聊聊dubbo的DubboApplicationContextInitializer

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本文主要研究一下 dubbo 的 DubboApplicationContextInitializer

DubboApplicationContextInitializer

dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-compatible/autoconfigure/src/main/java/org/apache/dubbo/spring/boot/context/DubboApplicationContextInitializer.java

public class DubboApplicationContextInitializer implements ApplicationContextInitializer, Ordered {

    @Override
    public void initialize(ConfigurableApplicationContext applicationContext) {overrideBeanDefinitions(applicationContext);
    }

    private void overrideBeanDefinitions(ConfigurableApplicationContext applicationContext) {applicationContext.addBeanFactoryPostProcessor(new OverrideBeanDefinitionRegistryPostProcessor());
        applicationContext.addBeanFactoryPostProcessor(new DubboConfigBeanDefinitionConflictProcessor());
    }

    @Override
    public int getOrder() {return HIGHEST_PRECEDENCE;}

}

• DubboApplicationContextInitializer 实现了 ApplicationContextInitializer, Ordered 接口，initialize 方法执行 overrideBeanDefinitions，它往 applicationContext 添加了 OverrideBeanDefinitionRegistryPostProcessor、DubboConfigBeanDefinitionConflictProcessor；getOrder 返回的是 HIGHEST_PRECEDENCE

OverrideBeanDefinitionRegistryPostProcessor

dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-compatible/autoconfigure/src/main/java/org/apache/dubbo/spring/boot/beans/factory/config/OverrideBeanDefinitionRegistryPostProcessor.java

public class OverrideBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {registerInfrastructureBean(registry, BEAN_NAME, DubboConfigBeanCustomizer.class);
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {}}

• OverrideBeanDefinitionRegistryPostProcessor 实现了 BeanDefinitionRegistryPostProcessor 接口，其 postProcessBeanDefinitionRegistry 方法调用了 BeanRegistrar.registerInfrastructureBean 方法注册 DubboConfigBeanCustomizer

BeanRegistrar

dubbo-2.7.3-sources.jar!/org/apache/dubbo/config/spring/util/BeanRegistrar.java

public class BeanRegistrar {

    /**
     * Register Infrastructure Bean
     *
     * @param beanDefinitionRegistry {@link BeanDefinitionRegistry}
     * @param beanType               the type of bean
     * @param beanName               the name of bean
     */
    public static void registerInfrastructureBean(BeanDefinitionRegistry beanDefinitionRegistry,
                                                  String beanName,
                                                  Class<?> beanType) {if (!beanDefinitionRegistry.containsBeanDefinition(beanName)) {RootBeanDefinition beanDefinition = new RootBeanDefinition(beanType);
            beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
            beanDefinitionRegistry.registerBeanDefinition(beanName, beanDefinition);
        }

    }

}

• registerInfrastructureBean 在 beanDefinitionRegistry 没有该 beanDefinition 的情况下会注册 BeanDefinition.ROLE_INFRASTRUCTURE 的 bean

DubboConfigBeanCustomizer

dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-compatible/autoconfigure/src/main/java/org/apache/dubbo/spring/boot/beans/factory/config/DubboConfigBeanCustomizer.java

@Deprecated
class DubboConfigBeanCustomizer extends NamePropertyDefaultValueDubboConfigBeanCustomizer {

    @Override
    public void customize(String beanName, AbstractConfig dubboConfigBean) {boolean valid = isValidPropertyName(dubboConfigBean, beanName);
        if (valid) {super.customize(beanName, dubboConfigBean);
        }
    }

    private boolean isValidPropertyName(AbstractConfig dubboConfigBean, String propertyValue) {
        boolean valid = true;
        String propertyName = "name";
        // AbstractConfig.checkName(String,String)
        Method method = findMethod(AbstractConfig.class, "checkName", String.class, String.class);
        try {if (!method.isAccessible()) {method.setAccessible(true);
            }
            if (BeanUtils.getPropertyDescriptor(dubboConfigBean.getClass(), propertyName) != null) {invokeMethod(method, null, propertyName, propertyValue);
            }
        } catch (IllegalStateException e) {valid = false;}

        return valid;
    }
}

• DubboConfigBeanCustomizer 继承了 NamePropertyDefaultValueDubboConfigBeanCustomizer，其 customize 方法会先校验 propertyName，在 valid 的情况下才会执行父类的 customize 方法

DubboConfigBeanDefinitionConflictProcessor

dubbo-spring-boot-project-2.7.3/dubbo-spring-boot-compatible/autoconfigure/src/main/java/org/apache/dubbo/spring/boot/beans/factory/config/DubboConfigBeanDefinitionConflictProcessor.java

public class DubboConfigBeanDefinitionConflictProcessor implements BeanDefinitionRegistryPostProcessor, Ordered {private final Logger logger = LoggerFactory.getLogger(getClass());

    private BeanDefinitionRegistry registry;

    private Environment environment;

    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {this.registry = registry;}

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {resolveUniqueApplicationConfigBean(registry, beanFactory);
    }

    /**
     * Resolve the unique {@link ApplicationConfig} Bean
     *
     * @param registry    {@link BeanDefinitionRegistry} instance
     * @param beanFactory {@link ConfigurableListableBeanFactory} instance
     * @see EnableDubboConfig
     */
    private void resolveUniqueApplicationConfigBean(BeanDefinitionRegistry registry,
                                                    ConfigurableListableBeanFactory beanFactory) {this.environment = beanFactory.getBean(ENVIRONMENT_BEAN_NAME, Environment.class);

        String[] beansNames = beanNamesForTypeIncludingAncestors(beanFactory, ApplicationConfig.class);

        if (beansNames.length < 2) { // If the number of ApplicationConfig beans is less than two, return immediately.
            return;
        }

        // Remove ApplicationConfig Beans that are configured by "dubbo.application.*"
        Stream.of(beansNames)
                .filter(this::isConfiguredApplicationConfigBeanName)
                .forEach(registry::removeBeanDefinition);

        beansNames = beanNamesForTypeIncludingAncestors(beanFactory, ApplicationConfig.class);

        if (beansNames.length > 1) {
            throw new IllegalStateException(String.format("There are more than one instances of %s, whose bean definitions : %s",
                    ApplicationConfig.class.getSimpleName(),
                    Stream.of(beansNames)
                            .map(registry::getBeanDefinition)
                            .collect(Collectors.toList()))
            );
        }
    }

    private boolean isConfiguredApplicationConfigBeanName(String beanName) {boolean removed = BeanFactoryUtils.isGeneratedBeanName(beanName)
                // Dubbo ApplicationConfig id as bean name
                || Objects.equals(beanName, environment.getProperty("dubbo.application.id"));

        if (removed) {if (logger.isWarnEnabled()) {logger.warn("The {} bean [name : {} ] has been removed!", ApplicationConfig.class.getSimpleName(), beanName);
            }
        }

        return removed;
    }


    @Override
    public int getOrder() {return LOWEST_PRECEDENCE;}
}

• DubboConfigBeanDefinitionConflictProcessor 实现了 BeanDefinitionRegistryPostProcessor, Ordered 接口；postProcessBeanFactory 方法会执行 resolveUniqueApplicationConfigBean，校验同一个 beanDefinition 是否会有多个实例，有的话会抛出 IllegalStateException；getOrder 返回的是 LOWEST_PRECEDENCE

小结

DubboApplicationContextInitializer 实现了 ApplicationContextInitializer, Ordered 接口，initialize 方法执行 overrideBeanDefinitions，它往 applicationContext 添加了 OverrideBeanDefinitionRegistryPostProcessor、DubboConfigBeanDefinitionConflictProcessor；getOrder 返回的是 HIGHEST_PRECEDENCE

doc

• DubboApplicationContextInitializer