dubbo原理系列2-reference代理生成过程

来源：互联网发布：grpc javascript 编辑：程序博客网时间：2024/06/14 01:19

这篇文章主要介绍dubbo消费者调用dubbo服务时，服务端代理类（在消费侧实际调用的是dubbo服务的代理类）生成的过程。

开始吧。

入口依然在DubboNamespaceHandler，如果想知道为什么会进入这里，你可以去了解下spring的NamespaceHandler。

public class DubboNamespaceHandler extends NamespaceHandlerSupport {    static {        Version.checkDuplicate(DubboNamespaceHandler.class);    }    public void init() {        registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));        registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));        registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));        registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));        registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));        registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));        registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));        registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));        registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));        registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));    }}

重点在这一行

registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));

先解释个疑问，在如下分析的流程代码，以及上一篇梳理
ServiceBean的代码逻辑，你会在AnnotationBean中也可以看到，不用奇怪，AnnotationBean是另一种配置方式，spring中配置后，会自动解析。

言归正传。

ReferenceBean的afterPropertiesSet方法

ReferenceBean实现了InitializingBean接口，那么spring容器加载该类的时候，会触发执行afterPropertiesSet执行

   public void afterPropertiesSet() throws Exception {     ...     Boolean b = isInit();        if (b == null && getConsumer() != null) {            b = getConsumer().isInit();        }        if (b != null && b.booleanValue()) {            getObject();        }   }

前面好多代码多是做校验与检查，重点看getObject方法

  public Object getObject() throws Exception {        return get();    }

  public synchronized T get() {        if (destroyed){            throw new IllegalStateException("Already destroyed!");        }        if (ref == null) {            init();        }        return ref;    }

 private void init() { ...    //attributes通过系统context进行存储.     StaticContext.getSystemContext().putAll(attributes);     ref = createProxy(map);}

核心方法

private T createProxy(Map<String, String> map) {        URL tmpUrl = new URL("temp", "localhost", 0, map);        final boolean isJvmRefer;        if (isInjvm() == null) {            if (url != null && url.length() > 0) { //指定URL的情况下，不做本地引用                isJvmRefer = false;            } else if (InjvmProtocol.getInjvmProtocol().isInjvmRefer(tmpUrl)) {                //默认情况下如果本地有服务暴露，则引用本地服务.                isJvmRefer = true;            } else {                isJvmRefer = false;            }        } else {            isJvmRefer = isInjvm().booleanValue();        }        if (isJvmRefer) {            URL url = new URL(Constants.LOCAL_PROTOCOL, NetUtils.LOCALHOST, 0, interfaceClass.getName()).addParameters(map);            invoker = refprotocol.refer(interfaceClass, url);            if (logger.isInfoEnabled()) {                logger.info("Using injvm service " + interfaceClass.getName());            }        } else {            if (url != null && url.length() > 0) { // 用户指定URL，指定的URL可能是对点对直连地址，也可能是注册中心URL                String[] us = Constants.SEMICOLON_SPLIT_PATTERN.split(url);                if (us != null && us.length > 0) {                    for (String u : us) {                        URL url = URL.valueOf(u);                        if (url.getPath() == null || url.getPath().length() == 0) {                            url = url.setPath(interfaceName);                        }                        if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {                            urls.add(url.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));                        } else {                            urls.add(ClusterUtils.mergeUrl(url, map));                        }                    }                }            } else { // 通过注册中心配置拼装URL                List<URL> us = loadRegistries(false);                if (us != null && us.size() > 0) {                    for (URL u : us) {                        URL monitorUrl = loadMonitor(u);                        if (monitorUrl != null) {                            map.put(Constants.MONITOR_KEY, URL.encode(monitorUrl.toFullString()));                        }                        urls.add(u.addParameterAndEncoded(Constants.REFER_KEY, StringUtils.toQueryString(map)));                    }                }                if (urls == null || urls.size() == 0) {                    throw new IllegalStateException("No such any registry to reference " + interfaceName  + " on the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", please config <dubbo:registry address=\"...\" /> to your spring config.");                }            }            if (urls.size() == 1) {                invoker = refprotocol.refer(interfaceClass, urls.get(0));            } else {                List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();                URL registryURL = null;                for (URL url : urls) {                    invokers.add(refprotocol.refer(interfaceClass, url));                    if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {                        registryURL = url; // 用了最后一个registry url                    }                }                if (registryURL != null) { // 有 注册中心协议的URL                    // 对有注册中心的Cluster 只用 AvailableCluster                    URL u = registryURL.addParameter(Constants.CLUSTER_KEY, AvailableCluster.NAME);                     invoker = cluster.join(new StaticDirectory(u, invokers));                }  else { // 不是 注册中心的URL                    invoker = cluster.join(new StaticDirectory(invokers));                }            }        }        Boolean c = check;        if (c == null && consumer != null) {            c = consumer.isCheck();        }        if (c == null) {            c = true; // default true        }        if (c && ! invoker.isAvailable()) {            throw new IllegalStateException("Failed to check the status of the service " + interfaceName + ". No provider available for the service " + (group == null ? "" : group + "/") + interfaceName + (version == null ? "" : ":" + version) + " from the url " + invoker.getUrl() + " to the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());        }        if (logger.isInfoEnabled()) {            logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());        }        // 创建服务代理        return (T) proxyFactory.getProxy(invoker);    }

这里调用的两个方法要注意
第一个 refprotocol.refer(…)

这里写图片描述

默认是DubboProtocol

DubboProtocol的refer方法

    public <T> Invoker<T> refer(Class<T> serviceType, URL url) throws RpcException {        // create rpc invoker.        DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);        invokers.add(invoker);        return invoker;    }

看到这里实际放的是DubboInvoker，返回结果也就是Invoker，这个Invoker是dubbo对服务的抽象代理，那么在客户端调用服务方的接口方法的时候，实际触发的就是Invoker的invoke方法。

你肯定看到了DubboInvoker的构造函数中第三个参数getClients类型是ExchangeClient集合，也即是dubbo客户端和服务端连接的封装类

dubbo客户端与服务端连接的创建

 private ExchangeClient[] getClients(URL url){        //是否共享连接        boolean service_share_connect = false;        int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);        //如果connections不配置，则共享连接，否则每服务每连接        if (connections == 0){            service_share_connect = true;            connections = 1;        }        ExchangeClient[] clients = new ExchangeClient[connections];        for (int i = 0; i < clients.length; i++) {            if (service_share_connect){                clients[i] = getSharedClient(url);            } else {                clients[i] = initClient(url);            }        }        return clients;    }

默认是共享连接，会进入getSharedClient

   /**     *获取共享连接      */    private ExchangeClient getSharedClient(URL url){        String key = url.getAddress();        ReferenceCountExchangeClient client = referenceClientMap.get(key);        if ( client != null ){            if ( !client.isClosed()){                client.incrementAndGetCount();                return client;            } else {//                logger.warn(new IllegalStateException("client is closed,but stay in clientmap .client :"+ client));                referenceClientMap.remove(key);            }        }        ExchangeClient exchagneclient = initClient(url);        client = new ReferenceCountExchangeClient(exchagneclient, ghostClientMap);        referenceClientMap.put(key, client);        ghostClientMap.remove(key);        return client;     }

看看initClient方法

 private ExchangeClient initClient(URL url) {        // client type setting.        String str = url.getParameter(Constants.CLIENT_KEY, url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_CLIENT));        String version = url.getParameter(Constants.DUBBO_VERSION_KEY);        boolean compatible = (version != null && version.startsWith("1.0."));        url = url.addParameter(Constants.CODEC_KEY, Version.isCompatibleVersion() && compatible ? COMPATIBLE_CODEC_NAME : DubboCodec.NAME);        //默认开启heartbeat        url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));        // BIO存在严重性能问题，暂时不允许使用        if (str != null && str.length() > 0 && ! ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {            throw new RpcException("Unsupported client type: " + str + "," +                    " supported client type is " + StringUtils.join(ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(), " "));        }        ExchangeClient client ;        try {            //设置连接应该是lazy的             if (url.getParameter(Constants.LAZY_CONNECT_KEY, false)){                client = new LazyConnectExchangeClient(url ,requestHandler);            } else {                client = Exchangers.connect(url ,requestHandler);            }        } catch (RemotingException e) {            throw new RpcException("Fail to create remoting client for service(" + url                    + "): " + e.getMessage(), e);        }        return client;    }

Exchangers.connect(url ,requestHandler);这一行

  public static ExchangeClient connect(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).connect(url, handler);    }

    public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {        return new HeaderExchangeClient(Transporters.connect(url, new DecodeHandler(new HeaderExchangeHandler(handler))));    }

这里写图片描述

默认进入NettyTransporter的connect方法

 public Client connect(URL url, ChannelHandler listener) throws RemotingException {        return new NettyClient(url, listener);    }

NettyClient构造方法会依次调用doOpen方法，doConnect方法

NettyClient

  @Override    protected void doOpen() throws Throwable {        NettyHelper.setNettyLoggerFactory();        bootstrap = new ClientBootstrap(channelFactory);        // config        // @see org.jboss.netty.channel.socket.SocketChannelConfig        bootstrap.setOption("keepAlive", true);        bootstrap.setOption("tcpNoDelay", true);        bootstrap.setOption("connectTimeoutMillis", getTimeout());        final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {            public ChannelPipeline getPipeline() {                NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyClient.this);                ChannelPipeline pipeline = Channels.pipeline();                pipeline.addLast("decoder", adapter.getDecoder());                pipeline.addLast("encoder", adapter.getEncoder());                pipeline.addLast("handler", nettyHandler);                return pipeline;            }        });    }

doConnect

protected void doConnect() throws Throwable {        long start = System.currentTimeMillis();        ChannelFuture future = bootstrap.connect(getConnectAddress());        try{            boolean ret = future.awaitUninterruptibly(getConnectTimeout(), TimeUnit.MILLISECONDS);            if (ret && future.isSuccess()) {                Channel newChannel = future.getChannel();                newChannel.setInterestOps(Channel.OP_READ_WRITE);                try {                    // 关闭旧的连接                    Channel oldChannel = NettyClient.this.channel; // copy reference                    if (oldChannel != null) {                        try {                            if (logger.isInfoEnabled()) {                                logger.info("Close old netty channel " + oldChannel + " on create new netty channel " + newChannel);                            }                            oldChannel.close();                        } finally {                            NettyChannel.removeChannelIfDisconnected(oldChannel);                        }                    }                } finally {                    if (NettyClient.this.isClosed()) {                        try {                            if (logger.isInfoEnabled()) {                                logger.info("Close new netty channel " + newChannel + ", because the client closed.");                            }                            newChannel.close();                        } finally {                            NettyClient.this.channel = null;                            NettyChannel.removeChannelIfDisconnected(newChannel);                        }                    } else {                        NettyClient.this.channel = newChannel;                    }                }            } else if (future.getCause() != null) {                throw new RemotingException(this, "client(url: " + getUrl() + ") failed to connect to server "                        + getRemoteAddress() + ", error message is:" + future.getCause().getMessage(), future.getCause());            } else {                throw new RemotingException(this, "client(url: " + getUrl() + ") failed to connect to server "                        + getRemoteAddress() + " client-side timeout "                        + getConnectTimeout() + "ms (elapsed: " + (System.currentTimeMillis() - start) + "ms) from netty client "                        + NetUtils.getLocalHost() + " using dubbo version " + Version.getVersion());            }        }finally{            if (! isConnected()) {                future.cancel();            }        }    }

到此可看到使用netty创建了连接。

继续回到创建代理类ReferenceConfig的createProxy

这里写图片描述

会进入StubProxyFactoryWrapper的getProxy方法

StubProxyFactoryWrapper的getProxy方法

   @SuppressWarnings({ "unchecked", "rawtypes" })    public <T> T getProxy(Invoker<T> invoker) throws RpcException {        T proxy = proxyFactory.getProxy(invoker);        if (GenericService.class != invoker.getInterface()) {            String stub = invoker.getUrl().getParameter(Constants.STUB_KEY, invoker.getUrl().getParameter(Constants.LOCAL_KEY));            if (ConfigUtils.isNotEmpty(stub)) {                Class<?> serviceType = invoker.getInterface();                if (ConfigUtils.isDefault(stub)) {                    if (invoker.getUrl().hasParameter(Constants.STUB_KEY)) {                        stub = serviceType.getName() + "Stub";                    } else {                        stub = serviceType.getName() + "Local";                    }                }                try {                    Class<?> stubClass = ReflectUtils.forName(stub);                    if (! serviceType.isAssignableFrom(stubClass)) {                        throw new IllegalStateException("The stub implemention class " + stubClass.getName() + " not implement interface " + serviceType.getName());                    }                    try {                        Constructor<?> constructor = ReflectUtils.findConstructor(stubClass, serviceType);                        proxy = (T) constructor.newInstance(new Object[] {proxy});                        //export stub service                        URL url = invoker.getUrl();                        if (url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT)){                            url = url.addParameter(Constants.STUB_EVENT_METHODS_KEY, StringUtils.join(Wrapper.getWrapper(proxy.getClass()).getDeclaredMethodNames(), ","));                            url = url.addParameter(Constants.IS_SERVER_KEY, Boolean.FALSE.toString());                            try{                                export(proxy, (Class)invoker.getInterface(), url);                            }catch (Exception e) {                                LOGGER.error("export a stub service error.", e);                            }                        }                    } catch (NoSuchMethodException e) {                        throw new IllegalStateException("No such constructor \"public " + stubClass.getSimpleName() + "(" + serviceType.getName() + ")\" in stub implemention class " + stubClass.getName(), e);                    }                } catch (Throwable t) {                    LOGGER.error("Failed to create stub implemention class " + stub + " in consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", cause: " + t.getMessage(), t);                    // ignore                }            }        }        return proxy;    }

关注下这一行，后面你会有一个地方用到
url = url.addParameter(Constants.STUB_EVENT_METHODS_KEY, StringUtils.join(Wrapper.getWrapper(proxy.getClass()).getDeclaredMethodNames(), “,”));

调用export方法

 private <T> Exporter<T> export(T instance, Class<T> type, URL url) {        return protocol.export(proxyFactory.getInvoker(instance, type, url));    }

这里写图片描述

可见最终进入DubboProtocol的export方法

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {        URL url = invoker.getUrl();        // export service.        String key = serviceKey(url);        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);            }        }        openServer(url);        return exporter;    }

看看这一行，知道上面为啥要关注那一行了吧！
Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY,Constants.DEFAULT_STUB_EVENT);

所以走的 if (isStubSupportEvent && !isCallbackservice)里的逻辑，再后面逻辑就和之前一篇类似了。

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