@ConfigurationProperties源码分析二什么时候注册的ConfigurationPropertiesBindingPostProcessor？

喜欢ヅ旅行 2022-03-07 11:52 181阅读 0赞

# 什么时候注册的ConfigurationPropertiesBindingPostProcessor？ #

接上一篇文章[@ConfigurationProperties源码分析 一][ConfigurationProperties_] 提出的问题  
什么时候注册的ConfigurationPropertiesBindingPostProcessor？

## SpringApplication ##

从应用启动类 main 说起

/**
     * @author Shaofeng Li
     */
    @SpringBootApplication
    
    public class NotifyServiceApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(NotifyServiceApplication.class, args);
        }
    
    }

然后会调用父类的refresh方法

@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();
    			}
    		}
    	}

委托PostProcessorRegistrationDelegate来处理  
调用所有实现BeanFactoryPostProcessor 接口的工厂类

/**
    	 * Instantiate and invoke all registered BeanFactoryPostProcessor beans,
    	 * respecting explicit order if given.
    	 * <p>Must be called before singleton instantiation.
    	 */
    	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()));
    		}
    	}

这里调用所有的实现BeanDefinitionRegistryPostProcessor 接口类  
BeanDefinitionRegistryPostProcessor 继承BeanFactoryPostProcessor 所有会被上面调用

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor

/**
    	 * Invoke the given BeanDefinitionRegistryPostProcessor beans.
    	 */
    	private static void invokeBeanDefinitionRegistryPostProcessors(
    			Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
    
    		for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
    			postProcessor.postProcessBeanDefinitionRegistry(registry);
    		}
    	}

## ConfigurationClassPostProcessor ##

ConfigurationClassPostProcessor实现了BeanDefinitionRegistryPostProcessor 所以会被上面调用  
[**那么是什么时候注册ConfigurationClassPostProcessor的呢？**][ConfigurationClassPostProcessor]  
获取configuration 注解 ，并处理

/**
    	 * Derive further bean definitions from the configuration classes in the registry.
    	 */
    	@Override
    	public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    		int registryId = System.identityHashCode(registry);
    		if (this.registriesPostProcessed.contains(registryId)) {
    			throw new IllegalStateException(
    					"postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
    		}
    		if (this.factoriesPostProcessed.contains(registryId)) {
    			throw new IllegalStateException(
    					"postProcessBeanFactory already called on this post-processor against " + registry);
    		}
    		this.registriesPostProcessed.add(registryId);
    
    		processConfigBeanDefinitions(registry);
    	}

/**
    	 * Build and validate a configuration model based on the registry of
    	 * {@link Configuration} classes.
    	 */
    	public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
    		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
    		String[] candidateNames = registry.getBeanDefinitionNames();
    
    		for (String beanName : candidateNames) {
    			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
    			if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
    					ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
    				if (logger.isDebugEnabled()) {
    					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
    				}
    			}
    			else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
    				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
    			}
    		}
    
    		// Return immediately if no @Configuration classes were found
    		if (configCandidates.isEmpty()) {
    			return;
    		}
    
    		// Sort by previously determined @Order value, if applicable
    		configCandidates.sort((bd1, bd2) -> {
    			int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
    			int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
    			return Integer.compare(i1, i2);
    		});
    
    		// Detect any custom bean name generation strategy supplied through the enclosing application context
    		SingletonBeanRegistry sbr = null;
    		if (registry instanceof SingletonBeanRegistry) {
    			sbr = (SingletonBeanRegistry) registry;
    			if (!this.localBeanNameGeneratorSet) {
    				BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
    				if (generator != null) {
    					this.componentScanBeanNameGenerator = generator;
    					this.importBeanNameGenerator = generator;
    				}
    			}
    		}
    
    		if (this.environment == null) {
    			this.environment = new StandardEnvironment();
    		}
    
    		// Parse each @Configuration class
    		ConfigurationClassParser parser = new ConfigurationClassParser(
    				this.metadataReaderFactory, this.problemReporter, this.environment,
    				this.resourceLoader, this.componentScanBeanNameGenerator, registry);
    
    		Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
    		Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
    		do {
    			parser.parse(candidates);
    			parser.validate();
    
    			Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
    			configClasses.removeAll(alreadyParsed);
    
    			// Read the model and create bean definitions based on its content
    			if (this.reader == null) {
    				this.reader = new ConfigurationClassBeanDefinitionReader(
    						registry, this.sourceExtractor, this.resourceLoader, this.environment,
    						this.importBeanNameGenerator, parser.getImportRegistry());
    			}
    			this.reader.loadBeanDefinitions(configClasses);
    			alreadyParsed.addAll(configClasses);
    
    			candidates.clear();
    			if (registry.getBeanDefinitionCount() > candidateNames.length) {
    				String[] newCandidateNames = registry.getBeanDefinitionNames();
    				Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
    				Set<String> alreadyParsedClasses = new HashSet<>();
    				for (ConfigurationClass configurationClass : alreadyParsed) {
    					alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
    				}
    				for (String candidateName : newCandidateNames) {
    					if (!oldCandidateNames.contains(candidateName)) {
    						BeanDefinition bd = registry.getBeanDefinition(candidateName);
    						if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
    								!alreadyParsedClasses.contains(bd.getBeanClassName())) {
    							candidates.add(new BeanDefinitionHolder(bd, candidateName));
    						}
    					}
    				}
    				candidateNames = newCandidateNames;
    			}
    		}
    		while (!candidates.isEmpty());
    
    		// Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
    		if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
    			sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
    		}
    
    		if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory) {
    			// Clear cache in externally provided MetadataReaderFactory; this is a no-op
    			// for a shared cache since it'll be cleared by the ApplicationContext.
    			((CachingMetadataReaderFactory) this.metadataReaderFactory).clearCache();
    		}
    	}

### ConfigurationClassBeanDefinitionReader ###

上面会new ConfigurationClassBeanDefinitionReaderl  
会调用所有ImportBeanDefinitionRegistrar接口的类

/**
    	 * Read {@code configurationModel}, registering bean definitions
    	 * with the registry based on its contents.
    	 */
    	public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
    		TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
    		for (ConfigurationClass configClass : configurationModel) {
    			loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
    		}
    	}

/**
    	 * Read a particular {@link ConfigurationClass}, registering bean definitions
    	 * for the class itself and all of its {@link Bean} methods.
    	 */
    	private void loadBeanDefinitionsForConfigurationClass(
    			ConfigurationClass configClass, TrackedConditionEvaluator trackedConditionEvaluator) {
    
    		if (trackedConditionEvaluator.shouldSkip(configClass)) {
    			String beanName = configClass.getBeanName();
    			if (StringUtils.hasLength(beanName) && this.registry.containsBeanDefinition(beanName)) {
    				this.registry.removeBeanDefinition(beanName);
    			}
    			this.importRegistry.removeImportingClass(configClass.getMetadata().getClassName());
    			return;
    		}
    
    		if (configClass.isImported()) {
    			registerBeanDefinitionForImportedConfigurationClass(configClass);
    		}
    		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
    			loadBeanDefinitionsForBeanMethod(beanMethod);
    		}
    
    		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
    		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
    	}

private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {
    		registrars.forEach((registrar, metadata) ->
    				registrar.registerBeanDefinitions(metadata, this.registry));
    	}

## ConfigurationPropertiesBindingPostProcessorRegistrar ##

ConfigurationPropertiesBindingPostProcessorRegistrar 实现了ImportBeanDefinitionRegistrar接口所以会被调用  
[**那么是什么时候注册ConfigurationPropertiesBindingPostProcessorRegistrar 的呢？**][ConfigurationPropertiesBindingPostProcessorRegistrar]

@Override
    	public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata,
    			BeanDefinitionRegistry registry) {
    		if (!registry.containsBeanDefinition(
    				ConfigurationPropertiesBindingPostProcessor.BEAN_NAME)) {
    			registerConfigurationPropertiesBindingPostProcessor(registry);
    			registerConfigurationBeanFactoryMetadata(registry);
    		}
    	}

private void registerConfigurationPropertiesBindingPostProcessor(
    			BeanDefinitionRegistry registry) {
    		GenericBeanDefinition definition = new GenericBeanDefinition();
    		definition.setBeanClass(ConfigurationPropertiesBindingPostProcessor.class);
    		definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
    		registry.registerBeanDefinition(
    		//这里注册ConfigurationPropertiesBindingPostProcessor的
    				ConfigurationPropertiesBindingPostProcessor.BEAN_NAME, definition);
    
    	}

**到这里就完成了ConfigurationPropertiesBindingPostProcessor的注入。**

# 总结 #

**什么时候注册的ConfigurationPropertiesBindingPostProcessor？  
应用启动Spring容器的时候会调用refresh方法，然后委托PostProcessorRegistrationDelegate来处理  
调用所有实现BeanFactoryPostProcessor 接口的工厂类，因为BeanDefinitionRegistryPostProcessor 继承BeanFactoryPostProcessor 所以所有的BeanDefinitionRegistryPostProcessor 接口类都会被调用。  
ConfigurationClassPostProcessor实现了BeanDefinitionRegistryPostProcessor会被调用，在ConfigurationClassPostProcessor会new ConfigurationClassBeanDefinitionReader对象来调用所有实现了ImportBeanDefinitionRegistrar接口的方法，ConfigurationPropertiesBindingPostProcessorRegistrar因为实现了ImportBeanDefinitionRegistrar接口所以会被调用，然后注册了ConfigurationPropertiesBindingPostProcessor对象。  
这样就完成了ConfigurationPropertiesBindingPostProcessor对象的注入**

[ConfigurationProperties_]: https://blog.csdn.net/qq_15288023/article/details/88605913
[ConfigurationClassPostProcessor]: https://blog.csdn.net/qq_15288023/article/details/88635168
[ConfigurationPropertiesBindingPostProcessorRegistrar]: https://blog.csdn.net/qq_15288023/article/details/88634483