前言：Dubbo捐献给Apache后，已有一段时间，以前粗略看过2.5.4版的源码（官网现在好像已经找不到这个版本），现在重新研究下Dubbo源码并记录下，由于英文水平待提高，主要结合 中文官方文档 和源码。
Dubbo 服务导出过程始于 Spring 容器发布刷新事件，Dubbo 在接收到事件后，会立即执行服务导出逻辑。整个逻辑大致可分为三个部分：
第一部分是前置工作，主要用于检查参数，组装 URL。
第二部分是导出服务，包含导出服务到本地 (JVM)，和导出服务到远程两个过程。
第三部分是向注册中心注册服务，用于服务发现。
服务导出的入口类是 ServiceBean,入口方法onApplicationEvent。
public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware, ApplicationEventPublisherAware { private static final long serialVersionUID = 213195494150089726L; private final transient Service service; private transient ApplicationContext applicationContext; private transient String beanName; private transient boolean supportedApplicationListener; private ApplicationEventPublisher applicationEventPublisher; public ServiceBean() { super(); this.service = null; } public ServiceBean(Service service) { super(service); this.service = service; } @Override public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext; SpringExtensionFactory.addApplicationContext(applicationContext); supportedApplicationListener = addApplicationListener(applicationContext, this); } @Override public void setBeanName(String name) { this.beanName = name; } /** * Gets associated {@link Service} * * @return associated {@link Service} */ public Service getService() { return service; } @Override public void onApplicationEvent(ContextRefreshedEvent event) { if (!isExported() && !isUnexported()) { if (logger.isInfoEnabled()) { logger.info("The service ready on spring started. service: " + getInterface()); } export(); } } @Override @SuppressWarnings({"unchecked", "deprecation"}) 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 (CollectionUtils.isEmptyMap(protocolConfigMap) && providerConfigMap.size() > 1) { // backward compatibility List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>(); for (ProviderConfig config : providerConfigMap.values()) { if (config.isDefault() != null && config.isDefault()) { providerConfigs.add(config); } } if (!providerConfigs.isEmpty()) { setProviders(providerConfigs); } } else { ProviderConfig providerConfig = null; for (ProviderConfig config : providerConfigMap.values()) { if (config.isDefault() == null || config.isDefault()) { 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 (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()) { if (moduleConfig != null) { throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config); } moduleConfig = config; } } if (moduleConfig != null) { setModule(moduleConfig); } } } if (StringUtils.isEmpty(getRegistryIds())) { if (getApplication() != null && StringUtils.isNotEmpty(getApplication().getRegistryIds())) { setRegistryIds(getApplication().getRegistryIds()); } if (getProvider() != null && StringUtils.isNotEmpty(getProvider().getRegistryIds())) { setRegistryIds(getProvider().getRegistryIds()); } } if ((CollectionUtils.isEmpty(getRegistries())) && (getProvider() == null || CollectionUtils.isEmpty(getProvider().getRegistries())) && (getApplication() == null || CollectionUtils.isEmpty(getApplication().getRegistries()))) { Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false); if (CollectionUtils.isNotEmptyMap(registryConfigMap)) { List<RegistryConfig> registryConfigs = new ArrayList<>(); if (StringUtils.isNotEmpty(registryIds)) { Arrays.stream(COMMA_SPLIT_PATTERN.split(registryIds)).forEach(id -> { if (registryConfigMap.containsKey(id)) { registryConfigs.add(registryConfigMap.get(id)); } }); } if (registryConfigs.isEmpty()) { for (RegistryConfig config : registryConfigMap.values()) { if (StringUtils.isEmpty(registryIds)) { registryConfigs.add(config); } } } if (!registryConfigs.isEmpty()) { super.setRegistries(registryConfigs); } } } if (getMetadataReportConfig() == null) { Map<String, MetadataReportConfig> metadataReportConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MetadataReportConfig.class, false, false); if (metadataReportConfigMap != null && metadataReportConfigMap.size() == 1) { super.setMetadataReportConfig(metadataReportConfigMap.values().iterator().next()); } else if (metadataReportConfigMap != null && metadataReportConfigMap.size() > 1) { throw new IllegalStateException("Multiple MetadataReport configs: " + metadataReportConfigMap); } } if (getConfigCenter() == null) { Map<String, ConfigCenterConfig> configenterMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ConfigCenterConfig.class, false, false); if (configenterMap != null && configenterMap.size() == 1) { super.setConfigCenter(configenterMap.values().iterator().next()); } else if (configenterMap != null && configenterMap.size() > 1) { throw new IllegalStateException("Multiple ConfigCenter found:" + configenterMap); } } 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()) { if (monitorConfig != null) { throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config); } monitorConfig = config; } } if (monitorConfig != null) { setMonitor(monitorConfig); } } } if (getMetrics() == null) { Map<String, MetricsConfig> metricsConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MetricsConfig.class, false, false); if (metricsConfigMap != null && metricsConfigMap.size() > 0) { MetricsConfig metricsConfig = null; for (MetricsConfig config : metricsConfigMap.values()) { if (metricsConfig != null) { throw new IllegalStateException("Duplicate metrics configs: " + metricsConfig + " and " + config); } metricsConfig = config; } if (metricsConfig != null) { setMetrics(metricsConfig); } } } if (StringUtils.isEmpty(getProtocolIds())) { if (getProvider() != null && StringUtils.isNotEmpty(getProvider().getProtocolIds())) { setProtocolIds(getProvider().getProtocolIds()); } } if (CollectionUtils.isEmpty(getProtocols()) && (getProvider() == null || CollectionUtils.isEmpty(getProvider().getProtocols()))) { 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>(); if (StringUtils.isNotEmpty(getProtocolIds())) { Arrays.stream(COMMA_SPLIT_PATTERN.split(getProtocolIds())) .forEach(id -> { if (protocolConfigMap.containsKey(id)) { protocolConfigs.add(protocolConfigMap.get(id)); } }); } if (protocolConfigs.isEmpty()) { for (ProtocolConfig config : protocolConfigMap.values()) { if (StringUtils.isEmpty(protocolIds)) { protocolConfigs.add(config); } } } if (!protocolConfigs.isEmpty()) { super.setProtocols(protocolConfigs); } } } if (StringUtils.isEmpty(getPath())) { if (StringUtils.isNotEmpty(beanName) && StringUtils.isNotEmpty(getInterface()) && beanName.startsWith(getInterface())) { setPath(beanName); } } if (!supportedApplicationListener) { export(); } } /** * Get the name of {@link ServiceBean} * * @return {@link ServiceBean}'s name * @since 2.6.5 */ public String getBeanName() { return this.beanName; } /** * @since 2.6.5 */ @Override public void export() { super.export(); // Publish ServiceBeanExportedEvent publishExportEvent(); } /** * @since 2.6.5 */ private void publishExportEvent() { ServiceBeanExportedEvent exportEvent = new ServiceBeanExportedEvent(this); applicationEventPublisher.publishEvent(exportEvent); } @Override public void destroy() throws Exception { // no need to call unexport() here, see // org.apache.dubbo.config.spring.extension.SpringExtensionFactory.ShutdownHookListener } // merged from dubbox @Override protected Class getServiceClass(T ref) { if (AopUtils.isAopProxy(ref)) { return AopUtils.getTargetClass(ref); } return super.getServiceClass(ref); } /** * @param applicationEventPublisher * @since 2.6.5 */ @Override public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) { this.applicationEventPublisher = applicationEventPublisher; } }
export 方法：开始导出服务
doExport方法：真正开始导出服务
private void doExportUrls() {
List<URL> registryURLs = loadRegistries(true);
for (ProtocolConfig protocolConfig : protocols) {
String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
// ProviderModel 表示服务提供者模型，此对象中存储了与服务提供者相关的信息。
// 比如服务的配置信息，服务实例等。每个被导出的服务对应一个 ProviderModel。
// ApplicationModel 持有所有的 ProviderModel。
ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
ApplicationModel.initProviderModel(pathKey, providerModel);
doExportUrlsFor1Protocol(protocolConfig, registryURLs);
}
}
loadRegistries作用：1.检测是否存在注册中心配置类，不存在则抛出异常 2.构建参数映射集合，也就是 map 3.构建注册中心链接列表 4.遍历链接列表，并根据条件决定是否将其添加到 registryList 中
protected List<URL> loadRegistries(boolean provider) { // check && override if necessary List<URL> registryList = new ArrayList<URL>(); if (CollectionUtils.isNotEmpty(registries)) { for (RegistryConfig config : registries) { String address = config.getAddress(); if (StringUtils.isEmpty(address)) { address = ANYHOST_VALUE; } if (!RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(address)) { Map<String, String> map = new HashMap<String, String>(); appendParameters(map, application); appendParameters(map, config); map.put(PATH_KEY, RegistryService.class.getName()); appendRuntimeParameters(map); if (!map.containsKey(PROTOCOL_KEY)) { map.put(PROTOCOL_KEY, DUBBO_PROTOCOL); } List<URL> urls = UrlUtils.parseURLs(address, map); for (URL url : urls) { url = URLBuilder.from(url) .addParameter(REGISTRY_KEY, url.getProtocol()) .setProtocol(REGISTRY_PROTOCOL) .build(); if ((provider && url.getParameter(REGISTER_KEY, true)) || (!provider && url.getParameter(SUBSCRIBE_KEY, true))) { registryList.add(url); } } } } } return registryList; }
doExportUrlsFor1Protocol：当前协议导出
Dubbo服务注册是基于URL驱动的，该方法前半段是组装URL,后半段才是导出Dubbo服务。
private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) { String name = protocolConfig.getName(); if (StringUtils.isEmpty(name)) { name = DUBBO; } Map<String, String> map = new HashMap<String, String>(); map.put(SIDE_KEY, PROVIDER_SIDE); appendRuntimeParameters(map); appendParameters(map, metrics); appendParameters(map, application); appendParameters(map, module); // remove 'default.' prefix for configs from ProviderConfig // appendParameters(map, provider, Constants.DEFAULT_KEY); appendParameters(map, provider); appendParameters(map, protocolConfig); appendParameters(map, this); if (CollectionUtils.isNotEmpty(methods)) { for (MethodConfig method : methods) { appendParameters(map, method, method.getName()); String retryKey = method.getName() + ".retry"; if (map.containsKey(retryKey)) { String retryValue = map.remove(retryKey); if (Boolean.FALSE.toString().equals(retryValue)) { map.put(method.getName() + ".retries", "0"); } } List<ArgumentConfig> arguments = method.getArguments(); if (CollectionUtils.isNotEmpty(arguments)) { for (ArgumentConfig argument : arguments) { // convert argument type if (argument.getType() != null && argument.getType().length() > 0) { Method[] methods = interfaceClass.getMethods(); // visit all methods if (methods != null && methods.length > 0) { for (int i = 0; i < methods.length; i++) { String methodName = methods[i].getName(); // target the method, and get its signature if (methodName.equals(method.getName())) { Class<?>[] argtypes = methods[i].getParameterTypes(); // one callback in the method 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 attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType()); } } else { // multiple callbacks in the method 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 attribute 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_KEY, generic); map.put(METHODS_KEY, ANY_VALUE); } else { String revision = Version.getVersion(interfaceClass, version); if (revision != null && revision.length() > 0) { map.put(REVISION_KEY, revision); } String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames(); if (methods.length == 0) { logger.warn("No method found in service interface " + interfaceClass.getName()); map.put(METHODS_KEY, ANY_VALUE); } else { map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ",")); } } if (!ConfigUtils.isEmpty(token)) { if (ConfigUtils.isDefault(token)) { map.put(TOKEN_KEY, UUID.randomUUID().toString()); } else { map.put(TOKEN_KEY, token); } } // export service String host = this.findConfigedHosts(protocolConfig, registryURLs, map); Integer port = this.findConfigedPorts(protocolConfig, name, map); URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(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(SCOPE_KEY); // don't export when none is configured if (!SCOPE_NONE.equalsIgnoreCase(scope)) { // export to local if the config is not remote (export to remote only when config is remote) if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) { exportLocal(url); } // export to remote if the config is not local (export to local only when config is local) if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) { if (!isOnlyInJvm() && logger.isInfoEnabled()) { logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url); } if (CollectionUtils.isNotEmpty(registryURLs)) { for (URL registryURL : registryURLs) { //if protocol is only injvm ,not register if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) { continue; } url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY)); URL monitorUrl = loadMonitor(registryURL); if (monitorUrl != null) { url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString()); } if (logger.isInfoEnabled()) { logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL); } // For providers, this is used to enable custom proxy to generate invoker String proxy = url.getParameter(PROXY_KEY); if (StringUtils.isNotEmpty(proxy)) { registryURL = registryURL.addParameter(PROXY_KEY, proxy); } Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString())); DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this); Exporter<?> exporter = protocol.export(wrapperInvoker); exporters.add(exporter); } } else { Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, url); DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this); Exporter<?> exporter = protocol.export(wrapperInvoker); exporters.add(exporter); } /** * @since 2.7.0 * ServiceData Store */ MetadataReportService metadataReportService = null; if ((metadataReportService = getMetadataReportService()) != null) { metadataReportService.publishProvider(url); } } } this.urls.add(url); }
根据 url 中的 scope 参数决定服务导出方式，分别如下：1.scope = none，不导出服务 2.scope != remote，导出到本地 3.scope != local，导出到远程
不管是导出到本地，还是远程。进行服务导出之前，均需要先创建 Invoker，这是一个很重要的步骤。因此下面先来分析 Invoker 的创建过程。
Invoker 创建过程：在 Dubbo 中，Invoker 是一个非常重要的模型。在服务提供端，以及服务引用端均会出现 Invoker。Dubbo 官方文档中对 Invoker 进行了说明，这里引用一下。Invoker 是实体域，它是 Dubbo 的核心模型，其它模型都向它靠扰，或转换成它，它代表一个可执行体，可向它发起 invoke 调用，它有可能是一个本地的实现，也可能是一个远程的实现，也可能一个集群实现。
Invoker 是由 ProxyFactory 创建而来，Dubbo 默认的 ProxyFactory 实现类是 JavassistProxyFactory。(基于Dubbo的SPI动态适配)
public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) { // 为目标类创建 Wrapper final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type); // 创建匿名 Invoker 类对象，并实现 doInvoke 方法。 return new AbstractProxyInvoker<T>(proxy, type, url) { @Override protected Object doInvoke(T proxy, String methodName, Class<?>[] parameterTypes, Object[] arguments) throws Throwable { // 调用 Wrapper 的 invokeMethod 方法，invokeMethod 最终会调用目标方法 return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments); } }; }
Wrapper 是一个抽象类，仅可通过 getWrapper(Class) 方法创建子类。在创建 Wrapper 子类的过程中，子类代码生成逻辑会对 getWrapper 方法传入的 Class 对象进行解析，拿到诸如类方法，类成员变量等信息。以及生成 invokeMethod 方法代码和其他一些方法代码。代码生成完毕后，通过 Javassist 生成 Class 对象，最后再通过反射创建 Wrapper 实例。相关的代码如下：
public static Wrapper getWrapper(Class<?> c) { while (ClassGenerator.isDynamicClass(c)) c = c.getSuperclass(); if (c == Object.class) return OBJECT_WRAPPER; // 从缓存中获取 Wrapper 实例 Wrapper ret = WRAPPER_MAP.get(c); if (ret == null) { // 缓存未命中，创建 Wrapper ret = makeWrapper(c); // 写入缓存 WRAPPER_MAP.put(c, ret); } return ret; }
makeWrapper 方法
private static Wrapper makeWrapper(Class<?> c) { if (c.isPrimitive()) { throw new IllegalArgumentException("Can not create wrapper for primitive type: " + c); } String name = c.getName(); ClassLoader cl = ClassUtils.getClassLoader(c); StringBuilder c1 = new StringBuilder("public void setPropertyValue(Object o, String n, Object v){ "); StringBuilder c2 = new StringBuilder("public Object getPropertyValue(Object o, String n){ "); StringBuilder c3 = new StringBuilder("public Object invokeMethod(Object o, String n, Class[] p, Object[] v) throws " + InvocationTargetException.class.getName() + "{ "); c1.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }"); c2.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }"); c3.append(name).append(" w; try{ w = ((").append(name).append(")$1); }catch(Throwable e){ throw new IllegalArgumentException(e); }"); Map<String, Class<?>> pts = new HashMap<>(); // <property name, property types> Map<String, Method> ms = new LinkedHashMap<>(); // <method desc, Method instance> List<String> mns = new ArrayList<>(); // method names. List<String> dmns = new ArrayList<>(); // declaring method names. // get all public field. for (Field f : c.getFields()) { String fn = f.getName(); Class<?> ft = f.getType(); if (Modifier.isStatic(f.getModifiers()) || Modifier.isTransient(f.getModifiers())) { continue; } c1.append(" if( $2.equals("").append(fn).append("") ){ w.").append(fn).append("=").append(arg(ft, "$3")).append("; return; }"); c2.append(" if( $2.equals("").append(fn).append("") ){ return ($w)w.").append(fn).append("; }"); pts.put(fn, ft); } Method[] methods = c.getMethods(); // get all public method. boolean hasMethod = hasMethods(methods); if (hasMethod) { c3.append(" try{"); for (Method m : methods) { //ignore Object's method. if (m.getDeclaringClass() == Object.class) { continue; } String mn = m.getName(); c3.append(" if( "").append(mn).append("".equals( $2 ) "); int len = m.getParameterTypes().length; c3.append(" && ").append(" $3.length == ").append(len); boolean override = false; for (Method m2 : methods) { if (m != m2 && m.getName().equals(m2.getName())) { override = true; break; } } if (override) { if (len > 0) { for (int l = 0; l < len; l++) { c3.append(" && ").append(" $3[").append(l).append("].getName().equals("") .append(m.getParameterTypes()[l].getName()).append("")"); } } } c3.append(" ) { "); if (m.getReturnType() == Void.TYPE) { c3.append(" w.").append(mn).append('(').append(args(m.getParameterTypes(), "$4")).append(");").append(" return null;"); } else { c3.append(" return ($w)w.").append(mn).append('(').append(args(m.getParameterTypes(), "$4")).append(");"); } c3.append(" }"); mns.add(mn); if (m.getDeclaringClass() == c) { dmns.add(mn); } ms.put(ReflectUtils.getDesc(m), m); } c3.append(" } catch(Throwable e) { "); c3.append(" throw new java.lang.reflect.InvocationTargetException(e); "); c3.append(" }"); } c3.append(" throw new " + NoSuchMethodException.class.getName() + "("Not found method \""+$2+"\" in class " + c.getName() + "."); }"); // deal with get/set method. Matcher matcher; for (Map.Entry<String, Method> entry : ms.entrySet()) { String md = entry.getKey(); Method method = entry.getValue(); if ((matcher = ReflectUtils.GETTER_METHOD_DESC_PATTERN.matcher(md)).matches()) { String pn = propertyName(matcher.group(1)); c2.append(" if( $2.equals("").append(pn).append("") ){ return ($w)w.").append(method.getName()).append("(); }"); pts.put(pn, method.getReturnType()); } else if ((matcher = ReflectUtils.IS_HAS_CAN_METHOD_DESC_PATTERN.matcher(md)).matches()) { String pn = propertyName(matcher.group(1)); c2.append(" if( $2.equals("").append(pn).append("") ){ return ($w)w.").append(method.getName()).append("(); }"); pts.put(pn, method.getReturnType()); } else if ((matcher = ReflectUtils.SETTER_METHOD_DESC_PATTERN.matcher(md)).matches()) { Class<?> pt = method.getParameterTypes()[0]; String pn = propertyName(matcher.group(1)); c1.append(" if( $2.equals("").append(pn).append("") ){ w.").append(method.getName()).append("(").append(arg(pt, "$3")).append("); return; }"); pts.put(pn, pt); } } c1.append(" throw new " + NoSuchPropertyException.class.getName() + "("Not found property \""+$2+"\" field or setter method in class " + c.getName() + "."); }"); c2.append(" throw new " + NoSuchPropertyException.class.getName() + "("Not found property \""+$2+"\" field or setter method in class " + c.getName() + "."); }"); // make class long id = WRAPPER_CLASS_COUNTER.getAndIncrement(); ClassGenerator cc = ClassGenerator.newInstance(cl); cc.setClassName((Modifier.isPublic(c.getModifiers()) ? Wrapper.class.getName() : c.getName() + "$sw") + id); cc.setSuperClass(Wrapper.class); cc.addDefaultConstructor(); cc.addField("public static String[] pns;"); // property name array. cc.addField("public static " + Map.class.getName() + " pts;"); // property type map. cc.addField("public static String[] mns;"); // all method name array. cc.addField("public static String[] dmns;"); // declared method name array. for (int i = 0, len = ms.size(); i < len; i++) { cc.addField("public static Class[] mts" + i + ";"); } cc.addMethod("public String[] getPropertyNames(){ return pns; }"); cc.addMethod("public boolean hasProperty(String n){ return pts.containsKey($1); }"); cc.addMethod("public Class getPropertyType(String n){ return (Class)pts.get($1); }"); cc.addMethod("public String[] getMethodNames(){ return mns; }"); cc.addMethod("public String[] getDeclaredMethodNames(){ return dmns; }"); cc.addMethod(c1.toString()); cc.addMethod(c2.toString()); cc.addMethod(c3.toString()); try { Class<?> wc = cc.toClass(); // setup static field. wc.getField("pts").set(null, pts); wc.getField("pns").set(null, pts.keySet().toArray(new String[0])); wc.getField("mns").set(null, mns.toArray(new String[0])); wc.getField("dmns").set(null, dmns.toArray(new String[0])); int ix = 0; for (Method m : ms.values()) { wc.getField("mts" + ix++).set(null, m.getParameterTypes()); } return (Wrapper) wc.newInstance(); } catch (RuntimeException e) { throw e; } catch (Throwable e) { throw new RuntimeException(e.getMessage(), e); } finally { cc.release(); ms.clear(); mns.clear(); dmns.clear(); } }
导出服务到远程：Exporter<?> exporter = protocol.export(wrapperInvoker);
包含了服务导出与服务注册两个过程。这两个过程涉及到了大量的调用，比较复杂。按照代码执行顺序，本节先来分析服务导出逻辑，服务注册逻辑将在下一节进行分析。下面开始分析，我们把目光移动到 RegistryProtocol 的 export 方法上。
@Override public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException { // 获取注册中心 URL，以 zookeeper 注册中心为例，得到的示例 URL 如下： // zookeeper://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.2&export=dubbo%3A%2F%2F172.17.48.52%3A20880%2Fcom.alibaba.dubbo.demo.DemoService%3Fanyhost%3Dtrue%26application%3Ddemo-provider URL registryUrl = getRegistryUrl(originInvoker); URL providerUrl = getProviderUrl(originInvoker); // 获取订阅 URL，比如： // provider://172.17.48.52:20880/com.alibaba.dubbo.demo.DemoService?category=configurators&check=false&anyhost=true&application=demo-provider&dubbo=2.0.2&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl); // 创建监听器 final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker); overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener); providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener); // 导出服务 final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl); // 根据 URL 加载 Registry 实现类，比如 ZookeeperRegistry final Registry registry = getRegistry(originInvoker); // 获取已注册的服务提供者 URL，比如： // dubbo://172.17.48.52:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.2&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl); ProviderInvokerWrapper<T> providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registeredProviderUrl); /// 根据 register 的值决定是否注册服务 boolean register = registeredProviderUrl.getParameter("register", true); if (register) { // 向注册中心注册服务 register(registryUrl, registeredProviderUrl); providerInvokerWrapper.setReg(true); } // 向注册中心进行订阅 override 数据 registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener); exporter.setRegisterUrl(registeredProviderUrl); exporter.setSubscribeUrl(overrideSubscribeUrl); // 创建并返回 DestroyableExporter return new DestroyableExporter<>(exporter); }
doLocalExport 方法的逻辑
private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker, URL providerUrl) { String key = getCacheKey(originInvoker); return (ExporterChangeableWrapper<T>) bounds.computeIfAbsent(key, s -> { Invoker<?> invokerDelegate = new InvokerDelegate<>(originInvoker, providerUrl);
//此处的 protocol 变量会在运行时加载 DubboProtocol，并调用 DubboProtocol 的 export 方法 return new ExporterChangeableWrapper<>((Exporter<T>) protocol.export(invokerDelegate), originInvoker); }); }
DubboProtocol的export逻辑
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException { URL url = invoker.getUrl(); // 获取服务标识，理解成服务坐标也行。由服务组名，服务名，服务版本号以及端口组成。比如： // demoGroup/com.alibaba.dubbo.demo.DemoService:1.0.1:20880 String key = serviceKey(url); // 创建 DubboExporter DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap); // 将 <key, exporter> 键值对放入缓存中 exporterMap.put(key, exporter); // 本地存根相关代码 Boolean isStubSupportEvent = url.getParameter(STUB_EVENT_KEY, DEFAULT_STUB_EVENT); Boolean isCallbackservice = url.getParameter(IS_CALLBACK_SERVICE, false); if (isStubSupportEvent && !isCallbackservice) { String stubServiceMethods = url.getParameter(STUB_EVENT_METHODS_KEY); if (stubServiceMethods == null || stubServiceMethods.length() == 0) { if (logger.isWarnEnabled()) { logger.warn(new IllegalStateException("consumer [" + url.getParameter(INTERFACE_KEY) + "], has set stubproxy support event ,but no stub methods founded.")); } } else { stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods); } } // 启动服务器 openServer(url); //优化系列化 optimizeSerialization(url); return exporter; }
DubboExporter 的创建以及 openServer 方法逻辑
private void openServer(URL url) { // 获取 host:port，并将其作为服务器实例的 key，用于标识当前的服务器实例 String key = url.getAddress(); boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true); if (isServer) { // 访问缓存 ExchangeServer server = serverMap.get(key); if (server == null) { // 创建服务器实例 serverMap.put(key, createServer(url)); } else { // 服务器已创建，则根据 url 中的配置重置服务器 server.reset(url); } } }
在同一台机器上（单网卡），同一个端口上仅允许启动一个服务器实例。若某个端口上已有服务器实例，此时则调用 reset 方法重置服务器的一些配置
createServer方法逻辑：三个核心的逻辑。第一是检测是否存在 server 参数所代表的 Transporter 拓展，不存在则抛出异常。第二是创建服务器实例。第三是检测是否支持 client 参数所表示的 Transporter 拓展，不存在也是抛出异常。
private ExchangeServer createServer(URL url) { url = URLBuilder.from(url) // 服务器关闭时发送readonly事件，默认情况下启用 .addParameterIfAbsent(CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString()) // 添加心跳检测配置到 url 中 .addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT)) // 添加编码解码器参数 .addParameter(CODEC_KEY, DubboCodec.NAME) .build(); //获取 server 参数，默认为 netty String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER); // 通过 SPI 检测是否存在 server 参数所代表的 Transporter 拓展，不存在则抛出异常 if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) { throw new RpcException("Unsupported server type: " + str + ", url: " + url); } ExchangeServer server; try { // 创建 ExchangeServer server = Exchangers.bind(url, requestHandler); } catch (RemotingException e) { throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e); } str = url.getParameter(CLIENT_KEY); if (str != null && str.length() > 0) { // 获取所有的 Transporter 实现类名称集合，比如 supportedTypes = [netty, mina] Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(); // 检测当前 Dubbo 所支持的 Transporter 实现类名称列表中， // 是否包含 client 所表示的 Transporter，若不包含，则抛出异常 if (!supportedTypes.contains(str)) { throw new RpcException("Unsupported client type: " + str); } } return server; }
bind逻辑
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); }
getExchanger逻辑：Exchanger的自定扩展点
public static Exchanger getExchanger(URL url) { String type = url.getParameter(Constants.EXCHANGER_KEY, Constants.DEFAULT_EXCHANGER); return getExchanger(type); } public static Exchanger getExchanger(String type) { return ExtensionLoader.getExtensionLoader(Exchanger.class).getExtension(type); }
HeaderExchanger.bind绑定逻辑
@Override public ExchangeServer bind(URL url, ExchangeHandler handler) throws RemotingException { return new HeaderExchangeServer(Transporters.bind(url, new DecodeHandler(new HeaderExchangeHandler(handler)))); }
Transporters.bind绑定逻辑
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 { // 如果 handlers 元素数量大于1，则创建 ChannelHandler 分发器 handler = new ChannelHandlerDispatcher(handlers); } // 获取自适应 Transporter 实例，并调用实例方法 return getTransporter().bind(url, handler); }
getTransporter() 方法获取的 Transporter 是在运行时动态创建的，类名为 TransporterAdaptive，也就是自适应拓展类。TransporterAdaptive 会在运行时根据传入的 URL 参数决定加载什么类型的 Transporter，默认为 NettyTransporter。
public Server bind(URL url, ChannelHandler listener) throws RemotingException { return new NettyServer(url, listener); }
NettyServer的构造：构造NettyServer
public class NettyServer extends AbstractServer implements Server { public NettyServer(URL url, ChannelHandler handler) throws RemotingException { // 调用父类构造方法 super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME))); } } public abstract class AbstractServer extends AbstractEndpoint implements Server { public AbstractServer(URL url, ChannelHandler handler) throws RemotingException { // 调用父类构造方法，这里就不用跟进去了，没什么复杂逻辑 super(url, handler); localAddress = getUrl().toInetSocketAddress(); // 获取 ip 和端口 String bindIp = getUrl().getParameter(Constants.BIND_IP_KEY, getUrl().getHost()); int bindPort = getUrl().getParameter(Constants.BIND_PORT_KEY, getUrl().getPort()); if (url.getParameter(Constants.ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(bindIp)) { // 设置 ip 为 0.0.0.0 bindIp = NetUtils.ANYHOST; } bindAddress = new InetSocketAddress(bindIp, bindPort); // 获取最大可接受连接数 this.accepts = url.getParameter(Constants.ACCEPTS_KEY, Constants.DEFAULT_ACCEPTS); this.idleTimeout = url.getParameter(Constants.IDLE_TIMEOUT_KEY, Constants.DEFAULT_IDLE_TIMEOUT); try { // 调用模板方法 doOpen 启动服务器 doOpen(); } catch (Throwable t) { throw new RemotingException("Failed to bind "); } DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension(); executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort())); } protected abstract void doOpen() throws Throwable; protected abstract void doClose() throws Throwable; }
doOpen 抽象方法，该方法需要子类（NettyServer ）实现：熟悉Netty这段代码应该不难
protected void doOpen() throws Throwable { NettyHelper.setNettyLoggerFactory(); // 创建 boss 和 worker 线程池 ExecutorService boss = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerBoss", true)); ExecutorService worker = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerWorker", true)); ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS)); // 创建 ServerBootstrap bootstrap = new ServerBootstrap(channelFactory); final NettyHandler nettyHandler = new NettyHandler(getUrl(), this); channels = nettyHandler.getChannels(); bootstrap.setOption("child.tcpNoDelay", true); // 设置 PipelineFactory bootstrap.setPipelineFactory(new ChannelPipelineFactory() { @Override public ChannelPipeline getPipeline() { NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this); ChannelPipeline pipeline = Channels.pipeline(); pipeline.addLast("decoder", adapter.getDecoder()); pipeline.addLast("encoder", adapter.getEncoder()); pipeline.addLast("handler", nettyHandler); return pipeline; } }); // 绑定到指定的 ip 和端口上 channel = bootstrap.bind(getBindAddress()); }
注意下：dubbo 默认使用的 NettyServer 是基于 netty 3.x 版本实现的，比较老了。因此 Dubbo 另外提供了 netty 4.x 版本的 NettyServer
服务导出的过程就基本结束
服务注册流程：服务注册操作对于 Dubbo 来说不是必需的，通过服务直连的方式就可以绕过注册中心。但通常我们不会这么做，直连方式不利于服务治理，仅推荐在测试服务时使用。对于 Dubbo 来说，注册中心虽不是必需，但却是必要的。
默认 Zookeeper 注册中心作为分析目标。下面从服务注册的入口方法开始分析，我们把目光再次移到 RegistryProtocol 的 export 方法上。
register(registryUrl, registeredProviderUrl) 逻辑
public void register(URL registryUrl, URL registedProviderUrl) { // 获取 Registry Registry registry = registryFactory.getRegistry(registryUrl); // 注册服务 registry.register(registedProviderUrl); }
registryFactory.getRegistry(registryUrl)：方法由 AbstractRegistryFactory 实现
public Registry getRegistry(URL url) { url = url.setPath(RegistryService.class.getName()) .addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName()) .removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY); String key = url.toServiceString(); LOCK.lock(); try { // 访问缓存 Registry registry = REGISTRIES.get(key); if (registry != null) { return registry; } // 缓存未命中，创建 Registry 实例 registry = createRegistry(url); if (registry == null) { throw new IllegalStateException("Can not create registry..."); } // 写入缓存 REGISTRIES.put(key, registry); return registry; } finally { LOCK.unlock(); } }
createRegistry逻辑：ZookeeperRegistryFactory 实现
public class ZookeeperRegistryFactory extends AbstractRegistryFactory { private ZookeeperTransporter zookeeperTransporter; /** * Invisible injection of zookeeper client via IOC/SPI * @param zookeeperTransporter */ public void setZookeeperTransporter(ZookeeperTransporter zookeeperTransporter) { this.zookeeperTransporter = zookeeperTransporter; } @Override public Registry createRegistry(URL url) { return new ZookeeperRegistry(url, zookeeperTransporter); } }
new ZookeeperRegistry（***）代码实现：创建zk注册
public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) { super(url); if (url.isAnyHost()) { throw new IllegalStateException("registry address == null"); } // 获取组名，默认为 dubbo String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT); if (!group.startsWith(Constants.PATH_SEPARATOR)) { // group = "/" + group group = Constants.PATH_SEPARATOR + group; } this.root = group; // 创建 Zookeeper 客户端，默认为 CuratorZookeeperTransporter zkClient = zookeeperTransporter.connect(url); // 添加状态监听器 zkClient.addStateListener(new StateListener() { @Override public void stateChanged(int state) { if (state == RECONNECTED) { try { recover(); } catch (Exception e) { logger.error(e.getMessage(), e); } } } }); }
zookeeperTransporter 类型为自适应拓展类，因此 connect 方法会在被调用时决定加载什么类型的 ZookeeperTransporter 拓展，默认为 CuratorZookeeperTransporter
Curator：对zk操作的框架
public class CuratorZookeeperClient extends AbstractZookeeperClient<CuratorWatcher> { private final CuratorFramework client; public CuratorZookeeperClient(URL url) { super(url); try { // 创建 CuratorFramework 构造器 CuratorFrameworkFactory.Builder builder = CuratorFrameworkFactory.builder() .connectString(url.getBackupAddress()) .retryPolicy(new RetryNTimes(1, 1000)) .connectionTimeoutMs(5000); String authority = url.getAuthority(); if (authority != null && authority.length() > 0) { builder = builder.authorization("digest", authority.getBytes()); } // 构建 CuratorFramework 实例 client = builder.build(); // 添加监听器 client.getConnectionStateListenable().addListener(new ConnectionStateListener() { @Override public void stateChanged(CuratorFramework client, ConnectionState state) { if (state == ConnectionState.LOST) { CuratorZookeeperClient.this.stateChanged(StateListener.DISCONNECTED); } else if (state == ConnectionState.CONNECTED) { CuratorZookeeperClient.this.stateChanged(StateListener.CONNECTED); } else if (state == ConnectionState.RECONNECTED) { CuratorZookeeperClient.this.stateChanged(StateListener.RECONNECTED); } } }); // 启动客户端 client.start(); } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } }
再回到RegistryProtocol中的register方法
registry.register方法：方法定义在 FailbackRegistry 抽象类
public void register(URL url) { super.register(url); failedRegistered.remove(url); failedUnregistered.remove(url); try { // 模板方法，由子类实现 doRegister(url); } catch (Exception e) { Throwable t = e; // 获取 check 参数，若 check = true 将会直接抛出异常 boolean check = getUrl().getParameter(Constants.CHECK_KEY, true) && url.getParameter(Constants.CHECK_KEY, true) && !Constants.CONSUMER_PROTOCOL.equals(url.getProtocol()); boolean skipFailback = t instanceof SkipFailbackWrapperException; if (check || skipFailback) { if (skipFailback) { t = t.getCause(); } throw new IllegalStateException("Failed to register"); } else { logger.error("Failed to register"); } // 记录注册失败的链接 failedRegistered.add(url); } }
doRegister方法：zk注册
public void doRegister(URL url) { try { zkClient.create(toUrlPath(url), url.getParameter(DYNAMIC_KEY, true)); } catch (Throwable e) { throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e); } }
create 方法：zk客户端的代码
public void create(String path, boolean ephemeral) { if (!ephemeral) { // 如果要创建的节点类型非临时节点，那么这里要检测节点是否存在 if (checkExists(path)) { return; } } int i = path.lastIndexOf('/'); if (i > 0) { // 递归创建上一级路径 create(path.substring(0, i), false); } // 根据 ephemeral 的值创建临时或持久节点 if (ephemeral) { createEphemeral(path); } else { createPersistent(path); } }
服务注册整个过程可简单总结为：先创建注册中心实例，之后再通过注册中心实例注册服务。
节点创建后再zk中体现：通过 Zookeeper 可视化客户端 ZooInspector 查看节点数据
