Spring Boot 3.x 自动配置详解

	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
		PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());

		// 如果beanFactory中是否包含LoadTimeWeaver，如果包含则使用临时ClassLoader进行处理，LoadTimeWeaver是一种类加载器的动态织入技术
		if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}
	}

public static void invokeBeanFactoryPostProcessors(
			ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

		Set<String> processedBeans = new HashSet<>();
		//如果beanFactory 是BeanDefinitionRegistry的实现，先处理BeanDefinitionRegistryPostProcessors
		if (beanFactory instanceof BeanDefinitionRegistry registry) {
			List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
			List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

			for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
				if (postProcessor instanceof BeanDefinitionRegistryPostProcessor registryProcessor) {
					registryProcessor.postProcessBeanDefinitionRegistry(registry);
					registryProcessors.add(registryProcessor);
				}
				else {
					regularPostProcessors.add(postProcessor);
				}
			}

			List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

			// 先处理 PriorityOrdered 的 BeanDefinitionRegistryPostProcessor
			String[] postProcessorNames =
					beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			
//处理BeanDefinitionRegistryPostProcessors
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
			currentRegistryProcessors.clear();

			// 再处理 Ordered 的 BeanDefinitionRegistryPostProcessor
			postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
			for (String ppName : postProcessorNames) {
				if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
					currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
					processedBeans.add(ppName);
				}
			}
			sortPostProcessors(currentRegistryProcessors, beanFactory);
			registryProcessors.addAll(currentRegistryProcessors);
			invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
			currentRegistryProcessors.clear();

			 // 最后处理剩余的 BeanDefinitionRegistryPostProcessor，直到没有新的 BeanDefinitionRegistryPostProcessor 添加为止
			boolean reiterate = true;
			while (reiterate) {
				reiterate = false;
				postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
				for (String ppName : postProcessorNames) {
					if (!processedBeans.contains(ppName)) {
						currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
						processedBeans.add(ppName);
						reiterate = true;
					}
				}
				sortPostProcessors(currentRegistryProcessors, beanFactory);
				registryProcessors.addAll(currentRegistryProcessors);
				invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
				currentRegistryProcessors.clear();
			}

			// 处理所有 BeanFactoryPostProcessor
			invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
			invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
		}

		else {
			// 处理普通的上下文中的BeanFactoryPostProcessor
	invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
		}

		//获取所有常规化Bean，但不初始化，保留让后期的post-processors处理
		String[] postProcessorNames =
				beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

		
		//分离实现PriorityOrdered、Ordered和其他的BeanFactoryPostProcessors
		List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
		List<String> orderedPostProcessorNames = new ArrayList<>();
		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
		for (String ppName : postProcessorNames) {
			if (processedBeans.contains(ppName)) {
				// 跳过已经处理的
			}
			else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
				priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
			}
			else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
				orderedPostProcessorNames.add(ppName);
			}
			else {
				nonOrderedPostProcessorNames.add(ppName);
			}
		}

		
		//首先处理实现了PriorityOrdered的BeanFactoryPostProcessors
		sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

		//处理实现了Ordered的BeanFactoryPostProcessors
		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
		for (String postProcessorName : orderedPostProcessorNames) {
			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		sortPostProcessors(orderedPostProcessors, beanFactory);
		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

		// 最后处理其他的BeanFactoryPostProcessors
		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
		for (String postProcessorName : nonOrderedPostProcessorNames) {
			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
		}
		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

		// 清除缓存
		beanFactory.clearMetadataCache();
	}

private static void invokeBeanDefinitionRegistryPostProcessors(
		Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) {

//循环处理BeanDefinitionRegistryPostProcessor实现
	for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
	//步骤日志记录
		StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process")
				.tag("postProcessor", postProcessor::toString);
		postProcessor.postProcessBeanDefinitionRegistry(registry);
		postProcessBeanDefRegistry.end();
	}
}

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
//计算hashcode
		int registryId = System.identityHashCode(registry);
		//判断是否处理过
		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);

//处理配置Bean定义信息
		processConfigBeanDefinitions(registry);
	}

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
		List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
		//获取容器中所有的bean定义名称
		String[] candidateNames = registry.getBeanDefinitionNames();

		for (String beanName : candidateNames) {
		// 获取 bean 的定义
			BeanDefinition beanDef = registry.getBeanDefinition(beanName);
			// 检查该 bean 是否已经被处理成配置类
			if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
				if (logger.isDebugEnabled()) {
					logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
				}
			}
			// 检查该 bean 是否是配置类候选者
			else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
				configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
			}
		}

		// 如果没有需要处理的配置类，则直接返回
		if (configCandidates.isEmpty()) {
			return;
		}

		// 对配置类候选者进行排序，按照先前确定的 @Order 值排序
		configCandidates.sort((bd1, bd2) -> {
			int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
			int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
			return Integer.compare(i1, i2);
		});

		// 检查是否有自定义的 bean 名称生成策略
		SingletonBeanRegistry sbr = null;
		if (registry instanceof SingletonBeanRegistry _sbr) {
			sbr = _sbr;
			if (!this.localBeanNameGeneratorSet) {
				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();
		}

		// 解析每个 @Configuration 类
		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 {
			StartupStep processConfig = this.applicationStartup.start("spring.context.config-classes.parse");
			//解析
			parser.parse(candidates);
			//验证
			parser.validate();

			Set<ConfigurationClass> configClasses = new LinkedHashSet<>(parser.getConfigurationClasses());
			//去除已经解析的类
			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);
			processConfig.tag("classCount", () -> String.valueOf(configClasses.size())).end();
// 检查新的 BeanDefinition 是否包含新的配置类候选者
			candidates.clear();
			if (registry.getBeanDefinitionCount() > candidateNames.length) {
				String[] newCandidateNames = registry.getBeanDefinitionNames();
				Set<String> oldCandidateNames = Set.of(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());

		// 注册 ImportRegistry 为一个 bean，以支持 @ImportAware ConfigurationClass
		if (sbr != null && !sbr.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
			sbr.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
		}

		// 存储 PropertySourceDescriptors，便于在AOT中使用
		this.propertySourceDescriptors = parser.getPropertySourceDescriptors();

		if (this.metadataReaderFactory instanceof CachingMetadataReaderFactory cachingMetadataReaderFactory) {
			// 清除缓存，防止由于缓存无法更新导致的出错问题
			cachingMetadataReaderFactory.clearCache();
		}
	}

public void parse(Set<BeanDefinitionHolder> configCandidates) {
		for (BeanDefinitionHolder holder : configCandidates) {
			BeanDefinition bd = holder.getBeanDefinition();
			try {
			// 如果 BeanDefinition 是一个 AnnotatedBeanDefinition，则需要解析该 BeanDefinition 中的注解信息
				if (bd instanceof AnnotatedBeanDefinition annotatedBeanDef) {
					parse(annotatedBeanDef.getMetadata(), holder.getBeanName());
				}
				// 如果 BeanDefinition 不是 AnnotatedBeanDefinition，并且具有 beanClass 属性，则解析该 beanClass 中的注解信息
				else if (bd instanceof AbstractBeanDefinition abstractBeanDef && abstractBeanDef.hasBeanClass()) {
					parse(abstractBeanDef.getBeanClass(), holder.getBeanName());
				}
				else {
				// 如果 BeanDefinition 没有 beanClass 属性，则解析该 BeanDefinition 中的 beanClassName 所指定的类中的注解信息
					parse(bd.getBeanClassName(), holder.getBeanName());
				}
			}
			catch (BeanDefinitionStoreException ex) {
				throw ex;
			}
			catch (Throwable ex) {
				throw new BeanDefinitionStoreException(
						"Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
			}
		}
		
		//处理所有的DeferredImportSelector实例
		this.deferredImportSelectorHandler.process();
	}

public void process() {
			List<DeferredImportSelectorHolder> deferredImports = this.deferredImportSelectors;
			this.deferredImportSelectors = null;
			try {
				if (deferredImports != null) {
					DeferredImportSelectorGroupingHandler handler = new DeferredImportSelectorGroupingHandler();
					deferredImports.sort(DEFERRED_IMPORT_COMPARATOR);
					deferredImports.forEach(handler::register);
					handler.processGroupImports();
				}
			}
			finally {
				this.deferredImportSelectors = new ArrayList<>();
			}
		}

public void processGroupImports() {
			//遍历所有分组
			for (DeferredImportSelectorGrouping grouping : this.groupings.values()) {
				//获取候选过滤器
				Predicate<String> exclusionFilter = grouping.getCandidateFilter();
				//遍历分组中的每个元素
				grouping.getImports().forEach(entry -> {
					ConfigurationClass configurationClass = this.configurationClasses.get(entry.getMetadata());
					try {
					//处理当前元素
						processImports(configurationClass, asSourceClass(configurationClass, exclusionFilter),
								Collections.singleton(asSourceClass(entry.getImportClassName(), exclusionFilter)),
								exclusionFilter, false);
					}
					catch (BeanDefinitionStoreException ex) {
						throw ex;
					}
					catch (Throwable ex) {
						throw new BeanDefinitionStoreException(
								"Failed to process import candidates for configuration class [" +
										configurationClass.getMetadata().getClassName() + "]", ex);
					}
				});
			}
		}

public Iterable<Group.Entry> getImports() {
	for (DeferredImportSelectorHolder deferredImport : this.deferredImports) {
//处理每个分组的DeferredImportSelectorHolder
		this.group.process(deferredImport.getConfigurationClass().getMetadata(),
				deferredImport.getImportSelector());
	}
	//返回需要导入的类
	return this.group.selectImports();
}

public void process(AnnotationMetadata annotationMetadata, DeferredImportSelector deferredImportSelector) {
	Assert.state(deferredImportSelector instanceof AutoConfigurationImportSelector,
			() -> String.format("Only %s implementations are supported, got %s",
					AutoConfigurationImportSelector.class.getSimpleName(),
					deferredImportSelector.getClass().getName()));
					
					//转为为AutoConfigurationImportSelector，获取AutoConfigurationEntry
	AutoConfigurationEntry autoConfigurationEntry = ((AutoConfigurationImportSelector) deferredImportSelector)
		.getAutoConfigurationEntry(annotationMetadata);
	
//添加到autoConfigurationEntries变量中，供后期使用
this.autoConfigurationEntries.add(autoConfigurationEntry);
//设置entries变量，导入的类名和元注解映射关系
	for (String importClassName : autoConfigurationEntry.getConfigurations()) {
		this.entries.putIfAbsent(importClassName, annotationMetadata);
	}
}

protected AutoConfigurationEntry getAutoConfigurationEntry(AnnotationMetadata annotationMetadata) {
    // 如果自动配置不可用，则返回 EMPTY_ENTRY
	if (!isEnabled(annotationMetadata)) {
		return EMPTY_ENTRY;
	}
	// 获取注解的属性
	AnnotationAttributes attributes = getAttributes(annotationMetadata);
	// 获取候选自动配置类，此文关键
	List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);
	// 去除重复的自动配置类
	configurations = removeDuplicates(configurations);
	// 获取需要排除的自动配置类，spring.autoconfigure.exclude配置
	Set<String> exclusions = getExclusions(annotationMetadata, attributes);
	// 检查是否有被排除的自动配置类
	checkExcludedClasses(configurations, exclusions);
	// 去除被排除的自动配置类
	configurations.removeAll(exclusions);
	// 使用 ConfigurationClassFilter 过滤自动配置类
	configurations = getConfigurationClassFilter().filter(configurations);
	// 发送自动配置事件
	fireAutoConfigurationImportEvents(configurations, exclusions);
	return new AutoConfigurationEntry(configurations, exclusions);
}

protected List<String> getCandidateConfigurations(AnnotationMetadata metadata, AnnotationAttributes attributes) {
//从类路径的META-INF/spring中载入名为AutoConfiguration全限定名的类
	List<String> configurations = ImportCandidates.load(AutoConfiguration.class, getBeanClassLoader())
		.getCandidates();
	Assert.notEmpty(configurations,
			"No auto configuration classes found in "
					+ "META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports. If you "
					+ "are using a custom packaging, make sure that file is correct.");
	return configurations;
}

public static ImportCandidates load(Class<?> annotation, ClassLoader classLoader) {
	Assert.notNull(annotation, "'annotation' must not be null");
	ClassLoader classLoaderToUse = decideClassloader(classLoader);
	//将META-INF/spring/%s.imports字符串格式化为指定的路径
	String location = String.format(LOCATION, annotation.getName());
	Enumeration<URL> urls = findUrlsInClasspath(classLoaderToUse, location);
	List<String> importCandidates = new ArrayList<>();
	while (urls.hasMoreElements()) {
		URL url = urls.nextElement();
		importCandidates.addAll(readCandidateConfigurations(url));
	}
	return new ImportCandidates(importCandidates);
}

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
        Collection<SourceClass> importCandidates, Predicate<String> exclusionFilter,
        boolean checkForCircularImports) {

    // 如果没有可导入的类，则直接返回
    if (importCandidates.isEmpty()) {
        return;
    }

    // 检查循环导入
    if (checkForCircularImports && isChainedImportOnStack(configClass)) {
        this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
    }
    else {
        // 将当前配置类推入导入栈中
        this.importStack.push(configClass);
        try {
            // 处理每个导入的类
            for (SourceClass candidate : importCandidates) {
                if (candidate.isAssignable(ImportSelector.class)) {
                    // Candidate class is an ImportSelector -> delegate to it to determine imports
                    // 如果候选类是 ImportSelector 的子类，则交由它来决定导入哪些类
                    Class<?> candidateClass = candidate.loadClass();
                    ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
                            this.environment, this.resourceLoader, this.registry);
                    Predicate<String> selectorFilter = selector.getExclusionFilter();
                    if (selectorFilter != null) {
                        exclusionFilter = exclusionFilter.or(selectorFilter);
                    }
                    if (selector instanceof DeferredImportSelector deferredImportSelector) {
                        this.deferredImportSelectorHandler.handle(configClass, deferredImportSelector);
                    }
                    else {
                        String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                        Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames, exclusionFilter);
                        processImports(configClass, currentSourceClass, importSourceClasses, exclusionFilter, false);
                    }
                }
                else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
                    // Candidate class is an ImportBeanDefinitionRegistrar ->
                    // delegate to it to register additional bean definitions
                    // 如果候选类是 ImportBeanDefinitionRegistrar 的子类，则交由它来注册更多的 Bean 定义
                    Class<?> candidateClass = candidate.loadClass();
                    ImportBeanDefinitionRegistrar registrar =
                            ParserStrategyUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class,
                                    this.environment, this.resourceLoader, this.registry);
                    configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
                }
                else {
                    // Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
                    // process it as an @Configuration class
                    // 如果候选类不是 ImportSelector 或 ImportBeanDefinitionRegistrar 的子类，则将其作为 @Configuration 类来处理
                    this.importStack.registerImport(
                            currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
                    processConfigurationClass(candidate.asConfigClass(configClass), exclusionFilter);
                }
            }
        }
        catch (BeanDefinitionStoreException ex) {
            throw ex;
        }
        catch (Throwable ex) {
            throw new BeanDefinitionStoreException(
                    "Failed to process import candidates for configuration class [" +
                    configClass.getMetadata().getClassName() + "]: " + ex.getMessage(), ex);
        }
        finally {
            this.importStack.pop();
        }
    }
}

protected void processConfigurationClass(ConfigurationClass configClass, Predicate<String> filter) throws IOException {
    // 如果该配置类被标记为跳过，则直接返回，不需要再处理
	if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
		return;
	}

    // 如果已经存在同名的配置类，则判断两者的导入情况并合并
	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);
		}
	}

    // 递归地处理该配置类及其父类的继承关系，解析 Bean 定义
	SourceClass sourceClass = asSourceClass(configClass, filter);
	do {
		sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
	}
	while (sourceClass != null);

    // 将该配置类加入到 configurationClasses 中
	this.configurationClasses.put(configClass, configClass);
}

protected final SourceClass doProcessConfigurationClass(
			ConfigurationClass configClass, SourceClass sourceClass, Predicate<String> filter)
			throws IOException {

		if (configClass.getMetadata().isAnnotated(Component.class.getName())) {
			// 如果该配置类被@Component注解标记，则递归处理任何嵌套类。
			processMemberClasses(configClass, sourceClass, filter);
		}

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

		// 处理@ComponentScan注解
		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());
				// 检查扫描的定义集是否有任何进一步的配置类，并在需要时递归解析

				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());
					}
				}
			}
		}

		// 处理@Import
		processImports(configClass, sourceClass, getImports(sourceClass), filter, true);

		// 处理@ImportResource
		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);
			}
		}

		// 处理单个的@Bean方法
		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
		for (MethodMetadata methodMetadata : beanMethods) {
			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
		}

		// 处理接口上的默认方法
		processInterfaces(configClass, sourceClass);

		// 处理超类
		if (sourceClass.getMetadata().hasSuperClass()) {
			String superclass = sourceClass.getMetadata().getSuperClassName();
			if (superclass != null && !superclass.startsWith("java") &&
					!this.knownSuperclasses.containsKey(superclass)) {
				this.knownSuperclasses.put(superclass, configClass);
				// 找到超类，返回其注释元数据并递归
				return sourceClass.getSuperClass();
			}
		}

		// 没有超类，完成
		return null;
	}