Dubbo学习总结(十)dubbo服务暴露

悠悠 2024-02-19 15:41 21阅读 0赞

**服务暴露：**

spring在解析配置文件的时候将service标签解析成了ServiceBean类，该类实现了InitializingBean与ApplicationListener<ContextRefreshedEvent>接口，并且实现了其中的方法，用户服务暴露。

public interface InitializingBean {
    
    
    	void afterPropertiesSet() throws Exception;
    
    }

该方法在解析完service标签后会进行回调该方法。

public interface ApplicationListener<E extends ApplicationEvent> extends EventListener {
    
    
    	void onApplicationEvent(E event);
    
    }

该方法实在springIOC容器刷新完成/所有对象都创建完成进行调用。

ServiceBean实现：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70][]

afterPropertiesSet():

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 1][]

该方法就是把从配置文件解析出来的数据保存起来。

onApplicationEvent方法用来进行服务暴露：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 2][]

首先获取注册中心：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 3][]

通过动态代理（com.alibaba.dubbo.rpc.ProxyFactory）获取需要注册的属性：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 4][]

然后同时不同的协议启动服务，向注册中心注册服务。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 5][]

DubboProtocol:

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(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) {
                // 省略日志打印代码
            } else {
                stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
            }
        }
    
        // 启动服务器
        openServer(url);
        // 优化序列化
        optimizeSerialization(url);
        return exporter;
    }

启动netty服务。

RegistryProtocol：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        // 导出服务
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
    
        // 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);
    
        // 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(originInvoker);
    
        // 获取 register 参数
        boolean register = registeredProviderUrl.getParameter("register", true);
    
        // 向服务提供者与消费者注册表中注册服务提供者
        ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registeredProviderUrl);
    
        // 根据 register 的值决定是否注册服务
        if (register) {
            // 向注册中心注册服务
            register(registryUrl, registeredProviderUrl);
            ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);
        }
    
        // 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(registeredProviderUrl);
        // 创建监听器
        final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
        // 向注册中心进行订阅 override 数据
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
        // 创建并返回 DestroyableExporter
        return new DestroyableExporter<T>(exporter, originInvoker, overrideSubscribeUrl, registeredProviderUrl);
    }

首先进入RegistryProtocol执行export，运行到doLocalExport方法，进行本地暴露，该方法中：

private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) {
        String key = getCacheKey(originInvoker);
        // 访问缓存
        ExporterChangeableWrapper<T> exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
        if (exporter == null) {
            synchronized (bounds) {
                exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
                if (exporter == null) {
                    // 创建 Invoker 为委托类对象
                    final Invoker<?> invokerDelegete = new InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));
                    // 调用 protocol 的 export 方法导出服务
                    exporter = new ExporterChangeableWrapper<T>((Exporter<T>) protocol.export(invokerDelegete), originInvoker);
                    
                    // 写缓存
                    bounds.put(key, exporter);
                }
            }
        }
        return exporter;
    }

执行protocol.export(invokerDelegete), originInvoker);进入DubboProtocol执行暴露，

DubboProtocol执行完openServer(url);后启动netty服务器，监听url，后重新进入RegistryProtocol，执行

ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);

保存在维护关联关系：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 6][]

最后向注册中心注册服务：

总结：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MzU0OTU3OA_size_16_color_FFFFFF_t_70 7][]

参考来源：[http://dubbo.apache.org/zh-cn/docs/user/configuration/xml.html][http_dubbo.apache.org_zh-cn_docs_user_configuration_xml.html]

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[http_dubbo.apache.org_zh-cn_docs_user_configuration_xml.html]: http://dubbo.apache.org/zh-cn/docs/user/configuration/xml.html