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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;
    }

}
複製程式碼

• DubboApplicationContextInitializer實現了ApplicationContextInitializer,Ordered介面，initialize方法執行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 {
    }
}
複製程式碼
 

• OverrideBeanDefinitionRegistryPostProcessor實現了BeanDefinitionRegistryPostProcessor介面，其postProcessBeanDefinitionRegistry方法呼叫了BeanRegistrar.registerInfrastructureBean方法註冊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);
        }

    }

}
複製程式碼

• registerInfrastructureBean在beanDefinitionRegistry沒有該beanDefinition的情況下會註冊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;
    }
}
複製程式碼

• DubboConfigBeanCustomizer繼承了NamePropertyDefaultValueDubboConfigBeanCustomizer，其customize方法會先校驗propertyName，在valid的情況下才會執行父類的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!",beanName);
            }
        }

        return removed;
    }


    @Override
    public int getOrder() {
        return LOWEST_PRECEDENCE;
    }
}
複製程式碼

• DubboConfigBeanDefinitionConflictProcessor實現了BeanDefinitionRegistryPostProcessor,Ordered介面；postProcessBeanFactory方法會執行resolveUniqueApplicationConfigBean，校驗同一個beanDefinition是否會有多個例項，有的話會丟擲IllegalStateException；getOrder返回的是LOWEST_PRECEDENCE

小結

DubboApplicationContextInitializer實現了ApplicationContextInitializer,Ordered介面，initialize方法執行overrideBeanDefinitions，它往applicationContext添加了OverrideBeanDefinitionRegistryPostProcessor、DubboConfigBeanDefinitionConflictProcessor；getOrder返回的是HIGHEST_PRECEDENCE

doc

• DubboApplicationContextInitializer