Spring IoC源码解析之invokeBeanFactoryPostProcessors

一、Bean工厂的后置处理器

　　Bean工厂的后置处理器：BeanFactoryPostProcessor（触发时机：bean定义注册之后bean实例化之前）和BeanDefinitionRegistryPostProcessor（触发时机：bean定义注册之前），所以可以在Bean工厂的后置处理器中修改Bean的定义信息，比如是否延迟加载、加入一些新的Bean的定义信息等

　　Bean工厂的后置处理器类继承图：

二、调用Bean工厂的后置处理器

　　invokeBeanFactoryPostProcessors(beanFactory)方法：

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        //传入Bean工厂并获取容器中的Bean工厂后置处理器(注意这里Bean工厂后置处理器还没有初始化)
        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()));
        }
    }

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

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

        Set processedBeans = new HashSet<>();

        //判断我们的beanFactory是否实现了BeanDefinitionRegistry
        if (beanFactory instanceof BeanDefinitionRegistry) {
            //强行把beanFactory转为BeanDefinitionRegistry
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            //保存BeanFactoryPostProcessor类型的后置处理器
            List regularPostProcessors = new ArrayList<>();
            //保存BeanDefinitionRegistryPostProcessor类型的后置处理器
            List registryProcessors = new ArrayList<>();

            //循环我们传递进来的beanFactoryPostProcessors
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                //判断我们的后置处理器是不是BeanDefinitionRegistryPostProcessor
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    //进行强制转化
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    //调用它的后置方法
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    //添加到我们用于保存的BeanDefinitionRegistryPostProcessor的集合中
                    registryProcessors.add(registryProcessor);
                }
                else {
     //若没有实现BeanDefinitionRegistryPostProcessor接口，那么他就是BeanFactoryPostProcessor 把当前的后置处理器加入到regularPostProcessors中
                    regularPostProcessors.add(postProcessor);
                }
            }

            //定义一个集合用户保存当前准备创建的BeanDefinitionRegistryPostProcessor
            List currentRegistryProcessors = new ArrayList<>();

            //第一步:去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
            String[] postProcessorNames =
                    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            //循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
            for (String ppName : postProcessorNames) {
                //判断是否实现了PriorityOrdered接口的
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    //显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    //同时也加入到processedBeans集合中去
                    processedBeans.add(ppName);
                }
            }
            //对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //把他加入到用于保存到registryProcessors中
            registryProcessors.addAll(currentRegistryProcessors);
            /**
             * 在这里典型的BeanDefinitionRegistryPostProcessor就是ConfigurationClassPostProcessor
             * 用于进行bean定义的加载 比如我们的包扫描，@import等
             */
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            //调用完之后，马上clear
            currentRegistryProcessors.clear();

            //下一步 又去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            //循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
            for (String ppName : postProcessorNames) {
                //表示没有被处理过,且实现了Ordered接口的
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    //显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    //同时也加入到processedBeans集合中去
                    processedBeans.add(ppName);
                }
            }
            //对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //把他加入到用于保存到registryProcessors中
            registryProcessors.addAll(currentRegistryProcessors);
            //调用他的后置处理方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            //调用完之后，马上clear
            currentRegistryProcessors.clear();

            //调用没有实现任何优先级接口的BeanDefinitionRegistryPostProcessor
            //定义一个重复处理的开关变量 默认值为true
            boolean reiterate = true;
            //第一次就可以进来
            while (reiterate) {
                //进入循环马上把开关变量给改为false
                reiterate = false;
                //去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                //循环上一步获取的BeanDefinitionRegistryPostProcessor的类型名称
                for (String ppName : postProcessorNames) {
                    //没有被处理过的
                    if (!processedBeans.contains(ppName)) {
                        //显示的调用getBean()的方式获取出该对象然后加入到currentRegistryProcessors集合中去
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        //同时也加入到processedBeans集合中去
                        processedBeans.add(ppName);
                        //再次设置为true
                        reiterate = true;
                    }
                }
                //对currentRegistryProcessors集合中BeanDefinitionRegistryPostProcessor进行排序
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                //把他加入到用于保存到registryProcessors中
                registryProcessors.addAll(currentRegistryProcessors);
                //调用他的后置处理方法
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                //进行clear
                currentRegistryProcessors.clear();
            }

            //调用实现了BeanDefinitionRegistryPostProcessor的接口 他是他也同时实现了BeanFactoryPostProcessor的方法
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            //调用BeanFactoryPostProcessor
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        }

        else { //若当前的beanFactory没有实现了BeanDefinitionRegistry 直接调用beanFactoryPostProcessor接口的方法进行后置处理
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        //最后一步 获取容器中所有的 BeanFactoryPostProcessor
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        //保存BeanFactoryPostProcessor类型实现了priorityOrdered
        List priorityOrderedPostProcessors = new ArrayList<>();
        //保存BeanFactoryPostProcessor类型实现了Ordered接口的
        List orderedPostProcessorNames = new ArrayList<>();
        //保存BeanFactoryPostProcessor没有实现任何优先级接口的
        List nonOrderedPostProcessorNames = new ArrayList<>();
        for (String ppName : postProcessorNames) {
            //processedBeans包含的话，表示在上面处理BeanDefinitionRegistryPostProcessor的时候处理过了
            if (processedBeans.contains(ppName)) {
                // skip - already processed in first phase above
            }
            //判断是否实现了PriorityOrdered
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            //判断是否实现了Ordered
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                orderedPostProcessorNames.add(ppName);
            }
            //没有实现任何的优先级接口的
            else {
                nonOrderedPostProcessorNames.add(ppName);
            }
        }

        //先调用BeanFactoryPostProcessor实现了PriorityOrdered接口的
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

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

        //调用没有实现任何方法接口的
        List 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:去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称
　　String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false)  Debug进去看到如下：为什么就一个ConfigurationClassPostProcessor，因为我们自定的BeanDefinitionRegistryPostProcessor还没有被加入到Spring容器中去

　　第一步里面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法：

/**
     * Invoke the given BeanDefinitionRegistryPostProcessor beans.
     */
    private static void invokeBeanDefinitionRegistryPostProcessors(
            Collectionextends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
        //获取容器中的ConfigurationClassPostProcessor的后置处理器进行Bean定义的扫描
        for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
            postProcessor.postProcessBeanDefinitionRegistry(registry);
        }
    }

　　接下来就会调用到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);
        //真正的解析我们的Bean定义
        processConfigBeanDefinitions(registry);
    }

　　进入到真正的解析processConfigBeanDefinitions方法中：

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
        List configCandidates = new ArrayList<>();
        //获取Spring IoC容器中目前所有Bean定义的名称
        String[] candidateNames = registry.getBeanDefinitionNames();

        //循环所有的Bean定义信息
        for (String beanName : candidateNames) {
            //通过Bean的名称来获取Bean的定义对象
            BeanDefinition beanDef = registry.getBeanDefinition(beanName);
            //判断是否有没有解析过
            if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
                    ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
                }
            }
            //判断是否是配置类
            else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
                //添加到候选的配置类集合中
                configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
            }
        }

        // 若没有找到配置类 直接返回
        if (configCandidates.isEmpty()) {
            return;
        }

        //对我们的配置类进行Order排序
        configCandidates.sort((bd1, bd2) -> {
            int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
            int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
            return Integer.compare(i1, i2);
        });

        //创建@CompentScan、@Import导入进来的bean名称的生成器
        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) {
                    //设置@CompentScan导入进来的bean的名称生成器
                    this.componentScanBeanNameGenerator = generator;
                    //设置@Import导入进来的bean的名称生成器
                    this.importBeanNameGenerator = generator;
                }
            }
        }

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

        //创建一个配置类解析器对象
        ConfigurationClassParser parser = new ConfigurationClassParser(
                this.metadataReaderFactory, this.problemReporter, this.environment,
                this.resourceLoader, this.componentScanBeanNameGenerator, registry);

        //创建一个集合用于保存我们的配置类BeanDefinitionHolder集合默认长度是配置类集合的长度
        Set candidates = new LinkedHashSet<>(configCandidates);
        //创建一个集合用于保存我们的已经解析的配置类，长度默认为解析出来默认的配置类的集合长度
        Set alreadyParsed = new HashSet<>(configCandidates.size());
        //do while
        do {
            //真正的解析我们的配置类
            parser.parse(candidates);
            parser.validate();

            //解析出来的配置类
            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());
            }
            //真正的把我们解析出来的配置类注册到容器中
            this.reader.loadBeanDefinitions(configClasses);
            //加入到已经解析的集合中
            alreadyParsed.addAll(configClasses);

            candidates.clear();
            //判断我们Spring IoC容器中Bean的定义数量是否 > 候选原始的bean定义的个数
            if (registry.getBeanDefinitionCount() > candidateNames.length) {
                //获取所有的bean定义
                String[] newCandidateNames = registry.getBeanDefinitionNames();
                //原始的老的候选的bean定义
                Set oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
                Set alreadyParsedClasses = new HashSet<>();
                //赋值已经解析的
                for (ConfigurationClass configurationClass : alreadyParsed) {
                    alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
                }

                for (String candidateName : newCandidateNames) {
                    //表示当前循环的还没有被解析过
                    if (!oldCandidateNames.contains(candidateName)) {
                        BeanDefinition bd = registry.getBeanDefinition(candidateName);
                        //判断有没有被解析过
                        if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
                                !alreadyParsedClasses.contains(bd.getBeanClassName())) {
                            candidates.add(new BeanDefinitionHolder(bd, candidateName));
                        }
                    }
                }
                candidateNames = newCandidateNames;
            }
        }
        //存在没有解析过的 需要循环解析
        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：

　　进入parser.parse(candidates)方法：

public void parse(Set configCandidates) {
        //用于保存延时的ImportSelectors
        this.deferredImportSelectors = new LinkedList<>();

        for (BeanDefinitionHolder holder : configCandidates) {
            BeanDefinition bd = holder.getBeanDefinition();
            try {
                //真正的解析我们的bean定义
                if (bd instanceof AnnotatedBeanDefinition) {
                    parse(((AnnotatedBeanDefinition) bd).getMetadata(), holder.getBeanName());
                }
                else if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
                    parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
                }
                else {
                    parse(bd.getBeanClassName(), holder.getBeanName());
                }
            }
            catch (BeanDefinitionStoreException ex) {
                throw ex;
            }
            catch (Throwable ex) {
                throw new BeanDefinitionStoreException(
                        "Failed to parse configuration class [" + bd.getBeanClassName() + "]", ex);
            }
        }
        //处理我们延时的DeferredImportSelectors Spring Boot就是通过这步进行spring.factories文件中的自定装配的对象
        processDeferredImportSelectors();
    }

　　Debug解析:

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

/**
     * 真正的解析我们的配置类
     * @param metadata 配置类的源信息
     * @param beanName 当前配置类的beanName
     * @throws IOException
     */
    protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
        //把我们的配置类源信息和beanName包装成一个ConfigurationClass对象
        processConfigurationClass(new ConfigurationClass(metadata, beanName));
    }

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

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

        //获取我们的配置类对象
        ConfigurationClass existingClass = this.configurationClasses.get(configClass);

        if (existingClass != null) {
            //传入的配置类是通过其他配置类的Import导入进来的
            if (configClass.isImported()) {
                if (existingClass.isImported()) {
                    //需要合并配置
                    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);
        //真正的进行配置类的解析
        do {
            //解析我们的配置类
            sourceClass = doProcessConfigurationClass(configClass, sourceClass);
        }
        while (sourceClass != null);

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

　　进入解析我们的配置类的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);

        //处理我们的@PropertySources注解的
        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");
            }
        }

        //接下来解析我们的@ComponentScans注解
        //从我们的配置类上解析@ComponentScans的对象集合属性
        Set componentScans = AnnotationConfigUtils.attributesForRepeatable(
                sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
        if (!componentScans.isEmpty() &&
                !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
            //循环解析（我们解析出来的AnnotationAttributes）
            for (AnnotationAttributes componentScan : componentScans) {
                //把我们扫描出来的类变为bean定义的集合
                Set scannedBeanDefinitions =
                        this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
                //循环处理我们包扫描出来的bean定义
                for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                    BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
                    if (bdCand == null) {
                        bdCand = holder.getBeanDefinition();
                    }
                    //判断当前扫描出来的bean定义是不是一个配置类,若是的话 直接进行递归解析
                    if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
                        //递归解析
                        parse(bdCand.getBeanClassName(), holder.getBeanName());
                    }
                }
            }
        }

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

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

        //处理@Bean methods获取到我们配置类中所有标注了@Bean的方法
        Set beanMethods = retrieveBeanMethodMetadata(sourceClass);

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

        //处理配置类接口的
        processInterfaces(configClass, sourceClass);

        //处理配置类的父类的
        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();
            }
        }

        //没有父类解析完成
        return null;
    }

　　Debug解析：

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

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

        //给扫描器设置beanName的生成器对象
        Classextends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
        boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
        scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
                BeanUtils.instantiateClass(generatorClass));

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

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

        //设置ComponentScan对象的includeFilters包含的属性
        for (AnnotationAttributes filter : componentScan.getAnnotationArray("includeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addIncludeFilter(typeFilter);
            }
        }
        //设置ComponentScan对象的excludeFilters不包含的属性
        for (AnnotationAttributes filter : componentScan.getAnnotationArray("excludeFilters")) {
            for (TypeFilter typeFilter : typeFiltersFor(filter)) {
                scanner.addExcludeFilter(typeFilter);
            }
        }
        
        //是否懒加载
        boolean lazyInit = componentScan.getBoolean("lazyInit");
        if (lazyInit) {
            scanner.getBeanDefinitionDefaults().setLazyInit(true);
        }

        //包路径
        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);
            }
        });
        //真正的进行扫描解析
        return scanner.doScan(StringUtils.toStringArray(basePackages));
    }

　　进入真正的进行扫描解析scanner.doScan(StringUtils.toStringArray(basePackages))方法：

protected Set doScan(String... basePackages) {
        Assert.notEmpty(basePackages, "At least one base package must be specified");
        //创建bean定义的holder对象用于保存扫描后生成的bean定义对象
        Set beanDefinitions = new LinkedHashSet<>();
        //循环我们的包路径集合
        for (String basePackage : basePackages) {
            //找到候选的@Component
            Set candidates = findCandidateComponents(basePackage);
            for (BeanDefinition candidate : candidates) {

                ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(candidate);
                candidate.setScope(scopeMetadata.getScopeName());
                //设置我们的beanName
                String beanName = this.beanNameGenerator.generateBeanName(candidate, this.registry);
                //处理@AutoWired相关的
                if (candidate instanceof AbstractBeanDefinition) {
                    postProcessBeanDefinition((AbstractBeanDefinition) candidate, beanName);
                }
                //处理jsr250相关的组件
                if (candidate instanceof AnnotatedBeanDefinition) {
                    AnnotationConfigUtils.processCommonDefinitionAnnotations((AnnotatedBeanDefinition) candidate);
                }
                //把我们解析出来的组件bean定义注册到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);
                    //注册到Spring IoC容器中
                    registerBeanDefinition(definitionHolder, this.registry);
                }
            }
        }
        return beanDefinitions;
    }

　　Debug解析：

　　进过org.springframework.context.annotation.ClassPathBeanDefinitionScanner#doScan处理，Spring IoC容器中Bean的定义有12个了；

　　② 接下来处理@Import注解导入的Bean组件：

　　进入处理@Import注解的processImports(configClass, sourceClass, getImports(sourceClass), true)方法：

private void processImports(ConfigurationClass configClass, SourceClass currentSourceClass,
            Collection 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 {
                //获取我们Import导入进来的所有组件
                for (SourceClass candidate : importCandidates) {
                    //判断该组件是不是实现了ImportSelector的
                    if (candidate.isAssignable(ImportSelector.class)) {
                        // Candidate class is an ImportSelector -> delegate to it to determine imports
                        Class candidateClass = candidate.loadClass();
                        //实例化我们的SelectImport组件
                        ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
                        //调用相关的aware方法
                        ParserStrategyUtils.invokeAwareMethods(
                                selector, this.environment, this.resourceLoader, this.registry);
                        //判断是不是延时的DeferredImportSelectors，是这个类型不进行处理
                        if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
                            this.deferredImportSelectors.add(
                                    new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
                        }
                        else {
     //不是延时的调用selector的selectImports
                            String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                            //反之SelectImport导入进来的又是Import进来的 所以递归解析
                            Collection importSourceClasses = asSourceClasses(importClassNames);
                            processImports(configClass, currentSourceClass, importSourceClasses, false);
                        }
                    }
                    //判断我们导入的组件是不是ImportBeanDefinitionRegistrar
                    else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
                        // Candidate class is an ImportBeanDefinitionRegistrar ->
                        // delegate to it to register additional bean definitions
                        Class candidateClass = candidate.loadClass();
                        //实例话我们的ImportBeanDefinitionRegistrar对象
                        ImportBeanDefinitionRegistrar registrar =
                                BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
                        ParserStrategyUtils.invokeAwareMethods(
                                registrar, this.environment, this.resourceLoader, this.registry);
                        //保存我们的ImportBeanDefinitionRegistrar对象
                        configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
                    }
                    else {
     //就是一个普通的组件  但是防止我们普通的组件是一个配置类 所以还是直接走了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 接下来处理@ImportSource比如@ImportResource("classpath:circulation-di.xml")，基于xml的（略）

　　 ④ 接下来处理@Bean：

　　至此解析完成，注意@Import、@ImportSource、@Bean的定义还未注册到Spring IoC的容器中去

　　接下来将剩余的Bean定义信息注册到Spring IoC容器中：

 　　进入真正的把我们解析出来的配置类注册到容器中this.reader.loadBeanDefinitions(configClasses)方法：

public void loadBeanDefinitions(Set configurationModel) {
        TrackedConditionEvaluator trackedConditionEvaluator = new TrackedConditionEvaluator();
        //注册我们的配置类到容器中
        for (ConfigurationClass configClass : configurationModel) {
            loadBeanDefinitionsForConfigurationClass(configClass, trackedConditionEvaluator);
        }
    }

　　进入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;
        }

        //是不是通过@Import导入进来的
        if (configClass.isImported()) {
            registerBeanDefinitionForImportedConfigurationClass(configClass);
        }
        //是不是通过我们的@Bean导入进来的组件
        for (BeanMethod beanMethod : configClass.getBeanMethods()) {
            loadBeanDefinitionsForBeanMethod(beanMethod);
        }

        //是不是通过@ImportResources导入进来的
        loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
        //是不是通过ImportBeanDefinition注解导入进来的
        loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
    }

　　① 通过@Import导入进来的执行registerBeanDefinitionForImportedConfigurationClass(configClass)方法：

private void registerBeanDefinitionForImportedConfigurationClass(ConfigurationClass configClass) {
        //获取我们的配置类的源信息
        AnnotationMetadata metadata = configClass.getMetadata();
        //构建为我们的bean定义
        AnnotatedGenericBeanDefinition configBeanDef = new AnnotatedGenericBeanDefinition(metadata);
        //设置他的scope
        ScopeMetadata scopeMetadata = scopeMetadataResolver.resolveScopeMetadata(configBeanDef);
        configBeanDef.setScope(scopeMetadata.getScopeName());
        //获取bean的名称
        String configBeanName = this.importBeanNameGenerator.generateBeanName(configBeanDef, this.registry);
        //处理我们的JRS250组件的
        AnnotationConfigUtils.processCommonDefinitionAnnotations(configBeanDef, metadata);

        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(configBeanDef, configBeanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        //注册我们的bean定义到我们的容器中
        this.registry.registerBeanDefinition(definitionHolder.getBeanName(), definitionHolder.getBeanDefinition());
        configClass.setBeanName(configBeanName);

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

 　　② 通过@Bean导入进来的执行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 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 通过@ImportResources导入进来的执行loadBeanDefinitionsFromImportedResources(configClass.getImportedResources())方法：

private void loadBeanDefinitionsFromImportedResources(
            Mapextends BeanDefinitionReader>> importedResources) {

        Map, 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 通过ImportBeanDefinition注解导入进来的执行loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars())方法：

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

 　　至此第一步里面的invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry)方法执行完毕！！！！

　　下一步：又去容器中获取BeanDefinitionRegistryPostProcessor的bean的处理器名称 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false) 此时就有了自己定义的BeanDefinitionRegistryPostProcessor了，接下来调用自定义的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry后置方法，然后再调用postProcessBeanFactory原因是BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor；

　　最后一步：获取容器中所有的BeanFactoryPostProcessor的名称 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false) 此时就有了自己定义的BeanFactoryPostProcessor了，接下来调用自定义的BeanFactoryPostProcessor的postProcessBeanFactory方法；

　　完整的Spring IoC源码解析见：Spring系列（三）：Spring IoC源码解析

三、Spring IoC扫描Bean的流程图

　　总结：通过调用我们的Bean工厂的后置处理器，第一步：ConfigurationClassPostProcessor，解析我们的配置类，将所有的Bean的定义信息注册到Spring IoC容器中；第二步调用自定义的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinition Registry后置方法，然后再调用postProcessBeanFactory；最后调用自定义的BeanFactoryPostProcessor的postProcessBean Factory方法

转载于:https://www.cnblogs.com/toby-xu/p/11332666.html