spring 源码解析一（bean定义）

spring容器的创建

public class MainClass {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(MainConfig.class);
    }
}

new AnnotationConfigApplicationContext ()做了哪些事

public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
        //调用无参构造器，会调用父类的无参构造器
        this();
        //注册配置类
        register(annotatedClasses);
        //容器刷新
        refresh();
    }

1首先调用父类的构造器，创建了ioc容器

public GenericApplicationContext() {
    //创建了spring容器，DefaultListableBeanFactory是真正可以作为一个可以独立使用的ioc容器
 
    this.beanFactory = new DefaultListableBeanFactory(); 

}

2然后调用本身类的无参构造器

public AnnotationConfigApplicationContext() {
        //为IOC容器赋值 AnnotatedBeanDefinitionReader（注解的Bean定义读取器）
        this.reader = new AnnotatedBeanDefinitionReader(this);
        //为IOC容器赋值   类路径下的bean定义扫描器
        this.scanner = new ClassPathBeanDefinitionScanner(this);
    }

2.1 new AnnotatedBeanDefinitionReader（this）

public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry) {
       //getOrCreateEnvironment创建环境

  this(registry, getOrCreateEnvironment(registry)); }

public AnnotatedBeanDefinitionReader(BeanDefinitionRegistry registry, Environment environment) {
        Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
        Assert.notNull(environment, "Environment must not be null");
        this.registry = registry;
        //创建了一个条件计算器
        this.conditionEvaluator = new ConditionEvaluator(registry, environment, null);
        //为容器中注册系统的bean定义信息
        AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
    }

2.1.1注册bean定义信息的一些处理器

public static void registerAnnotationConfigProcessors(BeanDefinitionRegistry registry) {
        registerAnnotationConfigProcessors(registry, null);
    }

public static Set<BeanDefinitionHolder> registerAnnotationConfigProcessors(
            BeanDefinitionRegistry registry, Object source) {
        //获取ioc容器
        DefaultListableBeanFactory beanFactory = unwrapDefaultListableBeanFactory(registry);
        if (beanFactory != null) {
            //设置默认的排序器
            if (!(beanFactory.getDependencyComparator() instanceof AnnotationAwareOrderComparator)) {
                beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
            }
            //ContextAnnotationAutoireCandidateResovler用于确定特定的Bean定义是否符合特定的依赖项的候选者
            //具体分析可见 https://blog.csdn.net/f641385712/article/details/93620967
            if (!(beanFactory.getAutowireCandidateResolver() instanceof ContextAnnotationAutowireCandidateResolver)) {
                beanFactory.setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
            }
        }
        Set<BeanDefinitionHolder> beanDefs = new LinkedHashSet<BeanDefinitionHolder>(8);
        if (!registry.containsBeanDefinition(CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME)) {
            //注册一个配置类解析器的bean定义（ConfigurationClassPostProcessor）
            //该类实现了BeanDefinitionRegistryPostProcessor,
            //在refresh方法中的invokeBeanFactoryPostProcessors的方法中会被调用
            RootBeanDefinition def = new RootBeanDefinition(ConfigurationClassPostProcessor.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, CONFIGURATION_ANNOTATION_PROCESSOR_BEAN_NAME));
        }

        if (!registry.containsBeanDefinition(AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
            //设置AutoWired注解解析器的bean定义信息 (AutowiredAnnotationBeanPostProcessor)
            //该类实现了InstantiationAwareBeanPostProcessor，
            //在实例化前后会被调用，自动注入autoire注解的类
            RootBeanDefinition def = new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, AUTOWIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
        }

        if (!registry.containsBeanDefinition(REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME)) {
            // 注册解析@Required 注解的处理器
            RootBeanDefinition def = new RootBeanDefinition(RequiredAnnotationBeanPostProcessor.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, REQUIRED_ANNOTATION_PROCESSOR_BEAN_NAME));
        }

        // Check for JSR-250 support, and if present add the CommonAnnotationBeanPostProcessor.
        if (jsr250Present && !registry.containsBeanDefinition(COMMON_ANNOTATION_PROCESSOR_BEAN_NAME)) {
            //检查是否支持JSR250规范，如何支持注册 解析JSR250规范的注解
            RootBeanDefinition def = new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, COMMON_ANNOTATION_PROCESSOR_BEAN_NAME));
        }

        // Check for JPA support, and if present add the PersistenceAnnotationBeanPostProcessor.
        if (jpaPresent && !registry.containsBeanDefinition(PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME)) {
            RootBeanDefinition def = new RootBeanDefinition();
            //检查是否支持jpa，若支持注册解析jpa规范的注解
            try {
                def.setBeanClass(ClassUtils.forName(PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME,
                        AnnotationConfigUtils.class.getClassLoader()));
            }
            catch (ClassNotFoundException ex) {
                throw new IllegalStateException(
                        "Cannot load optional framework class: " + PERSISTENCE_ANNOTATION_PROCESSOR_CLASS_NAME, ex);
            }
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, PERSISTENCE_ANNOTATION_PROCESSOR_BEAN_NAME));
        }

        if (!registry.containsBeanDefinition(EVENT_LISTENER_PROCESSOR_BEAN_NAME)) {
            //注册解析@EventListener的注解
            RootBeanDefinition def = new RootBeanDefinition(EventListenerMethodProcessor.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_PROCESSOR_BEAN_NAME));
        }

        if (!registry.containsBeanDefinition(EVENT_LISTENER_FACTORY_BEAN_NAME)) {
            RootBeanDefinition def = new RootBeanDefinition(DefaultEventListenerFactory.class);
            def.setSource(source);
            beanDefs.add(registerPostProcessor(registry, def, EVENT_LISTENER_FACTORY_BEAN_NAME));
        }

        return beanDefs;
    }

2.2 new ClassPathBeanDefinitionScanner(this)

public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry) {
        this(registry, true);
    }

public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters) {
        this(registry, useDefaultFilters, getOrCreateEnvironment(registry));
    }

public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
            Environment environment) {

        this(registry, useDefaultFilters, environment,
                (registry instanceof ResourceLoader ? (ResourceLoader) registry : null));
    }

public ClassPathBeanDefinitionScanner(BeanDefinitionRegistry registry, boolean useDefaultFilters,
            Environment environment, ResourceLoader resourceLoader) {

        Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
        this.registry = registry;
        //使用默认的代码扫描规则
        if (useDefaultFilters) {
            registerDefaultFilters();
        }
        //设置环境
        setEnvironment(environment);
        //设置资源加载器
        setResourceLoader(resourceLoader);
    }

这里虽然新建了一个扫描器，但是实际运用的时候还是重新new了一个，不过程序员在写代码的时候可以从容器中获取这个扫描器。

3注册配置类到容器中 register(annotatedClasses);

public void register(Class<?>... annotatedClasses) {
        Assert.notEmpty(annotatedClasses, "At least one annotated class must be specified");
        this.reader.register(annotatedClasses);
    }

public void register(Class<?>... annotatedClasses) {
        for (Class<?> annotatedClass : annotatedClasses) {
            registerBean(annotatedClass);
        }
    }

public void registerBean(Class<?> annotatedClass) {
        registerBean(annotatedClass, null, (Class<? extends Annotation>[]) null);
    }

public void registerBean(Class<?> annotatedClass, String name, Class<? extends Annotation>... qualifiers) {
        AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(annotatedClass);
        if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
            return;
        }

        ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
        abd.setScope(scopeMetadata.getScopeName());
        String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd, this.registry));
        AnnotationConfigUtils.processCommonDefinitionAnnotations(abd);
        if (qualifiers != null) {
            for (Class<? extends Annotation> qualifier : qualifiers) {
                if (Primary.class == qualifier) {
                    abd.setPrimary(true);
                }
                else if (Lazy.class == qualifier) {
                    abd.setLazyInit(true);
                }
                else {
                    abd.addQualifier(new AutowireCandidateQualifier(qualifier));
                }
            }
        }
        //注册自己传入的主配置类bean定义到容器中
        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd, beanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata, definitionHolder, this.registry);
        BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder, this.registry);
    }

4 refresh()方法

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                initMessageSource();

                // Initialize event multicaster for this context.
                initApplicationEventMulticaster();

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

                // Check for listener beans and register them.
                registerListeners();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                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 {
                // Reset common introspection caches in Spring's core, since we
                // might not ever need metadata for singleton beans anymore...
                resetCommonCaches();
            }
        }
    }

refresh方法中包含12步，内容众多，先只分析和bean定义相关的，后续再分析其他内容

4.1 invokeBeanFactoryPostProcessors(beanFactory)

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {

        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()));
        }
    }

4.2 PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors()

public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
         //这时候传进来的beanFactoryPostProcessors为null
        // Invoke BeanDefinitionRegistryPostProcessors first, if any.
        Set<String> processedBeans = new HashSet<String>();
        //DefaultListableBeanFactory继承了BeanDefinitionRegistry,所以会走进此分支
        if (beanFactory instanceof BeanDefinitionRegistry) {
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            //创建一个普通的BeanfactoryPostProcessors的list的组件
            List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
            //创建一个BeanDefinitionRegistryPostProcessor类型的list
            //BeanDefinitionRegistryPostProcessor是继承了BeanFactoryPostProcessor的
            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
             //处理容器硬编码(new 出来的)带入的beanFacotryPostProcessors
             //分别放入上面的相对应的集合中
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    registryProcessors.add(registryProcessor);
                }
                else {
                    regularPostProcessors.add(postProcessor);
                }
            }

            // Do not initialize FactoryBeans here: We need to leave all regular beans
            // uninitialized to let the bean factory post-processors apply to them!
            // Separate between BeanDefinitionRegistryPostProcessors that implement
            // PriorityOrdered, Ordered, and the rest.
            //创建一个当前注册的RegistryProcessors的集合
            List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
            // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
            //第一步:去容器中查询是否有BeanDefinitionRegistryPostProcessor类型的,实现了PriorityOrdered接口的，优先级最高
            //此时ConfigurationClassPostProcessor被查询出来，ConfigurationClassPostProcessor实现了PriorityOrdered，但是优先级最低
            String[] postProcessorNames =
                    beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    //加到已处理的list中
                    processedBeans.add(ppName);
                }
            }
            //排序当前的RegistryProcessors的集合
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            //注册RegistryProcessors的集合
            registryProcessors.addAll(currentRegistryProcessors);
            //触发当前的registryProcessors
            //ConfigurationClassPostProcessor在这里会被触发
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            //清除处理过的
            currentRegistryProcessors.clear();

            // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
            //第二步：去容器中查询是否有BeanDefinitionRegistryPostProcessor类型的,实现了Ordered接口的，优先级最高
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    processedBeans.add(ppName);
                }
            }
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            registryProcessors.addAll(currentRegistryProcessors);
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            currentRegistryProcessors.clear();

            // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
            //第三步：调用普通的BeanDefinitionRegistryPostProcessors没用实现PriorithOrdered和Ordered接口
            boolean reiterate = true;
            while (reiterate) {
                reiterate = false;
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                for (String ppName : postProcessorNames) {
                    if (!processedBeans.contains(ppName)) {
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        processedBeans.add(ppName);
                        reiterate = true;
                    }
                }
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                registryProcessors.addAll(currentRegistryProcessors);
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                currentRegistryProcessors.clear();
            }

            // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
            //调用上面查询出来的Processor,也实现了BeanFactoryPostProcessors的接口,调用该接口的方法
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        }

        else {
            // Invoke factory processors registered with the context instance.
            //如果beanFactory不是BeanDefinitionRegistry的对象，直接调用BeanFactoryPostProcessor的方法
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        // Do not initialize FactoryBeans here: We need to leave all regular beans
        // uninitialized to let the bean factory post-processors apply to them!
        //下面的是处理BeanFactoryPostProcessor接口的实现类，跟上面逻辑一样，先处理实现PrioityOrdered接口的，然后再处理Ordered接口的，然后再处理普通的
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        // Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
        // Ordered, and the rest.
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
        List<String> orderedPostProcessorNames = new ArrayList<String>();
        List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
        for (String ppName : postProcessorNames) {
            if (processedBeans.contains(ppName)) {
                // skip - already processed in first phase above
            }
            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);
            }
        }

        // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
        List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
        for (String postProcessorName : orderedPostProcessorNames) {
            orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
        }
        sortPostProcessors(orderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);

        // Finally, invoke all other BeanFactoryPostProcessors.
        List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
        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();
    }

可以看出BeanDefinitionRegistryPostProcessor的执行时机在BeanFactoryPostProcessor之前，

两个类自己的执行首先执行PriorityOrdered修饰的，然后执行Ordered，最后执行普通的

4.3 ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry()

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
        int registryId = System.identityHashCode(registry);
        if (this.registriesPostProcessed.contains(registryId)) {
            throw new IllegalStateException(
                    "postProcessBeanDefinitionRegistry already called on this post-processor against " + registry);
        }
        if (this.factoriesPostProcessed.contains(registryId)) {
            throw new IllegalStateException(
                    "postProcessBeanFactory already called on this post-processor against " + registry);
        }
        this.registriesPostProcessed.add(registryId);

        processConfigBeanDefinitions(registry);
    }

public void processConfigBeanDefinitions(BeanDefinitionRegistry registry) {
        List<BeanDefinitionHolder> configCandidates = new ArrayList<>();
        //没有解析之前，系统候选的bean定义配置(有自己的配置类，还有系统自带的)
        String[] candidateNames = registry.getBeanDefinitionNames();
        //循环Bean定义的名称 找出自己的传入的主配置类的bean定义信息
        for (String beanName : candidateNames) {
            BeanDefinition beanDef = registry.getBeanDefinition(beanName);
            //判断是不是配置类
            if (ConfigurationClassUtils.isFullConfigurationClass(beanDef) ||
                    ConfigurationClassUtils.isLiteConfigurationClass(beanDef)) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Bean definition has already been processed as a configuration class: " + beanDef);
                }
            }
            else if (ConfigurationClassUtils.checkConfigurationClassCandidate(beanDef, this.metadataReaderFactory)) {
                configCandidates.add(new BeanDefinitionHolder(beanDef, beanName));
            }
        }

        // Return immediately if no @Configuration classes were found
        if (configCandidates.isEmpty()) {
            return;
        }

        // Sort by previously determined @Order value, if applicable
        //检查配置类排序
        configCandidates.sort((bd1, bd2) -> {
            int i1 = ConfigurationClassUtils.getOrder(bd1.getBeanDefinition());
            int i2 = ConfigurationClassUtils.getOrder(bd2.getBeanDefinition());
            return Integer.compare(i1, i2);
        });
        
        // Detect any custom bean name generation strategy supplied through the enclosing application context
        //配置bean的名称生成策略
        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) {
                    this.componentScanBeanNameGenerator = generator;
                    this.importBeanNameGenerator = generator;
                }
            }
        }

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

        // Parse each @Configuration class
        //创建组件扫描器
        //metadataReaderFactory元数据工厂
        //problemReporter问题报告器
        //
        ConfigurationClassParser parser = new ConfigurationClassParser(
                this.metadataReaderFactory, this.problemReporter, this.environment,
                this.resourceLoader, this.componentScanBeanNameGenerator, registry);
        //将需要解析的类加入集合中
        Set<BeanDefinitionHolder> candidates = new LinkedHashSet<>(configCandidates);
        //创建已处理候选类集合，集合大小为候选类大小
        Set<ConfigurationClass> alreadyParsed = new HashSet<>(configCandidates.size());
        //循环处理候选配置类
        do {
            //解析配置类
            parser.parse(candidates);
            //进行校验
            parser.validate();
            //获取ConfigClass (把解析过的配置bean定义信息获取出来)
            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());
            }
            //@CompentScan是直接注册Bean定义信息的,但是通过获取@Import,@Bean这种的注解还没有注册的bean定义,
            this.reader.loadBeanDefinitions(configClasses);
            //把系统解析过我们自己的组件放在alreadyParsed
            alreadyParsed.addAll(configClasses);
            //清除解析过的类
            candidates.clear();
            //已经注册的bean定义个数大于最新 开始系统+主配置类的(发生过解析)
            if (registry.getBeanDefinitionCount() > candidateNames.length) {
                String[] newCandidateNames = registry.getBeanDefinitionNames();
                Set<String> oldCandidateNames = new HashSet<>(Arrays.asList(candidateNames));
                Set<String> alreadyParsedClasses = new HashSet<>();
                for (ConfigurationClass configurationClass : alreadyParsed) {
                    alreadyParsedClasses.add(configurationClass.getMetadata().getClassName());
                }
                for (String candidateName : newCandidateNames) {
                    if (!oldCandidateNames.contains(candidateName)) {
                        BeanDefinition bd = registry.getBeanDefinition(candidateName);
                        if (ConfigurationClassUtils.checkConfigurationClassCandidate(bd, this.metadataReaderFactory) &&
                                !alreadyParsedClasses.contains(bd.getBeanClassName())) {
                            candidates.add(new BeanDefinitionHolder(bd, candidateName));
                        }
                    }
                }
                candidateNames = newCandidateNames;
            }
        }
        while (!candidates.isEmpty());

        // 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();
        }
    }

 4.4 ConfigurationClassParser.parse(Set<BeanDefinitionHolder> configCandidates)

public void parse(Set<BeanDefinitionHolder> configCandidates) {
        this.deferredImportSelectors = new LinkedList<DeferredImportSelectorHolder>();

        for (BeanDefinitionHolder holder : configCandidates) {
            BeanDefinition bd = holder.getBeanDefinition();
            try {
                //这里根据Bean定义的不同类型走不同的分支，但是最终都会调用到方法
                //processConfigurationClass(ConfigurationClass configClass)
                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);
            }
        }

        processDeferredImportSelectors();
    }

4.4.1 ConfigurationClassParser.processConfigurationClass()

protected final void parse(AnnotationMetadata metadata, String beanName) throws IOException {
        processConfigurationClass(new ConfigurationClass(metadata, beanName));
    }

protected void processConfigurationClass(ConfigurationClass configClass) throws IOException {
        //检查当前解析的配置bean是否包含Conditional注解，如果不包含则不需要跳过 
        // 如果包含了则进行match方法得到匹配结果，如果是符合的并且设置的配置解析策略是解析阶段不需要调过
        if (this.conditionEvaluator.shouldSkip(configClass.getMetadata(), ConfigurationPhase.PARSE_CONFIGURATION)) {
            return;
        }

        ConfigurationClass existingClass = this.configurationClasses.get(configClass);
        if (existingClass != null) {
            if (configClass.isImported()) {
                if (existingClass.isImported()) {
                    existingClass.mergeImportedBy(configClass);
                }
                // Otherwise ignore new imported config class; existing non-imported class overrides it.
                return;
            }
            else {
                // Explicit bean definition found, probably replacing an import.
                // Let's remove the old one and go with the new one.
                this.configurationClasses.remove(configClass);
                for (Iterator<ConfigurationClass> it = this.knownSuperclasses.values().iterator(); it.hasNext();) {
                    if (configClass.equals(it.next())) {
                        it.remove();
                    }
                }
            }
        }

        // Recursively process the configuration class and its superclass hierarchy.
        SourceClass sourceClass = asSourceClass(configClass);
        //递归解析
        do {

            sourceClass = doProcessConfigurationClass(configClass, sourceClass);
        }
        while (sourceClass != null);
        // 添加到ConfigurationClassParser的configurationClasses中
        this.configurationClasses.put(configClass, configClass);
    }

4.4.2 ConfigurationClassParser#doProcessConfigurationClass

1.处理内部类

2.处理@PropertySource注解

3.处理@ComponentScan注解

4.处理@Import注解

5.处理@ImportResource注解

6.处理@Bean修饰的方法

7.处理接口定义的方法

8.处理父类

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

        // Recursively process any member (nested) classes first
        //处理内部类
        processMemberClasses(configClass, sourceClass);

        // Process any @PropertySource annotations
        //处理@PropertySource注解
        // @PropertySource注解用来加载properties文件
        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");
            }
        }
         
        // Process any @ComponentScan annotations
        //处理@ComponentScan注解
        Set<AnnotationAttributes> componentScans = AnnotationConfigUtils.attributesForRepeatable(
                sourceClass.getMetadata(), ComponentScans.class, ComponentScan.class);
        if (!componentScans.isEmpty() &&
                !this.conditionEvaluator.shouldSkip(sourceClass.getMetadata(), ConfigurationPhase.REGISTER_BEAN)) {
            for (AnnotationAttributes componentScan : componentScans) {
                // The config class is annotated with @ComponentScan -> perform the scan immediately
                Set<BeanDefinitionHolder> scannedBeanDefinitions =
                        this.componentScanParser.parse(componentScan, sourceClass.getMetadata().getClassName());
                // Check the set of scanned definitions for any further config classes and parse recursively if needed
                for (BeanDefinitionHolder holder : scannedBeanDefinitions) {
                    BeanDefinition bdCand = holder.getBeanDefinition().getOriginatingBeanDefinition();
                    if (bdCand == null) {
                        bdCand = holder.getBeanDefinition();
                    }
                    //遍历扫描到的配置类进行递归解析
                    if (ConfigurationClassUtils.checkConfigurationClassCandidate(bdCand, this.metadataReaderFactory)) {
                        parse(bdCand.getBeanClassName(), holder.getBeanName());
                    }
                }
            }
        }

        // Process any @Import annotations
        // 处理@Import注解
        //这里面处理了@ImportSelector的bean定义，但是@ImportBeanDefinitionRegistar的只是将类放到了配置中
        processImports(configClass, sourceClass, getImports(sourceClass), true);

        // Process any @ImportResource annotations
        // 处理@ImportResource 注解
        if (sourceClass.getMetadata().isAnnotated(ImportResource.class.getName())) {
            AnnotationAttributes importResource =
                    AnnotationConfigUtils.attributesFor(sourceClass.getMetadata(), ImportResource.class);
            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);
            }
        }

        // Process individual @Bean methods
        //处理@Bean修饰的方法
        Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
        for (MethodMetadata methodMetadata : beanMethods) {
            //这里还未注册bean定义，只是将@bean修饰的方法加入配置中，
            configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
        }

        // Process default methods on interfaces
        //处理接口
        processInterfaces(configClass, sourceClass);

        // Process superclass, if any
        //处理超类
        if (sourceClass.getMetadata().hasSuperClass()) {
            String superclass = sourceClass.getMetadata().getSuperClassName();
            if (!superclass.startsWith("java") && !this.knownSuperclasses.containsKey(superclass)) {
                this.knownSuperclasses.put(superclass, configClass);
                // Superclass found, return its annotation metadata and recurse
                return sourceClass.getSuperClass();
            }
        }

        // No superclass -> processing is complete
        return null;
    }

4.4.3 ComponentScanAnnotationParser#parse

public Set<BeanDefinitionHolder> parse(AnnotationAttributes componentScan, final String declaringClass) {
    // 创建 ClassPathBeanDefinitionScanner
    // 在 AnnotationConfigApplicationContext 的构造器中也创建了一个ClassPathBeanDefinitionScanner
    // 这里证明了,执行扫描 scanner 不是构造器中的,而是这里创建的
    ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(this.registry,
            componentScan.getBoolean("useDefaultFilters"), this.environment, this.resourceLoader);

    // @ComponentScan 中可以注册自定义的 BeanNameGenerator
    // 但是需要注意,通过源码可以明白,这里注册的自定义BeanNameGenerator 只对当前 scanner 有效
    Class<? extends BeanNameGenerator> generatorClass = componentScan.getClass("nameGenerator");
    boolean useInheritedGenerator = (BeanNameGenerator.class == generatorClass);
    scanner.setBeanNameGenerator(useInheritedGenerator ? this.beanNameGenerator :
            BeanUtils.instantiateClass(generatorClass));

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

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

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

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

    Set<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);
    }

    // @ComponentScan(basePackageClasses = Xx.class)
    // 可以指定basePackageClasses, 只要是与是这几个类所在包及其子包,就可以被Spring扫描
    // 经常会用一个空的类来作为basePackageClasses,默认取当前配置类所在包及其子包
    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);
        }
    });

    //执行扫描
    return scanner.doScan(StringUtils.toStringArray(basePackages));
}

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

4.4.4 ConfigurationClassParser.processImports

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 {
         for (SourceClass candidate : importCandidates) {
            //ImportSelector处理
            if (candidate.isAssignable(ImportSelector.class)) {
               // Candidate class is an ImportSelector -> delegate to it to determine imports
               Class<?> candidateClass = candidate.loadClass();
               ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
               ParserStrategyUtils.invokeAwareMethods(
                     selector, this.environment, this.resourceLoader, this.registry);
               if (this.deferredImportSelectors != null && selector instanceof DeferredImportSelector) {
                  this.deferredImportSelectors.add(
                        new DeferredImportSelectorHolder(configClass, (DeferredImportSelector) selector));
               }
               else {
                  //调用selectImports方法，找出需要真正导入的类
                  String[] importClassNames = selector.selectImports(currentSourceClass.getMetadata());
                  Collection<SourceClass> importSourceClasses = asSourceClasses(importClassNames);
                  //处理真正到要导入的类，循环处理每个bean定义
                  processImports(configClass, currentSourceClass, importSourceClasses, false);
               }
            }
            //ImportBeanDefinitionRegistrar处理
            else if (candidate.isAssignable(ImportBeanDefinitionRegistrar.class)) {
               // Candidate class is an ImportBeanDefinitionRegistrar ->
               // delegate to it to register additional bean definitions
               Class<?> candidateClass = candidate.loadClass();
               ImportBeanDefinitionRegistrar registrar =
                     BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
               ParserStrategyUtils.invokeAwareMethods(
                     registrar, this.environment, this.resourceLoader, this.registry);
               //这里并未处理，只是将ImportBeanDefinitionRegistrar的实现类加入配置中，接着往下看，是否会调用他的registerBeanDefinitions方法导入bean定义
               //事实上是在this.reader.loadBeanDefinitions(configClasses)中处理
               configClass.addImportBeanDefinitionRegistrar(registrar, currentSourceClass.getMetadata());
            }
            //导入普通类的处理
            else {
               // Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
               // process it as an @Configuration class
               this.importStack.registerImport(
                     currentSourceClass.getMetadata(), candidate.getMetadata().getClassName());
               processConfigurationClass(candidate.asConfigClass(configClass));
            }
         }
      }
      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();
      }
   }
}

4.5 this.reader.loadBeanDefinitions(configClasses);

4.3分析了parse方法， 但是可以看出来上面@ImportBeanDefinitionRegistrar和@Bean和@ImportResource犯法的bean定义并未注册，只是讲这些配置放到了成员变量中，这些bean定义都是在ader.loadBeanDefinitions中注册的，继续往下分析

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

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;
        }
        //判断主配置类是不是Improt导入的
        if (configClass.isImported()) {
            registerBeanDefinitionForImportedConfigurationClass(configClass);
        }
        //处理@Bean的bean定义
        for (BeanMethod beanMethod : configClass.getBeanMethods()) {
            loadBeanDefinitionsForBeanMethod(beanMethod);
        }
        //处理@ImportResource配置的bean定义
        loadBeanDefinitionsFromImportedResources(configClass.getImportedResources());
        //处理@ImportBeanDefinitionRegistrar的bean定义
        loadBeanDefinitionsFromRegistrars(configClass.getImportBeanDefinitionRegistrars());
    }