Dubbo服务发布

Dubbo服务发布影响流程的主要包括三个部分，依次是：

服务暴露心跳服务注册

服务暴露是对外提供服务及暴露端口，以便消费端可以正常调通服务。心跳机制保证服务器端及客户端正常长连接的保持，服务注册是向注册中心注册服务暴露服务的过程。

Dubbo服务暴露

此处只记录主要代码部分以便能快速定位到主要的核心代码：

ServiceConfig.java中代码

if (registryURLs != null && registryURLs.size() > 0 && url.getParameter("register", true)) { // 循环祖册中心 URL 数组 registryURLs for (URL registryURL : registryURLs) { // "dynamic" ：服务是否动态注册，如果设为false，注册后将显示后disable状态，需人工启用，并且服务提供者停止时，也不会自动取消册，需人工禁用。 url = url.addParameterIfAbsent("dynamic", registryURL.getParameter("dynamic")); // 获得监控中心 URL URL monitorUrl = loadMonitor(registryURL); if (monitorUrl != null) { // 将监控中心的 URL 作为 "monitor" 参数添加到服务提供者的 URL 中，并且需要编码。通过这样的方式，服务提供者的 URL 中，包含了监控中心的配置。 url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString()); } if (logger.isInfoEnabled()) { logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL); } // 使用 ProxyFactory 创建 Invoker 对象 // 调用 URL#addParameterAndEncoded(key, value) 方法，将服务体用这的 URL 作为 "export" 参数添加到注册中心的 URL 中。通过这样的方式，注册中心的 URL 中，包含了服务提供者的配置。 // 创建 Invoker 对象。该 Invoker 对象，执行 #invoke(invocation) 方法时，内部会调用 Service 对象( ref )对应的调用方法。 Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString())); // 使用 Protocol 暴露 Invoker 对象 /** * Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => RegistryProtocol * => * Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => DubboProtocol */ Exporter<?> exporter = protocol.export(invoker); // 添加到 `exporters` exporters.add(exporter); }}

循环注册中心，对每个注册中心都执行代码块中的执行过程

1.如果url中没有dynamic 参数，则从registerUrl中取值，并赋予url

dynamic是服务动态注册的标识，默认为true，如果设置为false,则服务注册后显示disable状态，需人工启动

2.加载注册中心对应的监控中心配置

3.如果注册中心不为空则设置url的 monitor参数

4.Invoker proxyFactory.getInvoker proxyFactory 默认为JavassistProxyFactory对象，这段代码为创建 ref 服务对象的代理对象。

proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString())); 获取ref的代理对象并在registryURL 中添加export属性，代理对象中属性参数如下

5.protocol.export(invoker) 为暴露服务的核心实现部分,协议的调用链如下：

/**

* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => RegistryProtocol

* =>

* Protocol$Adaptive => ProtocolFilterWrapper => ProtocolListenerWrapper => DubboProtocol

*/

其中DubboProtocol 实现了服务暴露及心跳检测功能

RegistryProtocol 调用了DubboProtocol及注册服务

接下来经过两个扩展类(包装器) ProtocolFilterWrapper和ProtocolListenerWrapper 进入RegistryProtocol 核心代码如下：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException { // 暴露服务 //export invoker final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker); //registry provider final Registry registry = getRegistry(originInvoker); // 获得服务提供者 URL final URL registedProviderUrl = getRegistedProviderUrl(originInvoker); registry.register(registedProviderUrl); // 订阅override数据 // FIXME 提供者订阅时，会影响同一JVM即暴露服务，又引用同一服务的的场景，因为subscribed以服务名为缓存的key，导致订阅信息覆盖。 final URL overrideSubscribeUrl = getSubscribedOverrideUrl(registedProviderUrl); final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker); overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener); registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener); //保证每次export都返回一个新的exporter实例 return new Exporter<T>() { public Invoker<T> getInvoker() { return exporter.getInvoker(); } public void unexport() { try { exporter.unexport(); } catch (Throwable t) { logger.warn(t.getMessage(), t); } try { registry.unregister(registedProviderUrl); } catch (Throwable t) { logger.warn(t.getMessage(), t); } try { overrideListeners.remove(overrideSubscribeUrl); registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener); } catch (Throwable t) { logger.warn(t.getMessage(), t); } } };}

/** * 暴露服务。 * * 此处的 Local 指的是，本地启动服务，但是不包括向注册中心注册服务的意思。 * @param originInvoker * @param <T> * @return */@SuppressWarnings("unchecked")private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) { // 获得在 `bounds` 中的缓存 Key //dubbo://192.168.20.218:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false& // interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=1760&side=provider&timestamp=1530150456618 String key = getCacheKey(originInvoker); ExporterChangeableWrapper<T> exporter = (ExporterChangeableWrapper<T>) bounds.get(key); if (exporter == null) { synchronized (bounds) { exporter = (ExporterChangeableWrapper<T>) bounds.get(key); // 未暴露过，进行暴露服务 if (exporter == null) { // InvokerDelegete 实现 com.alibaba.dubbo.rpc.protocol.InvokerWrapper 类，主要增加了 #getInvoker() 方法，获得真实的，非 InvokerDelegete 的 Invoker 对象。 // 因为，可能会存在 InvokerDelegete.invoker 也是 InvokerDelegete 类型的情况。 getProviderUrl 同上 key = getCacheKey final Invoker<?> invokerDelegete = new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker)); // 暴露服务，创建 Exporter 对象 Exporter<T> export = (Exporter<T>) protocol.export(invokerDelegete); // 使用 创建的Exporter对象 + originInvoker ，创建 ExporterChangeableWrapper 对象 exporter = new ExporterChangeableWrapper<T>(export, originInvoker); bounds.put(key, exporter); } } } return exporter;}

1.代用同步锁+double-check的方式来保证同样的服务不重复暴露。

2.new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));

InvokerDelegete 实现 com.alibaba.dubbo.rpc.protocol.InvokerWrapper（invoke） 类，主要增加了 #getInvoker() 方法，获得真实的，非 InvokerDelegete 的 Invoker 对象。

3.调用protocol.export接口 经过ProtocolFilterWrapper.invoker方法 创过滤器链再暴露服务：

protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));

/** * 构建过滤器链 * @param invoker injvm://127.0.0.1/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&default.accepts=1000&default.threadpool=fixed&default.threads=100&default.timeout=5000&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&owner=uce&pid=9932&side=provider&timestamp=1527930395583 * @param key service.filter 该参数用于获得 ServiceConfig 或 ReferenceConfig 配置的自定义过滤器 * 以 ServiceConfig 举例子，例如 url = injvm://127.0.0.1/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=192.168.3.17&bind.port=20880&default.delay=-1&default.retries=0&default.service.filter=demo&delay=-1&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=81844&qos.port=22222&service.filter=demo&side=provider&timestamp=1520682156043 中， * service.filter=demo，这是笔者配置自定义的 DemoFilter 过滤器。 * <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService" filter="demo" /> * @param group provider 属性，分组 * 在暴露服务时，group = provider 。 * 在引用服务时，group = consumer 。 * @param <T> * @return */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); /* EchoFilter ClassLoaderFilter GenericFilter ContextFilter TraceFilter TimeoutFilter MonitorFilter ExceptionFilter DemoFilter 【自定义】*/ //倒序循环 Filter ，创建带 Filter 链的 Invoker 对象。因为是通过嵌套声明匿名类循环调用的方式，所以要倒序。可以手工模拟下这个过程。通过这样的方式，实际过滤的顺序，还是我们上面看到的正序 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>() { @Override public Class<T> getInterface() { return invoker.getInterface(); } @Override public URL getUrl() { return invoker.getUrl(); } @Override public boolean isAvailable() { return invoker.isAvailable(); } @Override public Result invoke(Invocation invocation) throws RpcException { return filter.invoke(next, invocation); } @Override public void destroy() { invoker.destroy(); } @Override public String toString() { return invoker.toString(); } }; } } return last;}

List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);

获取Active的属于指定组的过过滤器列表

参考文章：

接下来执行DubboProrocol进行服务暴露的过程。

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException { URL url = invoker.getUrl(); // export service. String key = serviceKey(url); // 创建 DubboExporter 对象，并添加到 `exporterMap` 。 DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap); exporterMap.put(key, exporter); //export an stub service for dispaching event Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT); Boolean isCallbackservice = url.getParameter(Constants.IS_CALLBACK_SERVICE, false); if (isStubSupportEvent && !isCallbackservice) { String stubServiceMethods = url.getParameter(Constants.STUB_EVENT_METHODS_KEY); if (stubServiceMethods == null || stubServiceMethods.length() == 0) { if (logger.isWarnEnabled()) { logger.warn(new IllegalStateException("consumer [" + url.getParameter(Constants.INTERFACE_KEY) + "], has set stubproxy support event ,but no stub methods founded.")); } } else { stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods); } } // 启动服务器 openServer(url); return exporter;}

1.获取invoker的 URL信息

2.获取key信息 为URL中interface与暴露端口的拼装字符串：com.alibaba.dubbo.demo.DemoService:20880

3.创建DubboExporter对象 并且入参为exporterMap

4.将exporter对象添加到exporterMap中

 /** * 启动服务器 * * @param url URL */private void openServer(URL url) { // find server. String key = url.getAddress(); //client 也可以暴露一个只有server可以调用的服务。 boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true); if (isServer) { ExchangeServer server = serverMap.get(key); if (server == null) { serverMap.put(key, createServer(url)); } else { //server支持reset,配合override功能使用 server.reset(url); } }}

调用createServer()方法 并存入DubboProtocol的serverMap中

private ExchangeServer createServer(URL url) { //默认开启server关闭时发送readonly事件 url = url.addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString()); //默认开启heartbeat url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT)); String str = url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_SERVER); // 校验 Server 的 Dubbo SPI 拓展是否存在 if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) throw new RpcException("Unsupported server type: " + str + ", url: " + url); // 设置codec为 `"Dubbo"` url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME); ExchangeServer server; try { server = Exchangers.bind(url, requestHandler); } catch (RemotingException e) { throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e); } str = url.getParameter(Constants.CLIENT_KEY); if (str != null && str.length() > 0) { Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(); if (!supportedTypes.contains(str)) { throw new RpcException("Unsupported client type: " + str); } } return server;}

1.默认开启server 关闭时发送readonly事件：channel.readonly.sent : true

2.默认开启 heartbeat

3.获取服务暴露的 server 传输 ， 默认为netty

4.设置编码器为Dubbo也就是 DubboCountCodec

5.Exchangers#bind(url, requestHandler) 启动服务器，requestHandler结构如下

具体实现代码如下：

private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() { public Object reply(ExchangeChannel channel, Object message) throws RemotingException { if (message instanceof Invocation) { Invocation inv = (Invocation) message; Invoker<?> invoker = getInvoker(channel, inv); //如果是callback 需要处理高版本调用低版本的问题 if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))) { String methodsStr = invoker.getUrl().getParameters().get("methods"); boolean hasMethod = false; if (methodsStr == null || methodsStr.indexOf(",") == -1) { hasMethod = inv.getMethodName().equals(methodsStr); } else { String[] methods = methodsStr.split(","); for (String method : methods) { if (inv.getMethodName().equals(method)) { hasMethod = true; break; } } } if (!hasMethod) { logger.warn(new IllegalStateException("The methodName " + inv.getMethodName() + " not found in callback service interface ,invoke will be ignored. please update the api interface. url is:" + invoker.getUrl()) + " ,invocation is :" + inv); return null; } } RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress()); return invoker.invoke(inv); } throw new RemotingException(channel, "Unsupported request: " + message == null ? null : (message.getClass().getName() + ": " + message) + ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress()); } @Override public void received(Channel channel, Object message) throws RemotingException { if (message instanceof Invocation) { reply((ExchangeChannel) channel, message); } else { super.received(channel, message); } } @Override public void connected(Channel channel) throws RemotingException { invoke(channel, Constants.ON_CONNECT_KEY); } @Override public void disconnected(Channel channel) throws RemotingException { if (logger.isInfoEnabled()) { logger.info("disconected from " + channel.getRemoteAddress() + ",url:" + channel.getUrl()); } invoke(channel, Constants.ON_DISCONNECT_KEY); } private void invoke(Channel channel, String methodKey) { Invocation invocation = createInvocation(channel, channel.getUrl(), methodKey); if (invocation != null) { try { received(channel, invocation); } catch (Throwable t) { logger.warn("Failed to invoke event method " + invocation.getMethodName() + "(), cause: " + t.getMessage(), t); } } } private Invocation createInvocation(Channel channel, URL url, String methodKey) { String method = url.getParameter(methodKey); if (method == null || method.length() == 0) { return null; } RpcInvocation invocation = new RpcInvocation(method, new Class<?>[0], new Object[0]); invocation.setAttachment(Constants.PATH_KEY, url.getPath()); invocation.setAttachment(Constants.GROUP_KEY, url.getParameter(Constants.GROUP_KEY)); invocation.setAttachment(Constants.INTERFACE_KEY, url.getParameter(Constants.INTERFACE_KEY)); invocation.setAttachment(Constants.VERSION_KEY, url.getParameter(Constants.VERSION_KEY)); if (url.getParameter(Constants.STUB_EVENT_KEY, false)) { invocation.setAttachment(Constants.STUB_EVENT_KEY, Boolean.TRUE.toString()); } return invocation; }};

Exchangeers.bind(URL url, ExchangeHandler handler)

public static ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException { if (url == null) { throw new IllegalArgumentException("url == null"); } if (handler == null) { throw new IllegalArgumentException("handler == null"); } url = url.addParameterIfAbsent(Constants.CODEC_KEY, "exchange"); return getExchanger(url).bind(url, handler);}public static Exchanger getExchanger(URL url) { String type = url.getParameter(Constants.EXCHANGER_KEY, Constants.DEFAULT_EXCHANGER); return getExchanger(type);}public static Exchanger getExchanger(String type) { return ExtensionLoader.getExtensionLoader(Exchanger.class).getExtension(type);}

接口作用是设置exchanger params为header 并且获取Exchanger.class的header扩展接口HeaderExchanger， 并调用bind方法：

public class HeaderExchanger implements Exchanger { public static final String NAME = "header"; public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException { return new HeaderExchangeClient(Transporters.connect(url, new DecodeHandler(new HeaderExchangeHandler(handler))), true); } public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException { return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler)))); }}

先将 DubboProtocol入参 传过来的ExchangeHandler对象ExchangeHandlerAdapter() 进行包装组成handler链：最后返回ChannelHandler对象，接下来调用：Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler)))

Server Transporters.bind(URL url, ChannelHandler... handlers)

Transpoter$Adaptive.bind()

数据透传 NettyTransporter.java

Server NettyTransporter.bind(URL url, ChannelHandler listener)

public Server bind(URL url, ChannelHandler listener) throws RemotingException { return new NettyServer(url, listener);}

作用是：

返回一个NettyServer实例：

public NettyServer(URL url, ChannelHandler handler) throws RemotingException { super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));}

ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)) 只用是生成获取ThreadName的名称 为URL添加threadname的param

ChannelHandlers.wrap(ChannelHandler handler, URL url) 代码如下：

public class ChannelHandlers { private static ChannelHandlers INSTANCE = new ChannelHandlers(); protected ChannelHandlers() { } public static ChannelHandler wrap(ChannelHandler handler, URL url) { return ChannelHandlers.getInstance().wrapInternal(handler, url); } protected static ChannelHandlers getInstance() { return INSTANCE; } static void setTestingChannelHandlers(ChannelHandlers instance) { INSTANCE = instance; } protected ChannelHandler wrapInternal(ChannelHandler handler, URL url) { return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class) .getAdaptiveExtension().dispatch(handler, url))); }}

ExtensionLoader.getExtensionLoader(Dispatcher.class).getAdaptiveExtension().dispatch(handler, url)：

获取到AllDispatcher分发器进行透传：

public class AllDispatcher implements Dispatcher { public static final String NAME = "all"; public ChannelHandler dispatch(ChannelHandler handler, URL url) { return new AllChannelHandler(handler, url); }}

结构如图所示：

调用WrappedChannelHandler的构造方法：

public WrappedChannelHandler(ChannelHandler handler, URL url) { this.handler = handler; this.url = url; executor = (ExecutorService) ExtensionLoader.getExtensionLoader(ThreadPool.class).getAdaptiveExtension().getExecutor(url); String componentKey = Constants.EXECUTOR_SERVICE_COMPONENT_KEY; if (Constants.CONSUMER_SIDE.equalsIgnoreCase(url.getParameter(Constants.SIDE_KEY))) { componentKey = Constants.CONSUMER_SIDE; } DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension(); dataStore.put(componentKey, Integer.toString(url.getPort()), executor);}

这段代码的功能为：

1.将 之前头创的DecoderHandler对象再进包装 包装为AllChannelHandler

2.生成线程池对象Executor对象

3.获取默认的DataStore对象，并将线程池对象放入DataStore 中 key为 : java.util.concurrent.ExecutorService 字符串和服务暴露的端口 值为线程池对象

return new MultiMessageHandler(new HeartbeatHandler(ExtensionLoader.getExtensionLoader(Dispatcher.class)

.getAdaptiveExtension().dispatch(handler, url)));

接下来将返回的AllChannelHandler对象用HeartbeatHandler 和 MultiMessageHandler 进行包装处理并返回ChannelHandler.wrap() 的上一端。

NettyTransporter.bind(URL url, ChannelHandler listener) -> new NettyServer(URL url, ChannelHandler handler)

-> super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));

接下来是创建NettyServer对象的最后一步：

NettyServer ==>public NettyServer(URL url, ChannelHandler handler) throws RemotingException { super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));}AbstractServer==>public AbstractServer(URL url, ChannelHandler handler) throws RemotingException { super(url, handler); localAddress = getUrl().toInetSocketAddress(); String host = url.getParameter(Constants.ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(getUrl().getHost()) ? NetUtils.ANYHOST : getUrl().getHost(); bindAddress = new InetSocketAddress(host, getUrl().getPort()); this.accepts = url.getParameter(Constants.ACCEPTS_KEY, Constants.DEFAULT_ACCEPTS); this.idleTimeout = url.getParameter(Constants.IDLE_TIMEOUT_KEY, Constants.DEFAULT_IDLE_TIMEOUT); try { doOpen(); if (logger.isInfoEnabled()) { logger.info("Start " + getClass().getSimpleName() + " bind " + getBindAddress() + ", export " + getLocalAddress()); } } catch (Throwable t) { throw new RemotingException(url.toInetSocketAddress(), null, "Failed to bind " + getClass().getSimpleName() + " on " + getLocalAddress() + ", cause: " + t.getMessage(), t); } //fixme replace this with better method DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension(); executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));}AbstractEndpoint ==>public AbstractEndpoint(URL url, ChannelHandler handler) { super(url, handler); this.codec = getChannelCodec(url); this.timeout = url.getPositiveParameter(Constants.TIMEOUT_KEY, Constants.DEFAULT_TIMEOUT); this.connectTimeout = url.getPositiveParameter(Constants.CONNECT_TIMEOUT_KEY, Constants.DEFAULT_CONNECT_TIMEOUT);}AbstractPeer==>public AbstractPeer(URL url, ChannelHandler handler) { if (url == null) { throw new IllegalArgumentException("url == null"); } if (handler == null) { throw new IllegalArgumentException("handler == null"); } this.url = url; this.handler = handler;}

调用栈如上所示：

因为之前设置了codec为dubbo 所以返回DubboCountCodec实例

获取超时时间timeout ,和链接的超时时间connectTimeout

localAddress为本地IP:PORT port为服务暴露的端口

host 为0.0.0.0

bindAddress为 host:port port为服务暴露的端口

this.accept 为默认获取最大连接数

idleTimeout为 url中 idle.timeout

核心代码：doOpen()

@Overrideprotected void doOpen() throws Throwable { NettyHelper.setNettyLoggerFactory(); ExecutorService boss = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerBoss", true)); ExecutorService worker = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerWorker", true)); ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS)); bootstrap = new ServerBootstrap(channelFactory); final NettyHandler nettyHandler = new NettyHandler(getUrl(), this); channels = nettyHandler.getChannels(); //  //  // final Timer timer = new HashedWheelTimer(new NamedThreadFactory("NettyIdleTimer", true)); bootstrap.setPipelineFactory(new ChannelPipelineFactory() { public ChannelPipeline getPipeline() { NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this); ChannelPipeline pipeline = Channels.pipeline(); /*int idleTimeout = getIdleTimeout(); if (idleTimeout > 10000) { pipeline.addLast("timer", new IdleStateHandler(timer, idleTimeout / 1000, 0, 0)); }*/ pipeline.addLast("decoder", adapter.getDecoder()); pipeline.addLast("encoder", adapter.getEncoder()); pipeline.addLast("handler", nettyHandler); return pipeline; } }); // bind channel = bootstrap.bind(getBindAddress());}

1.首先进行Netty的日志配置

接下来先生成 NettyCodecAdapter 入参为之前生成的codec , URL信息(主要用到buffer属性配置Netty缓冲区)及 this (Handler) 对象

接下来就是设置Netty的Encoder Decoder 来进行数据的编码与解码 其会调用 this的handler链来进行数据处理。Dubbo2.5.6采用的是Netty3来进行通讯的，此处就不进行赘述。

AbstractServer 接下来获取到从DataStore对象中获取之前缓存的线程池 ，设置 NettyServer的 executor属性。

自此，Dubbo服务暴露的代码解析完毕，NettyServer的类结构图如下：

心跳服务

Dubbo provider的心跳服务是 HeaderExchanger bind代码执行的最后一步：参数是上面生成的Server对象 (NettyServer)。

public HeaderExchangeServer(Server server) { if (server == null) { throw new IllegalArgumentException("server == null"); } this.server = server; this.heartbeat = server.getUrl().getParameter(Constants.HEARTBEAT_KEY, 0); this.heartbeatTimeout = server.getUrl().getParameter(Constants.HEARTBEAT_TIMEOUT_KEY, heartbeat * 3); if (heartbeatTimeout < heartbeat * 2) { throw new IllegalStateException("heartbeatTimeout < heartbeatInterval * 2"); } startHeatbeatTimer();}

1.初始化 server信息

2.获取server URL中heartbeat信息 及心跳超时信息，默认为heartbeat的三倍

3.执行心跳代码 startHeatbeatTimer()

private void startHeatbeatTimer() { stopHeartbeatTimer(); if (heartbeat > 0) { heatbeatTimer = scheduled.scheduleWithFixedDelay( new HeartBeatTask(new HeartBeatTask.ChannelProvider() { public Collection<Channel> getChannels() { return Collections.unmodifiableCollection( HeaderExchangeServer.this.getChannels()); } }, heartbeat, heartbeatTimeout), heartbeat, heartbeat, TimeUnit.MILLISECONDS); }}

1.停止定时任务——首先停止定时器中所有任务，置空 beatbeatTimer；

2.重新设置定时器 ， 循环检测

接下来在DubboProtocol的openServer(URL) 方法中将创建的ExchangeServer对象放入 DubboProtocol的 serverMap 集合对象中

key为服务的ip:port 如 192.168.20.218:20880

value为之前创建的ExchangeServer对象

DubboProtocol export方法到此执行完毕，最终返回的是 DubboExporter对象包装了入参的invoker对象，serviceKey信息，及服务暴露的 exporterMap对象。

服务注册

我们接着来看RegistryProtocol 接下来的执行代码：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException { // 暴露服务 //export invoker final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker); //registry provider 添加定时任务 ping request response final Registry registry = getRegistry(originInvoker); // 获得服务提供者 URL final URL registedProviderUrl = getRegistedProviderUrl(originInvoker); registry.register(registedProviderUrl); // 订阅override数据 // FIXME 提供者订阅时，会影响同一JVM即暴露服务，又引用同一服务的的场景，因为subscribed以服务名为缓存的key，导致订阅信息覆盖。 final URL overrideSubscribeUrl = getSubscribedOverrideUrl(registedProviderUrl); final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker); overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener); registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener); //保证每次export都返回一个新的exporter实例 return new Exporter<T>() { public Invoker<T> getInvoker() { return exporter.getInvoker(); } public void unexport() { try { exporter.unexport(); } catch (Throwable t) { logger.warn(t.getMessage(), t); } try { registry.unregister(registedProviderUrl); } catch (Throwable t) { logger.warn(t.getMessage(), t); } try { overrideListeners.remove(overrideSubscribeUrl); registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener); } catch (Throwable t) { logger.warn(t.getMessage(), t); } } };}

1.ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) 为暴露服务的执行过程，上面流程已经走过。

返回的数据格式如下：

2.根据originInvoker中注册中心信息获取对应的Registry对象,因为这里是zookeeper协议，所以为ZookeeperRegistry对象

3.从注册中心的URL中获得 export 参数对应的值，即服务提供者的URL.

4.registry.register(registedProviderUrl); 用之前创建的注册中心对象注册服务

5.

// TODO

上面提到 Registry getRegistry(final Invoker<?> originInvoker) 是根据invoker的地址获取registry实例代码如下：

private Registry getRegistry(final Invoker<?> originInvoker) { // registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&export=dubbo%3A%2F%2F192.168.20.218%3A20880%2Fcom.alibaba.dubbo.demo.DemoService%3Fanyhost%3Dtrue%26application%3Ddemo-provider%26default.accepts%3D1000%26default.threadpool%3Dfixed%26default.threads%3D100%26default.timeout%3D5000%26dubbo%3D2.0.0%26generic%3Dfalse%26interface%3Dcom.alibaba.dubbo.demo.DemoService%26methods%3DsayHello%26owner%3Duce%26pid%3D12028%26side%3Dprovider%26timestamp%3D1531912729429&owner=uce&pid=12028&registry=zookeeper&timestamp=1531912729343 URL registryUrl = originInvoker.getUrl(); if (Constants.REGISTRY_PROTOCOL.equals(registryUrl.getProtocol())) { String protocol = registryUrl.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_DIRECTORY); registryUrl = registryUrl.setProtocol(protocol).removeParameter(Constants.REGISTRY_KEY); } // zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&export=dubbo%3A%2F%2F192.168.20.218%3A20880%2Fcom.alibaba.dubbo.demo.DemoService%3Fanyhost%3Dtrue%26application%3Ddemo-provider%26default.accepts%3D1000%26default.threadpool%3Dfixed%26default.threads%3D100%26default.timeout%3D5000%26dubbo%3D2.0.0%26generic%3Dfalse%26interface%3Dcom.alibaba.dubbo.demo.DemoService%26methods%3DsayHello%26owner%3Duce%26pid%3D12028%26side%3Dprovider%26timestamp%3D1531912729429&owner=uce&pid=12028&timestamp=1531912729343 return registryFactory.getRegistry(registryUrl);}

上面代码的意思是：

1.获取originalInvoker中的URL信息 (注册中心的配置信息)

2.将URL中信息中Param中registry参数获取到，并替换URL中的protocol属性，并删除Param中的registry信息，上面代码中的注释为执行前和执行后的的结果。

3.获取protocol 为 zookeeper对应的RegistryFactory接口的扩展对象 ZookeeperRegistryFactory 并执行getRegistry 方法：

ZookeeperRegistryFactory的继承结构和对应类中属性如下图所示：

其中REGISTRIES = new ConcurrentHashMap<String, Registry>(); 代表注册中心的配置，其中可以有多个注册中心配置

AbstractRegistryFactory.getRegistry执行代码如下：

public Registry getRegistry(URL url) { url = url.setPath(RegistryService.class.getName()) .addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName()) .removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY); String key = url.toServiceString(); // zookeeper://192.168.1.157:2181/com.alibaba.dubbo.registry.RegistryService // 锁定注册中心获取过程，保证注册中心单一实例 LOCK.lock(); try { Registry registry = REGISTRIES.get(key); if (registry != null) { return registry; } registry = createRegistry(url); if (registry == null) { throw new IllegalStateException("Can not create registry " + url); } REGISTRIES.put(key, registry); return registry; } finally { // 释放锁 LOCK.unlock(); }}

1.设置Path属性，添加interface参数信息，及移除export 和 refer 参数信息。执行结果如下：

zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&interface=com.alibaba.dubbo.registry.RegistryService&owner=uce&pid=12028&timestamp=1531912729343

2.获取url对应的serviceString信息：zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService，由于我使用的是本地的zookeeper 所以IP为 127.0.0.1

3.顺序地创建注册中心：Registry ZookeeperRegistryFactory.createRegistry(URL url);

public Registry createRegistry(URL url) { return new ZookeeperRegistry(url, zookeeperTransporter);}// 构造ZookeeperRegistry的调用链如下所示public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) { super(url); if (url.isAnyHost()) { throw new IllegalStateException("registry address == null"); } String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT); if (!group.startsWith(Constants.PATH_SEPARATOR)) { group = Constants.PATH_SEPARATOR + group; } this.root = group; zkClient = zookeeperTransporter.connect(url); zkClient.addStateListener(new StateListener() { public void stateChanged(int state) { if (state == RECONNECTED) { try { recover(); } catch (Exception e) { logger.error(e.getMessage(), e); } } } });}public FailbackRegistry(URL url) { super(url); int retryPeriod = url.getParameter(Constants.REGISTRY_RETRY_PERIOD_KEY, Constants.DEFAULT_REGISTRY_RETRY_PERIOD); this.retryFuture = retryExecutor.scheduleWithFixedDelay(new Runnable() { public void run() { // 检测并连接注册中心 try { retry(); } catch (Throwable t) { // 防御性容错 logger.error("Unexpected error occur at failed retry, cause: " + t.getMessage(), t); } } }, retryPeriod, retryPeriod, TimeUnit.MILLISECONDS);}public AbstractRegistry(URL url) { setUrl(url); // 启动文件保存定时器 syncSaveFile = url.getParameter(Constants.REGISTRY_FILESAVE_SYNC_KEY, false); String filename = url.getParameter(Constants.FILE_KEY, System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getHost() + ".cache"); File file = null; if (ConfigUtils.isNotEmpty(filename)) { file = new File(filename); if (!file.exists() && file.getParentFile() != null && !file.getParentFile().exists()) { if (!file.getParentFile().mkdirs()) { throw new IllegalArgumentException("Invalid registry store file " + file + ", cause: Failed to create directory " + file.getParentFile() + "!"); } } } this.file = file; loadProperties(); notify(url.getBackupUrls());}

ZookeeperRegistry 的类继承结构图如图所示：

ZooKeeperRegistry.FailbackRegistry.AbstractRegistry中

1.setUrl设置url属性信息

2.是否启用文件的异步保存

3.注册中心对应的本地文件保存的位置信息：如C:\Users\Administrator/.dubbo/dubbo-registry-127.0.0.1.cache

4.给file赋值 并且加载文件信息到properties属性中

5.notify(url.getBackupUrls) 这段代码不知道什么意思。

ZooKeeperRegistry.FailbackRegistry中

1.获取定时任务的时间间隔。

2.开启定时任务定时检测失败的注册，并重新注册。

ZooKeeperRegistry 中

1.获取注册中心的group参数 ，默认为/dubbo , 并未root赋予group值

2.zkClient = zookeeperTransporter.connect(url); 链接zookeeper信息并添加状态监听事件，具体再更文详述吧，代码如下：

public ZkclientZookeeperClient(URL url) { super(url); client = new ZkClient(url.getBackupAddress()); client.subscribeStateChanges(new IZkStateListener() { @Override public void handleStateChanged(KeeperState state) throws Exception { ZkclientZookeeperClient.this.state = state; if (state == KeeperState.Disconnected) { stateChanged(StateListener.DISCONNECTED); } else if (state == KeeperState.SyncConnected) { stateChanged(StateListener.CONNECTED); } } @Override public void handleNewSession() throws Exception { stateChanged(StateListener.RECONNECTED); } });}

3.添加重连状态的状态监听事件 调用 recover()方法。

至此 ZookeeperRegistry创建完毕。

ZookeeperRegistryFactory中最后将registry放入 ZookeeperRegistryFactory.REGISTRIES中

key 为zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService

value 为之前创建的ZookeeperRegistry对象。

接着返回RegistryProtocol 的export方法 ，

1.上面说到了调用doLocalExport(originInvoker);进行服务暴露的过程及调用getRegistry(originInvoker)方法通过ZookeeperRegistryFactory 工厂生成 ZookeeperRegistry 方法，然后加入到工厂REGISTRIES 缓存中，并返回ZookeeperRegistry 实例的过程。

2.接下来RegistryProtocol 的export方法中调用 final URL registedProviderUrl = getRegistedProviderUrl(originInvoker); 获取服务提供者的URL信息 ， 它是从注册中心的URL中获得export参数对应的值转换的URL信息。（去除掉不需要在注册中心上看到的字段）

3.接下来调用registry.register(registedProviderUrl); 进行服务的注册将暴露的服务信息注册到注册中心，并且将已经注册的服务URL缓存到ZookeeperRegistry.registered 已注册服务的缓存中。

FailbackRegistry.register/** * 进行服务注册逻辑的实现 */@Overridepublic void register(URL url) { if (destroyed.get()){ return; } // 调用AbstractRegistry.register进行服务对应URL的缓存 super.register(url); failedRegistered.remove(url); failedUnregistered.remove(url); try { // 向服务器端发送注册请求，将服务注册到注册中心，可以使用各个注册协议(注册中心)的实现 此处使用zookeeper ZookeeperRegistry.doRegister doRegister(url); } catch (Exception e) { Throwable t = e; // 如果开启了启动时检测，则直接抛出异常 boolean check = getUrl().getParameter(Constants.CHECK_KEY, true) && url.getParameter(Constants.CHECK_KEY, true) && !Constants.CONSUMER_PROTOCOL.equals(url.getProtocol()); boolean skipFailback = t instanceof SkipFailbackWrapperException; if (check || skipFailback) { if (skipFailback) { t = t.getCause(); } throw new IllegalStateException("Failed to register " + url + " to registry " + getUrl().getAddress() + ", cause: " + t.getMessage(), t); } else { logger.error("Failed to register " + url + ", waiting for retry, cause: " + t.getMessage(), t); } // 将失败的注册请求记录到失败列表，定时重试 failedRegistered.add(url); }}AbstractRegistry.registerpublic void register(URL url) { if (url == null) { throw new IllegalArgumentException("register url == null"); } if (logger.isInfoEnabled()) { logger.info("Register: " + url); } // 缓存已经注册的服务 registered.add(url);}ZookeeperRegistry.doRegisterprotected void doRegister(URL url) { try { // 此处为具体服务暴露的代码 toUrlPath 根据URL生成写入zk的路径信息 zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true)); } catch (Throwable e) { throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e); }}

4.由registryProviderUrl获取overrideSubscribeUrl 再构建OverrideListener