public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
        // 进入构造函数,要先调用父类的构造方法
        this();
        // register配置注册类
        register(componentClasses);
        // ioc容器shua新接口--非常重要
        refresh();
    }

　　private <T> void doRegisterBean(Class<T> beanClass,@Nullable String name,@Nullable Class<? extends Annotation>[] qualifiers,@Nullable Supplier<T> supplier,@Nullable BeanDefinitionCustomizer[] customizers) {
        // 将入参beanClass构建成AnnotatedGenericBeanDefinition对象
        AnnotatedGenericBeanDefinition abd = new AnnotatedGenericBeanDefinition(beanClass);
        if (this.conditionEvaluator.shouldSkip(abd.getMetadata())) {
            return;
        }
        abd.setInstanceSupplier(supplier);
        ScopeMetadata scopeMetadata = this.scopeMetadataResolver.resolveScopeMetadata(abd);
        abd.setScope(scopeMetadata.getScopeName());
        String beanName = (name != null ? name : this.beanNameGenerator.generateBeanName(abd,this.registry));
        // 处理通用定义注解
        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));
                }
            }
        }
        if (customizers != null) {
            for (BeanDefinitionCustomizer customizer : customizers) {
                customizer.customize(abd);
            }
        }
        BeanDefinitionHolder definitionHolder = new BeanDefinitionHolder(abd,beanName);
        definitionHolder = AnnotationConfigUtils.applyScopedProxyMode(scopeMetadata,definitionHolder,this.registry);
        BeanDefinitionReaderUtils.registerBeanDefinition(definitionHolder,this.registry);
    }

    public AnnotationConfigApplicationContext(Class<?>... componentClasses) {
        // 进入构造函数,要先调用父类的构造方法
        this();
        // register配置注册类
        register(componentClasses);
        // ioc容器shua新接口--非常重要
        refresh();
    }

    @Override
    public void refresh() throws BeansException,IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // 1. 准备刷新上下文环境
            prepareRefresh();
            // Tell the subclass to refresh the internal bean factory.
            //2. 获取告诉子类初始化bean工厂,不同工厂不同实现
            ConfigurableListablebeanfactory beanfactory = obtainFreshbeanfactory();
            // Prepare the bean factory for use in this context.
            //3. 对bean工厂进行填充属性
            preparebeanfactory(beanfactory);
            try {
                // Allows post-processing of the bean factory in context subclasses.
                // 4. 留个子类去实现该接口
                postProcessbeanfactory(beanfactory);
                // Invoke factory processors registered as beans in the context.
                /*
                 * 调用bean工厂的后置处理器
                 * 1. 会再次class扫描成BeanDefinition
                 */
                invokebeanfactoryPostProcessors(beanfactory);
                // Register bean processors that intercept bean creation.
                // 注册bean后置处理器
                registerBeanPostProcessors(beanfactory);
                // Initialize message source for this context.
                // 初始化国际化资源处理器
                initMessageSource();
                // Initialize event multicaster for this context.
                // 创建事件多播放器
                initApplicationEventMulticaster();
                // Initialize other special beans in specific context subclasses.
                // 这个方法通用也是留个子类实现的,spring boot也是从这个方法进行启动
                onRefresh();
                // Check for listener beans and register them.
                // 将事件监听器注册到多播放器上
                registerListeners();
                // Instantiate all remaining (non-lazy-init) singletons.
                // 实例化剩余的单实例bean
                /**
                 * 这个方法就是循环遍历BeanDefinitionMap,调用getBean,去生产bean
                 */
                finishbeanfactoryInitialization(beanfactory);
                // Last step: publish corresponding event.
                //最后容器刷新 发布刷新时间(spring cloud是从这里启动的 )
                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();
            }
        }
    }

    @Override
    public void freezeConfiguration() {
        this.configurationFrozen = true;
        this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
    }

Override
    protected Object createBean(String beanName,RootBeanDefinition mbd,@Nullable Object[] args)
            throws BeanCreationException {
        if (logger.isTraceEnabled()) {
            logger.trace("Creating instance of bean '" + beanName + "'");
        }
        RootBeanDefinition mbdToUse = mbd;
        // Make sure bean class is actually resolved at this point,and
        // clone the bean definition in case of a dynamically resolved Class
        // which cannot be stored in the shared merged bean definition.
        // 确保此时的bean已经被解析了
        Class<?> resolvedClass = resolveBeanClass(mbd,beanName);
        if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
            mbdToUse = new RootBeanDefinition(mbd);
            mbdToUse.setBeanClass(resolvedClass);
        }
        // Prepare method overrides.
        try {
            /**
             * 验证和准备覆盖方法(近在xml方式中)
             * lookup-method 和 replace-method
             * 这两个配置存放在BeanDefinition中的methodOverrides(仅在XML方式中)
             * 在XML方式中,bean实例化的过程中如果检测到存在methodOverrides
             * 则会动态的为当前bean生成代理并使用对应的拦截器为bean做增强处理
             * 具体的实现我们后续分析. 现在先看mbdtoUse.prepareMethodOverrides()代码块
             */
            mbdToUse.prepareMethodOverrides();
        }
        catch (BeanDefinitionValidationException ex) {
            throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),beanName,"Validation of method overrides Failed",ex);
        }
        try {
            // Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
            /**
             * 初始化之前的解析
             * 第一次调用bean后置处理器
             * 铜鼓bean的后置处理器来进行后置处理生成代理对象,一般情况下在此处不会生成代理对象
             * 为什么不能生成代理对象? 不管是我们的JDK还是cglib代理都不会在此处进行代理,因为我们的真实对象没有生成,* 所以在这里不会生成代理对象
             * 这一步是aop和事务的关键,因为在这解析我们的aop切面信息进行缓存.
             */
            Object bean = resolveBeforeInstantiation(beanName,mbdToUse);
            if (bean != null) {
                return bean;
            }
        }
        catch (Throwable ex) {
            throw new BeanCreationException(mbdToUse.getResourceDescription(),"BeanPostProcessor before instantiation of bean Failed",ex);
        }
        try {
            /*
             * 执行创建bean,这里就是执行创建bean的三个步骤
             * 1. 实例化
             * 2. 填充属性,@Autowired @Value
             * 3. 初始化  初始化initMethod方法和初始化destroy方法
             */
            Object beanInstance = doCreateBean(beanName,mbdToUse,args);
            if (logger.isTraceEnabled()) {
                logger.trace("Finished creating instance of bean '" + beanName + "'");
            }
            return beanInstance;
        }
        catch (BeanCreationException | ImplicitlyAppearedSingletonException ex) {
            // A prevIoUsly detected exception with proper bean creation context already,// or illegal singleton state to be communicated up to DefaultSingletonBeanRegistry.
            throw ex;
        }
        catch (Throwable ex) {
            throw new BeanCreationException(
                    mbdToUse.getResourceDescription(),"Unexpected exception during bean creation",ex);
        }
    }

protected Object doCreateBean(final String beanName,final RootBeanDefinition mbd,final @Nullable Object[] args)
            throws BeanCreationException {
        // Instantiate the bean.
        BeanWrapper instanceWrapper = null;
        if (mbd.isSingleton()) {
            instanceWrapper = this.factorybeanInstanceCache.remove(beanName);
        }
        if (instanceWrapper == null) {
            /**
             * 第一步: 实例化
             * 这里面的调用链非常深,后面再看
             * bean实例化有两种方式
             * 1. 使用反射:  使用反射也有两种方式,*         a. 通过无参构造函数 (默认的方式)
             *             从beanDefinition中可以得到beanClass,*             ClassName = BeanDefinition.beanclass
             *             Class clazz = Class.forName(ClassName);
             *             clazz.newInstance();
             *             这样就可以实例化bean了
             *
             *         b. 通过有参函数.
             *            ClassName = BeanDefinition.beanclass
             *             Class clazz = Class.forName(ClassName);
             *             Constractor con = class.getConstractor(args....)
             *             con.newInstance();
             *
             * 2. 使用工厂
             *         我们使用@Bean的方式,就是使用的工厂模式,自己控制实例化过程
             *
             */
            instanceWrapper = createBeanInstance(beanName,mbd,args);
        }
        // 这里使用了装饰器的设计模式
        final Object bean = instanceWrapper.getWrappedInstance();
        Class<?> beanType = instanceWrapper.getWrappedClass();
        if (beanType != NullBean.class) {
            mbd.resolvedTargetType = beanType;
        }
        // Allow post-processors to modify the merged bean definition.
        // 允许后置处理器修改已经合并的beanDefinition
        synchronized (mbd.postProcessingLock) {
            if (!mbd.postProcessed) {
                try {
                    applyMergedBeanDefinitionPostProcessors(mbd,beanType,beanName);
                }
                catch (Throwable ex) {
                    throw new BeanCreationException(mbd.getResourceDescription(),"Post-processing of merged bean definition Failed",ex);
                }
                mbd.postProcessed = true;
            }
        }
        // Eagerly cache singletons to be able to resolve circular references
        // even when triggered by lifecycle interfaces like beanfactoryAware.
        boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
                isSingletonCurrentlyInCreation(beanName));
        if (earlySingletonExposure) {
            if (logger.isTraceEnabled()) {
                logger.trace("Eagerly caching bean '" + beanName +
                        "' to allow for resolving potential circular references");
            }
            addSingletonFactory(beanName,() -> getEarlyBeanReference(beanName,bean));
        }
        // Initialize the bean instance.
        Object exposedObject = bean;
        try {
            // 第二步:填充属性,给属性赋值(调用set方法)  这里也是调用的后置处理器
            populateBean(beanName,instanceWrapper);
            // 第三步: 初始化.
            exposedObject = initializeBean(beanName,exposedObject,mbd);
        }
        catch (Throwable ex) {
            if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
                throw (BeanCreationException) ex;
            }
            else {
                throw new BeanCreationException(
                        mbd.getResourceDescription(),"Initialization of bean Failed",ex);
            }
        }
        if (earlySingletonExposure) {
            Object earlySingletonReference = getSingleton(beanName,false);
            if (earlySingletonReference != null) {
                if (exposedObject == bean) {
                    exposedObject = earlySingletonReference;
                }
                else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
                    String[] dependentBeans = getDependentBeans(beanName);
                    Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
                    for (String dependentBean : dependentBeans) {
                        if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
                            actualDependentBeans.add(dependentBean);
                        }
                    }
                    if (!actualDependentBeans.isEmpty()) {
                        throw new BeanCurrentlyInCreationException(beanName,"Bean with name '" + beanName + "' has been injected into other beans [" +
                                StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
                                "] in its raw version as part of a circular reference,but has eventually been " +
                                "wrapped. This means that said other beans do not use the final version of the " +
                                "bean. This is often the result of over-eager type matching - consider using " +
                                "'getBeanNamesForType' with the 'allowEagerInit' flag turned off,for example.");
                    }
                }
            }
        }
        // Register bean as disposable.
        try {
            registerDisposableBeanIfNecessary(beanName,bean,mbd);
        }
        catch (BeanDefinitionValidationException ex) {
            throw new BeanCreationException(
                    mbd.getResourceDescription(),"Invalid destruction signature",ex);
        }
        return exposedObject;
    }