Dubbo之架构源码公共知识-拓冰建站

1.ScopeModel

抽象这三个能力是为了实现 Dubbo 的多实例支持，FrameworkModel 是实现类似 JVM 租户级别的隔离，ApplicationModel 是为了实现一个机器上发布多个应用（如 demo-application1 和 demo-application2 一起发布），ModuleModel 是为了实现服务生命周期的独立管理（如一个 demo-application 可以由多个 Spring 容器共同提供）。

public class ModuleModel extends ScopeModel {private final ScopeModel parent;private final ExtensionScope scope;public ScopeModel(ScopeModel parent, ExtensionScope scope, boolean isInternal) {this.parent = parent;this.scope = scope;this.internalScope = isInternal;}protected void initialize() {this.extensionDirector = new ExtensionDirector(parent != null ? parent.getExtensionDirector() : null, scope, this);this.extensionDirector.addExtensionPostProcessor(new ScopeModelAwareExtensionProcessor(this));}
}

1.1.FrameworkModel

public class FrameworkModel extends ScopeModel {public FrameworkModel() {super(null, ExtensionScope.FRAMEWORK, false);...initialize();}@Overrideprotected void initialize() {super.initialize();TypeDefinitionBuilder.initBuilders(this);serviceRepository = new FrameworkServiceRepository(this);// 获取 ScopeModelInitializer 类型的扩展类ExtensionLoader<ScopeModelInitializer> initializerExtensionLoader = this.getExtensionLoader(ScopeModelInitializer.class);Set<ScopeModelInitializer> initializers = initializerExtensionLoader.getSupportedExtensionInstances();for (ScopeModelInitializer initializer : initializers) {initializer.initializeFrameworkModel(this);}// 将当前类作为 ApplicationModel 的父类internalApplicationModel = new ApplicationModel(this, true);internalApplicationModel.getApplicationConfigManager().setApplication(new ApplicationConfig(internalApplicationModel, CommonConstants.DUBBO_INTERNAL_APPLICATION));internalApplicationModel.setModelName(CommonConstants.DUBBO_INTERNAL_APPLICATION);}
}

1.2.ApplicationModel

public class ApplicationModel extends ScopeModel {public ApplicationModel(FrameworkModel frameworkModel, boolean isInternal) {super(frameworkModel, ExtensionScope.APPLICATION, isInternal);this.frameworkModel = frameworkModel;frameworkModel.addApplication(this);initialize();}@Overrideprotected void initialize() {super.initialize();// 将当前类作为 ModuleModel 的父类internalModule = new ModuleModel(this, true);this.serviceRepository = new ServiceRepository(this);// 加载 ApplicationInitListener类型 的扩展类ExtensionLoader<ApplicationInitListener> extensionLoader = this.getExtensionLoader(ApplicationInitListener.class);Set<String> listenerNames = extensionLoader.getSupportedExtensions();for (String listenerName : listenerNames) {extensionLoader.getExtension(listenerName).init();}initApplicationExts();// 加载 ScopeModelInitializer类型的 扩展类ExtensionLoader<ScopeModelInitializer> initializerExtensionLoader = this.getExtensionLoader(ScopeModelInitializer.class);Set<ScopeModelInitializer> initializers = initializerExtensionLoader.getSupportedExtensionInstances();for (ScopeModelInitializer initializer : initializers) {// 马上执行扩展类的核心方法initializer.initializeApplicationModel(this);}}
}

1.3.ModuleModel

public class ModuleModel extends ScopeModel {public ModuleModel(ApplicationModel applicationModel, boolean isInternal) {super(applicationModel, ExtensionScope.MODULE, isInternal);this.applicationModel = applicationModel;applicationModel.addModule(this, isInternal);initialize();}@Overrideprotected void initialize() {super.initialize();this.serviceRepository = new ModuleServiceRepository(this);this.moduleConfigManager = new ModuleConfigManager(this);this.moduleConfigManager.initialize();initModuleExt();// 加载 ScopeModelInitializer类型的扩展类ExtensionLoader<ScopeModelInitializer> initializerExtensionLoader = this.getExtensionLoader(ScopeModelInitializer.class);Set<ScopeModelInitializer> initializers = initializerExtensionLoader.getSupportedExtensionInstances();for (ScopeModelInitializer initializer : initializers) {// 马上执行扩展类的核心方法initializer.initializeModuleModel(this);}}
}

2.ExtensionAccessor

利用Spi机制获取扩展类都是通过当前类先获取ExtensionLoader，后续通过ExtensionLoader加载对应的扩展类。

获取ExtensionLoader存在两种方式：

通过ExtensionDirector直接获取。
通过ExtensionAccessor间接获取。这种方式其实是通过ScopeModel间接获取到ExtensionDirector，其目的是利用ScopeModel初始化ExtensionDirector的parent属性。

如果是通过 ScopeModel 的子类获取扩展类，则必然是通过第二种方式获取ExtensionLoader。

public interface ExtensionAccessor {// 由 ExtensionDirector 以及 ScopeModel 类实现该方法ExtensionDirector getExtensionDirector();default <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {return this.getExtensionDirector().getExtensionLoader(type);}//支持获取特定name对应的扩展类default <T> T getExtension(Class<T> type, String name) {ExtensionLoader<T> extensionLoader = getExtensionLoader(type);return extensionLoader != null ? extensionLoader.getExtension(name) : null;}default <T> T getAdaptiveExtension(Class<T> type) {ExtensionLoader<T> extensionLoader = getExtensionLoader(type);return extensionLoader != null ? extensionLoader.getAdaptiveExtension() : null;}default <T> T getDefaultExtension(Class<T> type) {ExtensionLoader<T> extensionLoader = getExtensionLoader(type);return extensionLoader != null ? extensionLoader.getDefaultExtension() : null;}}

内部方法参数type类型必须是被@SPI注解的类。

FrameworkModel、ApplicationModel、ModuleModel三者抽象父类ScopeModel实现了方法：

public interface ExtensionAccessor {ExtensionDirector getExtensionDirector();
}

2.1.ExtensionDirector

ExtensionDirector的作用其实就是获取扩展类的加载器ExtensionLoader。其实任何方式得到的扩展类的加载器都是ExtensionLoader，唯一的区别就是parent属性赋值与否。

ExtensionScope的取值涉及：FRAMEWORK、APPLICATION、MODULE、SELF。

public class ExtensionDirector implements ExtensionAccessor {public <T> ExtensionLoader<T> getExtensionLoader(Class<T> type) {...// 1. find in local cacheExtensionLoader<T> loader = (ExtensionLoader<T>) extensionLoadersMap.get(type);ExtensionScope scope = extensionScopeMap.get(type);if (scope == null) {SPI annotation = type.getAnnotation(SPI.class);scope = annotation.scope();extensionScopeMap.put(type, scope);}// 如果 type 的scope范围是SELF，则直接返回 ExtensionLoader，并不需要考虑 属性parent的功能if (loader == null && scope == ExtensionScope.SELF) {// create an instance in self scopeloader = createExtensionLoader0(type);}// 2. find in parentif (loader == null) {// 条件成立的条件是：必须是通过ScopeModel子类触发的扩展类加载if (this.parent != null) {// 递归的方式loader = this.parent.getExtensionLoader(type);}}// 3. create itif (loader == null) {loader = createExtensionLoader(type);}return loader;}
}