摘要：這個(gè)讀取器可以讀取注解標(biāo)注下的所有定義，并最終添加到的中。處理注解的配置類(lèi)讀取每一個(gè)配置類(lèi)中定義的，加入到容器中。

IOC的核心就是代碼入口就在AbstractApplictionContext

    public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // 在刷新容器前進(jìn)行一些準(zhǔn)備工作，例如設(shè)置容器的激活狀態(tài)，校驗(yàn)容器環(huán)境所必須的啟動(dòng)參數(shù)
            prepareRefresh();

            // 刷新內(nèi)部的BeanFactory，獲得一個(gè)新鮮的BeanFactory，這里面主要是讀取XML文件，將其轉(zhuǎn)換為BeanDefinition
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // 對(duì)BeanFactory進(jìn)行進(jìn)一步的完善，包括注冊(cè)應(yīng)用上下文感知以及監(jiān)聽(tīng)器感知的BeanPostProcessor，
            // 先注冊(cè)一些系統(tǒng)的環(huán)境Bean
            prepareBeanFactory(beanFactory);

            try {
                // 給子類(lèi)在初始化BeanFactory重寫(xiě)修改變動(dòng)beanFactory的權(quán)利
                postProcessBeanFactory(beanFactory);

                // 調(diào)用BeanFactoryPostProcessor，可以修改beanFactory，與上面不同的是，這里是類(lèi)似插件的形式，耦合度更低
                invokeBeanFactoryPostProcessors(beanFactory);

                // 提前注冊(cè)BeanPostProcessor，用于后期提供代理等功能
                registerBeanPostProcessors(beanFactory);

                // 初始化消息源，用于國(guó)際化
                initMessageSource();

                // 初始化應(yīng)用事件廣播器，用于廣播應(yīng)用上下文事件
                initApplicationEventMulticaster();

                // Initialize other special beans in specific context subclasses.
                onRefresh();

                // 為應(yīng)用事件廣播器初始化監(jiān)聽(tīng)器(ApplicationListener)
                registerListeners();

                // 實(shí)例化并注冊(cè)所有非懶加載的bean
                finishBeanFactoryInitialization(beanFactory);

                // 刷新容器后的額外工作，初始化生命周期執(zhí)行器，發(fā)布容器刷新完畢的應(yīng)用上下文事件
                finishRefresh();
            }

            catch (BeansException ex) {
                if (logger.isWarnEnabled()) {
                    logger.warn("Exception encountered during context initialization - " +
                            "cancelling refresh attempt: " + ex);
                }

                // Destroy already created singletons to avoid dangling resources.
                destroyBeans();

                // Reset "active" flag.
                cancelRefresh(ex);

                // Propagate exception to caller.
                throw ex;
            }

            finally {
                // 清除掉不再需要的緩存，節(jié)省空間
                resetCommonCaches();
            }
        }
    }

---分析一下上面代碼中的invokeBeanFactoryPostProcessors(beanFactory)源碼---開(kāi)始

    protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
        // 調(diào)用所有的BeanFactoryPostProcessors
        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()));
        }
    }

我們知道BeanFactoryPostProcessor可以對(duì)已經(jīng)生成好的BeanDefinition進(jìn)行修改，也可以動(dòng)態(tài)的添加來(lái)自第三方的BeanDefinition。比如我們熟知的Mybatis中的Mapper對(duì)象。如果我們使用Spring-Mybatis包中的注解@MapperScan則可以將我們定義的mapper對(duì)象加入到Spring容器中,便于我們?cè)陧?xiàng)目中注入到指定的地方。

@MapperScan("com.demo")
@Configuration
public class Configuration(){
}


@Service
public class Service{
@Autowired
private DemoMapper demoMapper;
}

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

        // 存放所有已經(jīng)調(diào)用過(guò)的BeanFactoryPostProcessor，避免重復(fù)執(zhí)行
        Set processedBeans = new HashSet();

        // Spring默認(rèn)使用的BeanFactory是DefaultListableBeanFactory，其已經(jīng)實(shí)現(xiàn)了BeanDefinitionRegistry接口
        if (beanFactory instanceof BeanDefinitionRegistry) {
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            // 用于存放普通的BeanFactoryPostProcessor
            List regularPostProcessors = new LinkedList();
            // 用于存放BeanDefinitionRegistryPostProcessor
            List registryPostProcessors =
                    new LinkedList();
           /* 執(zhí)行我們自定義的beanFactoryPostProcessor，Spring提供customizeContext()方法給予我們定制化構(gòu)建            
             ApplicationContext的機(jī)會(huì)，所以在這個(gè)方法中我們可以動(dòng)態(tài)的添加自定義的BeanFactoryPostProcessor。
             這里將普通的BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor區(qū)分開(kāi)分別執(zhí)行。
            */
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    BeanDefinitionRegistryPostProcessor registryPostProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    registryPostProcessor.postProcessBeanDefinitionRegistry(registry);
                    registryPostProcessors.add(registryPostProcessor);
                }
                else {
                    regularPostProcessors.add(postProcessor);
                }
            }

            
            String[] postProcessorNames =
                    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);

            // 調(diào)用實(shí)現(xiàn)了PriorityOrdered接口的BeanFactoryPostProcessor
            List priorityOrderedPostProcessors = new ArrayList();
            for (String ppName : postProcessorNames) {
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                }
            }
            // 按照權(quán)重排序
            sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
            registryPostProcessors.addAll(priorityOrderedPostProcessors);
            invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry);

            // 調(diào)用實(shí)現(xiàn)了 Ordered接口的，步驟跟上面一樣.
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            List orderedPostProcessors = new ArrayList();
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                }
            }
            sortPostProcessors(beanFactory, orderedPostProcessors);
            registryPostProcessors.addAll(orderedPostProcessors);
            invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry);

            // 最后調(diào)用其它的BeanFactoryPostProcessor
            // 如果有BeanDefinitionRegistryPostProcessor被執(zhí)行, 則有可能會(huì)產(chǎn)生新的BeanDefinitionRegistryPostProcessor,因此這邊將reiterate賦值為true, 代表需要再循環(huán)查找一次
            boolean reiterate = true;
            while (reiterate) {
                reiterate = false;
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                for (String ppName : postProcessorNames) {
                    if (!processedBeans.contains(ppName)) {
                        BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class);
                        registryPostProcessors.add(pp);
                        processedBeans.add(ppName);
                        pp.postProcessBeanDefinitionRegistry(registry);
                        reiterate = true;
                    }
                }
            }

            invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory);
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        }

        else {
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        /* 上面是通過(guò)customizeContext來(lái)動(dòng)態(tài)添加BeanPostProcessor，而從這里的代碼我們可以看出，只要我們寫(xiě)好一個(gè)
        BeanFactoryPostProcessor，使用任意方法將其加入到Spring容器中，Spring也可以解析后執(zhí)行。這里足以看出Spring強(qiáng)大的兼容性*/
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        List priorityOrderedPostProcessors = new ArrayList();
        List orderedPostProcessorNames = new ArrayList();
        List nonOrderedPostProcessorNames = new ArrayList();
        for (String ppName : postProcessorNames) {
            if (processedBeans.contains(ppName)) {
                // 跳過(guò)已經(jīng)執(zhí)行過(guò)的
            }
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
                orderedPostProcessorNames.add(ppName);
            }
            else {
                nonOrderedPostProcessorNames.add(ppName);
            }
        }

        sortPostProcessors(beanFactory, priorityOrderedPostProcessors);
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        List orderedPostProcessors = new ArrayList();
        for (String postProcessorName : orderedPostProcessorNames) {
            orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        sortPostProcessors(beanFactory, orderedPostProcessors);
        invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

        List nonOrderedPostProcessors = new ArrayList();
        for (String postProcessorName : nonOrderedPostProcessorNames) {
            nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);

        // 清空Bean工廠的元數(shù)據(jù)緩存，因?yàn)樵贐eanFactoryPostProcessor中可能已經(jīng)更改了BeanDefinition，所以這里需要清空
        beanFactory.clearMetadataCache();
    }

這個(gè)方法比較長(zhǎng)，我個(gè)人覺(jué)得spring應(yīng)當(dāng)將其拆分成一個(gè)個(gè)小的方法，使結(jié)構(gòu)更加清晰。

BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子接口，它提供了動(dòng)態(tài)注冊(cè)Bean的能力。
我們最常使用的是它的實(shí)現(xiàn)類(lèi)ConfigurationClassPostProcessor，其帶有一個(gè)Bean定義讀取器。這個(gè)讀取器可
以讀取@Configuration、@Import、@ImportResource注解標(biāo)注下的所有Bean定義，并最終添加到Spring的BeanFactory中。

public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPostProcessor,
        PriorityOrdered, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware {
***
private ConfigurationClassBeanDefinitionReader reader;
***
}

無(wú)論是在普通的Spring項(xiàng)目亦或是SpringBoot項(xiàng)目，只要我們開(kāi)啟了對(duì)注解配置的支持，那么系統(tǒng)就會(huì)自動(dòng)注冊(cè)ConfigurationClassPostProcessor

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
        /**
         * 獲取所有的配置定義，注意：此時(shí)系統(tǒng)中沒(méi)有任何我們自定義的@Configuration配置定義。
         * 但如果是SpringBoot項(xiàng)目，系統(tǒng)默認(rèn)會(huì)將啟動(dòng)類(lèi)SpringBootApplication加入到系統(tǒng)配置定義中去。
         */
        Set configCandidates = new LinkedHashSet();
        for (String beanName : registry.getBeanDefinitionNames()) {
            BeanDefinition beanDef = registry.getBeanDefinition(beanName);
            if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
                configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
            }
        }

        // 如果配置類(lèi)為空，立即返回
        if (configCandidates.isEmpty()) {
            return;
        }

        // 這里初始化一些生成器
        SingletonBeanRegistry singletonRegistry = null;
        if (registry instanceof SingletonBeanRegistry) {
            singletonRegistry = (SingletonBeanRegistry) registry;
            if (!this.localBeanNameGeneratorSet && singletonRegistry.containsSingleton(CONFIGURATION_BEAN_NAME_GENERATOR)) {
                BeanNameGenerator generator = (BeanNameGenerator) singletonRegistry.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
                this.componentScanBeanNameGenerator = generator;
                this.importBeanNameGenerator = generator;
            }
        }

        // 遞歸解析每一個(gè)@Configuration配置類(lèi)
        ConfigurationClassParser parser = new ConfigurationClassParser(
                this.metadataReaderFactory, this.problemReporter, this.environment,
                this.resourceLoader, this.componentScanBeanNameGenerator, registry);
        for (BeanDefinitionHolder holder : configCandidates) {
            BeanDefinition bd = holder.getBeanDefinition();
            try {
                if (bd instanceof AbstractBeanDefinition && ((AbstractBeanDefinition) bd).hasBeanClass()) {
                    parser.parse(((AbstractBeanDefinition) bd).getBeanClass(), holder.getBeanName());
                }
                else {
                    parser.parse(bd.getBeanClassName(), holder.getBeanName());
                }
            }
            catch (IOException ex) {
                throw new BeanDefinitionStoreException("Failed to load bean class: " + bd.getBeanClassName(), ex);
            }
        }
        /**
         * 校驗(yàn)解析出的所有@Configuration配置類(lèi)，例如如果是@Configuration注解標(biāo)注的full配置類(lèi)，那么類(lèi)不能被聲明為final，否則報(bào)錯(cuò)。因?yàn)镾pring會(huì)為
         * 每一個(gè)@Configuration配置類(lèi)創(chuàng)建一個(gè)CGLIB代理，我們知道CGLIB是通過(guò)繼承關(guān)系來(lái)實(shí)現(xiàn)代理的，既然用到繼承，其父類(lèi)肯定不能為final。
          */
        parser.validate();

        // 處理@PropertySource注解的配置類(lèi)
        Stack> parsedPropertySources = parser.getPropertySources();
        if (!parsedPropertySources.isEmpty()) {
            if (!(this.environment instanceof ConfigurableEnvironment)) {
                logger.warn("Ignoring @PropertySource annotations. " +
                        "Reason: Environment must implement ConfigurableEnvironment");
            }
            else {
                MutablePropertySources envPropertySources = ((ConfigurableEnvironment)this.environment).getPropertySources();
                while (!parsedPropertySources.isEmpty()) {
                    envPropertySources.addLast(parsedPropertySources.pop());
                }
            }
        }

        /* 讀取每一個(gè)@Configuration配置類(lèi)中定義的bean，加入到ioc容器中。包括使用@Bean注解標(biāo)注的方法，@Import導(dǎo)入的registry注冊(cè)器，
        * @ImportResource導(dǎo)入的xml資源
        */
        if (this.reader == null) {
            this.reader = new ConfigurationClassBeanDefinitionReader(
                    registry, this.sourceExtractor, this.problemReporter, this.metadataReaderFactory,
                    this.resourceLoader, this.environment, this.importBeanNameGenerator);
        }
        this.reader.loadBeanDefinitions(parser.getConfigurationClasses());

        // Register the ImportRegistry as a bean in order to support ImportAware @Configuration classes
        if (singletonRegistry != null) {
            if (!singletonRegistry.containsSingleton(IMPORT_REGISTRY_BEAN_NAME)) {
                singletonRegistry.registerSingleton(IMPORT_REGISTRY_BEAN_NAME, parser.getImportRegistry());
            }
        }
    }

---分析一下上面代碼中的invokeBeanFactoryPostProcessors(beanFactory)源碼---結(jié)束

未完待續(xù)。。。