對dubbo的擴展點作一些切面功能的擴展java
@SuppressWarnings("unchecked") private T createExtension(String name) { Class<?> clazz = getExtensionClasses().get(name); if (clazz == null) { throw findException(name); } try { T instance = (T) EXTENSION_INSTANCES.get(clazz); if (instance == null) { EXTENSION_INSTANCES.putIfAbsent(clazz, (T) clazz.newInstance()); instance = (T) EXTENSION_INSTANCES.get(clazz); } injectExtension(instance); Set<Class<?>> wrapperClasses = cachedWrapperClasses; //begin if (wrapperClasses != null && wrapperClasses.size() > 0) { for (Class<?> wrapperClass : wrapperClasses) { instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance)); } } //end return instance; } catch (Throwable t) { throw new IllegalStateException("Extension instance(name: " + name + ", class: " + type + ") could not be instantiated: " + t.getMessage(), t); } }
關鍵說明,設計模式
和ProtocolListenerWrapper。他們共同特徵就是帶有Protocol接口的構造函數。app
/** * ListenerProtocol * * @author william.liangf */ public class ProtocolFilterWrapper implements Protocol { private final Protocol protocol; public ProtocolFilterWrapper(Protocol protocol) { if (protocol == null) { throw new IllegalArgumentException("protocol == null"); } this.protocol = protocol; } private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) { Invoker<T> last = invoker; List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group); if (filters.size() > 0) { for (int i = filters.size() - 1; i >= 0; i--) { final Filter filter = filters.get(i); final Invoker<T> next = last; last = new Invoker<T>() { public Class<T> getInterface() { return invoker.getInterface(); } public URL getUrl() { return invoker.getUrl(); } public boolean isAvailable() { return invoker.isAvailable(); } public Result invoke(Invocation invocation) throws RpcException { return filter.invoke(next, invocation); } public void destroy() { invoker.destroy(); } @Override public String toString() { return invoker.toString(); } }; } } return last; } public int getDefaultPort() { return protocol.getDefaultPort(); } public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException { if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) { return protocol.export(invoker); } return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER)); } public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException { if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) { return protocol.refer(type, url); } return buildInvokerChain(protocol.refer(type, url), Constants.REFERENCE_FILTER_KEY, Constants.CONSUMER); } public void destroy() { protocol.destroy(); } }
經過這種方式dubbo實現了擴展點的AOPide
屢次使用裝飾類,實現了dubbo擴展點的AOP功能函數