ConfigurationClassPostProcessor 解析

SpringApplication#refresh方法中,会去调用BeanDefinitionPostProcessor去进行预处理,这里有一个很重要的 processor 就是 ConfigurationClassPostProcessor , 他主要负责将 config bean 加载到 beaDefinitionMap 中。

postProcessBeanDefinitionRegistry

我们先来看一下代码:

@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);
    }

主要做了两件事情:
1、生成当前 registry 的 id,然后到 registriesPostProcessedregistriesPostProcessed 中查找,是否存在,主要作用是去重。
2、假如没有重复调用 processConfigBeanDefinitions 去加载。

processConfigBeanDefinitions

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
        List configCandidates = new ArrayList<>();
// 获取已经注册的 bean 名称,这里一般是我们的启动 Application 类。
        String[] candidateNames = registry.getBeanDefinitionNames();

        for (String beanName : candidateNames) {
            BeanDefinition beanDef = registry.getBeanDefinition(beanName);
// 假如 beanDefinition 中的 ConfigurationClass 属性为 full 或者 lite 那代表已经解析过了,跳过。
            if (beanDef.getAttribute(ConfigurationClassUtils.CONFIGURATION_CLASS_ATTRIBUTE) != null) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
                }
            }
// 判断当前类是否是 config 类,假如是就加入到 configCandidates 中。
            else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
                configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
            }
        }
// 假如 configCandidates 为空就返回
        // Return immediately if no @Configuration classes were found
        if (configCandidates.isEmpty()) {
            return;
        }

        // Sort by previously determined @Order value, if applicable
// 对 configCandidates 使用 @Order 注解进行排序
        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(
                        AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR);
                if (generator != null) {
// 设置 beanNameGenerator
                    this.componentScanBeanNameGenerator = generator;
                    this.importBeanNameGenerator = generator;
                }
            }
        }

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

        // Parse each @Configuration class
//实例化 ConfigurationClassParser 为后续解析准备。
        ConfigurationClassParser parser = new ConfigurationClassParser(
                this.metadataReaderFactory, this.problemReporter, this.environment,
                this.resourceLoader, this.componentScanBeanNameGenerator, registry);
// 初始话 candidates 和 alreadyParsed 两个集合
        Set candidates = new LinkedHashSet<>(configCandidates);
        Set alreadyParsed = new HashSet<>(configCandidates.size());
        do {
// 进行解析
            parser.parse(candidates);
            parser.validate();
// 获取解析到的 ConfigurationClass
            Set 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());
            }
// 加载 ConfigurationClass 的 beanDefinition
            this.reader.loadBeanDefinitions(configClasses);
// 添加到 ConfigurationClass 中。
            alreadyParsed.addAll(configClasses);

            candidates.clear();
            if (registry.getBeanDefinitionCount() > candidateNames.length) {
                String[] newCandidateNames = registry.getBeanDefinitionNames();
                Set oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
                Set 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();
        }
    }

主要做了如下7件事情:
1、获取已经注册的bean名称进行遍历:
2、对configCandidates 进行 排序,按照@Order 配置的值进行排序。
3、如果BeanDefinitionRegistry 是SingletonBeanRegistry 子类的话,将registry强转为SingletonBeanRegistry。
4、实例化ConfigurationClassParser 为了解析各个配置类.实例化2个set,candidates 用于将之前加入的configCandidates 进行去重,alreadyParsed 用于判断是否处理过。
5、进行解析。
6、如果SingletonBeanRegistry 不包含org.springframework.context.annotation.ConfigurationClassPostProcessor.importRegistry,则注册一个,bean 为 ImportRegistry. 一般都会进行注册的。
7、清除缓存。
我们先来看一下判断该 bean 是否为 configClass 的方法。

ConfigurationClassUtils#checkConfigurationClassCandidate

public static boolean checkConfigurationClassCandidate(
            BeanDefinition beanDef, MetadataReaderFactory metadataReaderFactory) {
// 获取类名,假如不存在则返回。
        String className = beanDef.getBeanClassName();
        if (className == null || beanDef.getFactoryMethodName() != null) {
            return false;
        }
// 获取 AnnotationMetadata
        AnnotationMetadata metadata;
        if (beanDef instanceof AnnotatedBeanDefinition &&
                className.equals(((AnnotatedBeanDefinition) beanDef).getMetadata().getClassName())) {
            // Can reuse the pre-parsed metadata from the given BeanDefinition...
// 检查是否可以是 AnnotatedBeanDefinition ,是就直接从 BeanDefinition 中获取
            metadata = ((AnnotatedBeanDefinition) beanDef).getMetadata();
        }
        else if (beanDef instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) beanDef).hasBeanClass()) {
            // Check already loaded Class if present...
            // since we possibly can't even load the class file for this Class.
// 如果BeanDefinition 是 AnnotatedBeanDefinition的实例,并且beanDef 有 beanClass 属性存在没有则实例化StandardAnnotationMetadata
            Class beanClass = ((AbstractBeanDefinition) beanDef).getBeanClass();
            if (BeanFactoryPostProcessor.class.isAssignableFrom(beanClass) ||
                    BeanPostProcessor.class.isAssignableFrom(beanClass) ||
                    AopInfrastructureBean.class.isAssignableFrom(beanClass) ||
                    EventListenerFactory.class.isAssignableFrom(beanClass)) {
                return false;
            }
            metadata = AnnotationMetadata.introspect(beanClass);
        }
        else {
            try {
// 否则 通过MetadataReaderFactory 中的MetadataReader 进行读取
                MetadataReader metadataReader = metadataReaderFactory.getMetadataReader(className);
                metadata = metadataReader.getAnnotationMetadata();
            }
            catch (IOException ex) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Could not find class file for introspecting configuration annotations: " +
                            className, ex);
                }
                return false;
            }
        }
// 如果存在Configuration 注解,则为BeanDefinition 设置configurationClass属性为full
        Map config = metadata.getAnnotationAttributes(Configuration.class.getName());
        if (config != null && !Boolean.FALSE.equals(config.get("proxyBeanMethods"))) {
            beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_FULL);
        }
// 如果AnnotationMetadata 中有Component,ComponentScan,Import,ImportResource 注解中的任意一个,或者存在 被@bean 注解的方法,则返回true
        else if (config != null || isConfigurationCandidate(metadata)) {
            beanDef.setAttribute(CONFIGURATION_CLASS_ATTRIBUTE, CONFIGURATION_CLASS_LITE);
        }
        else {
            return false;
        }

        // It's a full or lite configuration candidate... Let's determine the order value, if any.
        Integer order = getOrder(metadata);
        if (order != null) {
            beanDef.setAttribute(ORDER_ATTRIBUTE, order);
        }

        return true;
    }

详细的内容都行卸载注释中了,其实主要是对该类的注解进行判断。

ConfigurationClassParser#parse

public void parse(Set configCandidates) {
        for (BeanDefinitionHolder holder : configCandidates) {
            BeanDefinition bd = holder.getBeanDefinition();
            try {
                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);
            }
        }

        this.deferredImportSelectorHandler.process();
    }

其主要做了两件事情:
1、遍历configCandidates ,进行处理.根据BeanDefinition 的类型 做不同的处理,一般都会调用ConfigurationClassParser#parse 进行解析。
2、处理ImportSelect。
我们先来看一下第一步:

ConfigurationClassParser#parse
protected void processConfigurationClass(ConfigurationClass configClass, Predicate filter) throws IOException {
        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.
        SourceClass sourceClass = asSourceClass(configClass, filter);
        do {
            sourceClass = doProcessConfigurationClass(configClass, sourceClass, filter);
        }
        while (sourceClass != null);

        this.configurationClasses.put(configClass, configClass);
    }

主要做如下4件事情:
1、调用 shouldSkip 方法来判断该 configClass 是否需要 跳过。
2、处理Imported 的情况。
3、递归调用进行解析。
4、添加到configurationClasses中。
我们先来看一下 shouldSkip 方法:

public boolean shouldSkip(@Nullable AnnotatedTypeMetadata metadata, @Nullable ConfigurationPhase phase) {
        if (metadata == null || !metadata.isAnnotated(Conditional.class.getName())) {
            return false;
        }

        if (phase == null) {
            if (metadata instanceof AnnotationMetadata &&
                    ConfigurationClassUtils.isConfigurationCandidate((AnnotationMetadata) metadata)) {
                return shouldSkip(metadata, ConfigurationPhase.PARSE_CONFIGURATION);
            }
            return shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN);
        }

        List conditions = new ArrayList<>();
        for (String[] conditionClasses : getConditionClasses(metadata)) {
            for (String conditionClass : conditionClasses) {
                Condition condition = getCondition(conditionClass, this.context.getClassLoader());
                conditions.add(condition);
            }
        }

        AnnotationAwareOrderComparator.sort(conditions);

        for (Condition condition : conditions) {
            ConfigurationPhase requiredPhase = null;
            if (condition instanceof ConfigurationCondition) {
                requiredPhase = ((ConfigurationCondition) condition).getConfigurationPhase();
            }
            if ((requiredPhase == null || requiredPhase == phase) && !condition.matches(this.context, metadata)) {
                return true;
            }
        }

        return false;
    }

主要做4件事情:
1、判断该类是否被 Condition 注解修饰,假如没有就直接返回。
2、如果参数中沒有设置条件注解的生效阶段
(1)、是配置类的话直接使用PARSE_CONFIGURATION阶段,递归调用shouldSkip 进行判断。
(2)、否则使用REGISTER_BEAN阶段,递归调用shouldSkip 进行判断。
3、获取配置类的条件注解得到条件数据,并添加到集合中.
4、遍历conditions,进行判断,如果阶段不满足条件的话,返回true并跳过这个bean的解析。
接下来我们看一下真正解析的步骤:

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

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

        // 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 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 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), filter, true);

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

        // Process individual @Bean methods
        Set 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;
    }

主要做了如下8件事情:
1、如果该类使用 @Component 注解,调用 processMemberClasses 方法,其主要作用是将类放到 importStack 中,并且判断是否有循环依赖度问题。
2、处理@PropertySource.通过遍历该类中的@PropertySource的注解,如果该类中的environment是ConfigurableEnvironment 子类的话,则调用processPropertySource进行处理。
3、处理@ComponentScan,通过遍历该类上的@ComponentScan 注解,并使用 conditionEvaluator.shouldSkip 进行判断是否需要跳过。没有就通过ComponentScanAnnotationParser#parse方法进行扫描:

public Set parse(AnnotationAttributes componentScan, final String declaringClass) {
        ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
                componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

        Class generatorClass = componentScan.getClass("nameGenerator");
        boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
        scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
                BeanUtils.instantiateClass(generatorClass));

        ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
        if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
            scanner.setScopedProxyMode(scopedProxyMode);
        }
        else {
            Class resolverClass = componentScan.getClass("scopeResolver");
            scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
        }

        scanner.setResourcePattern(componentScan.getString("resourcePattern"));

        for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addIncludeFilter(typeFilter);
            }
        }
        for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addExcludeFilter(typeFilter);
            }
        }

        boolean lazyInit = componentScan.getBoolean("lazyInit");
        if (lazyInit) {
            scanner.getBeanDefinitionDefaults().setLazyInit(true);
        }

        Set basePackages = new LinkedHashSet<>();
        String[] basePackagesArray = componentScan.getStringArray("basePackages");
        for (String pkg : basePackagesArray) {
            String[] tokenized = StringUtils.tokenizeToStringArray(this.environment.resolvePlaceholders(pkg),
                    ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS);
            Collections.addAll(basePackages, tokenized);
        }
        for (Class clazz : componentScan.getClassArray("basePackageClasses")) {
            basePackages.add(ClassUtils.getPackageName(clazz));
        }
        if (basePackages.isEmpty()) {
            basePackages.add(ClassUtils.getPackageName(declaringClass));
        }

        scanner.addExcludeFilter(new AbstractTypeHierarchyTraversingFilter(false, false) {
            @Override
            protected boolean matchClassName(String className) {
                return declaringClass.equals(className);
            }
        });
        return scanner.doScan(StringUtils.toStringArray(basePackages));
    }

1、初始化 ClassPathBeanDefinitionScanner。
2、为 ClassPathBeanDefinitionScanner 设置 nameGenerator、scopedProxy、scopeResolver、includeFilters 和 excludeFilters
3、调用 scanner.doScan 方法,进行扫描:

protected Set doScan(String... basePackages) {
        Assert.notEmpty(basePackages, "At least one base package must be specified");
        Set beanDefinitions = new LinkedHashSet<>();
        for (String basePackage : basePackages) {
            Set candidates = findCandidateComponents(basePackage);
            for (BeanDefinition candidate : candidates) {
                ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
                candidate.setScope(scopeMetadata.getScopeName());
                String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
                if (candidate instanceof AbstractBeanDefinition) {
                    postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
                }
                if (candidate instanceof AnnotatedBeanDefinition) {
                    AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
                }
                if (checkCandidate(beanName, candidate)) {
                    BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                    definitionHolder =
                            AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
                    beanDefinitions.add(definitionHolder);
                    registerBeanDefinition(definitionHolder, this.registry);
                }
            }
        }
        return beanDefinitions;
    }

1 、遍历basePackages,通过findCandidateComponents方法扫描basePackage路径下的java文件。
2、假如存在,就遍历这路径上的类:
(1)解析 scope属性。
(2)生成 name 属性
(3)检查当前bean是否已经注册,如果没有注册的话,则生成 BeanDefinitionHolder,并添加到 添加到beanDefinitions中
(4)向BeanDefinitionRegistry进行注册。
4、处理@Import 注解

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
            Collection importCandidates, Predicate exclusionFilter,
            boolean checkForCircularImports) {
// 假如 importCandidates 为空,就直接返回
        if (importCandidates.isEmpty()) {
            return;
        }
// 检查循环依赖问题,
        if (checkForCircularImports && isChainedImportOnStack(configClass)) {
            this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
        }
        else {
            this.importStack.push(configClass);
            try {
// 如果没有循环依赖问题,就遍历出路。
                for (SourceClass candidate : importCandidates) {
                    if (candidate.isAssignable(ImportSelector.class)) {
                        // Candidate class is an ImportSelector -> delegate to it to determine imports
                        Class candidateClass = candidate.loadClass();
                        ImportSelector selector = ParserStrategyUtils.instantiateClass(candidateClass, ImportSelector.class,
                                this.environment, this.resourceLoader, this.registry);
                        Predicate selectorFilter = selector.getExclusionFilter();
                        if (selectorFilter != null) {
                            exclusionFilter = exclusionFilter.or(selectorFilter);
                        }
                        if (selector instanceof DeferredImportSelector) {
                            this.deferredImportSelectorHandler.handle(configClass, (DeferredImportSelector) selector);
                        }
                        else {
                            String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                            Collection 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
                        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
                        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);
            }
            finally {
                this.importStack.pop();
            }
        }
    }

主要处理流程如下:
1、判断 importCandidates 是否为空,假如不是就返回。
2、对其进行循环依赖检查。
3、将其加入到 importstack 中,然后依次遍历。
(1)如果是importSelect 子类,就实例化 ImportSelector 对象,通过 ParserStrategyUtils#instantiateClass 方法。
[1]设置 ImportSelector exclusionFilter 属性。
[2]假如 selector 是 DeferredImportSelector 属性,就调用 deferredImportSelectorHandler#handle 方法。
[3]假如不是最后调用 processImports 方法。
(2) 如果该类是 ImportBeanDefinitionRegistrar的子类,,则实例化后,调用ParserStrategyUtils#invokeAwareMethods,添加到configClass中。
(3)最后假如都不是就加入到importStack后调用processConfigurationClass 进行处理。

5、处理 @ImportResource 注解,先重 config 类中查找是否存在该注解,假如存在,就获取其 location 属性,然后遍历 location 位置中的 bean,加入到 configClass 中的 ImportedResource。
6、处理 @Bean 的方法,遍历 @Bean 的方法,并放到 configClass 的 BeanMethod 中。
7、遍历 configClass 的所有接口的 @Bean 的方法,并放到 configClass 的 BeanMethod 中。
8、如果存在父类的话,就将父类放到 knownSuperclasses 中,并返回,返回就类似于递归调用。否则返回 null。
我们回到ConfigurationClassPostProcessor的processConfigBeanDefinitions方法中,接下来是调用 ConfigurationClassBeanDefinitionReader#loadBeanDefinitions 方法。

    public void loadBeanDefinitions(Set configurationModel) {
        TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
        for (ConfigurationClass configClass : configurationModel) {
            loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
        }
    }

如上,主要做两件事情:
1、实例化 TrackedConditionEvaluator;
2、遍历configurationModel ,使用loadBeanDefinitionsForConfigurationClass 方法加载 BeanDefinition。
loadBeanDefinitionsForConfigurationClass 方法如下:

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());
    }

主要做了如下几件事情:
1、调用 trackedConditionEvaluator 来判断条件注解,是否需要跳过这个 config 类。如果需要,就将这个类从容器中移除,并且从 importRegistry 中移除。
2、如果当前类中存在@Import 注解,调用 registerBeanDefinitionForImportedConfigurationClass 方法进行注册:

private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
        AnnotationMetadata metadata = configClass.getMetadata();
        AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);

        ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
        configBeanDef.setScope(scopeMetadata.getScopeName());
        String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
        AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);

        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
        configClass.setBeanName(configBeanName);

        if (logger.isTraceEnabled()) {
            logger.trace("Registered bean definition for imported class '" + configBeanName + "'");
        }
    }

主要做的事情如下:
1、根据 configClass 的 AnnotatedGenericBeanDefinition 生成 BeanDefinition。
2、对BeanDefinition 进行属性设置:

1、解析 configClass的Scope。
2、生成 bean 的 id。
3、设置 bean 的一些属性,如 lazy 和 primary 等。

回到上面 loadBeanDefinitionsForConfigurationClass 方法。
3、遍历BeanMethods,依次对其调用loadBeanDefinitionsForBeanMethod进行注册。

private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
// 获取父的 configClass
        ConfigurationClass configClass = beanMethod.getConfigurationClass();
// 获取 beanMethod 的 MethodMetadata 和 methodName
        MethodMetadata metadata = beanMethod.getMetadata();
        String methodName = metadata.getMethodName();
// 判断是否需要跳过,假如 conditionEvaluator#shouldSkip 返回 TRUE ,就将其放入 skippedBeanMethods 中并返回。
        // Do we need to mark the bean as skipped by its condition?
        if (this.conditionEvaluator.shouldSkip(metadata, ConfigurationPhase.REGISTER_BEAN)) {
            configClass.skippedBeanMethods.add(methodName);
            return;
        }
//  如果configClass的skippedBeanMethods包含该methodName的话,不进行处理,
        if (configClass.skippedBeanMethods.contains(methodName)) {
            return;
        }
// 从@Bean 注解中获取 name 假如为空就将 methodName 作为 name
        AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
        Assert.state(bean != null, "No @Bean annotation attributes");
// 
        // Consider name and any aliases
        List names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
        String beanName = (!names.isEmpty() ? names.remove(0) : methodName);
// 为 bean 设置 alias
        // Register aliases even when overridden
        for (String alias : names) {
            this.registry.registerAlias(beanName, alias);
        }
// 查看是否存在重复注册的场景
        // Has this effectively been overridden before (e.g. via XML)?
        if (isOverriddenByExistingDefinition(beanMethod, beanName)) {
            if (beanName.equals(beanMethod.getConfigurationClass().getBeanName())) {
                throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
                        beanName, "Bean name derived from @Bean method '" + beanMethod.getMetadata().getMethodName() +
                        "' clashes with bean name for containing configuration class; please make those names unique!");
            }
            return;
        }
// 实例化 ConfigurationClassBeanDefinition
        ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata, beanName);
        beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));
// 如果是静态方法,则设置 setBeanClassName,
        if (metadata.isStatic()) {
            // static @Bean method
            if (configClass.getMetadata() instanceof StandardAnnotationMetadata) {
                beanDef.setBeanClass(((StandardAnnotationMetadata) configClass.getMetadata()).getIntrospectedClass());
            }
            else {
                beanDef.setBeanClassName(configClass.getMetadata().getClassName());
            }
            beanDef.setUniqueFactoryMethodName(methodName);
        }
        else {
            // instance @Bean method
//  如果是实例方法的话,则将configClass的BeanName设置为FactoryBeanName,methodName设置为UniqueFactoryMethodName
            beanDef.setFactoryBeanName(configClass.getBeanName());
            beanDef.setUniqueFactoryMethodName(methodName);
        }

        if (metadata instanceof StandardMethodMetadata) {
            beanDef.setResolvedFactoryMethod(((StandardMethodMetadata) metadata).getIntrospectedMethod());
        }
// 设置注入模式为构造器注入模式
        beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
// 设置skipRequiredCheck属性为true       beanDef.setAttribute(org.springframework.beans.factory.annotation.RequiredAnnotationBeanPostProcessor.
                SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);
// 6.4 进行一些常用的属性设置
        AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);

        Autowire autowire = bean.getEnum("autowire");
        if (autowire.isAutowire()) {
            beanDef.setAutowireMode(autowire.value());
        }

        boolean autowireCandidate = bean.getBoolean("autowireCandidate");
        if (!autowireCandidate) {
            beanDef.setAutowireCandidate(false);
        }
// 设置 initMethod
        String initMethodName = bean.getString("initMethod");
        if (StringUtils.hasText(initMethodName)) {
            beanDef.setInitMethodName(initMethodName);
        }
// 设置 destroyMethod
        String destroyMethodName = bean.getString("destroyMethod");
        beanDef.setDestroyMethodName(destroyMethodName);
// 设置ScopedProxyMode
        // Consider scoping
        ScopedProxyMode proxyMode = ScopedProxyMode.NO;
        AnnotationAttributes attributes = AnnotationConfigUtils.attributesFor(metadata, Scope.class);
        if (attributes != null) {
            beanDef.setScope(attributes.getString("value"));
            proxyMode = attributes.getEnum("proxyMode");
            if (proxyMode == ScopedProxyMode.DEFAULT) {
                proxyMode = ScopedProxyMode.NO;
            }
        }
// 如果 ScopedProxyMode 为 NO 就生成代理
        // Replace the original bean definition with the target one, if necessary
        BeanDefinition beanDefToRegister = beanDef;
        if (proxyMode != ScopedProxyMode.NO) {
            BeanDefinitionHolder proxyDef = ScopedProxyCreator.createScopedProxy(
                    new BeanDefinitionHolder(beanDef, beanName), this.registry,
                    proxyMode == ScopedProxyMode.TARGET_CLASS);
            beanDefToRegister = new ConfigurationClassBeanDefinition(
                    (RootBeanDefinition) proxyDef.getBeanDefinition(), configClass, metadata, beanName);
        }

        if (logger.isTraceEnabled()) {
            logger.trace(String.format("Registering bean definition for @Bean method %s.%s()",
                    configClass.getMetadata().getClassName(), beanName));
        }
// 注册
        this.registry.registerBeanDefinition(beanName, beanDefToRegister);
    }

主要做了7件事情:
1、获取 configClass 、Methodname 和 MethodMetadata 。
2、判断是否需要跳过出来:
(1)、调用 conditionEvaluator#shouldSkip 方法是否需要跳过,需要返回。
(2)、查看 skippedBeanMethods 中是否包含该方法,有则返回。
3、从 @Bean 注解中获取 name 假如为空就查找 methodName ,设置为 bean name。
4、对 name 的别名进行注册。
5、 实例化 ConfigurationClassBeanDefinition ,如果该方法是静态方法,设置该方法为工厂方法,否则如果是实例方法的话,则将configClass的BeanName设置为FactoryBeanName,methodName设置为UniqueFactoryMethodName,然后设置 initmethod 和 destroymethod ,最后设置 ScopedProxyMode 设置为 NO 并生成代理。
6、 注册 Bean。

4、处理 @ImportResource 注解,具体如下:

private void loadBeanDefinitionsFromImportedResources(
            Map> importedResources) {

        Map, BeanDefinitionReader> readerInstanceCache = new HashMap<>();
// 遍历所有的 importedResources
        importedResources.forEach((resource, readerClass) -> {
            // Default reader selection necessary?
// 如果是 BeanDefinitionReader,就查看是否是 groovy 类,假如不是就使用 XmlBeanDefinitionReader 类
            if (BeanDefinitionReader.class == readerClass) {
                if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
                    // When clearly asking for Groovy, that's what they'll get...
                    readerClass = GroovyBeanDefinitionReader.class;
                }
                else {
                    // Primarily ".xml" files but for any other extension as well
                    readerClass = XmlBeanDefinitionReader.class;
                }
            }
// 尝试重 readerInstanceCache 读取 BeanDefinitionReader 假如没有就实例化。
            BeanDefinitionReader reader = readerInstanceCache.get(readerClass);
            if (reader == null) {
                try {
                    // Instantiate the specified BeanDefinitionReader
                    reader = readerClass.getConstructor(BeanDefinitionRegistry.class).newInstance(this.registry);
                    // Delegate the current ResourceLoader to it if possible
                    if (reader instanceof AbstractBeanDefinitionReader) {
                        AbstractBeanDefinitionReader abdr = ((AbstractBeanDefinitionReader) reader);
                        abdr.setResourceLoader(this.resourceLoader);
                        abdr.setEnvironment(this.environment);
                    }
                    readerInstanceCache.put(readerClass, reader);
                }
                catch (Throwable ex) {
                    throw new IllegalStateException(
                            "Could not instantiate BeanDefinitionReader class [" + readerClass.getName() + "]");
                }
            }
// 加载 bean
            // TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
            reader.loadBeanDefinitions(resource);
        });
    }

主要做了四件事情:
1、遍历所有的 importedResources 。
2、选择 BeanDefinitionReader,假如是 groovy 类,就使用 GroovyBeanDefinitionReader 不是就使用 XmlBeanDefinitionReader
3、尝试从readerInstanceCache中获取对应的BeanDefinitionReader,如果不存在,则实例化一个,然后放入到readerInstanceCache缓存中。
4、调用 BeanDefinitionReader#loadBeanDefinitions 进行加载 bean。

5、注册@Import注解中的ImportBeanDefinitionRegistrar接口的registerBeanDefinitions。

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

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