【知识库】--Dubbo ReferenceBean获取-- RegistryProtocol.Refer -- 源码过程（254）

看这里：上一篇文章介绍了ReferenceBean的获取过程，这里介绍如何根据registryUrl和RegistryFactory获取注册器，最终注册中心回调服务消费者暴露的回调接口，来对服务提供者的服务引用（refer），生成对应的可执行对象invoker。

1

@SuppressWarnings("unchecked")
private Invoker getClusterInvoker(List urls) {
    List> invokers = new ArrayList>();
    URL registryURL = null;
    for (URL url : urls) {
        invokers.add(refprotocol.refer(interfaceClass, url));//这里爆发
        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
        if (useUnitCluster()) {
            URL u = registryURL.addParameterIfAbsent(Constants.REGISTRY_KEY + "." + Constants.CLUSTER_KEY, FailfastCluster.NAME);
            return registryCluster.join(new UnitDirectory(u, invokers));
        } else {
            URL u = registryURL.addParameterIfAbsent(Constants.REGISTRY_KEY + "." + Constants.CLUSTER_KEY, AvailableCluster.NAME);
            return registryCluster.join(new StaticDirectory(u, invokers));
        }
    } else { // 不是 注册中心的URL
        return cluster.join(new StaticDirectory(invokers));
    }
}

2 看此方法

refprotocol.refer(interfaceClass, url)

其接口原型（com.alibaba.dubbo.rpc.Protocol）：

/**
 * 引用远程服务：

 * 1. 当用户调用refer()所返回的Invoker对象的invoke()方法时，协议需相应执行同URL远端export()传入的Invoker对象的invoke()方法。

 * 2. refer()返回的Invoker由协议实现，协议通常需要在此Invoker中发送远程请求。

 * 3. 当url中有设置check=false时，连接失败不能抛出异常，并内部自动恢复。

 * 
 * @param <T> 服务的类型
 * @param type 服务的类型
 * @param url 远程服务的URL地址
 * @return invoker 服务的本地代理
 * @throws RpcException 当连接服务提供方失败时抛出
 */
@Adaptive
<T> Invoker<T> refer(Class<T> type, URL url) throws RpcException;

仔细体会注释中的：refer()返回的Invoker由协议实现，协议通常需要在此Invoker中发送远程请求。

根据传入的url

registry://127.0.0.1:9098/com.alibaba.dubbo.registry.RegistryService?application=demo-consumer&dubbo=2.0.0&pid=2484&refer=application%3Ddemo-consumer%26dubbo%3D2.0.0%26interface%3Dcom.alibaba.dubbo.demo.DemoService%26methods%3DsayHello%26pid%3D2484%26side%3Dconsumer%26timestamp%3D1415879965901&registry=zookeeper×tamp=1415879990670

根据registry://协议 自适应到 com.alibaba.dubbo.registry.integration.RegistryProtocol 中的refer方法

@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
    url = url.setProtocol(url.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_REGISTRY)).removeParameter(Constants.REGISTRY_KEY);//重新设置协议--为了下一步获取注册器 默认 DEFAULT_REGISTRY = "dubbo"; 

    Registry registry = registryFactory.getRegistry(url);//此处获取可以自适应到 com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry 或者 默认 com.alibaba.dubbo.registry.dubbo.DubboRegistryFactory
    if (RegistryService.class.equals(type)) {
        return proxyFactory.getInvoker((T) registry, type, url);
    }

    // group="a,b" or group="*"
    Map, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(Constants.REFER_KEY));
    String group = qs.get(Constants.GROUP_KEY);
    if (group != null && group.length() > 0) {
        if ((Constants.COMMA_SPLIT_PATTERN.split(group)).length > 1
                || "*".equals(group)) {
            return doRefer(getMergeableCluster(), registry, type, url);
        }
    }
    return doRefer(cluster, registry, type, url);
}

经过上面url.setProtocol(...)方法后新的url 举例

zookeeper://127.0.0.1:9098/com.alibaba.dubbo.registry.RegistryService?application=demo-consumer&dubbo=2.0.0&pid=4524&refer=application%3Ddemo-consumer%26dubbo%3D2.0.0%26interface%3Dcom.alibaba.dubbo.demo.DemoService%26methods%3DsayHello%26pid%3D4524%26side%3Dconsumer%26timestamp%3D1415881461048×tamp=1415881461113 

3 根据自适应获取的注册中心ZookeeperRegistry，要获取的服务类型和重新设置协议后的url 获取服务类型

private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
    RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
    directory.setRegistry(registry);
    directory.setProtocol(protocol);
    URL subscribeUrl = new URL(Constants.CONSUMER_PROTOCOL, NetUtils.getLocalHost(), 0, type.getName(), directory.getUrl().
            removeParameter(Constants.CONSUMER_HOST_KEY).getParameters());
    if (!Constants.ANY_VALUE.equals(url.getServiceInterface())
            && url.getParameter(Constants.REGISTER_KEY, true)) {
        registry.register(subscribeUrl.addParameters(Constants.CATEGORY_KEY, Constants.CONSUMERS_CATEGORY, Constants.CHECK_KEY, String.valueOf(false)));
    }
    directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
            Constants.PROVIDERS_CATEGORY
                    + "," + Constants.CONFIGURATORS_CATEGORY
                    + "," + Constants.ROUTERS_CATEGORY));
    return cluster.join(directory);
}

4 构建引用服务的 subscribeUrl

consumer://10.5.24.221/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=consumers&check=false&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=8536&side=consumer×tamp=1415945205031 

5  构建目录服务 RegistryDirectory 另一文章再单独了解

6  构建订阅消费者订阅的 url  举例

directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
        Constants.PROVIDERS_CATEGORY
                + "," + Constants.CONFIGURATORS_CATEGORY
                + "," + Constants.ROUTERS_CATEGORY));

10.33.37.4 or 10.5.24.221 需要调试验证

consumer://10.33.37.4/com.alibaba.dubbo.demo.DemoService?application=demo-consumer&category=providers,configurators,routers&dubbo=2.0.0&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=9692&side=consumer×tamp=1415967547508 

7 注册中心 回调服务消费者暴露的回调接口来对服务供者的服务进行引用 ， refer 生成对应的可执行对象 invoker。服务供者与服务的消费建立连接

public void subscribe(URL url) {
    setConsumerUrl(url);
    registry.subscribe(url, this);
}

public synchronized void notify(List urls) {
    List invokerUrls = new ArrayList();
    List routerUrls = new ArrayList();
    List configuratorUrls = new ArrayList();

    for (URL url : urls) {
        String protocol = url.getProtocol();
        String category = url.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);
        if (Constants.ROUTERS_CATEGORY.equals(category) || Constants.ROUTE_PROTOCOL.equals(protocol)) {
            routerUrls.add(url);
        } else if (Constants.CONFIGURATORS_CATEGORY.equals(category) || Constants.OVERRIDE_PROTOCOL.equals(protocol)) {
            configuratorUrls.add(url);
        } else if (Constants.PROVIDERS_CATEGORY.equals(category)) {
            invokerUrls.add(url);
        } else {
            logger.warn("Unsupported category " + category + " in notified url: " + url + " from registry " + getUrl().getAddress() + " to consumer " + NetUtils.getLocalHost());
        }
    }

    // routers
    if (routerUrls.size() > 0) {
        List routers = toRouters(routerUrls);
        if (routers != null) { // null - do nothing
            setRouters(routers);
        }
    }

    // configurators
    if (configuratorUrls.size() > 0) {
        this.configurators = toConfigurators(configuratorUrls);
    }
    List localConfigurators = this.configurators; // local reference
    // 合并override参数
    this.overrideDirectoryUrl = directoryUrl;
    if (localConfigurators != null && localConfigurators.size() > 0) {
        for (Configurator configurator : localConfigurators) {
            this.overrideDirectoryUrl = configurator.configure(overrideDirectoryUrl);
        }
    }

    if (configuratorUrls.size() > 0) {
        logger.info("unconfigured directory url without provider params: " + this.directoryUrl
                + ", configured directory url without provider params: " + this.overrideDirectoryUrl);
    }

    // providers
    refreshInvoker(invokerUrls);
}

8 找到对应的服务提供者Invoker 举例

dubbo://10.33.37.4:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.5.4-SNAPSHOT&generic=false&interface=com.alibaba.dubbo.demo.DemoService&loadbalance=roundrobin&methods=sayHello&owner=william&pid=9828&side=provider×tamp=1415968955329