nacos服务注册--dubbo-spring-boot

dubbo-spring-boot-autoconfigure-compatible中注入ServiceAnnotationBeanPostProcessor进行初始化，ServiceAnnotationBeanPostProcessor继承了ServiceClassPostProcessor,ServiceClassPostProcessor实现了BeanDefinitionRegistryPostProcessor中的方法postProcessBeanDefinitionRegistry。
再看org.springframework.context.support.AbstractApplicationContext#refresh中的invokeBeanFactoryPostProcessors(beanFactory)用来找出所有beanFactory后置处理器，并且调用这些处理器来改变bean的定义。
invokeBeanFactoryPostProcessors(beanFactory)实际上是委托org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());方法处理的。
在PostProcessorRegistrationDelegate中invokeBeanFactoryPostProcessors方法调用了BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry接口，所有实现postProcessBeanDefinitionRegistry接口的bean都会被调用，包括ServiceClassPostProcessor,这里初始化了DubboBootstrapApplicationListener，当监听到ContextRefreshedEvent事件之后，触发dubbo服务启动dubboBootstrap.start(),调用ServiceConfig.export()，这个方法会启动一个网络监听，从而实现服务发布。具体怎么实现服务发布会在之后的文章做介绍

public class DubboAutoConfiguration {
  

    @ConditionalOnProperty(prefix = DUBBO_SCAN_PREFIX, name = BASE_PACKAGES_PROPERTY_NAME)
    @ConditionalOnBean(name = BASE_PACKAGES_PROPERTY_RESOLVER_BEAN_NAME)
    @Bean
    public ServiceAnnotationBeanPostProcessor serviceAnnotationBeanPostProcessor(
            @Qualifier(BASE_PACKAGES_PROPERTY_RESOLVER_BEAN_NAME) PropertyResolver propertyResolver) {
        Set<String> packagesToScan = propertyResolver.getProperty(BASE_PACKAGES_PROPERTY_NAME, Set.class, emptySet());
        return new ServiceAnnotationBeanPostProcessor(packagesToScan);
    }

    ......
}

public class ServiceAnnotationBeanPostProcessor extends ServiceClassPostProcessor {
    
    public ServiceAnnotationBeanPostProcessor(String... packagesToScan) {
        this(Arrays.asList(packagesToScan));
    }

    public ServiceAnnotationBeanPostProcessor(Collection<String> packagesToScan) {
        this(new LinkedHashSet<>(packagesToScan));
    }

    public ServiceAnnotationBeanPostProcessor(Set<String> packagesToScan) {
        super(packagesToScan);
    }

}

public class ServiceClassPostProcessor implements BeanDefinitionRegistryPostProcessor, EnvironmentAware,
        ResourceLoaderAware, BeanClassLoaderAware {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

        // @since 2.7.5
        registerBeans(registry, DubboBootstrapApplicationListener.class);

        Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);

        if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
            registerServiceBeans(resolvedPackagesToScan, registry);
        } else {
            if (logger.isWarnEnabled()) {
                logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
            }
        }

    }

    ......

}

public abstract class AbstractApplicationContext extends DefaultResourceLoader
        implements ConfigurableApplicationContext, DisposableBean {

    ......

    @Override
    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset 'active' flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // Reset common introspection caches in Spring's core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }

    ......

    protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

        // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
        // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
        if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
            beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
            beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
        }
    }
    
}

class PostProcessorRegistrationDelegate {
    public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

        // Invoke BeanDefinitionRegistryPostProcessors first, if any.
        Set<String> processedBeans = new HashSet<String>();

        if (beanFactory instanceof BeanDefinitionRegistry) {
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();

            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    registryProcessors.add(registryProcessor);
                }
                else {
                    regularPostProcessors.add(postProcessor);
                }
            }
        }
    }
    ......
}

public class ServiceClassPostProcessor implements BeanDefinitionRegistryPostProcessor, EnvironmentAware,
        ResourceLoaderAware, BeanClassLoaderAware {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

        // @since 2.7.5
        registerBeans(registry, DubboBootstrapApplicationListener.class);

        Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);

        if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
            registerServiceBeans(resolvedPackagesToScan, registry);
        } else {
            if (logger.isWarnEnabled()) {
                logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
            }
        }

    }

}

public class DubboBootstrapApplicationListener extends OneTimeExecutionApplicationContextEventListener
        implements Ordered {

    @Override
    public void onApplicationContextEvent(ApplicationContextEvent event) {
        if (event instanceof ContextRefreshedEvent) {
            onContextRefreshedEvent((ContextRefreshedEvent) event);
        } else if (event instanceof ContextClosedEvent) {
            onContextClosedEvent((ContextClosedEvent) event);
        }
    }

    private void onContextRefreshedEvent(ContextRefreshedEvent event) {
        dubboBootstrap.start();
    }

}