Dubbo源码学习--服务是如何发布的

ServiceBean

ServiceBean 实现ApplicationListener接口监听ContextRefreshedEvent事件(容器加载完成事件)

    public void onApplicationEvent(ApplicationEvent event) {
        if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
        	if (isDelay() && ! isExported() && ! isUnexported()) {
                if (logger.isInfoEnabled()) {
                    logger.info("The service ready on spring started. service: " + getInterface());
                }
                export();
            }
        }

在容器加载完成后执行export(); 开始暴露

ServiceConfig 类

方法执行顺序：export() -> doExport() -> doExportUrls() -> doExportUrlsFor1Protocol();

export() 判断是否延迟发布，如果延迟发布会新建个Daemon线程然后调用doExport(), 否则直接调用doExport()；

doExport() 给ServiceConfig 装载注册中心监控中心等。

doExportUrls()

   private void doExportUrls() {
        List<URL> registryURLs = loadRegistries(true);
        for (ProtocolConfig protocolConfig : protocols) {
            doExportUrlsFor1Protocol(protocolConfig, registryURLs);
        }
    }

执行loadRegistries()遍历注册中心，根据注册中心、Dubbo版本、Pid等生成要发布的URL;
URL示例： zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=ordercenter_serviceImpl
&dubbo=2.8.4&pid=15836&registry=zookeeper&timestamp=1484018365125
遍历服务协议，为每个协议执行doExportUrlsFor1Protocol()

doExportUrlsFor1Protocol()

Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
Exporter<?> exporter = protocol.export(invoker);

创建 Invoker
调用 protocol.export() 将Invoker 转换成Exporter

DubboProtocol类

方法执行顺序：export() -> openServer() ->createServer()

createServer() 通过Exchangers.bind() 创建 ExchangeServer

RegistryProtocol类

DubboProtocol export() 执行完成后最终返回上层包装类 RegistryProtocol类

RegistryProtocol export() 进行服务注册和变更订阅

    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        //export invoker
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
        //registry provider
        final Registry registry = getRegistry(originInvoker);
        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);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
        //....
    }