聊聊dubbo的ServiceBeanExportedEvent

序

本文主要研究一下 dubbo 的 ServiceBeanExportedEvent

ServiceBeanExportedEvent

dubbo-2.7.3/dubbo-config/dubbo-config-spring/src/main/java/org/apache/dubbo/config/spring/context/event/ServiceBeanExportedEvent.java

public class ServiceBeanExportedEvent extends ApplicationEvent {

    /**
     * Create a new ApplicationEvent.
     *
     * @param serviceBean {@link ServiceBean} bean
     */
    public ServiceBeanExportedEvent(ServiceBean serviceBean) {super(serviceBean);
    }

    /**
     * Get {@link ServiceBean} instance
     *
     * @return non-null
     */
    public ServiceBean getServiceBean() {return (ServiceBean) super.getSource();}
}

• ServiceBeanExportedEvent 继承了 ApplicationEvent，其 source 为 ServiceBean

ServiceBean

dubbo-2.7.3/dubbo-config/dubbo-config-spring/src/main/java/org/apache/dubbo/config/spring/ServiceBean.java

public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
        ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware,
        ApplicationEventPublisherAware {

        //......

    /**
     * @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);
    }

        //......
}

• ServiceBean 的 export 方法会 publishExportEvent

ReferenceAnnotationBeanPostProcessor

dubbo-2.7.3/dubbo-config/dubbo-config-spring/src/main/java/org/apache/dubbo/config/spring/beans/factory/annotation/ReferenceAnnotationBeanPostProcessor.java

public class ReferenceAnnotationBeanPostProcessor extends AnnotationInjectedBeanPostProcessor implements
        ApplicationContextAware, ApplicationListener {

        //......

    @Override
    public void onApplicationEvent(ApplicationEvent event) {if (event instanceof ServiceBeanExportedEvent) {onServiceBeanExportEvent((ServiceBeanExportedEvent) event);
        } else if (event instanceof ContextRefreshedEvent) {onContextRefreshedEvent((ContextRefreshedEvent) event);
        }
    }

    private void onServiceBeanExportEvent(ServiceBeanExportedEvent event) {ServiceBean serviceBean = event.getServiceBean();
        initReferenceBeanInvocationHandler(serviceBean);
    }

    private void initReferenceBeanInvocationHandler(ServiceBean serviceBean) {String serviceBeanName = serviceBean.getBeanName();
        // Remove ServiceBean when it's exported
        ReferenceBeanInvocationHandler handler = localReferenceBeanInvocationHandlerCache.remove(serviceBeanName);
        // Initialize
        if (handler != null) {handler.init();
        }
    }

        //......
}

• ReferenceAnnotationBeanPostProcessor 实现了 ApplicationListener 的 onApplicationEvent 方法，接收到 ServiceBeanExportedEvent 事件时执行 onServiceBeanExportEvent，这里从 localReferenceBeanInvocationHandlerCache 移除，然后执行 ReferenceBeanInvocationHandler 的 init 方法

小结

ServiceBeanExportedEvent 继承了 ApplicationEvent，其 source 为 ServiceBean；ServiceBean 的 export 方法会 publishExportEvent；ReferenceAnnotationBeanPostProcessor 实现了 ApplicationListener 的 onApplicationEvent 方法，接收到 ServiceBeanExportedEvent 事件时执行 onServiceBeanExportEvent，这里从 localReferenceBeanInvocationHandlerCache 移除，然后执行 ReferenceBeanInvocationHandler 的 init 方法

doc

• ServiceBeanExportedEvent