; clazz = getExtensionClasses().get(name);\n    \/\/ \u5982\u679c\u6ca1\u6709\u8be5\u63a5\u53e3\u7684\u6269\u5c55\uff0c\u6216\u8005\u8be5\u63a5\u53e3\u7684\u5b9e\u73b0\u7c7b\u4e0d\u5141\u8bb8\u91cd\u590d\u4f46\u5b9e\u9645\u4e0a\u91cd\u590d\u4e86\uff0c\u76f4\u63a5\u629b\u51fa\u5f02\u5e38    \n    if (clazz == null || unacceptableExceptions.contains(name)) {\n        throw findException(name);\n    }\n    try {\n        T instance = (T) EXTENSION_INSTANCES.get(clazz);\n        \/\/ \u8fd9\u6bb5\u4ee3\u7801\u4fdd\u8bc1\u4e86\u6269\u5c55\u7c7b\u53ea\u4f1a\u88ab\u6784\u9020\u4e00\u6b21\uff0c\u4e5f\u5c31\u662f\u5355\u4f8b\u7684.        \n        if (instance == null) {\n            EXTENSION_INSTANCES.putIfAbsent(clazz, clazz.getDeclaredConstructor().newInstance());\n            instance = (T) EXTENSION_INSTANCES.get(clazz);\n        }\n        \/\/ \u5411\u5b9e\u4f8b\u4e2d\u6ce8\u5165\u4f9d\u8d56        \n        injectExtension(instance);\n        \/\/ \u5982\u679c\u542f\u7528\u5305\u88c5\u7684\u8bdd\uff0c\u5219\u81ea\u52a8\u4e3a\u8fdb\u884c\u5305\u88c5.        \n        \/\/ \u6bd4\u5982\u6211\u57fa\u4e8e Protocol \u5b9a\u4e49\u4e86 DubboProtocol \u7684\u6269\u5c55\uff0c\u4f46\u5b9e\u9645\u4e0a\u5728 Dubbo \u4e2d\u4e0d\u662f\u76f4\u63a5\u4f7f\u7528\u7684 DubboProtocol, \u800c\u662f\u5176\u5305\u88c5\u7c7b  ProtocolListenerWrapper        \n        if (wrap) {\n            List&lt;Class&lt;?&gt;&gt; wrapperClassesList = new ArrayList&lt;&gt;();\n       \n            if (cachedWrapperClasses != null) {\n                wrapperClassesList.addAll(cachedWrapperClasses);\n            \n                wrapperClassesList.sort(WrapperComparator.COMPARATOR);\n                Collections.reverse(wrapperClassesList);\n            }\n\n            \/\/ \u5faa\u73af\u521b\u5efa Wrapper \u5b9e\u4f8b            \n            if (CollectionUtils.isNotEmpty(wrapperClassesList)) {\n                for (Class&lt;?&gt; wrapperClass : wrapperClassesList) {\n                    Wrapper wrapper = wrapperClass.getAnnotation(Wrapper.class);\n                    if (wrapper == null                            || (ArrayUtils.contains(wrapper.matches(), name) &amp;&amp; !ArrayUtils.contains(wrapper.mismatches(), name))) {\n                        \/\/ \u5c06\u5f53\u524d instance \u4f5c\u4e3a\u53c2\u6570\u4f20\u7ed9 Wrapper \u7684\u6784\u9020\u65b9\u6cd5\uff0c\u5e76\u901a\u8fc7\u53cd\u5c04\u521b\u5efa Wrapper \u5b9e\u4f8b\u3002                        \/\/ \u7136\u540e\u5411 Wrapper \u5b9e\u4f8b\u4e2d\u6ce8\u5165\u4f9d\u8d56\uff0c\u6700\u540e\u5c06 Wrapper \u5b9e\u4f8b\u518d\u6b21\u8d4b\u503c\u7ed9 instance \u53d8\u91cf                        \n                        instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));\n                    }\n                }\n            }\n        }\n        \/\/ \u521d\u59cb\u5316        \n        initExtension(instance);\n        return instance;\n    } catch (Throwable t) {\n        throw new IllegalStateException(&quot;Extension instance (name: &quot; + name + &quot;, class: &quot; +                type + &quot;) couldn't be instantiated: &quot; + t.getMessage(), t);\n    }\n}\n<\/code><\/pre>\n<p><strong>\u203b \u4e0a\u8ff0\u4ee3\u7801\u5168\u6d41\u7a0b<\/strong><\/p>\n<ul>\n<li>\u901a\u8fc7 getExtensionClasses \u83b7\u53d6\u6240\u6709\u7684\u62d3\u5c55\u7c7b<\/li>\n<li>\u901a\u8fc7\u53cd\u5c04\u521b\u5efa\u62d3\u5c55\u5bf9\u8c61<\/li>\n<li>\u5411\u62d3\u5c55\u5bf9\u8c61\u4e2d\u6ce8\u5165\u4f9d\u8d56<\/li>\n<li>\u5c06\u62d3\u5c55\u5bf9\u8c61\u5305\u88f9\u5728\u76f8\u5e94\u7684 Wrapper \u5bf9\u8c61\u4e2d<\/li>\n<li>\u521d\u59cb\u5316\u6269\u5c55\u5bf9\u8c61<\/li>\n<\/ul>\n<p>\u83b7\u53d6\u6240\u6709\u62d3\u5c55\u7c7b getExtensionClasses \u548c JDK SPI \u7c7b\u4f3c\uff0c\u4e5f\u662f\u5148\u4ece\u7f13\u5b58\u4e2d\u62ff\uff0c\u62ff\u4e0d\u5230\u52a0\u9501\u518d\u6b21\u67e5\u7f13\u5b58\uff0c\u8fd8\u62ff\u4e0d\u5230\u5219\u901a\u8fc7 loadExtensionClasses \u52a0\u8f7d\u62d3\u5c55\u7c7b\u3002<\/p>\n<pre><code>private Map&lt;String, Class&lt;?&gt;&gt; getExtensionClasses() {\n    Map&lt;String, Class&lt;?&gt;&gt; classes = (Map)this.cachedClasses.get();\n    if (classes == null) {\n        synchronized(this.cachedClasses) {\n            classes = (Map)this.cachedClasses.get();\n            if (classes == null) {\n                classes = this.loadExtensionClasses();\n                this.cachedClasses.set(classes);\n            }\n        }\n    }\n \n    return classes;\n}\n<\/code><\/pre>\n<p>loadExtensionClasses \u603b\u5171\u505a\u4e86\u4e24\u4ef6\u4e8b\u60c5\uff0c\u4e00\u662f\u89e3\u6790 @SPI \u6ce8\u89e3\uff0c\u4e8c\u662f\u8c03\u7528 loadDirectory \u65b9\u6cd5\u52a0\u8f7d\u6307\u5b9a\u6587\u4ef6\u5939\u914d\u7f6e\u6587\u4ef6\u3002<\/p>\n<pre><code>private Map&lt;String, Class&lt;?&gt;&gt; loadExtensionClasses() {\n    \/\/ \u7f13\u5b58\u9ed8\u8ba4\u7684 SPI \u6269\u5c55\u540d    \n    cacheDefaultExtensionName();\n \n    Map&lt;String, Class&lt;?&gt;&gt; extensionClasses = new HashMap&lt;&gt;();\n\n    \/\/ \u57fa\u4e8e\u7b56\u7565\u6765\u52a0\u8f7d\u6307\u5b9a\u6587\u4ef6\u5939\u4e0b\u7684\u6587\u4ef6    \n    \/\/ \u5206\u522b\u8bfb\u53d6 META-INF\/services\/ META-INF\/dubbo\/ META-INF\/dubbo\/internal\/ \u8fd9\u51e0\u4e2a\u76ee\u5f55\u4e0b\u7684\u914d\u7f6e\u6587\u4ef6    \n    for (LoadingStrategy strategy : strategies) {\n        loadDirectory(extensionClasses, strategy.directory(), type.getName(), strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());\n        loadDirectory(extensionClasses, strategy.directory(), type.getName().replace(&quot;org.apache&quot;, &quot;com.alibaba&quot;), strategy.preferExtensionClassLoader(), strategy.overridden(), strategy.excludedPackages());\n    }\n \n    return extensionClasses;\n}\n<\/code><\/pre>\n<p>\u5176\u4e2d loadDirectory \u65b9\u6cd5\u5219\u662f\u62ff\u5230\u6307\u5b9a\u6587\u4ef6\u5939\u4e0b\u6587\u4ef6\u7684\u5168\u8def\u5f84\u540d\uff0c\u8c03\u7528 loadResource \u53bb\u52a0\u8f7d\u8d44\u6e90\u3002<\/p>\n<pre><code>private void loadResource(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, ClassLoader classLoader, java.net.URL resourceURL, boolean overridden, String... excludedPackages) {\n    try {\n        BufferedReader reader = new BufferedReader(new InputStreamReader(resourceURL.openStream(), StandardCharsets.UTF_8));\n        Throwable var7 = null;\n       \n        try {\n            String line;\n            try {\n            \/\/ \u8bfb\u53d6\u914d\u7f6e\u6587\u4ef6\u4e2d\u6bcf\u4e00\u884c\n                while((line = reader.readLine()) != null) {\n                    \/\/ \u53ea\u8bfb\u53d6#\u524d\u9762\u7684\u5185\u5bb9\uff0c#\u540e\u9762\u7684\u4e3a\u6ce8\u91ca\n                    int ci = line.indexOf(35);\n                    if (ci &gt;= 0) {\n                        line = line.substring(0, ci);\n                    }\n            \n                    line = line.trim();\n                    if (line.length() &gt; 0) {\n                        try {\n                            String name = null;\n                            int i = line.indexOf(61);\n                            if (i &gt; 0) {\n                            \/\/ \u5206\u522b\u8bfb\u53d6=\u524d\u7684\u4f5c\u4e3aname\uff0c=\u540e\u9762\u7684\u4e3a\u5177\u4f53\u7684\u5b9e\u73b0\u7c7b\u5168\u8def\u5f84\u540d\n                                name = line.substring(0, i).trim();\n                                line = line.substring(i + 1).trim();\n                            }\n                  \n                            if (line.length() &gt; 0 &amp;&amp; !this.isExcluded(line, excludedPackages)) {\n                                this.loadClass(extensionClasses, resourceURL, Class.forName(line, true, classLoader), name, overridden);\n                            }\n                        } catch (Throwable var21) {\n                            Throwable t = var21;\n                            IllegalStateException e = new IllegalStateException(&quot;Failed to load extension class (interface: &quot; + this.type + &quot;, class line: &quot; + line + &quot;) in &quot; + resourceURL + &quot;, cause: &quot; + t.getMessage(), t);\n                            this.exceptions.put(line, e);\n                        }\n                    }\n                }\n            } catch (Throwable var22) {\n                var7 = var22;\n                throw var22;\n            }\n        } finally {\n            \/\/close ...\n        \n        }\n    } catch (Throwable var24) {\n        Throwable t = var24;\n        logger.error(&quot;Exception occurred when loading extension class (interface: &quot; + this.type + &quot;, class file: &quot; + resourceURL + &quot;) in &quot; + resourceURL, t);\n    }\n\n}\n<\/code><\/pre>\n<p>loadResource \u5219\u4e3b\u8981\u8bfb\u53d6\u914d\u7f6e\u6587\u4ef6\u4e2d\u6bcf\u4e00\u884c\uff0c\u5206\u4e3a key \u548c value \u4e24\u90e8\u5206\uff0ckey \u4e3a=\u524d\u9762\u7684\u5b9e\u73b0\u7c7b\u522b\u540d\uff0cvalue \u4e3a=\u540e\u9762\u7684\u5b9e\u73b0\u7c7b\u5b9e\u4f8b\uff0c\u52a0\u8f7d\u5b9e\u4f8b\u7684\u8fc7\u7a0b\u4e3a loadClass \u65b9\u6cd5\uff0c\u5982\u4e0b\uff1a<\/p>\n<pre><code>private void loadClass(Map&lt;String, Class&lt;?&gt;&gt; extensionClasses, java.net.URL resourceURL, Class&lt;?&gt; clazz, String name,                       boolean overridden) throws NoSuchMethodException {    if (!type.isAssignableFrom(clazz)) {        throw new IllegalStateException(&quot;Error occurred when loading extension class (interface: &quot; +                type + &quot;, class line: &quot; + clazz.getName() + &quot;), class &quot;                + clazz.getName() + &quot; is not subtype of interface.&quot;);    }    \/\/ \u68c0\u6d4b\u76ee\u6807\u7c7b\u4e0a\u662f\u5426\u6709 Adaptive \u6ce8\u89e3        if (clazz.isAnnotationPresent(Adaptive.class)) {        cacheAdaptiveClass(clazz, overridden);    } else if (isWrapperClass(clazz)) {        \/\/ \u7f13\u5b58\u5305\u88c5\u7c7b                cacheWrapperClass(clazz);    } else {        \/\/ \u8fdb\u5165\u5230\u8fd9\u91cc\uff0c\u8868\u660e\u53ea\u662f\u8be5\u7c7b\u53ea\u662f\u4e00\u4e2a\u666e\u901a\u7684\u62d3\u5c55\u7c7b                \/\/ \u68c0\u6d4b clazz \u662f\u5426\u6709\u9ed8\u8ba4\u7684\u6784\u9020\u65b9\u6cd5\uff0c\u5982\u679c\u6ca1\u6709\uff0c\u5219\u629b\u51fa\u5f02\u5e38                clazz.getConstructor();        if (StringUtils.isEmpty(name)) {            \/\/ \u5982\u679c name \u4e3a\u7a7a\uff0c\u5219\u5c1d\u8bd5\u4ece Extension \u6ce8\u89e3\u4e2d\u83b7\u53d6 name\uff0c\u6216\u4f7f\u7528\u5c0f\u5199\u7684\u7c7b\u540d\u4f5c\u4e3a name            name = findAnnotationName(clazz);            if (name.length() == 0) {                throw new IllegalStateException(&quot;No such extension name for the class &quot; + clazz.getName() + &quot; in the config &quot; + resourceURL);            }        }              String[] names = NAME_SEPARATOR.split(name);        if (ArrayUtils.isNotEmpty(names)) {            \/\/ \u5982\u679c\u7c7b\u4e0a\u6709 Activate \u6ce8\u89e3\uff0c\u5219\u4f7f\u7528 names \u6570\u7ec4\u7684\u7b2c\u4e00\u4e2a\u5143\u7d20\u4f5c\u4e3a\u952e\uff0c                        \/\/ \u5b58\u50a8 name \u5230 Activate \u6ce8\u89e3\u5bf9\u8c61\u7684\u6620\u5c04\u5173\u7cfb                        cacheActivateClass(clazz, names[0]);            for (String n : names) {                \/\/ \u5b58\u50a8 Class \u5230\u540d\u79f0\u7684\u6620\u5c04\u5173\u7cfb                                cacheName(clazz, n);                \/\/ \u5b58\u50a8 name \u5230 Class \u7684\u6620\u5c04\u5173\u7cfb.                                \/\/ \u5982\u679c\u5b58\u5728\u540c\u4e00\u4e2a\u6269\u5c55\u540d\u5bf9\u5e94\u591a\u4e2a\u5b9e\u73b0\u7c7b\uff0c\u57fa\u4e8e override \u53c2\u6570\u662f\u5426\u5141\u8bb8\u8986\u76d6\uff0c\u5982\u679c\u4e0d\u5141\u8bb8\uff0c\u5219\u629b\u51fa\u5f02\u5e38.                                saveInExtensionClass(extensionClasses, clazz, n, overridden);            }        }    }}\n<\/code><\/pre>\n<p><strong>Dubbo SPI \u5e94\u7528\u573a\u666f<\/strong><\/p>\n<p>\u203b \u534f\u8bae\u6269\u5c55<\/p>\n<pre><code># META-INF\/dubbo\/org.apache.dubbo.rpc.Protocoldubbo=org.apache.dubbo.rpc.protocol.dubbo.DubboProtocolhttp=org.apache.dubbo.rpc.protocol.http.HttpProtocolgrpc=org.apache.dubbo.rpc.protocol.grpc.GrpcProtocol\n<\/code><\/pre>\n<p>\u203b \u96c6\u7fa4\u5bb9\u9519<\/p>\n<pre><code>@SPI(FailoverCluster.NAME)public interface Cluster {    @Adaptive    &lt;T&gt; Invoker&lt;T&gt; join(Directory&lt;T&gt; directory) throws RpcException;}\n\/\/ \u4f7f\u7528\u793a\u4f8b&lt;dubbo:reference cluster=&quot;failfast&quot;\/&gt;\n<\/code><\/pre>\n<p>\u203b \u670d\u52a1\u6cbb\u7406 filter \u8fc7\u6ee4\u5668<\/p>\n<pre><code>@SPIpublic interface Filter {    Result invoke(Invoker&lt;?&gt; invoker, Invocation invocation) throws RpcException;        public interface Listener {        void onResponse(Result appResponse, Invoker&lt;?&gt; invoker, Invocation invocation);              void onError(Throwable t, Invoker&lt;?&gt; invoker, Invocation invocation);    }}\n<\/code><\/pre>\n<h2>\u56db\uff0c\u603b\u7ed3<\/h2>\n<p>\u503c\u5f97\u4e00\u63d0\u7684\u662f\uff0cSPI \u5728\u5b9e\u9645\u4f7f\u7528\u8fc7\u7a0b\u4e2d\u5b58\u5728\u4e00\u4e9b\u95ee\u9898\uff1a<\/p>\n<p><strong>\u203b \u8d44\u6e90\u6d6a\u8d39\u9884\u6027\u80fd\u95ee\u9898<\/strong><\/p>\n<p>\u7531\u4e0a\u6587\u6e90\u7801\u89e3\u6790\u53ef\u77e5\uff0cServiceLoader \u5728\u52a0\u8f7d\u65f6\u4f1a\u626b\u63cf META-INF\/services \u76ee\u5f55\u5e76\u89e3\u6790\u6587\u4ef6\uff0c\u4f1a\u901a\u8fc7\u53cd\u5c04\u5b9e\u4f8b\u5316\u6240\u6709\u5b9e\u73b0\u7c7b\uff0c\u5982\u679c\u5b9e\u73b0\u7c7b\u5f88\u591a\uff0c\u6216\u8005\u521d\u59cb\u5316\u5f88\u8017\u65f6\uff0c\u4f1a\u9020\u6210\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u7684\u6027\u80fd\u5f00\u9500\u548c\u8d44\u6e90\u6d6a\u8d39\uff0c\u6240\u4ee5 Dubbo \u7684 ExtensionLoader \u5728\u6b64\u4e4b\u4e0a\u8fdb\u884c\u4e86\u4f18\u5316\uff0c\u901a\u8fc7\u7f13\u5b58\u4ee5\u53ca\u5728\u914d\u7f6e\u6587\u4ef6\u4e2d\u6307\u5b9a key \u5b9e\u73b0\u53ea\u52a0\u8f7d\u90e8\u5206\u5b9e\u73b0\u7c7b\u3002<\/p>\n<p><strong>\u203b \u591a\u4e2a\u5b9e\u73b0\u7c7b\u52a0\u8f7d\u987a\u5e8f\u95ee\u9898<\/strong><\/p>\n<p>ServiceLoader \u52a0\u8f7d\u670d\u52a1\u63d0\u4f9b\u8005\u5b9e\u73b0\u7684\u987a\u5e8f\u7531 classpath \u4e2d jar \u5305\u7684\u987a\u5e8f\u51b3\u5b9a\uff0c\u5982\u679c\u4f60\u7684\u903b\u8f91\u4f9d\u8d56\u4e8e\u83b7\u53d6\u5230\u7684\u7b2c\u4e00\u4e2a\u5b9e\u73b0\uff0c\u5728\u4e0d\u540c\u73af\u5883\u4e0b\u53ef\u80fd\u4f1a\u51fa\u73b0\u52a0\u8f7d\u987a\u5e8f\u4e0d\u4e00\u81f4\u5bfc\u81f4\u7684\u5f02\u5e38\u95ee\u9898\uff0c\u6240\u4ee5\u5c3d\u53ef\u80fd\u907f\u514d\u4f9d\u8d56\u52a0\u8f7d\u987a\u5e8f\u3002<\/p>\n<p><strong>\u203b \u7c7b\u91cd\u590d\u52a0\u8f7d\u95ee\u9898<\/strong><\/p>\n<p>\u5982\u679c classpath \u4e2d\u5b58\u5728\u591a\u4e2a jar \u5305\u90fd\u7533\u660e\u4e86\u540c\u4e00\u4e2a\u63a5\u53e3\u7684\u76f8\u540c\u5b9e\u73b0\u7c7b\uff0c\u6216\u8005\u540c\u4e00\u4e2a jar \u5305\u88ab\u4e0d\u540c\u7c7b\u52a0\u8f7d\u5668\u52a0\u8f7d\u591a\u6b21\uff0c\u4f1a\u5bfc\u81f4\u540c\u4e00\u4e2a\u5b9e\u73b0\u7c7b\u88ab\u591a\u6b21\u52a0\u8f7d\u548c\u5b9e\u4f8b\u5316\uff0c\u53ef\u80fd\u5bfc\u81f4\u5355\u4f8b\u5931\u6548\u6216\u8d44\u6e90\u51b2\u7a81\u3002<\/p>\n<p>\u603b\u7684\u6765\u8bf4\uff0cSPI \u673a\u5236\u7684\u5e94\u7528\u573a\u666f\u8fd8\u662f\u5f88\u5e7f\u7684\uff0c\u5176\u6838\u5fc3\u5728\u4e8e\u901a\u8fc7\u8bfb\u53d6\u914d\u7f6e\u6587\u4ef6\u52a8\u6001\u52a0\u8f7d\u63a5\u53e3\u5b9e\u73b0\uff0c\u89e3\u8026\u4e86\u63a5\u53e3\u5b9a\u4e49\u4e0e\u5b9e\u73b0 \uff0c\u5b9e\u73b0\u4e86\u6846\u67b6\u53ef\u6269\u5c55\u6027\uff0c\u5728\u5404\u5927\u6846\u67b6\u4e2d\u90fd\u80fd\u770b\u5230\u5176\u8eab\u5f71\u3002<\/p>\n<h4>\u5f80\u671f\u56de\u987e<\/h4>\n<p>1.Java volatile \u5173\u952e\u5b57\u5230\u5e95\u662f\u4ec0\u4e48\uff5c\u5f97\u7269\u6280\u672f<\/p>\n<p>2.\u793e\u533a\u641c\u7d22\u79bb\u7ebf\u56de\u6eaf\u7cfb\u7edf\u8bbe\u8ba1\uff1a\u67b6\u6784\u3001\u6311\u6218\u4e0e\u6027\u80fd\u4f18\u5316\uff5c\u5f97\u7269\u6280\u672f<\/p>\n<p>3.\u4ece Rust \u6a21\u5757\u5316\u63a2\u7d22\u5230 DLB 2.0 \u5b9e\u8df5\uff5c\u5f97\u7269\u6280\u672f<\/p>\n<p>4.eBPF \u52a9\u529b NAS \u5206\u949f\u7ea7\u522b Pod \u5b9e\u4f8b\u6eaf\u6e90\uff5c\u5f97\u7269\u6280\u672f<\/p>\n<p>5.\u6b63\u54c1\u5e93\u62cd\u7167 PWA \u5e94\u7528\u7684\u5b9e\u73b0\u4e0e\u6027\u80fd\u4f18\u5316\uff5c\u5f97\u7269\u6280\u672f<\/p>\n<hr>\n<p>\u6587 \/ \u7409\u7483<br \/>\u5173\u6ce8\u5f97\u7269\u6280\u672f\uff0c\u6bcf\u5468\u4e8c\u3001\u56db\u66f4\u65b0\u6280\u672f\u5e72\u8d27<br \/>\u8981\u662f\u89c9\u5f97\u6587\u7ae0\u5bf9\u4f60\u6709\u5e2e\u52a9\u7684\u8bdd\uff0c\u6b22\u8fce\u8bc4\u8bba\u8f6c\u53d1\u70b9\u8d5e\uff5e<br \/>\u672a\u7ecf\u5f97\u7269\u6280\u672f\u8bb8\u53ef\u4e25\u7981\u8f6c\u8f7d\uff0c\u5426\u5219\u4f9d\u6cd5\u8ffd\u7a76\u6cd5\u5f8b\u8d23\u4efb\u3002<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000047146485\">https:\/\/segmentfault.com\/a\/1190000047146485<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e00\uff0c\u6982\u8ff0 \u4ec0\u4e48\u662f SPI SPI \u5373 Service Provider Interface \uff0c\u4e5f\u5c31\u662f\u201c\u670d\u52a1\u63d0\u4f9b [&hellip;]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10020946","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10020946","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10020946"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10020946\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10020946"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10020946"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10020946"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}