//from MockClusterInvoker
public Result invoke(Invocation invocation) throws RpcException {
        Result result = null;
        //獲取方法級(jí)別mock配置
        String value = directory.getUrl().getMethodParameter(invocation.getMethodName(), Constants.MOCK_KEY, Boolean.FALSE.toString()).trim();
        //沒(méi)有配置 或者 =false
        if (value.length() == 0 || value.equalsIgnoreCase("false")) {
            //no mock
            result = this.invoker.invoke(invocation);
        } else if (value.startsWith("force")) {
            // force 開(kāi)頭 強(qiáng)制進(jìn)行mock
            if (logger.isWarnEnabled()) {
                logger.warn("force-mock: " + invocation.getMethodName() + " force-mock enabled , url : " + directory.getUrl());
            }
            //force:direct mock
            result = doMockInvoke(invocation, null);
        } else {
            //不是force的話 是失敗了再進(jìn)行mock
            //fail-mock
            try {
                result = this.invoker.invoke(invocation);
            } catch (RpcException e) {
                //如果是業(yè)務(wù)異常不進(jìn)行mock
                if (e.isBiz()) {
                    throw e;
                }
                if (logger.isWarnEnabled()) {
                    logger.warn("fail-mock: " + invocation.getMethodName() + " fail-mock enabled , url : " + directory.getUrl(), e);
                }
                result = doMockInvoke(invocation, e);
            }
        }
        return result;
    }

//from DemoServiceComponent
@Reference(mock = "force:return null",check = false)
private DemoService demoService;

//from ProtocolFilterWrapper
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);
}

//from RegistryDirectory
private void refreshInvoker(List<URL> invokerUrls) {
        Assert.notNull(invokerUrls, "invokerUrls should not be null");
        //這邊為什么是一個(gè)，針對(duì)沒(méi)有提供者目錄，dubbo框架會(huì)自動(dòng)返回一個(gè)empty的url
        if (invokerUrls.size() == 1
                && invokerUrls.get(0) != null
                && Constants.EMPTY_PROTOCOL.equals(invokerUrls.get(0).getProtocol())) {
            this.forbidden = true; // Forbid to access
            this.invokers = Collections.emptyList();
            routerChain.setInvokers(this.invokers);
            destroyAllInvokers(); // Close all invokers
        }
        //...
}
public List<Invoker<T>> doList(Invocation invocation) {
        if (forbidden) {
            // 1. No service provider 2. Service providers are disabled
            throw new RpcException(RpcException.FORBIDDEN_EXCEPTION, "No provider available from registry " +
                    getUrl().getAddress() + " for service " + getConsumerUrl().getServiceKey() + " on consumer " +
                    NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() +
                    ", please check status of providers(disabled, not registered or in blacklist).");
        }
        //...
}