7.1 服务暴露前的准备-ServiceBean的装配

dubbo的服务暴露以第一章 第一个dubbo项目中的dubbo-demo-provider来讲述。

列出dubbo-demo-provider的xml配置：

 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
        xmlns="http://www.springframework.org/schema/beans"
        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
        http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">

     <!-- 提供方应用信息，用于计算依赖关系 -->
     <dubbo:application name="demo-provider"/>

     <!-- 使用zookeeper注册中心，并使用curator客户端 -->
     <dubbo:registry protocol="zookeeper" address="10.211.55.5:2181" client="curator"/>

     <!-- 用dubbo协议在20880端口暴露服务 -->
     <dubbo:protocol name="dubbo" port="20880"/>

     <!-- 和本地bean一样实现服务 -->
     <bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/>
     <!--<bean id="demo2Service" class="com.alibaba.dubbo.demo.provider.Demo2ServiceImpl"/>-->

     <!-- 声明需要暴露的服务接口 -->
     <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/>
     <!--<dubbo:service interface="com.alibaba.dubbo.demo.Demo2Service" ref="demo2Service"/>-->
 </beans>

服务暴露是由com.alibaba.dubbo.config.spring.ServiceBean这个类来实现的，这个类是spring通过解析<dubbo:service>节点创建的单例Bean，每一个<dubbo:service>都会创建一个ServiceBean。先看一下ServiceBean的继承类图：

看一下ServiceBean的源码：

 package com.alibaba.dubbo.config.spring;

 import com.alibaba.dubbo.config.ApplicationConfig;
 import com.alibaba.dubbo.config.ModuleConfig;
 import com.alibaba.dubbo.config.MonitorConfig;
 import com.alibaba.dubbo.config.ProtocolConfig;
 import com.alibaba.dubbo.config.ProviderConfig;
 import com.alibaba.dubbo.config.RegistryConfig;
 import com.alibaba.dubbo.config.ServiceConfig;
 import com.alibaba.dubbo.config.annotation.Service;
 import com.alibaba.dubbo.config.spring.extension.SpringExtensionFactory;

 import org.springframework.beans.factory.BeanFactoryUtils;
 import org.springframework.beans.factory.BeanNameAware;
 import org.springframework.beans.factory.DisposableBean;
 import org.springframework.beans.factory.InitializingBean;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationContextAware;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.ApplicationListener;
 import org.springframework.context.event.ContextRefreshedEvent;
 import org.springframework.context.support.AbstractApplicationContext;

 import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;

 /**
  * ServiceFactoryBean
  */
 public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener, BeanNameAware {
     private static final long serialVersionUID = 213195494150089726L;

     private static transient ApplicationContext SPRING_CONTEXT;

     private transient ApplicationContext applicationContext;

     private transient String beanName;

     private transient boolean supportedApplicationListener;

     public ServiceBean() {
         super();
     }

     public ServiceBean(Service service) {
         super(service);
     }

     public static ApplicationContext getSpringContext() {
         return SPRING_CONTEXT;
     }

     /**
      * ApplicationContextAware接口的方法
      * Set the ApplicationContext that this object runs in.
      * Invoked after population of normal bean properties but before an init callback such
      * as {@link org.springframework.beans.factory.InitializingBean#afterPropertiesSet()}
      * or a custom init-method.
      *
      * 流程：
      * 1 将applicationContext设置到SpringExtensionFactory中,用于后续从SpringExtensionFactory中获取Bean
      * 2 获取方法addApplicationListener(ApplicationListener<?> listener),之后将当前类（因为当前类监听了ContextRefreshedEvent事件）加入spring的监听器列表
      */
     @Override
     public void setApplicationContext(ApplicationContext applicationContext) {
         this.applicationContext = applicationContext;
         SpringExtensionFactory.addApplicationContext(applicationContext);
         if (applicationContext != null) {
             SPRING_CONTEXT = applicationContext;
             try {
                 /**  */
                 Method method = applicationContext.getClass().getMethod("addApplicationListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
                 method.invoke(applicationContext, new Object[]{this});
                 supportedApplicationListener = true;
             } catch (Throwable t) {
                 if (applicationContext instanceof AbstractApplicationContext) {
                     try {
                         Method method = AbstractApplicationContext.class.getDeclaredMethod("addListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
                         if (!method.isAccessible()) {
                             method.setAccessible(true);
                         }
                         method.invoke(applicationContext, new Object[]{this});
                         supportedApplicationListener = true;
                     } catch (Throwable t2) {
                     }
                 }
             }
         }
     }

     /**
      * BeanNameAware接口的方法
      * Set the name of the bean in the bean factory that created this bean.
      * Invoked after population of normal bean properties but before an
      * init callback such as {@link InitializingBean#afterPropertiesSet()}
      * or a custom init-method.
      */
     @Override
     public void setBeanName(String name) {
         this.beanName = name;
     }

     /**
      * ApplicationListener接口的方法
      * delay没有设置或者是-1 && 服务没有暴露 && 服务没有反注册，则进行服务暴露
      */
     @Override
     public void onApplicationEvent(ApplicationEvent event) {
         if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
             if (isDelay() && !isExported() && !isUnexported()) {
                 if (logger.isInfoEnabled()) {
                     logger.info("The service ready on spring started. service: " + getInterface());
                 }
                 export();
             }
         }
     }

     private boolean isDelay() {
         Integer delay = getDelay();
         ProviderConfig provider = getProvider();
         if (delay == null && provider != null) {
             delay = provider.getDelay();
         }
         return supportedApplicationListener && (delay == null || delay.intValue() == -1);
     }

     /**
      * InitializingBean接口的方法：
      * This method allows the bean instance to perform initialization only
      * possible when all bean properties have been set
      *
      * 流程：
      * 1 检查ServiceBean的ProviderConfig provider，如果为空，从applicationContext获取ProviderConfig类型的bean（这里查找的过程其实就是看有没有配置<dubbo:provider>），如果获取到了，进行设置
      * 2 后续会参照1分别进行
      *   -- ApplicationConfig application
      *   -- ModuleConfig module
      *   -- List<RegistryConfig> registries
      *   -- MonitorConfig monitor
      *   -- List<ProtocolConfig> protocols
      *   -- String path：服务名称
      * 3 判断延迟的事件是否大于0，如果是，执行export()，进行服务暴露，如果不是，结束（这种情况下服务暴露，会发生在发布上下文刷新事件的时候）
      */
     @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 ((protocolConfigMap == null || protocolConfigMap.size() == 0)
                         && providerConfigMap.size() > 1) { // 兼容旧版本
                     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()) {//设置的延迟时间大于0
             export();
         }
     }

     /**
      * DisposableBean接口的方法
      */
     @Override
     public void destroy() throws Exception {
         unexport();
     }
 }

这里最重要的两个方法：afterPropertiesSet()和onApplicationEvent(ApplicationEvent event)。

一 设置属性与服务暴露

当所有的Bean的属性被设置好之后，执行afterPropertiesSet()。该方法的流程：

1 设置属性

检查ServiceBean的某个属性（这里的属性包含如下6个）是否为空，如果为空，从applicationContext获取相应类型的bean，如果获取到了，则进行相应的设置。

• ProviderConfig provider：其实就是看有没有配置<dubbo:provider>
• ApplicationConfig application：其实就是看有没有配置<dubbo:application>
• ModuleConfig module：其实就是看有没有配置<dubbo:module>
• List<RegistryConfig> registries：其实就是看有没有配置<dubbo:registry>
• MonitorConfig monitor：其实就是看有没有配置<dubbo:monitor>
• List<ProtocolConfig> protocols：其实就是看有没有配置<dubbo:protocol>
• String path：服务名称

2 是否暴露服务

之后判断延迟的时间是否大于0，如果是，执行export()，进行服务暴露，如果不是，结束（这种情况下服务暴露会发生在容器发布上下文刷新事件的时候）。在这里，我们并没有指定delay，所以delay==null，服务暴露会发生在容器发布上下文刷新事件的时候。

当afterPropertiesSet()结束之后，来看一下此时的ServiceBean实例，实例的私有属性如下：（没有值的暂时不说）

 id = com.alibaba.dubbo.demo.DemoService
 applicationContext = ClassPathXmlApplicationContext实例
 beanName = com.alibaba.dubbo.demo.DemoService
 interfaceName = com.alibaba.dubbo.demo.DemoService
 supportedApplicationListener = true
 ref = DemoServiceImpl实例
 path = com.alibaba.dubbo.demo.DemoService

 application:
 -- id = demo-provider
 -- name = demo-provider

 registries = [
     RegistryConfig:
     -- id = com.alibaba.dubbo.config.RegistryConfig
     -- protocol = zookeeper
     -- address = 10.211.55.5:2181
     -- client = curator
 ]

 protocols = [
     ProtocolConfig:
     -- id = dubbo
     -- name = dubbo
     -- port = 20880
 ]

实际上在创建ServiceBean实例的时候，也会初始化其父类ServiceConfig的静态属性：

     private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
     private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();

其中protocol的实例是：Protocol$Adaptive实例，Protocol$Adaptive类的代码在5.2 dubbo-compiler源码解析已经列出。

下边来看一下第二句代码的源码。首先，看一下ProxyFactory的定义：

 package com.alibaba.dubbo.rpc;

 import com.alibaba.dubbo.common.Constants;
 import com.alibaba.dubbo.common.URL;
 import com.alibaba.dubbo.common.extension.Adaptive;
 import com.alibaba.dubbo.common.extension.SPI;

 /**
  * ProxyFactory. (API/SPI, Singleton, ThreadSafe)
  */
 @SPI("javassist")
 public interface ProxyFactory {
     /**
      * create proxy.
      */
     @Adaptive({Constants.PROXY_KEY})
     <T> T getProxy(Invoker<T> invoker) throws RpcException;

     /**
      * create invoker.
      */
     @Adaptive({Constants.PROXY_KEY})
     <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) throws RpcException;
 }

ExtensionLoader.getExtensionLoader(ProxyFactory.class)的实现结果还是：

ExtensionLoader<com.alibaba.dubbo.rpc.ProxyFactory> loader，最终的loader包含如下属性：

• Class<?> type = interface com.alibaba.dubbo.rpc.ProxyFactory
• ExtensionFactory objectFactory = AdaptiveExtensionFactory（适配类）
  • factories = [SpringExtensionFactory实例, SpiExtensionFactory实例]

之后，执行getAdaptiveExtension()。

来看一下：META-INF/dubbo/internal/com.alibaba.dubbo.rpc.ProxyFactory的内容：

 stub=com.alibaba.dubbo.rpc.proxy.wrapper.StubProxyFactoryWrapper
 jdk=com.alibaba.dubbo.rpc.proxy.jdk.JdkProxyFactory
 javassist=com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory

从ProxyFactory的@SPI("javassist")，默认选用的实现是com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory。com.alibaba.dubbo.rpc.proxy.wrapper.StubProxyFactoryWrapper是一个wrapper类，但是wrapper类只在getExtension("xxx")中会实现aop，而在getAdaptiveExtension()不会进行aop包裹。

这里的三个实现类没有一个类上带有@Adaptive注解，所以会动态创建类。动态生成的类ProxyFactory$Adaptive代码如下：

 package com.alibaba.dubbo.rpc;
 import com.alibaba.dubbo.common.extension.ExtensionLoader;

 public class ProxyFactory$Adaptive implements com.alibaba.dubbo.rpc.ProxyFactory {
     public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1, com.alibaba.dubbo.common.URL arg2) throws com.alibaba.dubbo.rpc.RpcException {
         if (arg2 == null)
             throw new IllegalArgumentException("url == null");
         com.alibaba.dubbo.common.URL url = arg2;
         String extName = url.getParameter("proxy", "javassist");
         if(extName == null)
             throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
         com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
         return extension.getInvoker(arg0, arg1, arg2);
     }

     public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {
         if (arg0 == null)
             throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
         if (arg0.getUrl() == null)
             throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();
         String extName = url.getParameter("proxy", "javassist");
         if(extName == null)
             throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
         com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
         return extension.getProxy(arg0);
     }
 }

所以ServiceConfig中的静态属性proxyFactory为ProxyFactory$Adaptive实例。

至此，一个ServiceBean实例完成了。

二 在上下文刷新时进行初始化

     /**
      * ApplicationListener接口的方法
      * delay没有设置或者是-1 && 服务没有暴露 && 服务没有反注册，则进行服务暴露
      */
     @Override
     public void onApplicationEvent(ApplicationEvent event) {
         if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
             if (isDelay() && !isExported() && !isUnexported()) {
                 if (logger.isInfoEnabled()) {
                     logger.info("The service ready on spring started. service: " + getInterface());
                 }
                 export();
             }
         }
     }

一切准备好之后，就在这里开始进行服务暴露！export()！！！