ApplicationContext ctx = new ClassPathXmlApplicationContext(new String[]{"classpath:motan_demo_client.xml"});        MotanDemoService service = (MotanDemoService) ctx.getBean("motanDemoReferer");

    <motan:registry regProtocol="zookeeper" name="registry" address="127.0.0.1:2181" connectTimeout="2000"/>    <!-- motan协议配置 -->    <motan:protocol default="true" name="motan" haStrategy="failover"                    loadbalance="roundrobin" maxClientConnection="10" minClientConnection="2"/>    <!-- 通用referer基础配置 -->    <motan:basicReferer requestTimeout="200" accessLog="false"                        retries="2" group="motan-demo-rpc" module="motan-demo-rpc"                        application="myMotanDemo" protocol="motan" registry="registry"                        id="motantestClientBasicConfig" throwException="false" check="true"/>    <!-- 具体referer配置。使用方通过beanid使用服务接口类 -->    <motan:referer id="motanDemoReferer"                   interface="com.weibo.motan.demo.service.MotanDemoService"                   connectTimeout="300" requestTimeout="300" basicReferer="motantestClientBasicConfig"/>

    public Object getRef()    {        if(ref == null)            initRef();//初始化        return ref;    }    public synchronized void initRef()    {        if(initialized.get())            return;        try        {            interfaceClass = Class.forName(interfaceClass.getName(), true, Thread.currentThread().getContextClassLoader());        }        catch(ClassNotFoundException e)        {            throw new MotanFrameworkException((new StringBuilder("ReferereConfig initRef Error: Class not found ")).append(interfaceClass.getName()).toString(), e, MotanErrorMsgConstant.FRAMEWORK_INIT_ERROR);        }        if(CollectionUtil.isEmpty(protocols))//protocol配置是否为空            throw new MotanFrameworkException(String.format("%s RefererConfig is malformed, for protocol not set correctly!", new Object[] {                interfaceClass.getName()            }));        checkInterfaceAndMethods(interfaceClass, methods);        clusterSupports = new ArrayList(protocols.size());//初始化集群支持类列表，可以支持多个        List clusters = new ArrayList(protocols.size());//初始化集群类列表，可以支持多个        String proxy = null;        ConfigHandler configHandler = (ConfigHandler)ExtensionLoader.getExtensionLoader(com/weibo/api/motan/config/handler/ConfigHandler).getExtension("default");//加载SimpleConfigHandler        List registryUrls = loadRegistryUrls();//加载注册中心url列表，可以支持多个注册中心        String localIp = getLocalHostAddress(registryUrls);        for(Iterator iterator = protocols.iterator(); iterator.hasNext();)        {            ProtocolConfig protocol = (ProtocolConfig)iterator.next();            LoggerUtil.info((new StringBuilder("ProtocolConfig‘s")).append(protocol.getName()).toString());            Map params = new HashMap();            params.put(URLParamType.nodeType.getName(), "referer");            params.put(URLParamType.version.getName(), URLParamType.version.getValue());            params.put(URLParamType.refreshTimestamp.getName(), String.valueOf(System.currentTimeMillis()));            collectConfigParams(params, new AbstractConfig[] {                protocol, basicReferer, extConfig, this            });            collectMethodConfigParams(params, getMethods());            URL refUrl = new URL(protocol.getName(), localIp, 0, interfaceClass.getName(), params);            ClusterSupport clusterSupport = createClusterSupport(refUrl, configHandler, registryUrls);            clusterSupports.add(clusterSupport);            clusters.add(clusterSupport.getCluster());            proxy = proxy != null ? proxy : refUrl.getParameter(URLParamType.proxy.getName(), URLParamType.proxy.getValue());        }        ref = configHandler.refer(interfaceClass, clusters, proxy);//调用SimpleConfigHandler的refer方法获取接口实现类        initialized.set(true);    }

    public <T> T refer(Class<T> interfaceClass, List<Cluster<T>> clusters, String proxyType) {        ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getExtension(proxyType);//创建代理工厂        return proxyFactory.getProxy(interfaceClass, new RefererInvocationHandler<T>(interfaceClass, clusters));//获取代理类    }public class JdkProxyFactory implements ProxyFactory {    @SuppressWarnings("unchecked")    public <T> T getProxy(Class<T> clz, InvocationHandler invocationHandler) {        return (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[] {clz}, invocationHandler);//使用jdk的动态代理，实际调用的代码是下面的的invoke方法    }}    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {        DefaultRequest request = new DefaultRequest();//封装通信用的request，request和response是在客户端和服务端通信的两个对象        request.setRequestId(RequestIdGenerator.getRequestId());        request.setArguments(args);        request.setMethodName(method.getName());        request.setParamtersDesc(ReflectUtil.getMethodParamDesc(method));        request.setInterfaceName(clz.getName());        request.setAttachment(URLParamType.requestIdFromClient.getName(), String.valueOf(RequestIdGenerator.getRequestIdFromClient()));        // 当 referer配置多个protocol的时候，比如A,B,C，        // 那么正常情况下只会使用A，如果A被开关降级，那么就会使用B，B也被降级，那么会使用C        for (Cluster<T> cluster : clusters) {//motan支持多个protocol的配置，也就是支持多个cluster，但是默认情况下只取第一个，如果前面的被降级，则取下一个            String protocolSwitcher = MotanConstants.PROTOCOL_SWITCHER_PREFIX + cluster.getUrl().getProtocol();            Switcher switcher = switcherService.getSwitcher(protocolSwitcher);            if (switcher != null && !switcher.isOn()) {                continue;            }            List<Referer<T>> referL = cluster.getReferers();//此段代码为我单独添加的，目的是证明客户端在配置多个注册中心的情况下，cluster可以支持跨注册中心的调用            for(Referer<T> refer : referL){                LoggerUtil.info(refer.getServiceUrl().getUri()+refer.getServiceUrl().getPath());            }            request.setAttachment(URLParamType.version.getName(), cluster.getUrl().getVersion());            request.setAttachment(URLParamType.clientGroup.getName(), cluster.getUrl().getGroup());            // 带上client的application和module            request.setAttachment(URLParamType.application.getName(), ApplicationInfo.getApplication(cluster.getUrl()).getApplication());            request.setAttachment(URLParamType.module.getName(), ApplicationInfo.getApplication(cluster.getUrl()).getModule());            Response response = null;            boolean throwException =                    Boolean.parseBoolean(cluster.getUrl().getParameter(URLParamType.throwException.getName(),                            URLParamType.throwException.getValue()));            try {                response = cluster.call(request);//调用cluster的call方法                return response.getValue();//获取返回信息            } catch (RuntimeException e) {                if (ExceptionUtil.isBizException(e)) {                    Throwable t = e.getCause();                    // 只抛出Exception，防止抛出远程的Error                    if (t != null && t instanceof Exception) {                        throw t;                    } else {                        String msg =                                t == null ? "biz exception cause is null" : ("biz exception cause is throwable error:" + t.getClass()                                        + ", errmsg:" + t.getMessage());                        throw new MotanServiceException(msg, MotanErrorMsgConstant.SERVICE_DEFAULT_ERROR);                    }                } else if (!throwException) {                    LoggerUtil.warn("RefererInvocationHandler invoke false, so return default value: uri=" + cluster.getUrl().getUri()                            + " " + MotanFrameworkUtil.toString(request), e);                    return getDefaultReturnValue(method.getReturnType());                } else {                    LoggerUtil.error(                            "RefererInvocationHandler invoke Error: uri=" + cluster.getUrl().getUri() + " "                                    + MotanFrameworkUtil.toString(request), e);                    throw e;                }            }        }        throw new MotanServiceException("Referer call Error: cluster not exist, interface=" + clz.getName() + " "                + MotanFrameworkUtil.toString(request), MotanErrorMsgConstant.SERVICE_UNFOUND);    }