一、Bean工廠的後置處理器

　　Bean工廠的後置處理器：BeanFactoryPostProcessor（觸發時機：bean定義註冊之後bean例項化之前）和BeanDefinitionRegistryPostProcessor（觸發時機：bean定義註冊之前），所以可以在Bean工廠的後置處理器中修改Bean的定義資訊，比如是否延遲載入、加入一些新的Bean的定義資訊等

　　Bean工廠的後置處理器類繼承圖：

二、呼叫Bean工廠的後置處理器

　　invokeBeanFactoryPostProcessors(beanFactory)方法：

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        //傳入Bean工廠並獲取容器中的Bean工廠後置處理器(注意這裡Bean工廠後置處理器還沒有初始化)
        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()));
        }
    }

　　進入PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())方法：

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

        Set<String> processedBeans = new HashSet<>();

        //判斷我們的beanFactory是否實現了BeanDefinitionRegistry
        if (beanFactory instanceof BeanDefinitionRegistry) {
            //強行把beanFactory轉為BeanDefinitionRegistry
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            //儲存BeanFactoryPostProcessor型別的後置處理器
            List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
            //儲存BeanDefinitionRegistryPostProcessor型別的後置處理器
            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

            //迴圈我們傳遞進來的beanFactoryPostProcessors
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                //判斷我們的後置處理器是不是BeanDefinitionRegistryPostProcessor
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    //進行強制轉化
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    //呼叫它的後置方法
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    //新增到我們用於儲存的BeanDefinitionRegistryPostProcessor的集合中
                    registryProcessors.add(registryProcessor);
                }
                else {//若沒有實現BeanDefinitionRegistryPostProcessor介面，那麼他就是BeanFactoryPostProcessor 把當前的後置處理器加入到regularPostProcessors中
                    regularPostProcessors.add(postProcessor);
                }
            }

            //定義一個集合使用者儲存當前準備建立的BeanDefinitionRegistryPostProcessor
            List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

            //第一步:去容器中獲取BeanDefinitionRegistryPostProcessor的bean的處理器名稱
            String[] postProcessorNames =
                    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            //迴圈上一步獲取的BeanDefinitionRegistryPostProcessor的型別名稱
            for (String ppName : postProcessorNames) {
                //判斷是否實現了PriorityOrdered介面的
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    //顯示的呼叫getBean()的方式獲取出該物件然後加入到currentRegistryProcessors集合中去
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    //同時也加入到processedBeans集合中去
                    processedBeans.add(ppName);
                }
            }
            //對currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor進行排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //把他加入到用於儲存到registryProcessors中
            registryProcessors.addAll(currentRegistryProcessors);
            /**
             * 在這裡典型的BeanDefinitionRegistryPostProcessor就是ConfigurationClassPostProcessor
             * 用於進行bean定義的載入 比如我們的包掃描，@import等
             */
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            //呼叫完之後，馬上clear
            currentRegistryProcessors.clear();

            //下一步 又去容器中獲取BeanDefinitionRegistryPostProcessor的bean的處理器名稱
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            //迴圈上一步獲取的BeanDefinitionRegistryPostProcessor的型別名稱
            for (String ppName : postProcessorNames) {
                //表示沒有被處理過,且實現了Ordered介面的
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    //顯示的呼叫getBean()的方式獲取出該物件然後加入到currentRegistryProcessors集合中去
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    //同時也加入到processedBeans集合中去
                    processedBeans.add(ppName);
                }
            }
            //對currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor進行排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //把他加入到用於儲存到registryProcessors中
            registryProcessors.addAll(currentRegistryProcessors);
            //呼叫他的後置處理方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            //呼叫完之後，馬上clear
            currentRegistryProcessors.clear();

            //呼叫沒有實現任何優先順序介面的BeanDefinitionRegistryPostProcessor
            //定義一個重複處理的開關變數 預設值為true
            boolean reiterate = true;
            //第一次就可以進來
            while (reiterate) {
                //進入迴圈馬上把開關變數給改為false
                reiterate = false;
                //去容器中獲取BeanDefinitionRegistryPostProcessor的bean的處理器名稱
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                //迴圈上一步獲取的BeanDefinitionRegistryPostProcessor的型別名稱
                for (String ppName : postProcessorNames) {
                    //沒有被處理過的
                    if (!processedBeans.contains(ppName)) {
                        //顯示的呼叫getBean()的方式獲取出該物件然後加入到currentRegistryProcessors集合中去
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        //同時也加入到processedBeans集合中去
                        processedBeans.add(ppName);
                        //再次設定為true
                        reiterate = true;
                    }
                }
                //對currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor進行排序
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                //把他加入到用於儲存到registryProcessors中
                registryProcessors.addAll(currentRegistryProcessors);
                //呼叫他的後置處理方法
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                //進行clear
                currentRegistryProcessors.clear();
            }

            //呼叫實現了BeanDefinitionRegistryPostProcessor的介面 他是他也同時實現了BeanFactoryPostProcessor的方法
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            //呼叫BeanFactoryPostProcessor
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        }

        else { //若當前的beanFactory沒有實現了BeanDefinitionRegistry 直接呼叫beanFactoryPostProcessor介面的方法進行後置處理
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        //最後一步 獲取容器中所有的 BeanFactoryPostProcessor
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        //儲存BeanFactoryPostProcessor型別實現了priorityOrdered
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        //儲存BeanFactoryPostProcessor型別實現了Ordered介面的
        List<String> orderedPostProcessorNames = new ArrayList<>();
        //儲存BeanFactoryPostProcessor沒有實現任何優先順序介面的
        List<String> nonOrderedPostProcessorNames = new ArrayList<>();
        for (String ppName : postProcessorNames) {
            //processedBeans包含的話，表示在上面處理BeanDefinitionRegistryPostProcessor的時候處理過了
            if (processedBeans.contains(ppName)) {
                // skip - already processed in first phase above
            }
            //判斷是否實現了PriorityOrdered
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            //判斷是否實現了Ordered
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                orderedPostProcessorNames.add(ppName);
            }
            //沒有實現任何的優先順序介面的
            else {
                nonOrderedPostProcessorNames.add(ppName);
            }
        }

        //先呼叫BeanFactoryPostProcessor實現了PriorityOrdered介面的
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        //再呼叫BeanFactoryPostProcessor實現了Ordered.
        List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
        for (String postProcessorName : orderedPostProcessorNames) {
            orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        sortPostProcessors(orderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

        //呼叫沒有實現任何方法介面的
        List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
        for (String postProcessorName : nonOrderedPostProcessorNames) {
            nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

        // Clear cached merged bean definitions since the post-processors might have
        // modified the original metadata, e.g. replacing placeholders in values...
        beanFactory.clearMetadataCache();
    }

　　第一步:去容器中獲取BeanDefinitionRegistryPostProcessor的bean的處理器名稱
　　String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false)  Debug進去看到如下：為什麼就一個ConfigurationClassPostProcessor，因為我們自定的BeanDefinitionRegistryPostProcessor還沒有被加入到Spring容器中去

　　第一步裡面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法：

/**
     * Invoke the given BeanDefinitionRegistryPostProcessor beans.
     */
    private static void invokeBeanDefinitionRegistryPostProcessors(
            Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
        //獲取容器中的ConfigurationClassPostProcessor的後置處理器進行Bean定義的掃描
        for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }
    }

　　接下來就會呼叫到org.springframework.context.annotation.ConfigurationClassPostProcessor#postProcessBeanDefinitionRegistry方法（很重要）：

/**
     * 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);
        //真正的解析我們的Bean定義
        processConfigBeanDefinitions(registry);
    }

　　進入到真正的解析processConfigBeanDefinitions方法中：

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
        List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
        //獲取Spring IoC容器中目前所有Bean定義的名稱
        String[] candidateNames = registry.getBeanDefinitionNames();

        //迴圈所有的Bean定義資訊
        for (String beanName : candidateNames) {
            //通過Bean的名稱來獲取Bean的定義物件
            BeanDefinition beanDef = registry.getBeanDefinition(beanName);
            //判斷是否有沒有解析過
            if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
                    ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
                }
            }
            //判斷是否是配置類
            else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
                //新增到候選的配置類集合中
                configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
            }
        }

        // 若沒有找到配置類 直接返回
        if (configCandidates.isEmpty()) {
            return;
        }

        //對我們的配置類進行Order排序
        configCandidates.sort((bd1, bd2) -> {
            int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
            int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
            return Integer.compare(i1, i2);
        });

        //建立@CompentScan、@Import匯入進來的bean名稱的生成器
        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) {
                    //設定@CompentScan匯入進來的bean的名稱生成器
                    this.componentScanBeanNameGenerator = generator;
                    //設定@Import匯入進來的bean的名稱生成器
                    this.importBeanNameGenerator = generator;
                }
            }
        }

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

        //建立一個配置類解析器物件
        ConfigurationClassParser parser = new ConfigurationClassParser(
                this.metadataReaderFactory, this.problemReporter, this.environment,
                this.resourceLoader, this.componentScanBeanNameGenerator, registry);

        //建立一個集合用於儲存我們的配置類BeanDefinitionHolder集合預設長度是配置類集合的長度
        Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
        //建立一個集合用於儲存我們的已經解析的配置類，長度預設為解析出來預設的配置類的集合長度
        Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
        //do while
        do {
            //真正的解析我們的配置類
            parser.parse(candidates);
            parser.validate();

            //解析出來的配置類
            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());
            }
            //真正的把我們解析出來的配置類註冊到容器中
            this.reader.loadBeanDefinitions(configClasses);
            //加入到已經解析的集合中
            alreadyParsed.addAll(configClasses);

            candidates.clear();
            //判斷我們Spring IoC容器中Bean的定義數量是否 > 候選原始的bean定義的個數
            if (registry.getBeanDefinitionCount() > candidateNames.length) {
                //獲取所有的bean定義
                String[] newCandidateNames = registry.getBeanDefinitionNames();
                //原始的老的候選的bean定義
                Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
                Set<String> alreadyParsedClasses = new HashSet<>();
                //賦值已經解析的
                for (ConfigurationClass configurationClass : alreadyParsed) {
                    alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
                }

                for (String candidateName : newCandidateNames) {
                    //表示當前迴圈的還沒有被解析過
                    if (!oldCandidateNames.contains(candidateName)) {
                        BeanDefinition bd = registry.getBeanDefinition(candidateName);
                        //判斷有沒有被解析過
                        if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
                                !alreadyParsedClasses.contains(bd.getBeanClassName())) {
                            candidates.add(new BeanDefinitionHolder(bd, candidateName));
                        }
                    }
                }
                candidateNames = newCandidateNames;
            }
        }
        //存在沒有解析過的 需要迴圈解析
        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();
        }
    }

　　Debug解析：

　　進入parser.parse(candidates)方法：

public void parse(Set<BeanDefinitionHolder> configCandidates) {
        //用於儲存延時的ImportSelectors
        this.deferredImportSelectors = new LinkedList<>();

        for (BeanDefinitionHolder holder : configCandidates) {
            BeanDefinition bd = holder.getBeanDefinition();
            try {
                //真正的解析我們的bean定義
                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);
            }
        }
        //處理我們延時的DeferredImportSelectors Spring Boot就是通過這步進行spring.factories檔案中的自定裝配的物件
        processDeferredImportSelectors();
    }

　　Debug解析:

　　進入parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName())方法：

/**
     * 真正的解析我們的配置類
     * @param metadata 配置類的源資訊
     * @param beanName 當前配置類的beanName
     * @throws IOException
     */
    protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
        //把我們的配置類源資訊和beanName包裝成一個ConfigurationClass物件
        processConfigurationClass(new ConfigurationClass(metadata, beanName));
    }

　　進入processConfigurationClass(new ConfigurationClass(metadata, beanName))方法：

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
        if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
            return;
        }

        //獲取我們的配置類物件
        ConfigurationClass existingClass = this.configurationClasses.get(configClass);

        if (existingClass != null) {
            //傳入的配置類是通過其他配置類的Import匯入進來的
            if (configClass.isImported()) {
                if (existingClass.isImported()) {
                    //需要合併配置
                    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);
        //真正的進行配置類的解析
        do {
            //解析我們的配置類
            sourceClass = doProcessConfigurationClass(configClass, sourceClass);
        }
        while (sourceClass != null);

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

　　進入解析我們的配置類的doProcessConfigurationClass(configClass, sourceClass)方法：

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

        // Recursively process any member (nested) classes first
        processMemberClasses(configClass, sourceClass);

        //處理我們的@PropertySources註解的
        for (AnnotationAttributes propertySource : AnnotationConfigUtils.attributesForRepeatable(
                sourceClass.getMetadata(), PropertySources.class,
                org.springframework.context.annotation.PropertySource.class)) {
            if (this.environment instanceof ConfigurableEnvironment) {
                processPropertySource(propertySource);
            }
            else {
                logger.warn("Ignoring @PropertySource annotation on [" + sourceClass.getMetadata().getClassName() +
                        "]. Reason: Environment must implement ConfigurableEnvironment");
            }
        }

        //接下來解析我們的@ComponentScans註解
        //從我們的配置類上解析@ComponentScans的物件集合屬性
        Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
                sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
        if (!componentScans.isEmpty() &&
                !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
            //迴圈解析（我們解析出來的AnnotationAttributes）
            for (AnnotationAttributes componentScan : componentScans) {
                //把我們掃描出來的類變為bean定義的集合
                Set<BeanDefinitionHolder> scannedBeanDefinitions =
                        this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
                //迴圈處理我們包掃描出來的bean定義
                for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                    BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
                    if (bdCand == null) {
                        bdCand = holder.getBeanDefinition();
                    }
                    //判斷當前掃描出來的bean定義是不是一個配置類,若是的話 直接進行遞迴解析
                    if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
                        //遞迴解析
                        parse(bdCand.getBeanClassName(), holder.getBeanName());
                    }
                }
            }
        }

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

        //處理@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);
            }
        }

        //處理@Bean methods獲取到我們配置類中所有標註了@Bean的方法
        Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);

        for (MethodMetadata methodMetadata : beanMethods) {
            configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
        }

        //處理配置類介面的
        processInterfaces(configClass, sourceClass);

        //處理配置類的父類的
        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();
            }
        }

        //沒有父類解析完成
        return null;
    }

　　Debug解析：

　　① 解析@ComponentScanthis.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName())方法：

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

        //給掃描器設定beanName的生成器物件
        Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
        boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
        scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
                BeanUtils.instantiateClass(generatorClass));

        //設定bean的域代理模型
        ScopedProxyMode scopedProxyMode = componentScan.getEnum("scopedProxy");
        if (scopedProxyMode != ScopedProxyMode.DEFAULT) {
            scanner.setScopedProxyMode(scopedProxyMode);
        }
        else {
            Class<? extends ScopeMetadataResolver> resolverClass = componentScan.getClass("scopeResolver");
            scanner.setScopeMetadataResolver(BeanUtils.instantiateClass(resolverClass));
        }

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

        //設定ComponentScan物件的includeFilters包含的屬性
        for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addIncludeFilter(typeFilter);
            }
        }
        //設定ComponentScan物件的excludeFilters不包含的屬性
        for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addExcludeFilter(typeFilter);
            }
        }
        
        //是否懶載入
        boolean lazyInit = componentScan.getBoolean("lazyInit");
        if (lazyInit) {
            scanner.getBeanDefinitionDefaults().setLazyInit(true);
        }

        //包路徑
        Set<String> 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);
            }
        });
        //真正的進行掃描解析
        return scanner.doScan(StringUtils.toStringArray(basePackages));
    }

　　進入真正的進行掃描解析scanner.doScan(StringUtils.toStringArray(basePackages))方法：

protected Set<BeanDefinitionHolder> doScan(String... basePackages) {
        Assert.notEmpty(basePackages, "At least one base package must be specified");
        //建立bean定義的holder物件用於儲存掃描後生成的bean定義物件
        Set<BeanDefinitionHolder> beanDefinitions = new LinkedHashSet<>();
        //迴圈我們的包路徑集合
        for (String basePackage : basePackages) {
            //找到候選的@Component
            Set<BeanDefinition> candidates = findCandidateComponents(basePackage);
            for (BeanDefinition candidate : candidates) {

                ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
                candidate.setScope(scopeMetadata.getScopeName());
                //設定我們的beanName
                String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
                //處理@AutoWired相關的
                if (candidate instanceof AbstractBeanDefinition) {
                    postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
                }
                //處理jsr250相關的元件
                if (candidate instanceof AnnotatedBeanDefinition) {
                    AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
                }
                //把我們解析出來的元件bean定義註冊到Spring IoC容器中
                if (checkCandidate(beanName, candidate)) {
                    BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(candidate, beanName);
                    definitionHolder =
                            AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
                    beanDefinitions.add(definitionHolder);
                    //註冊到Spring IoC容器中
                    registerBeanDefinition(definitionHolder, this.registry);
                }
            }
        }
        return beanDefinitions;
    }

　　Debug解析：

　　進過org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan處理，Spring IoC容器中Bean的定義有12個了；

　　② 接下來處理@Import註解匯入的Bean元件：

　　進入處理@Import註解的processImports(configClass, sourceClass, getImports(sourceClass), true)方法：

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

        if (importCandidates.isEmpty()) {
            return;
        }

        if (checkForCircularImports && isChainedImportOnStack(configClass)) {
            this.problemReporter.error(new CircularImportProblem(configClass, this.importStack));
        }
        else {
            this.importStack.push(configClass);
            try {
                //獲取我們Import匯入進來的所有元件
                for (SourceClass candidate : importCandidates) {
                    //判斷該元件是不是實現了ImportSelector的
                    if (candidate.isAssignable(ImportSelector.class)) {
                        // Candidate class is an ImportSelector -> delegate to it to determine imports
                        Class<?> candidateClass = candidate.loadClass();
                        //例項化我們的SelectImport元件
                        ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
                        //呼叫相關的aware方法
                        ParserStrategyUtils.invokeAwareMethods(
                                selector, this.environment, this.resourceLoader, this.registry);
                        //判斷是不是延時的DeferredImportSelectors，是這個型別不進行處理
                        if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
                            this.deferredImportSelectors.add(
                                    new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
                        }
                        else {//不是延時的呼叫selector的selectImports
                            String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                            //反之SelectImport匯入進來的又是Import進來的 所以遞迴解析
                            Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
                            processImports(configClass, currentSourceClass, importSourceClasses, false);
                        }
                    }
                    //判斷我們匯入的元件是不是ImportBeanDefinitionRegistrar
                    else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
                        // Candidate class is an ImportBeanDefinitionRegistrar ->
                        // delegate to it to register additional bean definitions
                        Class<?> candidateClass = candidate.loadClass();
                        //例項話我們的ImportBeanDefinitionRegistrar物件
                        ImportBeanDefinitionRegistrar registrar =
                                BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
                        ParserStrategyUtils.invokeAwareMethods(
                                registrar, this.environment, this.resourceLoader, this.registry);
                        //儲存我們的ImportBeanDefinitionRegistrar物件
                        configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
                    }
                    else {//就是一個普通的元件  但是防止我們普通的元件是一個配置類 所以還是直接走了processConfigurationClass()方法
                        this.importStack.registerImport(
                                currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
                        processConfigurationClass(candidate.asConfigClass(configClass));
                    }
                }
            }
            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();
            }
        }
    }

 　　③ 接下來處理@ImportSource比如@ImportResource("classpath:circulation-di.xml")，基於xml的（略）

　　 ④ 接下來處理@Bean：

　　至此解析完成，注意@Import、@ImportSource、@Bean的定義還未註冊到Spring IoC的容器中去

　　接下來將剩餘的Bean定義資訊註冊到Spring IoC容器中：

 　　進入真正的把我們解析出來的配置類註冊到容器中this.reader.loadBeanDefinitions(configClasses)方法：

public void loadBeanDefinitions(Set<ConfigurationClass> configurationModel) {
        TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
        //註冊我們的配置類到容器中
        for (ConfigurationClass configClass : configurationModel) {
            loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
        }
    }

　　進入loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator)方法：

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;
        }

        //是不是通過@Import匯入進來的
        if (configClass.isImported()) {
            registerBeanDefinitionForImportedConfigurationClass(configClass);
        }
        //是不是通過我們的@Bean匯入進來的元件
        for (BeanMethod beanMethod : configClass.getBeanMethods()) {
            loadBeanDefinitionsForBeanMethod(beanMethod);
        }

        //是不是通過@ImportResources匯入進來的
        loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
        //是不是通過ImportBeanDefinition註解匯入進來的
        loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
    }

　　① 通過@Import匯入進來的執行registerBeanDefinitionForImportedConfigurationClass(configClass)方法：

private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
        //獲取我們的配置類的源資訊
        AnnotationMetadata metadata = configClass.getMetadata();
        //構建為我們的bean定義
        AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);
        //設定他的scope
        ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
        configBeanDef.setScope(scopeMetadata.getScopeName());
        //獲取bean的名稱
        String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
        //處理我們的JRS250元件的
        AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);

        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        //註冊我們的bean定義到我們的容器中
        this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
        configClass.setBeanName(configBeanName);

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

 　　② 通過@Bean匯入進來的執行loadBeanDefinitionsForBeanMethod(beanMethod)方法：

private void loadBeanDefinitionsForBeanMethod(BeanMethod beanMethod) {
        ConfigurationClass configClass = beanMethod.getConfigurationClass();
        MethodMetadata metadata = beanMethod.getMetadata();
        String methodName = metadata.getMethodName();

        // 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;
        }
        if (configClass.skippedBeanMethods.contains(methodName)) {
            return;
        }

        AnnotationAttributes bean = AnnotationConfigUtils.attributesFor(metadata, Bean.class);
        Assert.state(bean != null, "No @Bean annotation attributes");

        // Consider name and any aliases
        List<String> names = new ArrayList<>(Arrays.asList(bean.getStringArray("name")));
        String beanName = (!names.isEmpty() ? names.remove(0) : methodName);

        // Register aliases even when overridden
        for (String alias : names) {
            this.registry.registerAlias(beanName, alias);
        }

        // 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;
        }

        ConfigurationClassBeanDefinition beanDef = new ConfigurationClassBeanDefinition(configClass, metadata);
        beanDef.setResource(configClass.getResource());
        beanDef.setSource(this.sourceExtractor.extractSource(metadata, configClass.getResource()));

        if (metadata.isStatic()) {
            // static @Bean method
            beanDef.setBeanClassName(configClass.getMetadata().getClassName());
            beanDef.setFactoryMethodName(methodName);
        }
        else {
            // instance @Bean method
            beanDef.setFactoryBeanName(configClass.getBeanName());
            beanDef.setUniqueFactoryMethodName(methodName);
        }
        beanDef.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_CONSTRUCTOR);
        beanDef.setAttribute(RequiredAnnotationBeanPostProcessor.SKIP_REQUIRED_CHECK_ATTRIBUTE, Boolean.TRUE);

        AnnotationConfigUtils.processCommonDefinitionAnnotations(beanDef, metadata);

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

        String initMethodName = bean.getString("initMethod");
        if (StringUtils.hasText(initMethodName)) {
            beanDef.setInitMethodName(initMethodName);
        }

        String destroyMethodName = bean.getString("destroyMethod");
        beanDef.setDestroyMethodName(destroyMethodName);

        // 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;
            }
        }

        // 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);
        }

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

　　③ 通過@ImportResources匯入進來的執行loadBeanDefinitionsFromImportedResources(configClass.getImportedResources())方法：

private void loadBeanDefinitionsFromImportedResources(
            Map<String, Class<? extends BeanDefinitionReader>> importedResources) {

        Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<>();

        importedResources.forEach((resource, readerClass) -> {
            // Default reader selection necessary?
            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;
                }
            }

            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() + "]");
                }
            }

            // TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
            reader.loadBeanDefinitions(resource);
        });
    }

　　④ 通過ImportBeanDefinition註解匯入進來的執行loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars())方法：

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

 　　至此第一步裡面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法執行完畢！！！！

　　下一步：又去容器中獲取BeanDefinitionRegistryPostProcessor的bean的處理器名稱 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false) 此時就有了自己定義的BeanDefinitionRegistryPostProcessor了，接下來呼叫自定義的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry後置方法，然後再呼叫postProcessBeanFactory原因是BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor；

　　最後一步：獲取容器中所有的BeanFactoryPostProcessor的名稱 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false) 此時就有了自己定義的BeanFactoryPostProcessor了，接下來呼叫自定義的BeanFactoryPostProcessor的postProcessBeanFactory方法；

　　完整的Spring IoC原始碼解析見：Spring系列（三）：Spring IoC原始碼解析

三、Spring IoC掃描Bean的流程圖

　　總結：通過呼叫我們的Bean工廠的後置處理器，第一步：ConfigurationClassPostProcessor，解析我們的配置類，將所有的Bean的定義資訊註冊到Spring IoC容器中；第二步呼叫自定義的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry後置方法，然後再呼叫postProcessBeanFactory；最後呼叫自定義的BeanFactoryPostProcessor的postProcessBeanFactory