spring ----- ConfigurationClassPostProcessor

一、

 ConfigurationClassPostProcessor是针对@Configuration、@ComponentScan、@ComponentScans、@Import、@Bean这些注解的解析。它是Spring内置的一个BeanFactory后置处理器，实现了继承了BeanFactoryPostProcessor的BeanDefinitionRegistryPostProcessor接口。而其中的解析方法主要是通过postProcessBeanDefinitionRegistry()和postProcessBeanFactory()实现的。

整个解析大致流程图。

二、源码

  

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
        
            this.registriesPostProcessed.add(registryId);
            //解析构建配置类
            this.processConfigBeanDefinitions(registry);
    }

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
		String[] candidateNames = registry.getBeanDefinitionNames();

		for (String beanName : candidateNames) {
			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
			if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
				if (logger.isDebugEnabled()) {
					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
				}
			}
			//判断是否为一个配置类，并为BeanDefinition设置属性full或lite，若为Configuration则设置为full
			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) {
				//将解析出的配置类通过BeanNameGenerator生成beanName
				BeanNameGenerator generator = (BeanNameGenerator) sbr.getSingleton(
						AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
				if (generator != null) {
					this.componentScanBeanNameGenerator = generator;
					this.importBeanNameGenerator = generator;
				}
			}
		}

		if (this.environment == null) {
			this.environment = new StandardEnvironment();
		}

		// 解析 @Configuration 的所有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 {
			//这一步会解析出@PropertySource、@ComponentScan、@Import、@ImportResource这些注解的所有class
			parser.parse(candidates);
			//校验@Bean注解的方法不能为static或overridable
			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());
			}
			//将解析完后的类装载BeanDefinition，
			this.reader.loadBeanDefinitions(configClasses);
			alreadyParsed.addAll(configClasses);

			candidates.clear();
			//是否有新的BeanDefinition,有重新装载。
			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();
		}
	}

ConfigurationClassUtils.checkConfigurationClassCandidate()

static {
		candidateIndicators.add(Component.class.getName());
		candidateIndicators.add(ComponentScan.class.getName());
		candidateIndicators.add(Import.class.getName());
		candidateIndicators.add(ImportResource.class.getName());
	}
....................................
Map<String, Object> config = metadata.getAnnotationAttributes(Configuration.class.getName());
		if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
		}
		else if (config != null || isConfigurationCandidate(metadata)) {
			beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
		}
		else {
			return false;
		}

ConfigurationClassParser.parse();

public void parse(Set<BeanDefinitionHolder> configCandidates) {
		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
				//根据BeanDefinition类型的不同，调用parse()不同的重载方法。
				// 最终都收processConfigurationClass()
				if (bd instanceof AnnotatedBeanDefinition) {
					parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
				}
				else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
					parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
				}
				else {
					parse(bd.getBeanClassName(), holder.getBeanName());
				}
			}
			catch (BeanDefinitionStoreException ex) {
				throw ex;
			}
			catch (Throwable ex) {
				throw new BeanDefinitionStoreException(
						"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
			}
		}
        //处理延迟importSelector
		this.deferredImportSelectorHandler.process();
	}
.....................................................
protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
		// 根据@Conditional判断是否加载
		if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
			return;
		}

		ConfigurationClass existingClass = this.configurationClasses.get(configClass);
		if (existingClass != null) {
			if (configClass.isImported()) {
				if (existingClass.isImported()) {
					existingClass.mergeImportedBy(configClass);
				}
				// Otherwise ignore new imported config class; existing non-imported class overrides it.
				return;
			}
			else {
				// Explicit bean definition found, probably replacing an import.
				// Let's remove the old one and go with the new one.
				this.configurationClasses.remove(configClass);
				this.knownSuperclasses.values().removeIf(configClass::equals);
			}
		}
		// Recursively process the configuration class and its superclass hierarchy.
		//统一的方式去处理带有注解的类
		SourceClass sourceClass = asSourceClass(configClass);
		do {
			//
			sourceClass = doProcessConfigurationClass(configClass, sourceClass);
		}
		while (sourceClass != null);
		this.configurationClasses.put(configClass, configClass);
	}
...............................................................
//解析注解
protected final SourceClass doProcessConfigurationClass(ConfigurationClass configClass, SourceClass sourceClass)
			throws IOException {

		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// Recursively process any member (nested) classes first
			//处理嵌套类 
			processMemberClasses(configClass, sourceClass);
		}

		// Process any @PropertySource annotations
		for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), PropertySources.class,
				org.springframework.context.annotation.PropertySource.class)) {
			if (this.environment instanceof ConfigurableEnvironment) {
				processPropertySource(propertySource);
			}
			else {
				logger.info("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
						"]. Reason: Environment must implement ConfigurableEnvironment");
			}
		}

		// Process any @ComponentScan annotations
		Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
				sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
		if (!componentScans.isEmpty() &&
				!this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
			for (AnnotationAttributes componentScan : componentScans) {
				// The config class is annotated with @ComponentScan -> perform the scan immediately
				Set<BeanDefinitionHolder> scannedBeanDefinitions =
						this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
				// Check the set of scanned definitions for any further config classes and parse recursively if needed
				for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
					BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
					if (bdCand == null) {
						bdCand = holder.getBeanDefinition();
					}
					if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
						parse(bdCand.getBeanClassName(), holder.getBeanName());
					}
				}
			}
		}

		// Process any @Import annotations
		processImports(configClass, sourceClass, getImports(sourceClass), true);

		// Process any @ImportResource annotations
		AnnotationAttributes importResource =
				AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
		if (importResource != null) {
			String[] resources = importResource.getStringArray("locations");
			Class<? extends BeanDefinitionReader> readerClass = importResource.getClass("reader");
			for (String resource : resources) {
				String resolvedResource = this.environment.resolveRequiredPlaceholders(resource);
				configClass.addImportedResource(resolvedResource, readerClass);
			}
		}

		// Process individual @Bean methods
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		// Process default methods on interfaces
		processInterfaces(configClass, sourceClass);

		// Process superclass, if any
		if (sourceClass.getMetadata().hasSuperClass()) {
			String superclass = sourceClass.getMetadata().getSuperClassName();
			if (superclass != null && !superclass.startsWith("java") &&
					!this.knownSuperclasses.containsKey(superclass)) {
				this.knownSuperclasses.put(superclass, configClass);
				// Superclass found, return its annotation metadata and recurse
				return sourceClass.getSuperClass();
			}
		}

		// No superclass -> processing is complete
		return null;
	}

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;
		}
        //是否通过@Import(ImportSelector)的方式添加到容器。
		if (configClass.isImported()) {
			registerBeanDefinitionForImportedConfigurationClass(configClass);
		}
		//是否有@Bean注解方法
		for (BeanMethod beanMethod : configClass.getBeanMethods()) {
			loadBeanDefinitionsForBeanMethod(beanMethod);
		}
		loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
		//@import是否实现了ImportBeanDefinitionRegistrar接口,实现
		//则执行ImportBeanDefinitionRegistrar的registerBeanDefinitions()方法。自己实现的registerBeanDefinitions()方法
		loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
	}

postProcessBeanFactory() ，(1)对加了@Configuration注解的类进行CGLIB代理。(2)向Spring中添加一个后置处理器ImportAwareBeanPostProcessor。

/**
	 * Prepare the Configuration classes for servicing bean requests at runtime
	 * by replacing them with CGLIB-enhanced subclasses.
	 */
	@Override
	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		int factoryId = System.identityHashCode(beanFactory);
		if (this.factoriesPostProcessed.contains(factoryId)) {
			throw new IllegalStateException(
					"postProcessBeanFactory already called on this post-processor against " + beanFactory);
		}
		this.factoriesPostProcessed.add(factoryId);
		if (!this.registriesPostProcessed.contains(factoryId)) {
			// BeanDefinitionRegistryPostProcessor hook apparently not supported...
			// Simply call processConfigurationClasses lazily at this point then.
			processConfigBeanDefinitions((BeanDefinitionRegistry) beanFactory);
		}
		//对full属性的BeanDefinition进行增强
		enhanceConfigurationClasses(beanFactory);
		//添加一个实现了InstantiationAwareBeanPostProcessorAdapter的后处理器
		//在AutowiredAnnotationBeanPostProcessor的postProcessProperties方法尝试自动装配其他配置bean之前，请插入BeanFactory。
		beanFactory.addBeanPostProcessor(new ImportAwareBeanPostProcessor(beanFactory));
	}

/**
	 * Loads the specified class and generates a CGLIB subclass of it equipped with
	 * container-aware callbacks capable of respecting scoping and other bean semantics.
	 * @return the enhanced subclass
	 */
	public Class<?> enhance(Class<?> configClass, @Nullable ClassLoader classLoader) {
		if (EnhancedConfiguration.class.isAssignableFrom(configClass)) {
			if (logger.isDebugEnabled()) {
				logger.debug(String.format("Ignoring request to enhance %s as it has " +
						"already been enhanced. This usually indicates that more than one " +
						"ConfigurationClassPostProcessor has been registered (e.g. via " +
						"<context:annotation-config>). This is harmless, but you may " +
						"want check your configuration and remove one CCPP if possible",
						configClass.getName()));
			}
			return configClass;
		}
		//添加了两个MethodInterceptor(BeanMethodInterceptor和BeanFactoryAwareMethodInterceptor)
		//前者是对加了@Bean注解的方法进行增强，后者是为代理对象的beanFactory属性进行增强
		Class<?> enhancedClass = createClass(newEnhancer(configClass, classLoader));
		if (logger.isTraceEnabled()) {
			logger.trace(String.format("Successfully enhanced %s; enhanced class name is: %s",
					configClass.getName(), enhancedClass.getName()));
		}
		return enhancedClass;
	}

	/**
	 * Creates a new CGLIB {@link Enhancer} instance.
	 */
	private Enhancer newEnhancer(Class<?> configSuperClass, @Nullable ClassLoader classLoader) {
		Enhancer enhancer = new Enhancer();
		enhancer.setSuperclass(configSuperClass);
		enhancer.setInterfaces(new Class<?>[] {EnhancedConfiguration.class});
		enhancer.setUseFactory(false);
		enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
		enhancer.setStrategy(new BeanFactoryAwareGeneratorStrategy(classLoader));
		enhancer.setCallbackFilter(CALLBACK_FILTER);
		enhancer.setCallbackTypes(CALLBACK_FILTER.getCallbackTypes());
		return enhancer;
	}

private static class ImportAwareBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter {

		private final BeanFactory beanFactory;

		public ImportAwareBeanPostProcessor(BeanFactory beanFactory) {
			this.beanFactory = beanFactory;
		}

		@Override
		public PropertyValues postProcessProperties(@Nullable PropertyValues pvs, Object bean, String beanName) {
			// Inject the BeanFactory before AutowiredAnnotationBeanPostProcessor's
			// postProcessProperties method attempts to autowire other configuration beans.
            //为被CGLIB增强时实现了EnhancedConfiguration接口的代理类，设置beanFactory属性
			if (bean instanceof EnhancedConfiguration) {
				((EnhancedConfiguration) bean).setBeanFactory(this.beanFactory);
			}
			return pvs;
		}

		@Override
		public Object postProcessBeforeInitialization(Object bean, String beanName) {
			if (bean instanceof ImportAware) {
				ImportRegistry ir = this.beanFactory.getBean(IMPORT_REGISTRY_BEAN_NAME, ImportRegistry.class);
				AnnotationMetadata importingClass = ir.getImportingClassFor(ClassUtils.getUserClass(bean).getName());
				if (importingClass != null) {
					((ImportAware) bean).setImportMetadata(importingClass);
				}
			}
			return bean;
		}
	}