Dubbo源代码分析（三）：Dubbo之服务端（Service）

如上图所看到的的Dubbo的暴露服务的过程，不难看出它也和消费者端非常像，也须要一个像reference的对象来维护service关联的全部对象及其属性。这里的reference就是provider。因为ServiceBean实现了



InitializingBean接口，全部在Spring实例化这个bean后会调用接口方法afterPropertiesSet：

public void afterPropertiesSet() throws Exception {
    	//假设没有配置provider
        if (getProvider() == null) {
        	//获取IOC容器里的全部provider
            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) { // 兼容旧版本号
                    List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
                    for (ProviderConfig config : providerConfigMap.values()) {
                        if (config.isDefault() != null && config.isDefault().booleanValue()) {
                            providerConfigs.add(config);
                        }
                    }
                    //关联全部providers
                    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);
                    }
                }
            }
        }
        //假设没有配置application，且没有配置provider
        if (getApplication() == null
                && (getProvider() == null || getProvider().getApplication() == null)) {
            //获取全部applications
        	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;
                    }
                }
                //关联application
                if (applicationConfig != null) {
                    setApplication(applicationConfig);
                }
            }
        }
        //假设没有配置module。且没有配置provider
        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;
                    }
                }
                //关联module
                if (moduleConfig != null) {
                    setModule(moduleConfig);
                }
            }
        }
        //假设没有配置registries。且没有配置provider
        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);
                    }
                }
                //关联registries
                if (registryConfigs != null && registryConfigs.size() > 0) {
                    super.setRegistries(registryConfigs);
                }
            }
        }
        //假设没有配置monitor，且没有配置provider
        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;
                    }
                }
                //关联monitor
                if (monitorConfig != null) {
                    setMonitor(monitorConfig);
                }
            }
        }
        //假设没有配置protocol，且没有配置provider
        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);
                    }
                }
                //关联protocol
                if (protocolConfigs != null && protocolConfigs.size() > 0) {
                    super.setProtocols(protocolConfigs);
                }
            }
        }
        //假设没有配置path
        if (getPath() == null || getPath().length() == 0) {
            if (beanName != null && beanName.length() > 0
                    && getInterface() != null && getInterface().length() > 0
                    && beanName.startsWith(getInterface())) {
                setPath(beanName);
            }
        }
        //暴露provider
        if (! isDelay()) {
            export();
        }
    }

Dubbo在确认了全部相关对象都配置后调用export方法開始暴露过程：

public synchronized void export() {
    	//假设provider没有配置
        if (provider != null) {
        	//假设exporter没有配置使用provider所关联的exporter
            if (export == null) {
                export = provider.getExport();
            }
            //假设delay（延迟暴露）没有配置，获取provider的delay
            if (delay == null) {
                delay = provider.getDelay();
            }
        }
        //假设不须要暴露接口则直接返回
        if (export != null && ! export.booleanValue()) {
            return;
        }
        //假设延迟暴露的时间（毫秒级）是存在的，开启线程并等待delay毫秒后開始暴露接口，否则直接运行暴露接口过程
        if (delay != null && delay > 0) {
            Thread thread = new Thread(new Runnable() {
                public void run() {
                    try {
                        Thread.sleep(delay);
                    } catch (Throwable e) {
                    }
                    doExport();
                }
            });
            thread.setDaemon(true);
            thread.setName("DelayExportServiceThread");
            thread.start();
        } else {
            doExport();
        }
    }

protected synchronized void doExport() {
    	//假设不须要暴露接口则抛出异常
        if (unexported) {
            throw new IllegalStateException("Already unexported!");
        }
        //假设已经暴露则不须要反复暴露
        if (exported) {
            return;
        }
        exported = true;
        //假设interfaceName没配置（这样dubbo就无法找到须要暴露的service对象）则抛出异常
        if (interfaceName == null || interfaceName.length() == 0) {
            throw new IllegalStateException("<dubbo:service interface=\"\" /> interface not allow null!");
        }
        checkDefault();
        //provider已经配置的情况下，假设application、module、registries、monitor、protocol中有未配置的均能够从provider获取
        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();
        }
        //假设是本地服务
        if(local !=null){
        	//假设是本地服务在interfaceName属性后面加上Local
            if(local=="true"){
                local=interfaceName+"Local";
            }
            Class<?> localClass;
            try {
            	//载入service
                localClass = ClassHelper.forNameWithThreadContextClassLoader(local);
            } catch (ClassNotFoundException e) {
                throw new IllegalStateException(e.getMessage(), e);
            }
            if(!interfaceClass.isAssignableFrom(localClass)){
                throw new IllegalStateException("The local implemention class " + localClass.getName() + " not implement interface " + interfaceName);
            }
        }
        //假设是远程服务
        if(stub !=null){
            if(stub=="true"){
                stub=interfaceName+"Stub";
            }
            Class<?> stubClass;
            try {
            	//载入service
                stubClass = ClassHelper.forNameWithThreadContextClassLoader(stub);
            } catch (ClassNotFoundException e) {
                throw new IllegalStateException(e.getMessage(), e);
            }
            if(!interfaceClass.isAssignableFrom(stubClass)){
                throw new IllegalStateException("The stub implemention class " + stubClass.getName() + " not implement interface " + interfaceName);
            }
        }
        //检查application
        checkApplication();
        //检查registries
        checkRegistry();
        //检查protocol
        checkProtocol();
        //将全部这些对象的属性关联到provider
        appendProperties(this);
        checkStubAndMock(interfaceClass);
        if (path == null || path.length() == 0) {
            path = interfaceName;
        }
        //暴露地址
        doExportUrls();
    }

private void doExportUrls() {
    	//将注冊的全部url匹配上相应的协议在服务端暴露出来
        List<URL> registryURLs = loadRegistries(true);
        for (ProtocolConfig protocolConfig : protocols) {
            doExportUrlsFor1Protocol(protocolConfig, registryURLs);
        }
    }

private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
        //假设没配置protocol则默认使用dubbo协议
    	String name = protocolConfig.getName();
        if (name == null || name.length() == 0) {
            name = "dubbo";
        }
        //获取主机地址
        String host = protocolConfig.getHost();
        if (provider != null && (host == null || host.length() == 0)) {
            host = provider.getHost();
        }
        boolean anyhost = false;
        if (NetUtils.isInvalidLocalHost(host)) {
            anyhost = true;
            try {
                host = InetAddress.getLocalHost().getHostAddress();
            } catch (UnknownHostException e) {
                logger.warn(e.getMessage(), e);
            }
            if (NetUtils.isInvalidLocalHost(host)) {
                if (registryURLs != null && registryURLs.size() > 0) {
                    for (URL registryURL : registryURLs) {
                        try {
                        	//创建socket，连接到注冊中心
                            Socket socket = new Socket();
                            try {
                                SocketAddress addr = new InetSocketAddress(registryURL.getHost(), registryURL.getPort());
                                socket.connect(addr, 1000);
                                //获取服务所在主机地址
                                host = socket.getLocalAddress().getHostAddress();
                                break;
                            } finally {
                                try {
                                    socket.close();
                                } catch (Throwable e) {}
                            }
                        } catch (Exception e) {
                            logger.warn(e.getMessage(), e);
                        }
                    }
                }
                if (NetUtils.isInvalidLocalHost(host)) {
                    host = NetUtils.getLocalHost();
                }
            }
        }
        //获取协议接口号
        Integer port = protocolConfig.getPort();
        if (provider != null && (port == null || port == 0)) {
            port = provider.getPort();
        }
        final int defaultPort = ExtensionLoader.getExtensionLoader(Protocol.class).getExtension(name).getDefaultPort();
        if (port == null || port == 0) {
            port = defaultPort;
        }
        if (port == null || port <= 0) {
            port = getRandomPort(name);
            if (port == null || port < 0) {
                port = NetUtils.getAvailablePort(defaultPort);
                putRandomPort(name, port);
            }
            logger.warn("Use random available port(" + port + ") for protocol " + name);
        }

        //获取application、module、provider、protocol、exporter、registries、monitor全部属性
        Map<String, String> map = new HashMap<String, String>();
        if (anyhost) {
            map.put(Constants.ANYHOST_KEY, "true");
        }
        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) {
                        //类型自己主动转换.
                        if(argument.getType() != null && argument.getType().length() >0){
                            Method[] methods = interfaceClass.getMethods();
                            //遍历全部方法
                            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();
        }
        //创建服务所在url
        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，则表示仅仅暴露远程服务)
            if (!Constants.SCOPE_REMOTE.toString().equalsIgnoreCase(scope)) {
            	//暴露的地址是localhost所以远端无法訪问
                exportLocal(url);
            }
            //假设配置不是local则暴露为远程服务.(配置为local，则表示仅仅暴露远程服务)
            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);
                        }
                        //获取invoker
                        Invoker<?

> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
                        //依据协议将invoker暴露成exporter，详细过程是创建一个ExchangeServer，它会绑定一个ServerSocket到配置端口
                        Exporter<?> exporter = protocol.export(invoker);
                        //将创建的exporter放进链表便于管理
                        exporters.add(exporter);
                    }
                } else {
                    Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url);

                    Exporter<?> exporter = protocol.export(invoker);
                    exporters.add(exporter);
                }
            }
        }
        this.urls.add(url);
    }

整个暴露服务的流程就是首先检查配置是否完整然后获取协议和port信息，通知registries自己已经注冊能够提供服务最后创建Server绑定port。这样用户就能够从配置的信息连接到Server并和Server通信远程调用方法了。