前言

dubbo实际上就是提供方将服务暴露出来，消费方找到服务进行调用。所以我们重点分析就是这两点，其他地方以后有时间再分析。

dubbo的启动

我们平常启动dubbo都是通过一个Main函数，这个函数是dubbo中内置的。

    public static void main(String[] args) {        try {            if (args == null || args.length == 0) {            //这里利用的是@SPI注解，返回的是spring                String config = ConfigUtils.getProperty(CONTAINER_KEY, loader.getDefaultExtensionName());                args = Constants.COMMA_SPLIT_PATTERN.split(config);            }            final List<Container> containers = new ArrayList<Container>();            for (int i = 0; i < args.length; i++) {            //这里返回的是SpringContainer                containers.add(loader.getExtension(args[i]));            }            logger.info("Use container type(" + Arrays.toString(args) + ") to run dubbo serivce.");            if ("true".equals(System.getProperty(SHUTDOWN_HOOK_KEY))) {                Runtime.getRuntime().addShutdownHook(new Thread() {                    public void run() {                        for (Container container : containers) {                            try {                                container.stop();                                logger.info("Dubbo " + container.getClass().getSimpleName() + " stopped!");                            } catch (Throwable t) {                                logger.error(t.getMessage(), t);                            }                            try {                                LOCK.lock();                                STOP.signal();                            } finally {                                LOCK.unlock();                            }                        }                    }                });            }            for (Container container : containers) {            //这里调用的是SpringContainer的start方法                container.start();                logger.info("Dubbo " + container.getClass().getSimpleName() + " started!");            }            System.out.println(new SimpleDateFormat("[yyyy-MM-dd HH:mm:ss]").format(new Date()) + " Dubbo service server started!");        } catch (RuntimeException e) {            e.printStackTrace();            logger.error(e.getMessage(), e);            System.exit(1);        }        try {            LOCK.lock();            STOP.await();        } catch (InterruptedException e) {            logger.warn("Dubbo service server stopped, interrupted by other thread!", e);        } finally {            LOCK.unlock();        }    }

  public void start() {        String configPath = ConfigUtils.getProperty(SPRING_CONFIG);        if (configPath == null || configPath.length() == 0) {            configPath = DEFAULT_SPRING_CONFIG;        }        //加载classpath*:META-INF/spring/*.xml路径下的xml文件        context = new ClassPathXmlApplicationContext(configPath.split("[,\\s]+"));        context.start();    }

ClassPathXmlApplicationContext这个是spring的内容了，前面我们分析过spring的流程，这里不再分析了。大概说下，这里就是加载dubbo的jar包中spring.schemas文件内容，这个文件又引用了dubbo.xsd，dubbo.xsd是用来校验xml配置的。

最重要的是spring.handlers中定义的DubboNamespaceHandler，这个是用来处理dubbo标签的。

DubboNamespaceHandler

DubboNamespaceHandler继承NamespaceHandlerSupport。这个是专门处理对应名称空间的，这个里面有个init方法。

 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));    }

是不是很眼熟了，这里就是注册处理不同dubbo标签的不同的类。我们这里只看下注册、暴露和发现。

ServiceBean

ServiceBean实现了很多接口，这里不多说，最重要的是其在最后调用的export方法。

 public void afterPropertiesSet() throws Exception {        if (getProvider() == null) {            Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);            if (providerConfigMap != null && providerConfigMap.size() > 0) {                Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);                if ((protocolConfigMap == null || protocolConfigMap.size() == 0)                        && providerConfigMap.size() > 1) {                     List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();                    for (ProviderConfig config : providerConfigMap.values()) {                        if (config.isDefault() != null && config.isDefault().booleanValue()) {                            providerConfigs.add(config);                        }                    }                    if (providerConfigs.size() > 0) {                        setProviders(providerConfigs);                    }                } else {                    ProviderConfig providerConfig = null;                    for (ProviderConfig config : providerConfigMap.values()) {                        if (config.isDefault() == null || config.isDefault().booleanValue()) {                            if (providerConfig != null) {                                throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);                            }                            providerConfig = config;                        }                    }                    if (providerConfig != null) {                        setProvider(providerConfig);                    }                }            }        }        if (getApplication() == null                && (getProvider() == null || getProvider().getApplication() == null)) {            Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class, false, false);            if (applicationConfigMap != null && applicationConfigMap.size() > 0) {                ApplicationConfig applicationConfig = null;                for (ApplicationConfig config : applicationConfigMap.values()) {                    if (config.isDefault() == null || config.isDefault().booleanValue()) {                        if (applicationConfig != null) {                            throw new IllegalStateException("Duplicate application configs: " + applicationConfig + " and " + config);                        }                        applicationConfig = config;                    }                }                if (applicationConfig != null) {                    setApplication(applicationConfig);                }            }        }        if (getModule() == null                && (getProvider() == null || getProvider().getModule() == null)) {            Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class, false, false);            if (moduleConfigMap != null && moduleConfigMap.size() > 0) {                ModuleConfig moduleConfig = null;                for (ModuleConfig config : moduleConfigMap.values()) {                    if (config.isDefault() == null || config.isDefault().booleanValue()) {                        if (moduleConfig != null) {                            throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config);                        }                        moduleConfig = config;                    }                }                if (moduleConfig != null) {                    setModule(moduleConfig);                }            }        }        if ((getRegistries() == null || getRegistries().size() == 0)                && (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().size() == 0)                && (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().size() == 0)) {            Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false);            if (registryConfigMap != null && registryConfigMap.size() > 0) {                List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>();                for (RegistryConfig config : registryConfigMap.values()) {                    if (config.isDefault() == null || config.isDefault().booleanValue()) {                        registryConfigs.add(config);                    }                }                if (registryConfigs != null && registryConfigs.size() > 0) {                    super.setRegistries(registryConfigs);                }            }        }        if (getMonitor() == null                && (getProvider() == null || getProvider().getMonitor() == null)                && (getApplication() == null || getApplication().getMonitor() == null)) {            Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class, false, false);            if (monitorConfigMap != null && monitorConfigMap.size() > 0) {                MonitorConfig monitorConfig = null;                for (MonitorConfig config : monitorConfigMap.values()) {                    if (config.isDefault() == null || config.isDefault().booleanValue()) {                        if (monitorConfig != null) {                            throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config);                        }                        monitorConfig = config;                    }                }                if (monitorConfig != null) {                    setMonitor(monitorConfig);                }            }        }        if ((getProtocols() == null || getProtocols().size() == 0)                && (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().size() == 0)) {            Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);            if (protocolConfigMap != null && protocolConfigMap.size() > 0) {                List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>();                for (ProtocolConfig config : protocolConfigMap.values()) {                    if (config.isDefault() == null || config.isDefault().booleanValue()) {                        protocolConfigs.add(config);                    }                }                if (protocolConfigs != null && protocolConfigs.size() > 0) {                    super.setProtocols(protocolConfigs);                }            }        }        if (getPath() == null || getPath().length() == 0) {            if (beanName != null && beanName.length() > 0                    && getInterface() != null && getInterface().length() > 0                    && beanName.startsWith(getInterface())) {                setPath(beanName);            }        }        if (!isDelay()) {            export();        }    }

export调用的是ServiceConfig的方法，这个方法最后有调用了doExport方法。

 public synchronized void export() {        if (provider != null) {            if (export == null) {                export = provider.getExport();            }            if (delay == null) {                delay = provider.getDelay();            }        }        if (export != null && !export) {            return;        }        if (delay != null && delay > 0) {            delayExportExecutor.schedule(new Runnable() {                public void run() {                    doExport();                }            }, delay, TimeUnit.MILLISECONDS);        } else {            doExport();        }    }

doExport方法最后又调用了doExportUrls方法。

  protected synchronized void doExport() {        if (unexported) {            throw new IllegalStateException("Already unexported!");        }        if (exported) {            return;        }        exported = true;        if (interfaceName == null || interfaceName.length() == 0) {            throw new IllegalStateException("<dubbo:service interface=\"\" /> interface not allow null!");        }        checkDefault();        if (provider != null) {            if (application == null) {                application = provider.getApplication();            }            if (module == null) {                module = provider.getModule();            }            if (registries == null) {                registries = provider.getRegistries();            }            if (monitor == null) {                monitor = provider.getMonitor();            }            if (protocols == null) {                protocols = provider.getProtocols();            }        }        if (module != null) {            if (registries == null) {                registries = module.getRegistries();            }            if (monitor == null) {                monitor = module.getMonitor();            }        }        if (application != null) {            if (registries == null) {                registries = application.getRegistries();            }            if (monitor == null) {                monitor = application.getMonitor();            }        }        if (ref instanceof GenericService) {            interfaceClass = GenericService.class;            if (StringUtils.isEmpty(generic)) {                generic = Boolean.TRUE.toString();            }        } else {            try {                interfaceClass = Class.forName(interfaceName, true, Thread.currentThread()                        .getContextClassLoader());            } catch (ClassNotFoundException e) {                throw new IllegalStateException(e.getMessage(), e);            }            checkInterfaceAndMethods(interfaceClass, methods);            checkRef();            generic = Boolean.FALSE.toString();        }        if (local != null) {            if ("true".equals(local)) {                local = interfaceName + "Local";            }            Class<?> localClass;            try {                localClass = ClassHelper.forNameWithThreadContextClassLoader(local);            } catch (ClassNotFoundException e) {                throw new IllegalStateException(e.getMessage(), e);            }            if (!interfaceClass.isAssignableFrom(localClass)) {                throw new IllegalStateException("The local implementation class " + localClass.getName() + " not implement interface " + interfaceName);            }        }        if (stub != null) {            if ("true".equals(stub)) {                stub = interfaceName + "Stub";            }            Class<?> stubClass;            try {                stubClass = ClassHelper.forNameWithThreadContextClassLoader(stub);            } catch (ClassNotFoundException e) {                throw new IllegalStateException(e.getMessage(), e);            }            if (!interfaceClass.isAssignableFrom(stubClass)) {                throw new IllegalStateException("The stub implementation class " + stubClass.getName() + " not implement interface " + interfaceName);            }        }        checkApplication();        checkRegistry();        checkProtocol();        appendProperties(this);        checkStubAndMock(interfaceClass);        if (path == null || path.length() == 0) {            path = interfaceName;        }        doExportUrls();    }

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

 private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {        String name = protocolConfig.getName();        if (name == null || name.length() == 0) {            name = "dubbo";        }        Map<String, String> map = new HashMap<String, String>();        map.put(Constants.SIDE_KEY, Constants.PROVIDER_SIDE);        map.put(Constants.DUBBO_VERSION_KEY, Version.getVersion());        map.put(Constants.TIMESTAMP_KEY, String.valueOf(System.currentTimeMillis()));        if (ConfigUtils.getPid() > 0) {            map.put(Constants.PID_KEY, String.valueOf(ConfigUtils.getPid()));        }        appendParameters(map, application);        appendParameters(map, module);        appendParameters(map, provider, Constants.DEFAULT_KEY);        appendParameters(map, protocolConfig);        appendParameters(map, this);        if (methods != null && methods.size() > 0) {            for (MethodConfig method : methods) {                appendParameters(map, method, method.getName());                String retryKey = method.getName() + ".retry";                if (map.containsKey(retryKey)) {                    String retryValue = map.remove(retryKey);                    if ("false".equals(retryValue)) {                        map.put(method.getName() + ".retries", "0");                    }                }                List<ArgumentConfig> arguments = method.getArguments();                if (arguments != null && arguments.size() > 0) {                    for (ArgumentConfig argument : arguments) {                        //类型自动转换.                        if (argument.getType() != null && argument.getType().length() > 0) {                            Method[] methods = interfaceClass.getMethods();                            //遍历所有方法                            if (methods != null && methods.length > 0) {                                for (int i = 0; i < methods.length; i++) {                                    String methodName = methods[i].getName();                                    //匹配方法名称，获取方法签名.                                    if (methodName.equals(method.getName())) {                                        Class<?>[] argtypes = methods[i].getParameterTypes();                                        //一个方法中单个callback                                        if (argument.getIndex() != -1) {                                            if (argtypes[argument.getIndex()].getName().equals(argument.getType())) {                                                appendParameters(map, argument, method.getName() + "." + argument.getIndex());                                            } else {                                                throw new IllegalArgumentException("argument config error : the index attribute and type attirbute not match :index :" + argument.getIndex() + ", type:" + argument.getType());                                            }                                        } else {                                            //一个方法中多个callback                                            for (int j = 0; j < argtypes.length; j++) {                                                Class<?> argclazz = argtypes[j];                                                if (argclazz.getName().equals(argument.getType())) {                                                    appendParameters(map, argument, method.getName() + "." + j);                                                    if (argument.getIndex() != -1 && argument.getIndex() != j) {                                                        throw new IllegalArgumentException("argument config error : the index attribute and type attirbute not match :index :" + argument.getIndex() + ", type:" + argument.getType());                                                    }                                                }                                            }                                        }                                    }                                }                            }                        } else if (argument.getIndex() != -1) {                            appendParameters(map, argument, method.getName() + "." + argument.getIndex());                        } else {                            throw new IllegalArgumentException("argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>");                        }                    }                }            } // end of methods for        }        if (ProtocolUtils.isGeneric(generic)) {            map.put("generic", generic);            map.put("methods", Constants.ANY_VALUE);        } else {            String revision = Version.getVersion(interfaceClass, version);            if (revision != null && revision.length() > 0) {                map.put("revision", revision);            }            String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();            if (methods.length == 0) {                logger.warn("NO method found in service interface " + interfaceClass.getName());                map.put("methods", Constants.ANY_VALUE);            } else {                map.put("methods", StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));            }        }        if (!ConfigUtils.isEmpty(token)) {            if (ConfigUtils.isDefault(token)) {                map.put("token", UUID.randomUUID().toString());            } else {                map.put("token", token);            }        }        if ("injvm".equals(protocolConfig.getName())) {            protocolConfig.setRegister(false);            map.put("notify", "false");        }        // 导出服务        String contextPath = protocolConfig.getContextpath();        if ((contextPath == null || contextPath.length() == 0) && provider != null) {            contextPath = provider.getContextpath();        }        String host = this.findConfigedHosts(protocolConfig, registryURLs, map);        Integer port = this.findConfigedPorts(protocolConfig, name, map);        URL url = new URL(name, host, port, (contextPath == null || contextPath.length() == 0 ? "" : contextPath + "/") + path, map);        if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)                .hasExtension(url.getProtocol())) {            url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)                    .getExtension(url.getProtocol()).getConfigurator(url).configure(url);        }        String scope = url.getParameter(Constants.SCOPE_KEY);        //配置为none不暴露        if (!Constants.SCOPE_NONE.toString().equalsIgnoreCase(scope)) {            //配置不是remote的情况下做本地暴露 (配置为remote，则表示只暴露远程服务)            if (!Constants.SCOPE_REMOTE.toString().equalsIgnoreCase(scope)) {                exportLocal(url);            }            //如果配置不是local则暴露为远程服务.(配置为local，则表示只暴露本地服务)            if (!Constants.SCOPE_LOCAL.toString().equalsIgnoreCase(scope)) {                if (logger.isInfoEnabled()) {                    logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);                }                if (registryURLs != null && registryURLs.size() > 0                        && url.getParameter("register", true)) {                    for (URL registryURL : registryURLs) {                        url = url.addParameterIfAbsent("dynamic", registryURL.getParameter("dynamic"));                        URL monitorUrl = loadMonitor(registryURL);                        if (monitorUrl != null) {                            url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());                        }                        if (logger.isInfoEnabled()) {                            logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);                        }                        Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));                        Exporter<?> exporter = protocol.export(invoker);                        exporters.add(exporter);                    }                } else {                    Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url);                    Exporter<?> exporter = protocol.export(invoker);                    exporters.add(exporter);                }            }        }        this.urls.add(url);    }

上述方法最后调用的是protocol.export。protocol就是dubbo中的各种协议。我们这里就看下dubbo协议。

export

 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;    }

最后调用了openServer方法。

openServer

    private void openServer(URL url) {        // find server.        String key = url.getAddress();        //client 也可以暴露一个只有server可以调用的服务。        boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true);        if (isServer) {            ExchangeServer server = serverMap.get(key);            if (server == null) {                serverMap.put(key, createServer(url));            } else {                //server支持reset,配合override功能使用                server.reset(url);            }        }

private ExchangeServer createServer(URL url) {        //默认开启server关闭时发送readonly事件        url = url.addParameterIfAbsent(Constants.CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString());        //默认开启heartbeat        url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));        String str = url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_SERVER);        if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str))            throw new RpcException("Unsupported server type: " + str + ", url: " + url);        url = url.addParameter(Constants.CODEC_KEY, DubboCodec.NAME);        ExchangeServer server;        try {            server = Exchangers.bind(url, requestHandler);        } catch (RemotingException e) {            throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);        }        str = url.getParameter(Constants.CLIENT_KEY);        if (str != null && str.length() > 0) {            Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();            if (!supportedTypes.contains(str)) {                throw new RpcException("Unsupported client type: " + str);            }        }        return server;

public static ExchangeServer bind(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).bind(url, handler);    }

 public static Exchanger getExchanger(String type) {        return ExtensionLoader.getExtensionLoader(Exchanger.class).getExtension(type);    }

这里又利用@SPI注解，这里使用了HeaderExchanger的bind方法。

       public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException {        return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler))));    }

     public static Server bind(URL url, ChannelHandler... handlers) throws RemotingException {        if (url == null) {            throw new IllegalArgumentException("url == null");        }        if (handlers == null || handlers.length == 0) {            throw new IllegalArgumentException("handlers == null");        }        ChannelHandler handler;        if (handlers.length == 1) {            handler = handlers[0];        } else {            handler = new ChannelHandlerDispatcher(handlers);        }        return getTransporter().bind(url, handler);    }

 public static Transporter getTransporter() {        return ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();    }

这里又利用@SPI注解，这里使用了netty的bind方法。

NettyTransporter的bind

     public Server bind(URL url, ChannelHandler listener) throws RemotingException {        return new NettyServer(url, listener);    }

到这里有比较熟悉了，这是netty的内容了。

所以到这里服务的发布流程大致比较清晰了，就是使用netty在指定端口监听，然后又请求时，找到具体实现类，根据反射调用方法返回。

最后

感谢你能看到最后，如有不对之处还请指正，觉得文章对你有帮助的话记得给我点个赞！