老规矩，从框架的使用方式入手分析，类似mybatis，dubbo也有个扫描服务的注解：org.apache.dubbo.config.spring.context.annotation.DubboComponentScan
同样地，配套一个@Import：org.apache.dubbo.config.spring.context.annotation.DubboComponentScanRegistrar，作用就是把BeanDefinitionRegistry交给你全权处理，
对应这里就是构建一个org.apache.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor的BeanDefinition，然后加入BeanDefinitionRegistry。
这是个BeanDefinitionRegistry后处理bean，主要逻辑在父类org.apache.dubbo.config.spring.beans.factory.annotation.ServiceClassPostProcessor，最新版本直接就用了父类。
在如下dubbo springboot自动配置包中有个自动配置类，也是通过该后置bean解析@dubboService类的，不同的是，该自动配置的方式是从yaml获取服务类所在的包路径：
自动配置类org.apache.dubbo.spring.boot.autoconfigure.DubboAutoConfiguration：
对应yaml文件内容如下，这种方式配置的好处是可以把该配置项放到配置中心统一管理：
下面我们具体看下这个类：
实现了接口BeanDefinitionRegistryPostProcessor，对BeanDefinitionRegistry进行后处理，主要逻辑在org.apache.dubbo.config.spring.beans.factory.annotation.ServiceClassPostProcessor#registerServiceBeans方法：
private void registerServiceBeans(Set<String> packagesToScan, BeanDefinitionRegistry registry) { DubboClassPathBeanDefinitionScanner scanner = new DubboClassPathBeanDefinitionScanner(registry, environment, resourceLoader); BeanNameGenerator beanNameGenerator = resolveBeanNameGenerator(registry); scanner.setBeanNameGenerator(beanNameGenerator); // refactor @since 2.7.7 serviceAnnotationTypes.forEach(annotationType -> {
// 设置扫描的包下被指定注解标注的类是需要处理的serviceAnnotationTypes包含如下几个注解
// org.apache.dubbo.config.annotation.DubboService,2.7.7版本后直接用这个注解暴露服务
// org.apache.dubbo.config.annotation.Service,@Deprecated
// com.alibaba.dubbo.config.annotation.Service,@Deprecated scanner.addIncludeFilter(new AnnotationTypeFilter(annotationType)); }); for (String packageToScan : packagesToScan) { // 注册注解标注的类BeanDefinition // Registers @Service Bean first scanner.scan(packageToScan); // Finds all BeanDefinitionHolders of @Service whether @ComponentScan scans or not. Set<BeanDefinitionHolder> beanDefinitionHolders = findServiceBeanDefinitionHolders(scanner, packageToScan, registry, beanNameGenerator); if (!CollectionUtils.isEmpty(beanDefinitionHolders)) { for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
// 构建org.apache.dubbo.config.spring.ServiceBean对应的BeanDefinition并注册到BeandefinitionRegistry registerServiceBean(beanDefinitionHolder, registry, scanner); } if (logger.isInfoEnabled()) { logger.info(beanDefinitionHolders.size() + " annotated Dubbo‘s @Service Components { " + beanDefinitionHolders + " } were scanned under package[" + packageToScan + "]"); } } else { if (logger.isWarnEnabled()) { logger.warn("No Spring Bean annotating Dubbo‘s @Service was found under package[" + packageToScan + "]"); } } } }
重点看下注册ServiceBean代码：
private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry, DubboClassPathBeanDefinitionScanner scanner) { Class<?> beanClass = resolveClass(beanDefinitionHolder); Annotation service = findServiceAnnotation(beanClass); /** * The {@link AnnotationAttributes} of @Service annotation */ AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false); // 服务接口类，可通过@DubboService的interfaceClass或者interfaceName指定，默认为注解标注类对应的接口class Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass); String annotatedServiceBeanName = beanDefinitionHolder.getBeanName(); // 构建ServiceBean的BeanDefinition用于注册 AbstractBeanDefinition serviceBeanDefinition = buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName); // ServiceBean Bean name String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass); if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean
// 注册ServiceBean的BeanDefinition registry.registerBeanDefinition(beanName, serviceBeanDefinition); if (logger.isInfoEnabled()) { logger.info("The BeanDefinition[" + serviceBeanDefinition + "] of ServiceBean has been registered with name : " + beanName); } } else { if (logger.isWarnEnabled()) { logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition + "] of ServiceBean[ bean name : " + beanName + "] was be found , Did @DubboComponentScan scan to same package in many times?"); } } }
private AbstractBeanDefinition buildServiceBeanDefinition(Annotation serviceAnnotation, AnnotationAttributes serviceAnnotationAttributes, Class<?> interfaceClass, String annotatedServiceBeanName) { BeanDefinitionBuilder builder = rootBeanDefinition(ServiceBean.class); AbstractBeanDefinition beanDefinition = builder.getBeanDefinition(); MutablePropertyValues propertyValues = beanDefinition.getPropertyValues(); String[] ignoreAttributeNames = of("provider", "monitor", "application", "module", "registry", "protocol", "interface", "interfaceName", "parameters"); propertyValues.addPropertyValues(new AnnotationPropertyValuesAdapter(serviceAnnotation, environment, ignoreAttributeNames)); // References "ref" property to annotated-@Service Bean
// 指向标注@DubboService注解的原始Bean(在服务暴露的时候会用到) addPropertyReference(builder, "ref", annotatedServiceBeanName); // Set interface
// 指向@DubboService配置的服务接口类名，默认为标注类的接口类（在服务暴露的时候会用到） builder.addPropertyValue("interface", interfaceClass.getName()); // Convert parameters into map builder.addPropertyValue("parameters", convertParameters(serviceAnnotationAttributes.getStringArray("parameters"))); // Add methods parameters List<MethodConfig> methodConfigs = convertMethodConfigs(serviceAnnotationAttributes.get("methods")); if (!methodConfigs.isEmpty()) { builder.addPropertyValue("methods", methodConfigs); } /** * Add {@link org.apache.dubbo.config.ProviderConfig} Bean reference */ String providerConfigBeanName = serviceAnnotationAttributes.getString("provider"); if (StringUtils.hasText(providerConfigBeanName)) { addPropertyReference(builder, "provider", providerConfigBeanName); } /** * Add {@link org.apache.dubbo.config.MonitorConfig} Bean reference */ String monitorConfigBeanName = serviceAnnotationAttributes.getString("monitor"); if (StringUtils.hasText(monitorConfigBeanName)) { addPropertyReference(builder, "monitor", monitorConfigBeanName); } /** * Add {@link org.apache.dubbo.config.ApplicationConfig} Bean reference */ String applicationConfigBeanName = serviceAnnotationAttributes.getString("application"); if (StringUtils.hasText(applicationConfigBeanName)) { addPropertyReference(builder, "application", applicationConfigBeanName); } /** * Add {@link org.apache.dubbo.config.ModuleConfig} Bean reference */ String moduleConfigBeanName = serviceAnnotationAttributes.getString("module"); if (StringUtils.hasText(moduleConfigBeanName)) { addPropertyReference(builder, "module", moduleConfigBeanName); } /** * Add {@link org.apache.dubbo.config.RegistryConfig} Bean reference */ String[] registryConfigBeanNames = serviceAnnotationAttributes.getStringArray("registry"); List<RuntimeBeanReference> registryRuntimeBeanReferences = toRuntimeBeanReferences(registryConfigBeanNames); if (!registryRuntimeBeanReferences.isEmpty()) { builder.addPropertyValue("registries", registryRuntimeBeanReferences); } /** * Add {@link org.apache.dubbo.config.ProtocolConfig} Bean reference */ String[] protocolConfigBeanNames = serviceAnnotationAttributes.getStringArray("protocol"); List<RuntimeBeanReference> protocolRuntimeBeanReferences = toRuntimeBeanReferences(protocolConfigBeanNames); if (!protocolRuntimeBeanReferences.isEmpty()) { builder.addPropertyValue("protocols", protocolRuntimeBeanReferences); } return builder.getBeanDefinition(); }