前言

在Spring IOC机制里面，BeanFactory是其中最最核心的一个组件。之所以说它是一个组件，而不是一个类，是因为它具有相对较复杂的继承关系，同时将工厂设计模式的精髓发挥得玲离尽致。我们平时使用Spring IOC的时候，绝大多数情况是使用ApplicationContext及其子类，而非BeanFactory。而ApplicationContext的实现类，内部仍然是通过引用BeanFactory实例的方式来增强其bean管理的特性。

因此，在本文中，我们将从BeanFactory的继承关系出发，详细分析BeanFactory作为bean管理容器可能存在的功能。

继承关系图

首先，我们来看看继承关系，如下图所示。

BeanFactory继承关系

红框内的类，正是BeanFactory涉及到的继承的基础。每一个接口都定义了一部分功能，而每一个类都基于接口实现了一部分功能逻辑。而最核心的类在于DefaultListableBeanFactory，它是BeanFactory的最终实现类。

BeanFactory

public interface BeanFactory {

    /**
     * 工厂Bean在BeanFactory中的bean名称前缀，用于区别于由其创建的Bean。
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>This method allows a Spring BeanFactory to be used as a replacement for the
     * Singleton or Prototype design pattern. Callers may retain references to
     * returned objects in the case of Singleton beans.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no bean with the specified name
     * @throws BeansException if the bean could not be obtained
     */
    String FACTORY_BEAN_PREFIX = "&";


    /**
     * 根据bean名称，获取bean实例。
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
     * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
     * required type. This means that ClassCastException can't be thrown on casting
     * the result correctly, as can happen with {@link #getBean(String)}.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanNotOfRequiredTypeException if the bean is not of the required type
     * @throws BeansException if the bean could not be created
     */
    Object getBean(String name) throws BeansException;

    /**
     * 根据bean名称，获取特定类型的bean实例，当类型不匹配时抛出异常。
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * @param name the name of the bean to retrieve
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 2.5
     */
    <T> T getBean(String name, Class<T> requiredType) throws BeansException;

    /**
     * 根据bean名称，获取bean实例，并且创建bean的时候需要根据args参数进行创建。
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * @param name the name of the bean to retrieve
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 2.5
     */
    Object getBean(String name, Object... args) throws BeansException;

    /**
     * 根据bean的类型，获取bean实例。
     * 当未获取到bean实例，或者获取到的bean实例数超过1个，则抛出异常。
     * Return the bean instance that uniquely matches the given object type, if any.
     * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
     * but may also be translated into a conventional by-name lookup based on the name
     * of the given type. For more extensive retrieval operations across sets of beans,
     * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return an instance of the single bean matching the required type
     * @throws NoSuchBeanDefinitionException if no bean of the given type was found
     * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
     * @throws BeansException if the bean could not be created
     * @since 3.0
     * @see ListableBeanFactory
     */
    <T> T getBean(Class<T> requiredType) throws BeansException;

    /**
     * 根据bean的类型，获取bean实例，并且创建bean的时候需要根据args参数进行创建。
     * 当未获取到bean实例，或者获取到的bean实例数超过1个，则抛出异常。
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
     * but may also be translated into a conventional by-name lookup based on the name
     * of the given type. For more extensive retrieval operations across sets of beans,
     * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 4.1
     */
    <T> T getBean(Class<T> requiredType, Object... args) throws BeansException;

    /**
     * 获取bean提供者对象，用于延迟创建。
     * Return a provider for the specified bean, allowing for lazy on-demand retrieval
     * of instances, including availability and uniqueness options.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return a corresponding provider handle
     * @since 5.1
     * @see #getBeanProvider(ResolvableType)
     */
    <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType);

    /**
     * 根据特定类型获取bean提供者对象，用于延迟创建
     * Return a provider for the specified bean, allowing for lazy on-demand retrieval
     * of instances, including availability and uniqueness options.
     * @param requiredType type the bean must match; can be a generic type declaration.
     * Note that collection types are not supported here, in contrast to reflective
     * injection points. For programmatically retrieving a list of beans matching a
     * specific type, specify the actual bean type as an argument here and subsequently
     * use {@link ObjectProvider#orderedStream()} or its lazy streaming/iteration options.
     * @return a corresponding provider handle
     * @since 5.1
     * @see ObjectProvider#iterator()
     * @see ObjectProvider#stream()
     * @see ObjectProvider#orderedStream()
     */
    <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType);

    /**
     * 是否包含特定名称的bean实例
     * Does this bean factory contain a bean definition or externally registered singleton
     * instance with the given name?
     * <p>If the given name is an alias, it will be translated back to the corresponding
     * canonical bean name.
     * <p>If this factory is hierarchical, will ask any parent factory if the bean cannot
     * be found in this factory instance.
     * <p>If a bean definition or singleton instance matching the given name is found,
     * this method will return {@code true} whether the named bean definition is concrete
     * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}
     * return value from this method does not necessarily indicate that {@link #getBean}
     * will be able to obtain an instance for the same name.
     * @param name the name of the bean to query
     * @return whether a bean with the given name is present
     */
    boolean containsBean(String name);

    /**
     * 特定名称的bean类型是否为单例
     * Is this bean a shared singleton? That is, will {@link #getBean} always
     * return the same instance?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * independent instances. It indicates non-singleton instances, which may correspond
     * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly
     * check for independent instances.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean corresponds to a singleton instance
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @see #getBean
     * @see #isPrototype
     */
    boolean isSingleton(String name) throws NoSuchBeanDefinitionException;

    /**
     * 特定名称的bean类型是否为原型类型
     * Is this bean a prototype? That is, will {@link #getBean} always return
     * independent instances?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * a singleton object. It indicates non-independent instances, which may correspond
     * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly
     * check for a shared singleton instance.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean will always deliver independent instances
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.3
     * @see #getBean
     * @see #isSingleton
     */
    boolean isPrototype(String name) throws NoSuchBeanDefinitionException;

    /**
     * 特定名称的bean的类型，是否和传入的类型匹配，这儿的类型指的是Spring通用类型
     * Check whether the bean with the given name matches the specified type.
     * More specifically, check whether a {@link #getBean} call for the given name
     * would return an object that is assignable to the specified target type.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param typeToMatch the type to match against (as a {@code ResolvableType})
     * @return {@code true} if the bean type matches,
     * {@code false} if it doesn't match or cannot be determined yet
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 4.2
     * @see #getBean
     * @see #getType
     */
    boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;

    /**
     * 特定名称的bean的类型，是否和传入的类型匹配，这儿的类型指的是Class
     * Check whether the bean with the given name matches the specified type.
     * More specifically, check whether a {@link #getBean} call for the given name
     * would return an object that is assignable to the specified target type.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param typeToMatch the type to match against (as a {@code Class})
     * @return {@code true} if the bean type matches,
     * {@code false} if it doesn't match or cannot be determined yet
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.1
     * @see #getBean
     * @see #getType
     */
    boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;

    /**
     * 根据bean的名称，获取bean的类型（Class）
     * Determine the type of the bean with the given name. More specifically,
     * determine the type of object that {@link #getBean} would return for the given name.
     * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
     * as exposed by {@link FactoryBean#getObjectType()}. This may lead to the initialization
     * of a previously uninitialized {@code FactoryBean} (see {@link #getType(String, boolean)}).
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return the type of the bean, or {@code null} if not determinable
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 1.1.2
     * @see #getBean
     * @see #isTypeMatch
     */
    @Nullable
    Class<?> getType(String name) throws NoSuchBeanDefinitionException;

    /**
     * 根据bean的名称，获取bean的类型（Class），同时根据参数判断是否允许进行FactoryBean的初始化
     * Determine the type of the bean with the given name. More specifically,
     * determine the type of object that {@link #getBean} would return for the given name.
     * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
     * as exposed by {@link FactoryBean#getObjectType()}. Depending on the
     * {@code allowFactoryBeanInit} flag, this may lead to the initialization of a previously
     * uninitialized {@code FactoryBean} if no early type information is available.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param allowFactoryBeanInit whether a {@code FactoryBean} may get initialized
     * just for the purpose of determining its object type
     * @return the type of the bean, or {@code null} if not determinable
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 5.2
     * @see #getBean
     * @see #isTypeMatch
     */
    @Nullable
    Class<?> getType(String name, boolean allowFactoryBeanInit) throws NoSuchBeanDefinitionException;

    /**
     * 获取指定名称bean的所有别名数组
     * Return the aliases for the given bean name, if any.
     * All of those aliases point to the same bean when used in a {@link #getBean} call.
     * <p>If the given name is an alias, the corresponding original bean name
     * and other aliases (if any) will be returned, with the original bean name
     * being the first element in the array.
     * <p>Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the bean name to check for aliases
     * @return the aliases, or an empty array if none
     * @see #getBean
     */
    String[] getAliases(String name);
}

HierarchicalBeanFactory

public interface HierarchicalBeanFactory extends BeanFactory {

    /**
     * 获取父类beanFactory
     * Return the parent bean factory, or {@code null} if there is none.
     */
    @Nullable
    BeanFactory getParentBeanFactory();

    /**
     * 判断指定名称的bean是否包含在当前的beanFactory中
     * 【注意】：如果包含在继承的beanFactory中，那么返回false
     * Return whether the local bean factory contains a bean of the given name,
     * ignoring beans defined in ancestor contexts.
     * <p>This is an alternative to {@code containsBean}, ignoring a bean
     * of the given name from an ancestor bean factory.
     * @param name the name of the bean to query
     * @return whether a bean with the given name is defined in the local factory
     * @see BeanFactory#containsBean
     */
    boolean containsLocalBean(String name);
}

ConfigurableBeanFactory

public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, SingletonBeanRegistry {

    /**
     * 单例bean范围的标识符
     */
    String SCOPE_SINGLETON = "singleton";

    /**
     * 原型bean范围的标识符
     */
    String SCOPE_PROTOTYPE = "prototype";

    /**
     * 设置父类工厂
     */
    void setParentBeanFactory(BeanFactory parentBeanFactory) throws IllegalStateException;

    /**
     * 设置bean的类加载器
     */
    void setBeanClassLoader(@Nullable ClassLoader beanClassLoader);

    /**
     * 获取bean的类加载器
     */
    @Nullable
    ClassLoader getBeanClassLoader();

    /**
     * 设置临时的类加载器，临时的类加载器，主要在`load-time weaving`场景使用，以确保bean的加载尽可能地延迟。
     * 当所有bean加载完成之后，该类加载器将从Beanfactory自动移除。
     */
    void setTempClassLoader(@Nullable ClassLoader tempClassLoader);

    /**
     * 获取临时的类加载器
     * @since 2.5
     */
    @Nullable
    ClassLoader getTempClassLoader();

    /**
     * 设置是否缓存bean元数据，例如BeanDefination。
     */
    void setCacheBeanMetadata(boolean cacheBeanMetadata);

    /**
     * 获取是否缓存bean元数据
     */
    boolean isCacheBeanMetadata();

    /**
     * 设置bean表达式处理器，例如`#{...}`的操作。
     * Specify the resolution strategy for expressions in bean definition values.
     * <p>There is no expression support active in a BeanFactory by default.
     * An ApplicationContext will typically set a standard expression strategy
     * here, supporting "#{...}" expressions in a Unified EL compatible style.
     * @since 3.0
     */
    void setBeanExpressionResolver(@Nullable BeanExpressionResolver resolver);

    /**
     * 获取bean表达式处理器
     * Return the resolution strategy for expressions in bean definition values.
     * @since 3.0
     */
    @Nullable
    BeanExpressionResolver getBeanExpressionResolver();

    /**
     * 设置转换服务
     * @since 3.0
     */
    void setConversionService(@Nullable ConversionService conversionService);

    /**
     * 获取转换服务
     * @since 3.0
     */
    @Nullable
    ConversionService getConversionService();

    /**
     * 添加一个属性编辑器注册器，用于所有bean的创建过程。
     * 每个bean在创建的时候都会创建一个独立的属性编辑器实例，因此它是线程安全的
     * Add a PropertyEditorRegistrar to be applied to all bean creation processes.
     * <p>Such a registrar creates new PropertyEditor instances and registers them
     * on the given registry, fresh for each bean creation attempt. This avoids
     * the need for synchronization on custom editors; hence, it is generally
     * preferable to use this method instead of {@link #registerCustomEditor}.
     * @param registrar the PropertyEditorRegistrar to register
     */
    void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar);

    /**
     * 注册一个自定义属性编辑器
     * 所有的bean都公用这个属性编辑器，因此它会在锁环境下使用，目的是确保线程安全。
     * Register the given custom property editor for all properties of the
     * given type. To be invoked during factory configuration.
     * <p>Note that this method will register a shared custom editor instance;
     * access to that instance will be synchronized for thread-safety. It is
     * generally preferable to use {@link #addPropertyEditorRegistrar} instead
     * of this method, to avoid for the need for synchronization on custom editors.
     * @param requiredType type of the property
     * @param propertyEditorClass the {@link PropertyEditor} class to register
     */
    void registerCustomEditor(Class<?> requiredType, Class<? extends PropertyEditor> propertyEditorClass);

    /**
     * 拷贝属性编辑器注册器
     * Initialize the given PropertyEditorRegistry with the custom editors
     * that have been registered with this BeanFactory.
     * @param registry the PropertyEditorRegistry to initialize
     */
    void copyRegisteredEditorsTo(PropertyEditorRegistry registry);

    /**
     * 设置自定义的类型转换器
     * Set a custom type converter that this BeanFactory should use for converting
     * bean property values, constructor argument values, etc.
     * <p>This will override the default PropertyEditor mechanism and hence make
     * any custom editors or custom editor registrars irrelevant.
     * @since 2.5
     * @see #addPropertyEditorRegistrar
     * @see #registerCustomEditor
     */
    void setTypeConverter(TypeConverter typeConverter);

    /**
     * 获取自定义类型转换器
     * Obtain a type converter as used by this BeanFactory. This may be a fresh
     * instance for each call, since TypeConverters are usually <i>not</i> thread-safe.
     * <p>If the default PropertyEditor mechanism is active, the returned
     * TypeConverter will be aware of all custom editors that have been registered.
     * @since 2.5
     */
    TypeConverter getTypeConverter();

    /**
     * 获取内嵌的值处理器
     * Add a String resolver for embedded values such as annotation attributes.
     * @param valueResolver the String resolver to apply to embedded values
     * @since 3.0
     */
    void addEmbeddedValueResolver(StringValueResolver valueResolver);

    /**
     * 判断是否有内嵌的值处理器
     * Determine whether an embedded value resolver has been registered with this
     * bean factory, to be applied through {@link #resolveEmbeddedValue(String)}.
     * @since 4.3
     */
    boolean hasEmbeddedValueResolver();

    /**
     * 使用内嵌的值处理器对值进行处理。
     * Resolve the given embedded value, e.g. an annotation attribute.
     * @param value the value to resolve
     * @return the resolved value (may be the original value as-is)
     * @since 3.0
     */
    @Nullable
    String resolveEmbeddedValue(String value);

    /**
     * 添加一个BeanPostProcessor实例
     * Add a new BeanPostProcessor that will get applied to beans created
     * by this factory. To be invoked during factory configuration.
     * <p>Note: Post-processors submitted here will be applied in the order of
     * registration; any ordering semantics expressed through implementing the
     * {@link org.springframework.core.Ordered} interface will be ignored. Note
     * that autodetected post-processors (e.g. as beans in an ApplicationContext)
     * will always be applied after programmatically registered ones.
     * @param beanPostProcessor the post-processor to register
     */
    void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);

    /**
     * 获取BeanPostProcessor实例数
     * Return the current number of registered BeanPostProcessors, if any.
     */
    int getBeanPostProcessorCount();

    /**
     * 注册特定类型的scope，比如Request或者Session
     * Register the given scope, backed by the given Scope implementation.
     * @param scopeName the scope identifier
     * @param scope the backing Scope implementation
     */
    void registerScope(String scopeName, Scope scope);

    /**
     * 获取已注册scope名称数组
     * Return the names of all currently registered scopes.
     * <p>This will only return the names of explicitly registered scopes.
     * Built-in scopes such as "singleton" and "prototype" won't be exposed.
     * @return the array of scope names, or an empty array if none
     * @see #registerScope
     */
    String[] getRegisteredScopeNames();

    /**
     * 获取特定名称的scope
     * Return the Scope implementation for the given scope name, if any.
     * <p>This will only return explicitly registered scopes.
     * Built-in scopes such as "singleton" and "prototype" won't be exposed.
     * @param scopeName the name of the scope
     * @return the registered Scope implementation, or {@code null} if none
     * @see #registerScope
     */
    @Nullable
    Scope getRegisteredScope(String scopeName);

    /**
     * 获取访问控制上下文
     * Provides a security access control context relevant to this factory.
     * @return the applicable AccessControlContext (never {@code null})
     * @since 3.0
     */
    AccessControlContext getAccessControlContext();

    /**
     * 从特定的可配置BeanFactory实例中拷贝配置。注意，这儿说的是“配置”
     * 包括：BeanPostProcessors, Scopes, and factory-specific internal settings.
     * 不包括： any metadata of actual bean definitions,
     * 
     * Copy all relevant configuration from the given other factory.
     * <p>Should include all standard configuration settings as well as
     * BeanPostProcessors, Scopes, and factory-specific internal settings.
     * Should not include any metadata of actual bean definitions,
     * such as BeanDefinition objects and bean name aliases.
     * @param otherFactory the other BeanFactory to copy from
     */
    void copyConfigurationFrom(ConfigurableBeanFactory otherFactory);

    /**
     * 给bean注册别名
     * Given a bean name, create an alias. We typically use this method to
     * support names that are illegal within XML ids (used for bean names).
     * <p>Typically invoked during factory configuration, but can also be
     * used for runtime registration of aliases. Therefore, a factory
     * implementation should synchronize alias access.
     * @param beanName the canonical name of the target bean
     * @param alias the alias to be registered for the bean
     * @throws BeanDefinitionStoreException if the alias is already in use
     */
    void registerAlias(String beanName, String alias) throws BeanDefinitionStoreException;

    /**
     * 使用特定的值处理器，处理所有别名
     * Resolve all alias target names and aliases registered in this
     * factory, applying the given StringValueResolver to them.
     * <p>The value resolver may for example resolve placeholders
     * in target bean names and even in alias names.
     * @param valueResolver the StringValueResolver to apply
     * @since 2.5
     */
    void resolveAliases(StringValueResolver valueResolver);

    /**
     * 获取一个合并的BeanDefinition，子类的话，可以将父类的属性也合并过来
     * Return a merged BeanDefinition for the given bean name,
     * merging a child bean definition with its parent if necessary.
     * Considers bean definitions in ancestor factories as well.
     * @param beanName the name of the bean to retrieve the merged definition for
     * @return a (potentially merged) BeanDefinition for the given bean
     * @throws NoSuchBeanDefinitionException if there is no bean definition with the given name
     * @since 2.5
     */
    BeanDefinition getMergedBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    /**
     * 是否工厂bean
     * Determine whether the bean with the given name is a FactoryBean.
     * @param name the name of the bean to check
     * @return whether the bean is a FactoryBean
     * ({@code false} means the bean exists but is not a FactoryBean)
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.5
     */
    boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException;

    /**
     * 设置特定名称的bean是否在创建过程中
     * Explicitly control the current in-creation status of the specified bean.
     * For container-internal use only.
     * @param beanName the name of the bean
     * @param inCreation whether the bean is currently in creation
     * @since 3.1
     */
    void setCurrentlyInCreation(String beanName, boolean inCreation);

    /**
     * 判断特定名称的bean是否在创建过程中
     * Determine whether the specified bean is currently in creation.
     * @param beanName the name of the bean
     * @return whether the bean is currently in creation
     * @since 2.5
     */
    boolean isCurrentlyInCreation(String beanName);

    /**
     * 注册bean之间的依赖关系
     * Register a dependent bean for the given bean,
     * to be destroyed before the given bean is destroyed.
     * @param beanName the name of the bean
     * @param dependentBeanName the name of the dependent bean
     * @since 2.5
     */
    void registerDependentBean(String beanName, String dependentBeanName);

    /**
     * 获取所有依赖特定名称bean的bean名称
     * Return the names of all beans which depend on the specified bean, if any.
     * @param beanName the name of the bean
     * @return the array of dependent bean names, or an empty array if none
     * @since 2.5
     */
    String[] getDependentBeans(String beanName);

    /**
     * 获取特定名称bean的所有依赖bean
     * Return the names of all beans that the specified bean depends on, if any.
     * @param beanName the name of the bean
     * @return the array of names of beans which the bean depends on,
     * or an empty array if none
     * @since 2.5
     */
    String[] getDependenciesForBean(String beanName);

    /**
     * 销毁bean
     * Destroy the given bean instance (usually a prototype instance
     * obtained from this factory) according to its bean definition.
     * <p>Any exception that arises during destruction should be caught
     * and logged instead of propagated to the caller of this method.
     * @param beanName the name of the bean definition
     * @param beanInstance the bean instance to destroy
     */
    void destroyBean(String beanName, Object beanInstance);

    /**
     * 在特定scope下，销毁指定名称的bean对象
     * Destroy the specified scoped bean in the current target scope, if any.
     * <p>Any exception that arises during destruction should be caught
     * and logged instead of propagated to the caller of this method.
     * @param beanName the name of the scoped bean
     */
    void destroyScopedBean(String beanName);

    /**
     * 销毁单例
     * Destroy all singleton beans in this factory, including inner beans that have
     * been registered as disposable. To be called on shutdown of a factory.
     * <p>Any exception that arises during destruction should be caught
     * and logged instead of propagated to the caller of this method.
     */
    void destroySingletons();
}

AutowireCapableBeanFactory

public interface AutowireCapableBeanFactory extends BeanFactory {

    /**
     * 没有外部依赖的注入方式
     * Constant that indicates no externally defined autowiring. Note that
     * BeanFactoryAware etc and annotation-driven injection will still be applied.
     * @see #createBean
     * @see #autowire
     * @see #autowireBeanProperties
     */
    int AUTOWIRE_NO = 0;

    /**
     * 按照名称注入
     * Constant that indicates autowiring bean properties by name
     * (applying to all bean property setters).
     * @see #createBean
     * @see #autowire
     * @see #autowireBeanProperties
     */
    int AUTOWIRE_BY_NAME = 1;

    /**
     * 按照类型注入
     * Constant that indicates autowiring bean properties by type
     * (applying to all bean property setters).
     * @see #createBean
     * @see #autowire
     * @see #autowireBeanProperties
     */
    int AUTOWIRE_BY_TYPE = 2;

    /**
     * 以构造器的方式注入
     * Constant that indicates autowiring the greediest constructor that
     * can be satisfied (involves resolving the appropriate constructor).
     * @see #createBean
     * @see #autowire
     */
    int AUTOWIRE_CONSTRUCTOR = 3;

    /**
     * 自动检测的方式注入，目前已废弃。
     * Constant that indicates determining an appropriate autowire strategy
     * through introspection of the bean class.
     * @see #createBean
     * @see #autowire
     * @deprecated as of Spring 3.0: If you are using mixed autowiring strategies,
     * prefer annotation-based autowiring for clearer demarcation of autowiring needs.
     */
    @Deprecated
    int AUTOWIRE_AUTODETECT = 4;

    /**
     * Suffix for the "original instance" convention when initializing an existing
     * bean instance: to be appended to the fully-qualified bean class name,
     * e.g. "com.mypackage.MyClass.ORIGINAL", in order to enforce the given instance
     * to be returned, i.e. no proxies etc.
     * @since 5.1
     * @see #initializeBean(Object, String)
     * @see #applyBeanPostProcessorsBeforeInitialization(Object, String)
     * @see #applyBeanPostProcessorsAfterInitialization(Object, String)
     */
    String ORIGINAL_INSTANCE_SUFFIX = ".ORIGINAL";


    //-------------------------------------------------------------------------
    // Typical methods for creating and populating external bean instances
    //-------------------------------------------------------------------------

    /**
     * 创建特定类型的bean实例，将会执行完整的bean初始化，包括BeanPostProcessors操作。
     * Fully create a new bean instance of the given class.
     * <p>Performs full initialization of the bean, including all applicable
     * {@link BeanPostProcessor BeanPostProcessors}.
     * <p>Note: This is intended for creating a fresh instance, populating annotated
     * fields and methods as well as applying all standard bean initialization callbacks.
     * It does <i>not</i> imply traditional by-name or by-type autowiring of properties;
     * use {@link #createBean(Class, int, boolean)} for those purposes.
     * @param beanClass the class of the bean to create
     * @return the new bean instance
     * @throws BeansException if instantiation or wiring failed
     */
    <T> T createBean(Class<T> beanClass) throws BeansException;

    /**
     * 注入bean
     * Populate the given bean instance through applying after-instantiation callbacks
     * and bean property post-processing (e.g. for annotation-driven injection).
     * <p>Note: This is essentially intended for (re-)populating annotated fields and
     * methods, either for new instances or for deserialized instances. It does
     * <i>not</i> imply traditional by-name or by-type autowiring of properties;
     * use {@link #autowireBeanProperties} for those purposes.
     * @param existingBean the existing bean instance
     * @throws BeansException if wiring failed
     */
    void autowireBean(Object existingBean) throws BeansException;

    /**
     * 配置bean，包括注入属性，解决bean属性值，应用bean工厂回调，应用beanPostProcessor
     * Configure the given raw bean: autowiring bean properties, applying
     * bean property values, applying factory callbacks such as {@code setBeanName}
     * and {@code setBeanFactory}, and also applying all bean post processors
     * (including ones which might wrap the given raw bean).
     * <p>This is effectively a superset of what {@link #initializeBean} provides,
     * fully applying the configuration specified by the corresponding bean definition.
     * <b>Note: This method requires a bean definition for the given name!</b>
     * @param existingBean the existing bean instance
     * @param beanName the name of the bean, to be passed to it if necessary
     * (a bean definition of that name has to be available)
     * @return the bean instance to use, either the original or a wrapped one
     * @throws org.springframework.beans.factory.NoSuchBeanDefinitionException
     * if there is no bean definition with the given name
     * @throws BeansException if the initialization failed
     * @see #initializeBean
     */
    Object configureBean(Object existingBean, String beanName) throws BeansException;


    //-------------------------------------------------------------------------
    // Specialized methods for fine-grained control over the bean lifecycle
    //-------------------------------------------------------------------------

    /**
     * 创建bean
     * Fully create a new bean instance of the given class with the specified
     * autowire strategy. All constants defined in this interface are supported here.
     * <p>Performs full initialization of the bean, including all applicable
     * {@link BeanPostProcessor BeanPostProcessors}. This is effectively a superset
     * of what {@link #autowire} provides, adding {@link #initializeBean} behavior.
     * @param beanClass the class of the bean to create
     * @param autowireMode by name or type, using the constants in this interface
     * @param dependencyCheck whether to perform a dependency check for objects
     * (not applicable to autowiring a constructor, thus ignored there)
     * @return the new bean instance
     * @throws BeansException if instantiation or wiring failed
     * @see #AUTOWIRE_NO
     * @see #AUTOWIRE_BY_NAME
     * @see #AUTOWIRE_BY_TYPE
     * @see #AUTOWIRE_CONSTRUCTOR
     */
    Object createBean(Class<?> beanClass, int autowireMode, boolean dependencyCheck) throws BeansException;

    /**
     * 使用特定的注入策略，实例化并注入一个bean
     * Instantiate a new bean instance of the given class with the specified autowire
     * strategy. All constants defined in this interface are supported here.
     * Can also be invoked with {@code AUTOWIRE_NO} in order to just apply
     * before-instantiation callbacks (e.g. for annotation-driven injection).
     * <p>Does <i>not</i> apply standard {@link BeanPostProcessor BeanPostProcessors}
     * callbacks or perform any further initialization of the bean. This interface
     * offers distinct, fine-grained operations for those purposes, for example
     * {@link #initializeBean}. However, {@link InstantiationAwareBeanPostProcessor}
     * callbacks are applied, if applicable to the construction of the instance.
     * @param beanClass the class of the bean to instantiate
     * @param autowireMode by name or type, using the constants in this interface
     * @param dependencyCheck whether to perform a dependency check for object
     * references in the bean instance (not applicable to autowiring a constructor,
     * thus ignored there)
     * @return the new bean instance
     * @throws BeansException if instantiation or wiring failed
     * @see #AUTOWIRE_NO
     * @see #AUTOWIRE_BY_NAME
     * @see #AUTOWIRE_BY_TYPE
     * @see #AUTOWIRE_CONSTRUCTOR
     * @see #AUTOWIRE_AUTODETECT
     * @see #initializeBean
     * @see #applyBeanPostProcessorsBeforeInitialization
     * @see #applyBeanPostProcessorsAfterInitialization
     */
    Object autowire(Class<?> beanClass, int autowireMode, boolean dependencyCheck) throws BeansException;

    /**
     * 使用特定的注入策略，注入指定bean的所有属性
     * Autowire the bean properties of the given bean instance by name or type.
     * Can also be invoked with {@code AUTOWIRE_NO} in order to just apply
     * after-instantiation callbacks (e.g. for annotation-driven injection).
     * <p>Does <i>not</i> apply standard {@link BeanPostProcessor BeanPostProcessors}
     * callbacks or perform any further initialization of the bean. This interface
     * offers distinct, fine-grained operations for those purposes, for example
     * {@link #initializeBean}. However, {@link InstantiationAwareBeanPostProcessor}
     * callbacks are applied, if applicable to the configuration of the instance.
     * @param existingBean the existing bean instance
     * @param autowireMode by name or type, using the constants in this interface
     * @param dependencyCheck whether to perform a dependency check for object
     * references in the bean instance
     * @throws BeansException if wiring failed
     * @see #AUTOWIRE_BY_NAME
     * @see #AUTOWIRE_BY_TYPE
     * @see #AUTOWIRE_NO
     */
    void autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck)
            throws BeansException;

    /**
     * 解决bean属性的值，该方法不会注入bean的属性，而只是应用已经存在的属性。
     * 我们可以使用`autowireBeanProperties`来注入属性
     * Apply the property values of the bean definition with the given name to
     * the given bean instance. The bean definition can either define a fully
     * self-contained bean, reusing its property values, or just property values
     * meant to be used for existing bean instances.
     * <p>This method does <i>not</i> autowire bean properties; it just applies
     * explicitly defined property values. Use the {@link #autowireBeanProperties}
     * method to autowire an existing bean instance.
     * <b>Note: This method requires a bean definition for the given name!</b>
     * <p>Does <i>not</i> apply standard {@link BeanPostProcessor BeanPostProcessors}
     * callbacks or perform any further initialization of the bean. This interface
     * offers distinct, fine-grained operations for those purposes, for example
     * {@link #initializeBean}. However, {@link InstantiationAwareBeanPostProcessor}
     * callbacks are applied, if applicable to the configuration of the instance.
     * @param existingBean the existing bean instance
     * @param beanName the name of the bean definition in the bean factory
     * (a bean definition of that name has to be available)
     * @throws org.springframework.beans.factory.NoSuchBeanDefinitionException
     * if there is no bean definition with the given name
     * @throws BeansException if applying the property values failed
     * @see #autowireBeanProperties
     */
    void applyBeanPropertyValues(Object existingBean, String beanName) throws BeansException;

    /**
     * 初始化bean
     * Initialize the given raw bean, applying factory callbacks
     * such as {@code setBeanName} and {@code setBeanFactory},
     * also applying all bean post processors (including ones which
     * might wrap the given raw bean).
     * <p>Note that no bean definition of the given name has to exist
     * in the bean factory. The passed-in bean name will simply be used
     * for callbacks but not checked against the registered bean definitions.
     * @param existingBean the existing bean instance
     * @param beanName the name of the bean, to be passed to it if necessary
     * (only passed to {@link BeanPostProcessor BeanPostProcessors};
     * can follow the {@link #ORIGINAL_INSTANCE_SUFFIX} convention in order to
     * enforce the given instance to be returned, i.e. no proxies etc)
     * @return the bean instance to use, either the original or a wrapped one
     * @throws BeansException if the initialization failed
     * @see #ORIGINAL_INSTANCE_SUFFIX
     */
    Object initializeBean(Object existingBean, String beanName) throws BeansException;

    /**
     * 应用`BeanPostProcessor`进行bean实例化后，初始化前的处理
     * Apply {@link BeanPostProcessor BeanPostProcessors} to the given existing bean
     * instance, invoking their {@code postProcessBeforeInitialization} methods.
     * The returned bean instance may be a wrapper around the original.
     * @param existingBean the existing bean instance
     * @param beanName the name of the bean, to be passed to it if necessary
     * (only passed to {@link BeanPostProcessor BeanPostProcessors};
     * can follow the {@link #ORIGINAL_INSTANCE_SUFFIX} convention in order to
     * enforce the given instance to be returned, i.e. no proxies etc)
     * @return the bean instance to use, either the original or a wrapped one
     * @throws BeansException if any post-processing failed
     * @see BeanPostProcessor#postProcessBeforeInitialization
     * @see #ORIGINAL_INSTANCE_SUFFIX
     */
    Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
            throws BeansException;

    /**
     * 应用`BeanPostProcessor`进行bean初始化后的处理
     * Apply {@link BeanPostProcessor BeanPostProcessors} to the given existing bean
     * instance, invoking their {@code postProcessAfterInitialization} methods.
     * The returned bean instance may be a wrapper around the original.
     * @param existingBean the existing bean instance
     * @param beanName the name of the bean, to be passed to it if necessary
     * (only passed to {@link BeanPostProcessor BeanPostProcessors};
     * can follow the {@link #ORIGINAL_INSTANCE_SUFFIX} convention in order to
     * enforce the given instance to be returned, i.e. no proxies etc)
     * @return the bean instance to use, either the original or a wrapped one
     * @throws BeansException if any post-processing failed
     * @see BeanPostProcessor#postProcessAfterInitialization
     * @see #ORIGINAL_INSTANCE_SUFFIX
     */
    Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
            throws BeansException;

    /**
     * 销毁一个已存在的bean
     * Destroy the given bean instance (typically coming from {@link #createBean}),
     * applying the {@link org.springframework.beans.factory.DisposableBean} contract as well as
     * registered {@link DestructionAwareBeanPostProcessor DestructionAwareBeanPostProcessors}.
     * <p>Any exception that arises during destruction should be caught
     * and logged instead of propagated to the caller of this method.
     * @param existingBean the bean instance to destroy
     */
    void destroyBean(Object existingBean);


    //-------------------------------------------------------------------------
    // Delegate methods for resolving injection points
    //-------------------------------------------------------------------------

    /**
     * 根据类型，获取bean名称持有者对象，bean不存在或超过一个，都将抛出异常。
     * Resolve the bean instance that uniquely matches the given object type, if any,
     * including its bean name.
     * <p>This is effectively a variant of {@link #getBean(Class)} which preserves the
     * bean name of the matching instance.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return the bean name plus bean instance
     * @throws NoSuchBeanDefinitionException if no matching bean was found
     * @throws NoUniqueBeanDefinitionException if more than one matching bean was found
     * @throws BeansException if the bean could not be created
     * @since 4.3.3
     * @see #getBean(Class)
     */
    <T> NamedBeanHolder<T> resolveNamedBean(Class<T> requiredType) throws BeansException;

    /**
     * 根据名称，获取bean名称持有者对象，bean不存在，将抛出异常。
     * Resolve a bean instance for the given bean name, providing a dependency descriptor
     * for exposure to target factory methods.
     * <p>This is effectively a variant of {@link #getBean(String, Class)} which supports
     * factory methods with an {@link org.springframework.beans.factory.InjectionPoint}
     * argument.
     * @param name the name of the bean to look up
     * @param descriptor the dependency descriptor for the requesting injection point
     * @return the corresponding bean instance
     * @throws NoSuchBeanDefinitionException if there is no bean with the specified name
     * @throws BeansException if the bean could not be created
     * @since 5.1.5
     * @see #getBean(String, Class)
     */
    Object resolveBeanByName(String name, DependencyDescriptor descriptor) throws BeansException;

    /**
     * Resolve the specified dependency against the beans defined in this factory.
     * @param descriptor the descriptor for the dependency (field/method/constructor)
     * @param requestingBeanName the name of the bean which declares the given dependency
     * @return the resolved object, or {@code null} if none found
     * @throws NoSuchBeanDefinitionException if no matching bean was found
     * @throws NoUniqueBeanDefinitionException if more than one matching bean was found
     * @throws BeansException if dependency resolution failed for any other reason
     * @since 2.5
     * @see #resolveDependency(DependencyDescriptor, String, Set, TypeConverter)
     */
    @Nullable
    Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName) throws BeansException;

    /**
     * Resolve the specified dependency against the beans defined in this factory.
     * @param descriptor the descriptor for the dependency (field/method/constructor)
     * @param requestingBeanName the name of the bean which declares the given dependency
     * @param autowiredBeanNames a Set that all names of autowired beans (used for
     * resolving the given dependency) are supposed to be added to
     * @param typeConverter the TypeConverter to use for populating arrays and collections
     * @return the resolved object, or {@code null} if none found
     * @throws NoSuchBeanDefinitionException if no matching bean was found
     * @throws NoUniqueBeanDefinitionException if more than one matching bean was found
     * @throws BeansException if dependency resolution failed for any other reason
     * @since 2.5
     * @see DependencyDescriptor
     */
    @Nullable
    Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
            @Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException;

}

这个工厂的应用场景，可参考文章：https://www.jianshu.com/p/d564335fafab

ListableBeanFactory

public interface ListableBeanFactory extends BeanFactory {

    /**
     * 是否包含bean的定义
     */
    boolean containsBeanDefinition(String beanName);

    /**
     * 获取bean的定义数
     */
    int getBeanDefinitionCount();

    /**
     * 获取bean定义名称数组
     */
    String[] getBeanDefinitionNames();

    /**
     * 获取特定类型的bean名称数组
     */
    String[] getBeanNamesForType(ResolvableType type);

    /**
     * 获取特定类型的bean名称数组，同时去掉非单例类型，且允许提前初始化
     */
    String[] getBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit);

    /**
     * 获取特定类型的bean名称数组
     */
    String[] getBeanNamesForType(@Nullable Class<?> type);

    /**
     * 获取特定类型的bean名称数组，同时去掉非单例类型，且允许提前初始化
     */
    String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit);

    /**
     * 获取特定类型的bean map，key为bean的名称，value为bean对象
     */
    <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException;

    /**
     * 获取特定类型的bean map，key为bean的名称，value为bean对象
     * 同时去掉非单例类型，且允许提前初始化
     */
    <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
            throws BeansException;

    /**
     * 获取有特定注解修饰的bean名称数组
     */
    String[] getBeanNamesForAnnotation(Class<? extends Annotation> annotationType);

    /**
     * 获取有特定注解修饰的bean map，key为bean的名称，value为bean对象
     */
    Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> annotationType) throws BeansException;

    /**
     * 获取特定名称的bean的特定类型注解
     */
    @Nullable
    <A extends Annotation> A findAnnotationOnBean(String beanName, Class<A> annotationType)
            throws NoSuchBeanDefinitionException;
}

ConfigurableListableBeanFactory

public interface ConfigurableListableBeanFactory
        extends ListableBeanFactory, AutowireCapableBeanFactory, ConfigurableBeanFactory {

    /**
     * 在注入的时候，忽略特定类型的依赖
     */
    void ignoreDependencyType(Class<?> type);

    /**
     * 忽略特定接口的依赖注入，
     * 比如BeanFactory会忽略BeanFactoryAware的注入
     * 再比如ApplicationContext会忽略ApplicationContextAware的注入
     * Ignore the given dependency interface for autowiring.
     * <p>This will typically be used by application contexts to register
     * dependencies that are resolved in other ways, like BeanFactory through
     * BeanFactoryAware or ApplicationContext through ApplicationContextAware.
     * <p>By default, only the BeanFactoryAware interface is ignored.
     * For further types to ignore, invoke this method for each type.
     * @param ifc the dependency interface to ignore
     * @see org.springframework.beans.factory.BeanFactoryAware
     * @see org.springframework.context.ApplicationContextAware
     */
    void ignoreDependencyInterface(Class<?> ifc);

    /**
     * 针对特定类型，注入特定的值，
     * 比如一个单例bean依赖ApplicationContext，而ApplicationContext并非一个bean对象
     * Register a special dependency type with corresponding autowired value.
     * <p>This is intended for factory/context references that are supposed
     * to be autowirable but are not defined as beans in the factory:
     * e.g. a dependency of type ApplicationContext resolved to the
     * ApplicationContext instance that the bean is living in.
     * <p>Note: There are no such default types registered in a plain BeanFactory,
     * not even for the BeanFactory interface itself.
     * @param dependencyType the dependency type to register. This will typically
     * be a base interface such as BeanFactory, with extensions of it resolved
     * as well if declared as an autowiring dependency (e.g. ListableBeanFactory),
     * as long as the given value actually implements the extended interface.
     * @param autowiredValue the corresponding autowired value. This may also be an
     * implementation of the {@link org.springframework.beans.factory.ObjectFactory}
     * interface, which allows for lazy resolution of the actual target value.
     */
    void registerResolvableDependency(Class<?> dependencyType, @Nullable Object autowiredValue);

    /**
     * bean是否作为一个注入的候选者
     * Determine whether the specified bean qualifies as an autowire candidate,
     * to be injected into other beans which declare a dependency of matching type.
     * <p>This method checks ancestor factories as well.
     * @param beanName the name of the bean to check
     * @param descriptor the descriptor of the dependency to resolve
     * @return whether the bean should be considered as autowire candidate
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     */
    boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor)
            throws NoSuchBeanDefinitionException;

    /**
     * 获取bean定义
     * Return the registered BeanDefinition for the specified bean, allowing access
     * to its property values and constructor argument value (which can be
     * modified during bean factory post-processing).
     * <p>A returned BeanDefinition object should not be a copy but the original
     * definition object as registered in the factory. This means that it should
     * be castable to a more specific implementation type, if necessary.
     * <p><b>NOTE:</b> This method does <i>not</i> consider ancestor factories.
     * It is only meant for accessing local bean definitions of this factory.
     * @param beanName the name of the bean
     * @return the registered BeanDefinition
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * defined in this factory
     */
    BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    /**
     * 获取bean名称迭代器
     * Return a unified view over all bean names managed by this factory.
     * <p>Includes bean definition names as well as names of manually registered
     * singleton instances, with bean definition names consistently coming first,
     * analogous to how type/annotation specific retrieval of bean names works.
     * @return the composite iterator for the bean names view
     * @since 4.1.2
     * @see #containsBeanDefinition
     * @see #registerSingleton
     * @see #getBeanNamesForType
     * @see #getBeanNamesForAnnotation
     */
    Iterator<String> getBeanNamesIterator();

    /**
     * 清除元数据缓存
     * Clear the merged bean definition cache, removing entries for beans
     * which are not considered eligible for full metadata caching yet.
     * <p>Typically triggered after changes to the original bean definitions,
     * e.g. after applying a {@link BeanFactoryPostProcessor}. Note that metadata
     * for beans which have already been created at this point will be kept around.
     * @since 4.2
     * @see #getBeanDefinition
     * @see #getMergedBeanDefinition
     */
    void clearMetadataCache();

    /**
     * 冻结bean配置，从而导致bean定义不能被修改，也不能进一步操作
     * Freeze all bean definitions, signalling that the registered bean definitions
     * will not be modified or post-processed any further.
     * <p>This allows the factory to aggressively cache bean definition metadata.
     */
    void freezeConfiguration();

    /**
     * bean配置是否被冻结
     * Return whether this factory's bean definitions are frozen,
     * i.e. are not supposed to be modified or post-processed any further.
     * @return {@code true} if the factory's configuration is considered frozen
     */
    boolean isConfigurationFrozen();

    /**
     * 预初始化单例bean对象
     * Ensure that all non-lazy-init singletons are instantiated, also considering
     * {@link org.springframework.beans.factory.FactoryBean FactoryBeans}.
     * Typically invoked at the end of factory setup, if desired.
     * @throws BeansException if one of the singleton beans could not be created.
     * Note: This may have left the factory with some beans already initialized!
     * Call {@link #destroySingletons()} for full cleanup in this case.
     * @see #destroySingletons()
     */
    void preInstantiateSingletons() throws BeansException;
}

总结

本文分析了Spring自带的、我们经常使用到的BeanFactory相关接口，功能繁多，但结构清晰。

我们对此进行了详细分析，已经基本知道其包含的内容，以及要实现的功能了。