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繼承了ApplicationEvent，其source爲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方法會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實現了ApplicationListener的onApplicationEvent方法，接收到ServiceBeanExportedEvent事件時執行onServiceBeanExportEvent，這裏從localReferenceBeanInvocationHandlerCache移除，而後執行ReferenceBeanInvocationHandler的init方法

小結

ServiceBeanExportedEvent繼承了ApplicationEvent，其source爲ServiceBean；ServiceBean的export方法會publishExportEvent；ReferenceAnnotationBeanPostProcessor實現了ApplicationListener的onApplicationEvent方法，接收到ServiceBeanExportedEvent事件時執行onServiceBeanExportEvent，這裏從localReferenceBeanInvocationHandlerCache移除，而後執行ReferenceBeanInvocationHandler的init方法

doc

• ServiceBeanExportedEvent