Spring源码分析——BeanFactory体系

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一、BeanFactory的基本类体系结构（接口为主）：

　　具体：
　　1、BeanFactory作为一个主接口不继承任何接口，暂且称为一级接口。
　　2、有3个子接口继承了它，进行功能上的增强。这3个子接口称为二级接口。
　　3、ConfigurableBeanFactory可以被称为三级接口，对二级接口HierarchicalBeanFactory进行了再次增强，它还继承了另一个外来的接口SingletonBeanRegistry
　　4、ConfigurableListableBeanFactory是一个更强大的接口，继承了上述的所有接口，无所不包，称为四级接口。
　　（这4级接口是BeanFactory的基本接口体系。继续，下面是继承关系的2个抽象类和2个实现类：）
　　5、AbstractBeanFactory作为一个抽象类，实现了三级接口ConfigurableBeanFactory大部分功能。
　　6、AbstractAutowireCapableBeanFactory同样是抽象类，继承自AbstractBeanFactory，并额外实现了二级接口AutowireCapableBeanFactory
　　7、DefaultListableBeanFactory继承自AbstractAutowireCapableBeanFactory，实现了最强大的四级接口ConfigurableListableBeanFactory，并实现了一个外来接口BeanDefinitionRegistry，它并非抽象类。
　　8、最后是最强大的XmlBeanFactory，继承自DefaultListableBeanFactory，重写了一些功能，使自己更强大。
总结：BeanFactory的类体系结构看似繁杂混乱，实际上由上而下井井有条，非常容易理解。

二、IOC的始祖——BeanFactory

来看一下BeanFactory的源码

package org.springframework.beans.factory;

public interface BeanFactory {

    /**
     * 用来引用一个实例，或把它和工厂产生的Bean区分开，就是说，如果一个FactoryBean的名字为a，那么，&a会得到那个Factory
     */
    String FACTORY_BEAN_PREFIX = "&";

    /*
     * 四个不同形式的getBean方法，获取实例
     */
    Object getBean(String name) throws BeansException;

    <T> T getBean(String name, Class<T> requiredType) throws BeansException;

    <T> T getBean(Class<T> requiredType) throws BeansException;

    Object getBean(String name, Object... args) throws BeansException;

    boolean containsBean(String name); // 是否存在

    boolean isSingleton(String name) throws NoSuchBeanDefinitionException;// 是否为单实例

    boolean isPrototype(String name) throws NoSuchBeanDefinitionException;// 是否为原型（多实例）

    boolean isTypeMatch(String name, Class<?> targetType)
            throws NoSuchBeanDefinitionException;// 名称、类型是否匹配

    Class<?> getType(String name) throws NoSuchBeanDefinitionException; // 获取类型

    String[] getAliases(String name);// 根据实例的名字获取实例的别名

}

具体：
　　1、4个获取实例的方法。getBean的重载方法。
　　2、4个判断的方法。判断是否存在，是否为单例、原型，名称类型是否匹配。
　　3、1个获取类型的方法、一个获取别名的方法。根据名称获取类型、根据名称获取别名。一目了然！
总结：
　　这10个方法，很明显，这是一个典型的工厂模式的工厂接口。

三、可将Bean逐一列出的工厂——ListableBeanFactory

源码：

public interface ListableBeanFactory extends BeanFactory {

    boolean containsBeanDefinition(String beanName); // 对于给定的名字是否含有BeanDefinition

    int getBeanDefinitionCount(); // 返回工厂的BeanDefinition总数

    String[] getBeanDefinitionNames(); // 返回工厂中所有Bean的名字

    String[] getBeanNamesForType(Class<?> type); // 返回对于指定类型Bean（包括子类）的所有名字

    /*
     * 返回指定类型的名字 includeNonSingletons为false表示只取单例Bean，true则不是
     * allowEagerInit为true表示立刻加载，false表示延迟加载。 注意：FactoryBeans都是立刻加载的。
     */
    String[] getBeanNamesForType(Class<?> type, boolean includeNonSingletons,
            boolean allowEagerInit);

    <T> Map<String, T> getBeansOfType(Class<T> type) throws BeansException; // 根据类型（包括子类）返回指定Bean名和Bean的Map

    <T> Map<String, T> getBeansOfType(Class<T> type,
            boolean includeNonSingletons, boolean allowEagerInit)
            throws BeansException;

    Map<String, Object> getBeansWithAnnotation(
            Class<? extends Annotation> annotationType) throws BeansException; // 根据注解类型，查找所有有这个注解的Bean名和Bean的Map

    <A extends Annotation> A findAnnotationOnBean(String beanName,
            Class<A> annotationType);// 根据指定Bean名和注解类型查找指定的Bean

}

具体：
　　1、3个跟BeanDefinition有关的总体操作。包括BeanDefinition的总数、名字的集合、指定类型的名字的集合。
　　（这里指出，BeanDefinition是Spring中非常重要的一个类，每个BeanDefinition实例都包含一个类在Spring工厂中所有属性。）
　　2、2个getBeanNamesForType重载方法。根据指定类型（包括子类）获取其对应的所有Bean名字。
　　3、2个getBeansOfType重载方法。根据类型（包括子类）返回指定Bean名和Bean的Map。
　　4、2个跟注解查找有关的方法。根据注解类型，查找Bean名和Bean的Map。以及根据指定Bean名和注解类型查找指定的Bean。
总结：
　　正如这个工厂接口的名字所示，这个工厂接口最大的特点就是可以列出工厂可以生产的所有实例。当然，工厂并没有直接提供返回所有实例的方法，也没这个必要。它可以返回指定类型的所有的实例。而且你可以通过getBeanDefinitionNames()得到工厂所有bean的名字，然后根据这些名字得到所有的Bean。这个工厂接口扩展了BeanFactory的功能，作为上文指出的BeanFactory二级接口，有9个独有的方法，扩展了跟BeanDefinition的功能，提供了BeanDefinition、BeanName、注解有关的各种操作。它可以根据条件返回Bean的集合，这就是它名字的由来——ListableBeanFactory。

四、分层的Bean工厂——HierarchicalBeanFactory

源码：

public interface HierarchicalBeanFactory extends BeanFactory {

    BeanFactory getParentBeanFactory();    //  返回本Bean工厂的父工厂

    boolean containsLocalBean(String name);    //  本地工厂是否包含这个Bean
}

具体：
　　1、第一个方法返回本Bean工厂的父工厂。这个方法实现了工厂的分层。
　　2、第二个方法判断本地工厂是否包含这个Bean（忽略其他所有父工厂）。这也是分层思想的体现。
总结：这个工厂接口非常简单，实现了Bean工厂的分层。这个工厂接口也是继承自BeanFacotory，也是一个二级接口，相对于父接口，它只扩展了一个重要的功能——工厂分层。

五、自动装配的Bean工厂——AutowireCapableBeanFactory

源码：

public interface AutowireCapableBeanFactory extends BeanFactory {

    int AUTOWIRE_NO = 0;   //  这个常量表明工厂没有自动装配的Bean

    int AUTOWIRE_BY_NAME = 1;  //表明根据名称自动装配

    int AUTOWIRE_BY_TYPE = 2;  //表明根据类型自动装配

    int AUTOWIRE_CONSTRUCTOR = 3;  //表明根据构造方法快速装配
    @Deprecated
    int AUTOWIRE_AUTODETECT = 4;   //表明通过Bean的class的内部来自动装配（有没翻译错...）Spring3.0被弃用。

    <T> T createBean(Class<T> beanClass) throws BeansException;    //  根据指定Class创建一个全新的Bean实例

    void autowireBean(Object existingBean) throws BeansException;  //  给定对象，根据注释、后处理器等，进行自动装配

    /*
     * 根据Bean名的BeanDefinition装配这个未加工的Object，执行回调和各种后处理器。
     */
    Object configureBean(Object existingBean, String beanName) throws BeansException;

    /*
     * 分解Bean在工厂中定义的这个指定的依赖descriptor
     */
    Object resolveDependency(DependencyDescriptor descriptor, String beanName) throws BeansException;

    /*
     * 根据给定的类型和指定的装配策略，创建一个新的Bean实例
     */
    Object createBean(Class<?> beanClass, int autowireMode, boolean dependencyCheck) throws BeansException;

    /*
     * 与上面类似，不过稍有不同。
     */
    Object autowire(Class<?> beanClass, int autowireMode, boolean dependencyCheck) throws BeansException;

    /*
     * 根据名称或类型自动装配
     */
    void autowireBeanProperties(Object existingBean, int autowireMode, boolean dependencyCheck)
            throws BeansException;

    /*
     * 也是自动装配
     */
    void applyBeanPropertyValues(Object existingBean, String beanName) throws BeansException;

    /*
     * 初始化一个Bean...
     */
    Object initializeBean(Object existingBean, String beanName) throws BeansException;

    /*
     * 初始化之前执行BeanPostProcessors
     */
    Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
            throws BeansException;
    /*
     * 初始化之后执行BeanPostProcessors
     */
    Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
            throws BeansException;

    /*
     * 分解指定的依赖
     */
    Object resolveDependency(DependencyDescriptor descriptor, String beanName,
            Set<String> autowiredBeanNames, TypeConverter typeConverter) throws BeansException;

}

具体：
　　1、总共5个静态不可变常量来指明装配策略，其中一个常量被Spring3.0废弃、一个常量表示没有自动装配，另外3个常量指明不同的装配策略——根据名称、根据类型、根据构造方法。
　　2、8个跟自动装配有关的方法，实在是繁杂，具体的意义我们研究类的时候再分辨吧。
　　3、2个执行BeanPostProcessors的方法。
　　4、2个分解指定依赖的方法
总结：这个工厂接口继承自BeanFacotory，它扩展了自动装配的功能，根据类定义BeanDefinition装配Bean、执行前、后处理器等。

六、复杂的配置Bean工厂——ConfigurableBeanFactory

源码：

public interface ConfigurableBeanFactory extends HierarchicalBeanFactory, SingletonBeanRegistry {

    String SCOPE_SINGLETON = "singleton";  //  单例
    String SCOPE_PROTOTYPE = "prototype";  //  原型

    /*
     * 搭配HierarchicalBeanFactory接口的getParentBeanFactory方法
     */
    void setParentBeanFactory(BeanFactory parentBeanFactory) throws IllegalStateException;

    /*
     * 设置、返回工厂的类加载器
     */
    void setBeanClassLoader(ClassLoader beanClassLoader);

    ClassLoader getBeanClassLoader();

    /*
     * 设置、返回一个临时的类加载器
     */
    void setTempClassLoader(ClassLoader tempClassLoader);

    ClassLoader getTempClassLoader();

    /*
     * 设置、是否缓存元数据，如果false，那么每次请求实例，都会从类加载器重新加载（热加载）

     */
    void setCacheBeanMetadata(boolean cacheBeanMetadata);
    
    boolean isCacheBeanMetadata();//是否缓存元数据

    /*
     * Bean表达式分解器
     */
    void setBeanExpressionResolver(BeanExpressionResolver resolver);
    
    BeanExpressionResolver getBeanExpressionResolver();

    /*
     * 设置、返回一个转换服务
     */
    void setConversionService(ConversionService conversionService);

    ConversionService getConversionService();

    /*
     * 设置属性编辑登记员...
     */
    void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar);

    /*
     * 注册常用属性编辑器
     */
    void registerCustomEditor(Class<?> requiredType, Class<? extends PropertyEditor> propertyEditorClass);

    /*
     * 用工厂中注册的通用的编辑器初始化指定的属性编辑注册器
     */
    void copyRegisteredEditorsTo(PropertyEditorRegistry registry);

    /*
     * 设置、得到一个类型转换器
     */
    void setTypeConverter(TypeConverter typeConverter);

    TypeConverter getTypeConverter();

    /*
     * 增加一个嵌入式的StringValueResolver
     */
    void addEmbeddedValueResolver(StringValueResolver valueResolver);

    String resolveEmbeddedValue(String value);//分解指定的嵌入式的值

    void addBeanPostProcessor(BeanPostProcessor beanPostProcessor);//设置一个Bean后处理器

    int getBeanPostProcessorCount();//返回Bean后处理器的数量

    void registerScope(String scopeName, Scope scope);//注册范围
    String[] getRegisteredScopeNames();//返回注册的范围名
    Scope getRegisteredScope(String scopeName);//返回指定的范围
    AccessControlContext getAccessControlContext();//返回本工厂的一个安全访问上下文

    void copyConfigurationFrom(ConfigurableBeanFactory otherFactory);//从其他的工厂复制相关的所有配置

    /*
     * 给指定的Bean注册别名
     */
    void registerAlias(String beanName, String alias) throws BeanDefinitionStoreException;

    void resolveAliases(StringValueResolver valueResolver);//根据指定的StringValueResolver移除所有的别名

    /*
     * 返回指定Bean合并后的Bean定义
     */
    BeanDefinition getMergedBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException;//判断指定Bean是否为一个工厂Bean

    void setCurrentlyInCreation(String beanName, boolean inCreation);//设置一个Bean是否正在创建

    boolean isCurrentlyInCreation(String beanName);//返回指定Bean是否已经成功创建

    void registerDependentBean(String beanName, String dependentBeanName);//注册一个依赖于指定bean的Bean
    String[] getDependentBeans(String beanName);//返回依赖于指定Bean的所欲Bean名
    String[] getDependenciesForBean(String beanName);//返回指定Bean依赖的所有Bean名

    void destroyBean(String beanName, Object beanInstance);//销毁指定的Bean

    void destroyScopedBean(String beanName);//销毁指定的范围Bean

    void destroySingletons();  //销毁所有的单例类
}

在具体介绍之前，先看一下接口SingletonBeanRegistry的源码：

public interface SingletonBeanRegistry {

    void registerSingleton(String beanName, Object singletonObject); //在容器内注册一个单例类      
    Object getSingleton(String beanName);//返回给定名称对应的单例类

    boolean containsSingleton(String beanName);//给定名称是否对应单例类
    String[] getSingletonNames();//返回容器内所有单例类的名字

    int getSingletonCount();//返回容器内注册的单例类数量
}

可以看到，SingletonBeanRegistry这个接口非常简单，5个方法，实现了单例类注册的功能。
ConfigurableBeanFactory同时继承了HierarchicalBeanFactory 和 SingletonBeanRegistry 这两个接口，即同时继承了分层和单例类注册的功能。
具体：
　　1、2个静态不可变常量分别代表单例类和原型类。
　　2、1个设置父工厂的方法，跟HierarchicalBeanFactory接口的getParentBeanFactory方法互补。
　　3、4个跟类加载器有关的方法：get/set工厂类加载器和get/set临时类加载器。
　　4、2个设置、是否缓存元数据的方法（热加载开关）。
　　5、11个处理Bean注册、加载等细节的方法，包括：Bean表达式分解器、转换服务、属性编辑登记员、属性编辑器、属性编辑注册器、类型转换器、嵌入式的字符串分解器
　　6、2个处理Bean后处理器的方法。
　　7、3个跟注册范围相关的方法。
　　8、1个返回安全访问上下文的方法、1个从其他的工厂复制相关的所有配置的方法。
　　9、2个跟Bean别名相关的方法、1个返回合并后的Bean定义的方法。
　　10、1个判断是否为工厂Bean的方法、2个跟当前Bean创建时机相关的方法。
　　11、3个跟Bean依赖相关的方法、3个销毁Bean相关的方法。
总结：这个巨大的工厂接口，继承自HierarchicalBeanFactory 和 SingletonBeanRegistry 这两个接口，并额外独有37个方法！！！（看的我都快疯了…）这37个方法包含了工厂创建、注册一个Bean的众多细节。这个工厂名为ConfigurableBeanFactory，真是名不虚传！统计一下此时的ConfigurableBeanFactory的方法数吧。自有的37个方法、HierarchicalBeanFactory的2个方法、SingletonBeanRegistry的5个方法、爷爷接口BeanFactory的10个方法，共有54个方法！虽然方法繁多，还算井井有条！

七、BeanFactory的集大成者——ConfigurableListableBeanFactory

源码：　　

public interface ConfigurableListableBeanFactory
        extends ListableBeanFactory, AutowireCapableBeanFactory, ConfigurableBeanFactory {

    void ignoreDependencyType(Class<?> type);//忽略自动装配的依赖类型

    void ignoreDependencyInterface(Class<?> ifc);//忽略自动装配的接口

    /*
     * 注册一个可分解的依赖
     */
    void registerResolvableDependency(Class<?> dependencyType, Object autowiredValue);

    /*
     * 判断指定的Bean是否有资格作为自动装配的候选者
     */
    boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor)
            throws NoSuchBeanDefinitionException;

    /*
     * 返回注册的Bean定义
     */
    BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    void freezeConfiguration();//暂时冻结所有的Bean配置

    boolean isConfigurationFrozen();//判断本工厂配置是否被冻结

    void preInstantiateSingletons() throws BeansException;//使所有的非延迟加载的单例类都实例化。
}

具体：
　　1、2个忽略自动装配的的方法。
　　2、1个注册一个可分解依赖的方法。
　　3、1个判断指定的Bean是否有资格作为自动装配的候选者的方法。
　　4、1个根据指定bean名，返回注册的Bean定义的方法。
　　5、2个冻结所有的Bean配置相关的方法。
　　6、1个使所有的非延迟加载的单例类都实例化的方法。
总结：工厂接口ConfigurableListableBeanFactory同时继承了3个接口，ListableBeanFactory、AutowireCapableBeanFactory 和 ConfigurableBeanFactory，扩展之后，加上自有的这8个方法，这个工厂接口总共有83个方法，实在是巨大到不行了。这个工厂接口的自有方法总体上只是对父类接口功能的补充，包含了BeanFactory体系目前的所有方法，可以说是接口的集大成者。

八、额外的接口——BeanDefinitionRegistry

这个接口基本用来操作定义在工厂内部的BeanDefinition的。我们先来看一下这个接口的父接口：

public interface AliasRegistry {

    void registerAlias(String name, String alias);//对指定的名称注册别名

    void removeAlias(String alias);//从当前容器移除指定别名

    boolean isAlias(String beanName);//判断指定名称是否为别名
    String[] getAliases(String name);//返回指定名称的所有别名
}

可以看到这4个方法都非常简单，都是用来操作别名的。
再来看一下BeanDefinitionRegistry的源码：

public interface BeanDefinitionRegistry extends AliasRegistry {

    void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
            throws BeanDefinitionStoreException;//给定bean名称，注册一个新的bean定义

    /*
     * 根据指定Bean名移除对应的Bean定义
     */
    void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    /*
     * 根据指定bean名得到对应的Bean定义
     */
    BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException;

    /*
     * 查找，指定的Bean名是否包含Bean定义
     */
    boolean containsBeanDefinition(String beanName);

    String[] getBeanDefinitionNames();//返回本容器内所有注册的Bean定义名称

    int getBeanDefinitionCount();//返回本容器内注册的Bean定义数目

    boolean isBeanNameInUse(String beanName);//指定Bean名是否被注册过。
}

这7个方法都是用来操作容器内的BeanDefinition的。

一、BeanFactory的基本类体系结构（类为主）：

　　上图可与 Spring源码分析——BeanFactory体系之接口详细分析 的图结合分析，一个以接口为主，一个以类为主（PS：Spring的体系结构要分析清楚，不得不曲线救国啊！不然27寸屏幕给我画估计都装不下。）。

具体：

　　1、7层的类体系继承。

　　2、AbstractBeanFactory实现了最重要的ConfigurableBeanFactory接口，DefaultSingletonBeanRegistry实现了SingletonBeanRegistry单例类注册接口，SimpleAliasRegistry实现了AliasRegistry别名注册接口。

　　3、祖先类SimpleAliasRegistry、DefaultSingletonBeanRegistry和子孙类XmlBeanFactory、DefaultListableBeanFactory是完整的类，而中间的类FactoryBeanRegistrySupport、AbstractBeanFactory、AbstractAutowireCapableBeanFactory都是抽象类。

总结：

　　具体上来说，XmlBeanFactory光是父类就有6个了，加上自身，总共7层了。实际上分析接口结构就会看到，作为IOC类工厂而言，XmlBeanFactory的类体系结构实际是从祖先AbstractBeanFactory这个类开始的，因为是它实现了BeanFactory的子接口ConfigurableBeanFactory，虽然它继承自FactoryBeanRegistrySupport，但可以说这只是工厂功能的扩充，扩展了对工厂Bean以及工厂所产生的Bean的操作。

二、简单的别名注册器——SimpleAliasRegistry

　　上篇已经讲过AliasRegistry，非常简单的4个方法，体现了对别名注册的支持，而SimpleAliasRegistry就是它的简单实现。

源码：

public class SimpleAliasRegistry implements AliasRegistry {

    /*
     *用一个支持高并发的ConcurrentHashMap来放置所有的别名
     */
    private final Map<String, String> aliasMap = new ConcurrentHashMap<String, String>(
            16);

    // AliasRegistry的接口方法，注册别名。不允许重复注册。
    public void registerAlias(String name, String alias) {
        Assert.hasText(name, "'name' must not be empty");
        Assert.hasText(alias, "'alias' must not be empty");
        if (alias.equals(name)) {
            this.aliasMap.remove(alias);
        } else {
            if (!allowAliasOverriding()) {
                String registeredName = this.aliasMap.get(alias);
                if (registeredName != null && !registeredName.equals(name)) {
                    throw new IllegalStateException("Cannot register alias '"
                            + alias + "' for name '" + name
                            + "': It is already registered for name '"
                            + registeredName + "'.");
                }
            }
            checkForAliasCircle(name, alias);//alias不能等于name在map中最后的对应（详见checkForAliasCircle方法）
            this.aliasMap.put(alias, name);//alias是key,name是value
        }
    }

    /**
     * 返回是否允许Alias重写，默认为允许
     */
    protected boolean allowAliasOverriding() {
        return true;
    }

    // AliasRegistry的接口方法，移除别名，如果别名未注册，则抛出异常
    public void removeAlias(String alias) {
        String name = this.aliasMap.remove(alias);
        if (name == null) {
            throw new IllegalStateException("No alias '" + alias
                    + "' registered");
        }
    }

    // AliasRegistry的接口方法，给定名称判断是否为别名
    public boolean isAlias(String name) {
        return this.aliasMap.containsKey(name);
    }

    // AliasRegistry的接口方法
    public String[] getAliases(String name) {
        List<String> result = new ArrayList<String>();
        synchronized (this.aliasMap) {
            retrieveAliases(name, result);
        }
        return StringUtils.toStringArray(result);
    }

    /*
     * 找出名字说对应的所有别名。
     */
    private void retrieveAliases(String name, List<String> result) {
        for (Map.Entry<String, String> entry : this.aliasMap.entrySet()) {//遍历aliasMap
            String registeredName = entry.getValue();//取aliasMap的每个value
            if (registeredName.equals(name)) {//如果value等于指定的这个name
                String alias = entry.getKey();//取value对应的key
                result.add(alias);//将alias加入
                retrieveAliases(alias, result);//继续查看以alias为value的key
            }
        }
    }

    /*
     * 处理所有的别名，如果处理正确，把原来的用解析后的替换
     */
    public void resolveAliases(StringValueResolver valueResolver) {
        Assert.notNull(valueResolver, "StringValueResolver must not be null");
        synchronized (this.aliasMap) {
            Map<String, String> aliasCopy = new HashMap<String, String>(
                    this.aliasMap);
            for (String alias : aliasCopy.keySet()) {
                String registeredName = aliasCopy.get(alias);//取出key对应的value
                String resolvedAlias = valueResolver.resolveStringValue(alias);//解析后的key
                String resolvedName = valueResolver
                        .resolveStringValue(registeredName);//解析后的value
                if (resolvedAlias.equals(resolvedName)) {//若解析后的key、name相等，就把它们从aliasMap中移除
                    this.aliasMap.remove(alias);
                } else if (!resolvedAlias.equals(alias)) {//若解析后的key不等于原来的Key
                    String existingName = this.aliasMap.get(resolvedAlias);//取出解析后的key对应的value
                    if (existingName != null//如果不为空且不等于解析后的value，就抛出异常
                            && !existingName.equals(resolvedName)) {
                        throw new IllegalStateException(
                                "Cannot register resolved alias '"
                                        + resolvedAlias
                                        + "' (original: '"
                                        + alias
                                        + "') for name '"
                                        + resolvedName
                                        + "': It is already registered for name '"
                                        + registeredName + "'.");
                    }
                    checkForAliasCircle(resolvedName, resolvedAlias);
                    this.aliasMap.remove(alias);
                    this.aliasMap.put(resolvedAlias, resolvedName);
                } else if (!registeredName.equals(resolvedName)) {
                    this.aliasMap.put(alias, resolvedName);
                }
            }
        }
    }

    /*
     * 根据name这个Key，在aliasMap中不断循环的取对应的value，如果取得到，就继续根据这个value取值，不断循环继续。
     * 直到取不到，就把这个在aliasMap中无对应值的key返回。
     */
    public String canonicalName(String name) {
        String canonicalName = name;    //规范名
        // Handle aliasing...
        String resolvedName;//已解析名
        do {
            resolvedName = this.aliasMap.get(canonicalName);//aliasMap中规范名对应的值赋值给已解析名
            if (resolvedName != null) {//如果已解析名存在（即规范名在aliasMap中有对应的值）
                canonicalName = resolvedName;   // 这个已解析名赋值给标准名
            }
        } while (resolvedName != null);//不断循环，直到已解析名不存在
        return canonicalName;
    }

    /*
     * 如果别名alias等于canonicalName(name)就抛出异常
     */
    protected void checkForAliasCircle(String name, String alias) {
        if (alias.equals(canonicalName(name))) {
            throw new IllegalStateException("Cannot register alias '" + alias
                    + "' for name '" + name + "': Circular reference - '"
                    + name + "' is a direct or indirect alias for '" + alias
                    + "' already");
        }
    }

}

具体：

　　1、1个支持高并发的ConcurrentHashMap来放置所有的别名，其中key是别名，value是真名。

　　2、4个方法实现了SimpleAliasRegistry。

　　3、3个用来辅助实现4个接口方法的方法。其中canonicalName(String name)的实现非常优雅，用来循环来回判断，把aliasMap中无对应值的key返回。

　　4、2个添加额外功能的方法 retrieveAliases 和 resolveAliases ，前者是找出名字对应的所有别名，后者是用一个StringValueResolver处理解析所有的别名-名称。

总结：

　　这是一个非常简单的别名注册器，一个简单的接口实现。不过其中包含了非常优雅的方法实现，值得一看！

三、默认单例注册类——DefaultSingletonBeanRegistry

源码：　　

public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {

    protected static final Object NULL_OBJECT = new Object();//空object


    /** Logger available to subclasses */
    protected final Log logger = LogFactory.getLog(getClass());

    /** 单例缓存: bean name --> bean instance */
    private final Map<String, Object> singletonObjects = new ConcurrentHashMap<String, Object>(64);

    /** 单例工厂缓存: bean name --> ObjectFactory */
    private final Map<String, ObjectFactory> singletonFactories = new HashMap<String, ObjectFactory>(16);

    /** 早期单例对象缓存: bean name --> bean instance */
    private final Map<String, Object> earlySingletonObjects = new HashMap<String, Object>(16);

    /** 注册过的单例类（单例工厂） */
    private final Set<String> registeredSingletons = new LinkedHashSet<String>(64);

    /** 即将创建的单例类 (using a ConcurrentHashMap as a Set) */
    private final Map<String, Boolean> singletonsCurrentlyInCreation = new ConcurrentHashMap<String, Boolean>(16);

    /** 正在创建的单例类 (using a ConcurrentHashMap as a Set) */
    private final Map<String, Boolean> inCreationCheckExclusions = new ConcurrentHashMap<String, Boolean>(16);

    /** 被压制的异常集合 */
    private Set<Exception> suppressedExceptions;

    /** 单例类是否真正被销毁 */
    private boolean singletonsCurrentlyInDestruction = false;

    /** Disposable接口的实例: bean name --> disposable instance */
    private final Map<String, Object>   = new LinkedHashMap<String, Object>();

    /** bean名称和bean所有包含的Bean的名称的map: bean name --> Set of bean names that the bean contains */
    private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<String, Set<String>>(16);

    /** bean名称和所有依赖于Bean的名称的map: bean name --> Set of dependent bean names */
    private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<String, Set<String>>(64);

    /** bean名称和bean所依赖的所有名称的map --> Set of bean names for the bean's dependencies */
    private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<String, Set<String>>(64);

    //SingletonBeanRegistry接口的实现类————注册单例Bean，不能重复注册
    public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
        Assert.notNull(beanName, "'beanName' must not be null");
        synchronized (this.singletonObjects) {
            Object oldObject = this.singletonObjects.get(beanName);
            if (oldObject != null) {
                throw new IllegalStateException("Could not register object [" + singletonObject +
                        "] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
            }
            addSingleton(beanName, singletonObject);
        }
    }

    //注册一个单例类，注册之后，从singletonFactories、earlySingletonObjects中删去
    protected void addSingleton(String beanName, Object singletonObject) {
        synchronized (this.singletonObjects) {
            this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);//
            this.registeredSingletons.add(beanName);//加入，注册过的单例类集合
        }
    }

    //注册一个单例工厂类，注册后从earlySingletonObjects移除
    protected void addSingletonFactory(String beanName, ObjectFactory singletonFactory) {
        Assert.notNull(singletonFactory, "Singleton factory must not be null");
        synchronized (this.singletonObjects) {
            if (!this.singletonObjects.containsKey(beanName)) {    //单例工厂类不能和单例类同名
                this.singletonFactories.put(beanName, singletonFactory);
                this.earlySingletonObjects.remove(beanName);
                this.registeredSingletons.add(beanName);
            }
        }
    }

    //SingletonBeanRegistry接口的实现类
    public Object getSingleton(String beanName) {
        return getSingleton(beanName, true);
    }

    //根据beanName返回单例类
    protected Object getSingleton(String beanName, boolean allowEarlyReference) {
        Object singletonObject = this.singletonObjects.get(beanName);
        if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {    //    如果取不到，且该bean正在创建
            synchronized (this.singletonObjects) {
                singletonObject = this.earlySingletonObjects.get(beanName);
                if (singletonObject == null && allowEarlyReference) {    //    如果从早期单例缓存中获取不到，且允许早期引用
                    ObjectFactory singletonFactory = this.singletonFactories.get(beanName);    //    那么就从单例工厂缓存中获取单例工厂
                    if (singletonFactory != null) {    //    如果还是获取不到，就创建一个单例工厂，并把它放进早期单例缓存中，并返回
                        singletonObject = singletonFactory.getObject();
                        this.earlySingletonObjects.put(beanName, singletonObject);
                        this.singletonFactories.remove(beanName);
                    }
                }
            }
        }
        return (singletonObject != NULL_OBJECT ? singletonObject : null);
    }

    //获取指定的单例Bean，如果取不到就调用指定的singletonFactory的getObject来返回
    public Object getSingleton(String beanName, ObjectFactory singletonFactory) {
        Assert.notNull(beanName, "'beanName' must not be null");
        synchronized (this.singletonObjects) {
            Object singletonObject = this.singletonObjects.get(beanName);//从单例缓存中获取
            if (singletonObject == null) {
                if (this.singletonsCurrentlyInDestruction) {//如果单例类正在被销毁，就抛出异常
                    throw new BeanCreationNotAllowedException(beanName,
                            "Singleton bean creation not allowed while the singletons of this factory are in destruction " +
                            "(Do not request a bean from a BeanFactory in a destroy method implementation!)");
                }
                if (logger.isDebugEnabled()) {
                    logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
                }
                //如果不在inCreationCheckExclusions中，且可以向singletonsCurrentlyInCreation中添加，就抛出异常
                beforeSingletonCreation(beanName);
                //是否有记录被压制的异常
                boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
                if (recordSuppressedExceptions) {//如果没有记录，即没有被压制的异常，就创建被压制的异常容器
                    this.suppressedExceptions = new LinkedHashSet<Exception>();
                }
                try {
                    singletonObject = singletonFactory.getObject();//以上都没有异常产生，那么就从指定的facgtory中取
                }
                catch (BeanCreationException ex) {
                    if (recordSuppressedExceptions) {
                        for (Exception suppressedException : this.suppressedExceptions) {
                            ex.addRelatedCause(suppressedException);
                        }
                    }
                    throw ex;
                }
                finally {
                    if (recordSuppressedExceptions) {
                        this.suppressedExceptions = null;
                    }
                    afterSingletonCreation(beanName);
                }
                addSingleton(beanName, singletonObject);//取成功就放进singletonObjects中
            }
            return (singletonObject != NULL_OBJECT ? singletonObject : null);
        }
    }

    //添加一个被压制的异常
    protected void onSuppressedException(Exception ex) {
        synchronized (this.singletonObjects) {
            if (this.suppressedExceptions != null) {
                this.suppressedExceptions.add(ex);
            }
        }
    }

    //根据名称移除本容器中缓存的对应的单例Bean，把对应的单例从Bean集合、单例工厂集合、早期单例对象集合、注册过的单例集合都统统移除
    protected void removeSingleton(String beanName) {
        synchronized (this.singletonObjects) {
            this.singletonObjects.remove(beanName);
            this.singletonFactories.remove(beanName);
            this.earlySingletonObjects.remove(beanName);
            this.registeredSingletons.remove(beanName);
        }
    }
    //SingletonBeanRegistry接口的实现类
    public boolean containsSingleton(String beanName) {
        return (this.singletonObjects.containsKey(beanName));
    }

    //SingletonBeanRegistry接口的实现类
    public String[] getSingletonNames() {
        synchronized (this.singletonObjects) {
            return StringUtils.toStringArray(this.registeredSingletons);
        }
    }
    //SingletonBeanRegistry接口的实现类
    public int getSingletonCount() {
        synchronized (this.singletonObjects) {
            return this.registeredSingletons.size();
        }
    }

    // 设置某个Bean是否正在创建
    public void setCurrentlyInCreation(String beanName, boolean inCreation) {
        Assert.notNull(beanName, "Bean name must not be null");
        if (!inCreation) {
            this.inCreationCheckExclusions.put(beanName, Boolean.TRUE);
        }
        else {
            this.inCreationCheckExclusions.remove(beanName);
        }
    }

    //判断某个Bean是否正在被创建
    public boolean isCurrentlyInCreation(String beanName) {
        Assert.notNull(beanName, "Bean name must not be null");
        return (!this.inCreationCheckExclusions.containsKey(beanName) && isActuallyInCreation(beanName));
    }

    protected boolean isActuallyInCreation(String beanName) {
        return isSingletonCurrentlyInCreation(beanName);
    }

    //是否即将被创建
    public boolean isSingletonCurrentlyInCreation(String beanName) {
        return this.singletonsCurrentlyInCreation.containsKey(beanName);
    }

    //单例类创建开始之前调用
    //如果不在正在创建的单例类集合中，且可以向即将创建的单例类中添加，就抛出异常
    protected void beforeSingletonCreation(String beanName) {
        if (!this.inCreationCheckExclusions.containsKey(beanName) &&
                this.singletonsCurrentlyInCreation.put(beanName, Boolean.TRUE) != null) {
            throw new BeanCurrentlyInCreationException(beanName);
        }
    }

    //单例类创建之后调用
    //如果不在正在创建的单例类中，也不在即将创建的单例类中移除失败，就抛出异常
    protected void afterSingletonCreation(String beanName) {
        if (!this.inCreationCheckExclusions.containsKey(beanName) &&
                !this.singletonsCurrentlyInCreation.remove(beanName)) {
            throw new IllegalStateException("Singleton '" + beanName + "' isn't currently in creation");
        }
    }

    //往Disposable实例集合注册Disposable实例
    public void registerDisposableBean(String beanName, DisposableBean bean) {
        synchronized (this.disposableBeans) {
            this.disposableBeans.put(beanName, bean);
        }
    }

    //注册一个被包含的Bean和一个包含它的Bean（子->父）
    public void registerContainedBean(String containedBeanName, String containingBeanName) {
        synchronized (this.containedBeanMap) {
            Set<String> containedBeans = this.containedBeanMap.get(containingBeanName);
            if (containedBeans == null) {
                containedBeans = new LinkedHashSet<String>(8);//containedBeans的初始容量为8
                this.containedBeanMap.put(containingBeanName, containedBeans);//注意！containedBeanMap的Key是父bean，value是其所包含的所有子Bean（父->子）
            }
            containedBeans.add(containedBeanName);
        }
        registerDependentBean(containedBeanName, containingBeanName);//因为包含也是依赖的一种，所以此时也要注册在dependentBeanMap中
    }

    //给指定的Bean注册一个其依赖的Bean
    public void registerDependentBean(String beanName, String dependentBeanName) {
        String canonicalName = canonicalName(beanName);//在aliasMap中取规范名
        synchronized (this.dependentBeanMap) {    //    这里是注册依赖BeanMap，key是bean的名称，value是依赖这个bean的所有bean的名称
            Set<String> dependentBeans = this.dependentBeanMap.get(canonicalName);
            if (dependentBeans == null) {
                dependentBeans = new LinkedHashSet<String>(8);//dependentBeans的初始容量也为8
                this.dependentBeanMap.put(canonicalName, dependentBeans);//dependentBeanMap中Key为beanName的规范名，value是依赖它的所有Bean的名称
            }
            dependentBeans.add(dependentBeanName);
        }
        synchronized (this.dependenciesForBeanMap) {    //    这里相反，注册的是某个Bean和其所依赖的Bean的集合，key是这个beanName，value是这个Bean的依赖的所有Bean的Name
            Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(dependentBeanName);
            if (dependenciesForBean == null) {
                dependenciesForBean = new LinkedHashSet<String>(8);
                this.dependenciesForBeanMap.put(dependentBeanName, dependenciesForBean);
            }
            dependenciesForBean.add(canonicalName);
        }
    }

    //判断某个Bean是否被其他Bean所依赖
    protected boolean hasDependentBean(String beanName) {
        return this.dependentBeanMap.containsKey(beanName);
    }

    //返回依赖于给定Bean的Bean名称的集合
    public String[] getDependentBeans(String beanName) {
        Set<String> dependentBeans = this.dependentBeanMap.get(beanName);
        if (dependentBeans == null) {
            return new String[0];
        }
        return StringUtils.toStringArray(dependentBeans);
    }

    //返回某个Bean所依赖的所有Bean的名称
    public String[] getDependenciesForBean(String beanName) {
        Set<String> dependenciesForBean = this.dependenciesForBeanMap.get(beanName);
        if (dependenciesForBean == null) {
            return new String[0];
        }
        return dependenciesForBean.toArray(new String[dependenciesForBean.size()]);
    }

    //这个方法居然连注释都没有？太奇怪了！
    public void destroySingletons() {
        if (logger.isInfoEnabled()) {
            logger.info("Destroying singletons in " + this);
        }
        synchronized (this.singletonObjects) {//首先标记，所有的单例Bean正在被销毁，那么getSingleton就无法获得单例Bean了
            this.singletonsCurrentlyInDestruction = true;
        }

        String[] disposableBeanNames;
        synchronized (this.disposableBeans) {//然后把所有的disposableBean都放进数组，一个个按名称销毁
            disposableBeanNames = StringUtils.toStringArray(this.disposableBeans.keySet());
        }
        for (int i = disposableBeanNames.length - 1; i >= 0; i--) {
            destroySingleton(disposableBeanNames[i]);
        }
        //    把本容器的所有的包含关系、依赖关系、被依赖关系的集合全部清空
        this.containedBeanMap.clear();
        this.dependentBeanMap.clear();
        this.dependenciesForBeanMap.clear();

        //然后把本容器的所有其他集合全部清空
        synchronized (this.singletonObjects) {
            this.singletonObjects.clear();
            this.singletonFactories.clear();
            this.earlySingletonObjects.clear();
            this.registeredSingletons.clear();
            this.singletonsCurrentlyInDestruction = false;
        }
    }

    //销毁某个单例Bean
    public void destroySingleton(String beanName) {
        // Remove a registered singleton of the given name, if any.
        removeSingleton(beanName);//先把它销毁

        DisposableBean disposableBean;//它相应的DisposableBean实例
        synchronized (this.disposableBeans) {
            disposableBean = (DisposableBean) this.disposableBeans.remove(beanName);//从disposableBeans移除这个实例
        }
        destroyBean(beanName, disposableBean);
    }

    // 销毁指定名称的Bean，且销毁依赖于它的所有Bean
    protected void destroyBean(String beanName, DisposableBean bean) {
        // 首先销毁依赖它的所有Bean
        Set<String> dependencies = this.dependentBeanMap.remove(beanName);//取依赖于指定Bean的所有Bean
        if (dependencies != null) {
            if (logger.isDebugEnabled()) {
                logger.debug("Retrieved dependent beans for bean '" + beanName + "': " + dependencies);
            }
            for (String dependentBeanName : dependencies) {
                destroySingleton(dependentBeanName);//一个个销毁
            }
        }

        // 然后销毁它
        if (bean != null) {
            try {
                bean.destroy();
            }
            catch (Throwable ex) {
                logger.error("Destroy method on bean with name '" + beanName + "' threw an exception", ex);
            }
        }

        // 然后销毁它所包含的Bean
        Set<String> containedBeans = this.containedBeanMap.remove(beanName);
        if (containedBeans != null) {
            for (String containedBeanName : containedBeans) {
                destroySingleton(containedBeanName);
            }
        }

        // 然后把所有它依赖的Bean的依赖关系删除，首先删除dependentBeanMap中的依赖关系
        synchronized (this.dependentBeanMap) {
            //这样的for循环用法实在是经典
            for (Iterator<Map.Entry<String, Set<String>>> it = this.dependentBeanMap.entrySet().iterator(); it.hasNext();) {
                Map.Entry<String, Set<String>> entry = it.next();
                Set<String> dependenciesToClean = entry.getValue();
                dependenciesToClean.remove(beanName);
                if (dependenciesToClean.isEmpty()) {
                    it.remove();
                }
            }
        }

        // 然后删除dependenciesForBeanMap中的依赖关系
        this.dependenciesForBeanMap.remove(beanName);
    }

    /**
     * Expose the singleton mutex to subclasses.
     * <p>Subclasses should synchronize on the given Object if they perform
     * any sort of extended singleton creation phase. In particular, subclasses
     * should <i>not</i> have their own mutexes involved in singleton creation,
     * to avoid the potential for deadlocks in lazy-init situations.
     */
    //返回子类单例类的互斥体？这个暂且放着。
    protected final Object getSingletonMutex() {
        return this.singletonObjects;
    }

}

具体：

　　1、一个静态不可变的空对象NULL_OBJECT、一个简单的日志对象。

　　2、本类有如下集合：

　　　　（1）、一个单例缓存集合——singletonObjects

　　　　（2）、一个单例工厂缓存集合——singletonFactories

　　　　（3）、一个早期单例对象缓存集合——earlySingletonObjects

　　　　（4）、一个注册过的单例类（单例工厂）集合——registeredSingletons

　　　　（5）、一个即将创建的单例类集合——singletonsCurrentlyInCreation

　　　　（6）、一个正在创建的单例类集合——inCreationCheckExclusions

　　　　（7）、一个被压制的异常集合——suppressedExceptions（这种设计模式实在是经典！）

　　　　（8）、一个判断所有单例类是否马上被销毁的标记——singletonsCurrentlyInDestruction

　　　　（9）、一个Disposable接口（即可以自定义回收资源的接口）实例的集合——disposableBeans

　　　　（10）、一个bean名称和bean所有包含的Bean的名称的集合——containedBeanMap

　　　　（11）、bean名称和所有依赖于Bean的名称的集合——dependentBeanMap

　　　　（12）、bean名称和bean所依赖的所有名称的集合——dependenciesForBeanMap

　　3、2个注册单例方法，实际是暴露在外的SingletonBeanRegistry接口的实现方法registerSingleton加锁后调用另一个addSingleton方法。

　　4、1个注册单例工厂的方法。单例工厂类不能和单例类同名。

　　5、3个获取单例类的方法。一种是从单例类集合中获取，如果获取不到，boolean控制要么返回空对象，要么返回一个单例工厂。另一种是从单例集合中获取，如果取不到，就从指定的工厂中获取。还有一种？呵，就是暴露在外的SingletonBeanRegistry接口方法呗，直接调用第一种。

　　6、1个添加被压制的异常集合中添加异常的方法，我觉得这个设计非常经典。但需要记录异常，却不想处理的时候，可以采用这种设计模式。

　　7、1个移除单例的方法、1个判断是否包含单例的方法、1个返回所有单例名数组的方法、1个返回单例总数目的方法。

　　8、1个设置某个Bean是否正在创建的方法、1个判断某个Bean是否正在被创建的方法、2个判断某个Bean是否即将被创建的方法（一个调用另一个，用于重写）。

　　9、1个单例类创建开始之前调用的方法、1个单单例类创建之后调用的方法

　　10、1个往Disposable实例集合注册Disposable实例的方法，这个是Bean销毁前的准备。

　　11、1个注册一个被包含的Bean和一个包含的Bean的名称到containedBeanMap集合的方法。这个方法设置了Bean之间的包含关系。

　　12、1个给指定的Bean注册一个其依赖的Bean的方法。这个方法设置了Bean自己的依赖关系。

　　13、1个判断是否被依赖的方法、1个返回给定Bean名称的所有依赖的数组的方法、1个返回依赖于给定Bean的所有Bean名的数组的方法。

　　14、1个销毁所有单例类的方法（这个方法居然完全没有注释，有没搞错！）、1个销毁某个单例的方法、1个// 销毁指定名称的Bean，且销毁依赖于它的所有Bean的方法。

　　15、1个返回子类单例类的互斥体的方法。这个暂且待下一篇分析子类再看。

总结：

　　类如其名，默认的单例注册器。这个工厂的写法实在功能丰富，为了监控到一个单例类构建过程中的方方面面，简直就是不择手段啊，居然准备了12个集合，除了一个一个被压制的异常集合，其余全是跟单例类有直接关系的。可以说，这个单例注册器监听、实现了Spring单例注册的各个过程，具体的解读分析，在上面的源代码中可以看到，读者阅读我注释过的源代码应该会很轻松。

一、工厂Bean注册支持——FactoryBeanRegistrySupport

废话不多说，直接看我注释的源码：

/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory.support;

import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanCreationException;
import org.springframework.beans.factory.BeanCurrentlyInCreationException;
import org.springframework.beans.factory.FactoryBean;
import org.springframework.beans.factory.FactoryBeanNotInitializedException;

/**
 * Support base class for singleton registries which need to handle
 * {@link org.springframework.beans.factory.FactoryBean} instances,
 * integrated with {@link DefaultSingletonBeanRegistry}'s singleton management.
 *
 * <p>Serves as base class for {@link AbstractBeanFactory}.
 *
 * @author Juergen Hoeller
 * @since 2.5.1
 */
public abstract class FactoryBeanRegistrySupport extends DefaultSingletonBeanRegistry {

    /** 工厂Bean生产的单例的集合: FactoryBean name --> object */
    private final Map<String, Object> factoryBeanObjectCache = new ConcurrentHashMap<String, Object>(16);

    //返回指定FactoryBean的类型
    protected Class getTypeForFactoryBean(final FactoryBean factoryBean) {
        try {
            if (System.getSecurityManager() != null) {//如果当前系统存在安全管理器
                return AccessController.doPrivileged(new PrivilegedAction<Class>() {//那么返回factoryBean的类型这个操作不做权限检查，直接调用
                    public Class run() {
                        return factoryBean.getObjectType();
                    }
                }, getAccessControlContext());
            }
            else {//不存在安全管理器，就直接调用！
                return factoryBean.getObjectType();
            }
        }
        catch (Throwable ex) {
            logger.warn("FactoryBean threw exception from getObjectType, despite the contract saying " +
                    "that it should return null if the type of its object cannot be determined yet", ex);
            return null;
        }
    }

    //根据FactoryBean名，返回其生产的Object，从缓存中取
    protected Object getCachedObjectForFactoryBean(String beanName) {
        Object object = this.factoryBeanObjectCache.get(beanName);
        return (object != NULL_OBJECT ? object : null);
    }

    //从工厂Bean中取实例，实际调用下面的doGetObjectFromFactoryBean方法。
    protected Object getObjectFromFactoryBean(FactoryBean factory, String beanName, boolean shouldPostProcess) {
        if (factory.isSingleton() && containsSingleton(beanName)) {//若工厂是单例，且本容器包含beanName对应的单例类
            synchronized (getSingletonMutex()) {//以所有的单例集合为锁
                Object object = this.factoryBeanObjectCache.get(beanName);//根据beanName从factoryBeanObjectCache中取
                if (object == null) {//若取不到
                    object = doGetObjectFromFactoryBean(factory, beanName, shouldPostProcess);
                    this.factoryBeanObjectCache.put(beanName, (object != null ? object : NULL_OBJECT));//放进factoryBeanObjectCache
                }
                return (object != NULL_OBJECT ? object : null);
            }
        }
        else {//否则，直接
            return doGetObjectFromFactoryBean(factory, beanName, shouldPostProcess);
        }
    }

    //从工厂Bean中取实例
    private Object doGetObjectFromFactoryBean(
            final FactoryBean factory, final String beanName, final boolean shouldPostProcess)
            throws BeanCreationException {

        Object object;
        //跟getTypeForFactoryBean的实现一样。
        try {
            if (System.getSecurityManager() != null) {//若系统存在安全管理器
                AccessControlContext acc = getAccessControlContext();//得到当前容器的安全访问上下文
                try {//返回factoryBean的类型这个操作不做权限检查，直接调用
                    object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                        public Object run() throws Exception {
                                return factory.getObject();
                            }
                        }, acc);
                }
                catch (PrivilegedActionException pae) {
                    throw pae.getException();
                }
            }
            else {//否则直接取
                object = factory.getObject();
            }
        }
        catch (FactoryBeanNotInitializedException ex) {
            throw new BeanCurrentlyInCreationException(beanName, ex.toString());
        }
        catch (Throwable ex) {
            throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
        }

        //如果从beanFactory取不到，且这个实例即将被创建，抛出异常
        if (object == null && isSingletonCurrentlyInCreation(beanName)) {
            throw new BeanCurrentlyInCreationException(
                    beanName, "FactoryBean which is currently in creation returned null from getObject");
        }
        //若取不到，且这个实例允许前处理
        if (object != null && shouldPostProcess) {
            try {
                object = postProcessObjectFromFactoryBean(object, beanName);//这里简单返回，前处理的功能留给子类重写
            }
            catch (Throwable ex) {
                throw new BeanCreationException(beanName, "Post-processing of the FactoryBean's object failed", ex);
            }
        }

        return object;
    }

    //这里简单返回Object，留给子类重写
    protected Object postProcessObjectFromFactoryBean(Object object, String beanName) throws BeansException {
        return object;
    }

    //如果这个Object是FactoryBean类型，就转换成FactoryBean返回
    protected FactoryBean getFactoryBean(String beanName, Object beanInstance) throws BeansException {
        if (!(beanInstance instanceof FactoryBean)) {
            throw new BeanCreationException(beanName,
                    "Bean instance of type [" + beanInstance.getClass() + "] is not a FactoryBean");
        }
        return (FactoryBean) beanInstance;
    }

    //移除单例类这个方法重写，父类的移除之外，还要移除factoryBeanObjectCache中的。
    @Override
    protected void removeSingleton(String beanName) {
        super.removeSingleton(beanName);
        this.factoryBeanObjectCache.remove(beanName);
    }

    //返回当前容器的安全访问上下文
    protected AccessControlContext getAccessControlContext() {
        return AccessController.getContext();
    }

}

具体：

　　1、1个不可变的实例属性ConcurrentHashMap来存放工厂Bean生产的单例的集合：FactoryBean name –> object。

　　2、1个方法返回指定FactoryBean的类型的方法。

　　3、1个根据FactoryBean名，返回其生产的Object的方法。

　　4、2个从工厂Bean中取实例的方法。实际是一个方法调用另一个，取不到则返回空。

　　5、1个postProcessObjectFromFactoryBean的方法，留给子类重写。

　　6、1个取工厂Bean的方法——如果这个Object是FactoryBean类型，就转换成FactoryBean返回

　　7、1个重写父类的removeSingleton方法，移除单例的时候，父类的移除之外，还要移除factoryBeanObjectCache中的。

　　8、1个返回当前容器的安全访问上下文的方法。

总结：

　　这个类FactoryBeanRegistrySupport，类如其名，实现了对工厂Bean注册的支持。值得注意的是，这个类有较多类似如下的写法：

if (System.getSecurityManager() != null) {//如果当前系统存在安全管理器
                return AccessController.doPrivileged(new PrivilegedAction<Class>() {
                    public Class run() {
                        //实际处理
                    }
                }, getAccessControlContext());
            }
            else {//不存在安全管理器，就直接调用！
                //实际处理
            }     

　　这个方法的意思是，如果当前系统存在安全管理器，那么接下来的操作不做权限检查，直接调用。而如果不存在，OK，那当然是直接调用了。这是JDK层面的一个系统安全管理工具，某些情况下，可以避免系统进行安全检查。这里稍作了解即可。在学习JVM的时候可仔细了解原理。

　　除此之外，这里可以了解一下这个类比较重要的方法doGetObjectFromFactoryBean，是从工厂Bean中取实例的方法，源码已经给出，这里重点指出一下：

//从工厂Bean中取实例，shouldPostProcess指的是是否允许提前处理

private Object doGetObjectFromFactoryBean(
            final FactoryBean factory, final String beanName, final boolean shouldPostProcess)
            throws BeanCreationException {

        Object object;
        //跟getTypeForFactoryBean的实现一样。
        try {
            if (System.getSecurityManager() != null) {//若系统存在安全管理器
                AccessControlContext acc = getAccessControlContext();//得到当前容器的安全访问上下文
                try {//返回factoryBean的类型这个操作不做权限检查，直接调用
                    object = AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
                        public Object run() throws Exception {
                                return factory.getObject();
                            }
                        }, acc);
                }
                catch (PrivilegedActionException pae) {
                    throw pae.getException();
                }
            }
            else {//否则直接取
                object = factory.getObject();
            }
        }
        catch (FactoryBeanNotInitializedException ex) {
            throw new BeanCurrentlyInCreationException(beanName, ex.toString());
        }
        catch (Throwable ex) {
            throw new BeanCreationException(beanName, "FactoryBean threw exception on object creation", ex);
        }

        //如果从beanFactory取不到，且这个实例即将被创建，抛出异常
        if (object == null && isSingletonCurrentlyInCreation(beanName)) {
            throw new BeanCurrentlyInCreationException(
                    beanName, "FactoryBean which is currently in creation returned null from getObject");
        }
        //若取不到，并非即将创建、且这个实例允许前处理
        if (object != null && shouldPostProcess) {
            try {
                object = postProcessObjectFromFactoryBean(object, beanName);//这里简单返回，前处理的功能留给子类重写
            }
            catch (Throwable ex) {
                throw new BeanCreationException(beanName, "Post-processing of the FactoryBean's object failed", ex);
            }
        }

        return object;
    }

　　相信上面已经解释的很清楚了。

二、最重要的抽象类——AbstractBeanFactory

　　（PS：这个类的方法实在是多的骇人，看得我实在是头都大了。不多看到后面，发现很多方法其实也就是那么回事。源码注释了大部分，且看看咯！）

public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport implements ConfigurableBeanFactory {

    //父工厂的引用
    private BeanFactory parentBeanFactory;

    //类加载器
    private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

    //临时类加载器
    private ClassLoader tempClassLoader;

    /** Whether to cache bean metadata or rather reobtain it for every access */
    private boolean cacheBeanMetadata = true;

    //Bean表达式分解器，用来分解Bean定义中的表达式
    private BeanExpressionResolver beanExpressionResolver;

    //转换服务，用来替代属性编辑器的
    private ConversionService conversionService;

    //属性编辑登记员集合，容量为4的LinkedHashSet
    private final Set<PropertyEditorRegistrar> propertyEditorRegistrars =
            new LinkedHashSet<PropertyEditorRegistrar>(4);

    //通用的类型转换器，重写了默认的属相编辑器机制
    private TypeConverter typeConverter;

    //默认的属性编辑器集合
    private final Map<Class<?>, Class<? extends PropertyEditor>> customEditors =
            new HashMap<Class<?>, Class<? extends PropertyEditor>>(4);

    //嵌入值转换器集合
    private final List<StringValueResolver> embeddedValueResolvers = new LinkedList<StringValueResolver>();

    //BeanPostProcessor处理器集合
    private final List<BeanPostProcessor> beanPostProcessors = new ArrayList<BeanPostProcessor>();

    //标记是否有InstantiationAwareBeanPostProcessors实例被注册
    private boolean hasInstantiationAwareBeanPostProcessors;

    //标记是否有DestructionAwareBeanPostProcessors实例被注册
    private boolean hasDestructionAwareBeanPostProcessors;

    //范围标识符和Scope实例的对应的Map
    private final Map<String, Scope> scopes = new HashMap<String, Scope>(8);

    //安全上下文Provider，可以得到安全管理器的安全上下文
    private SecurityContextProvider securityContextProvider;

    //合并后的Bean根定义的集合
    private final Map<String, RootBeanDefinition> mergedBeanDefinitions =
            new ConcurrentHashMap<String, RootBeanDefinition>(64);

    //至少被创建过一次的Bean的集合
    private final Map<String, Boolean> alreadyCreated = new ConcurrentHashMap<String, Boolean>(64);

    //当前正在创建的原型，当前线程相关
    private final ThreadLocal<Object> prototypesCurrentlyInCreation =
            new NamedThreadLocal<Object>("Prototype beans currently in creation");


    //空构造方法
    public AbstractBeanFactory() {
    }

    //指定父Bean工厂的构造方法
    public AbstractBeanFactory(BeanFactory parentBeanFactory) {
        this.parentBeanFactory = parentBeanFactory;
    }


    //---------------------------------------------------------------------
    // 3个getBean，BeanFactory接口的实现方法，实质是在调用doGetBean
    //---------------------------------------------------------------------

    public Object getBean(String name) throws BeansException {
        return doGetBean(name, null, null, false);
    }

    public <T> T getBean(String name, Class<T> requiredType) throws BeansException {
        return doGetBean(name, requiredType, null, false);
    }

    public Object getBean(String name, Object... args) throws BeansException {
        return doGetBean(name, null, args, false);
    }

    //    提供创建时需要参数列表的getBean
    public <T> T getBean(String name, Class<T> requiredType, Object... args) throws BeansException {
        return doGetBean(name, requiredType, args, false);
    }

    //从容器中获取bean的基本方法。
    @SuppressWarnings("unchecked")
    protected <T> T doGetBean(
            final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {

        final String beanName = transformedBeanName(name);//在aliasMap中取得的标准名
        Object bean;

        // Eagerly check singleton cache for manually registered singletons.
        Object sharedInstance = getSingleton(beanName);//首先在单例集合中取
        if (sharedInstance != null && args == null) {//如果取得到，没有指定参数
            if (logger.isDebugEnabled()) {//若Log允许调试
                if (isSingletonCurrentlyInCreation(beanName)) {//若正准备创建，输出日志
                    logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
                            "' that is not fully initialized yet - a consequence of a circular reference");
                }
                else {
                    logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
                }
            }
            ////根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            if (isPrototypeCurrentlyInCreation(beanName)) {//如果正在被创建，就抛出异常
                throw new BeanCurrentlyInCreationException(beanName);
            }

            BeanFactory parentBeanFactory = getParentBeanFactory();//取本容器的父容器
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {//若存在父容器，且本容器不存在对应的Bean定义
                String nameToLookup = originalBeanName(name);//取原始的Bean名
                if (args != null) {//若参数列表存在
                    // 那么用父容器根据原始Bean名和参数列表返回
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else {
                    // 参数列表不要求，那就直接根据原始名称和要求的类型返回
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }

            //如果不需要类型检查，标记其已经被创建
            if (!typeCheckOnly) {
                markBeanAsCreated(beanName);
            }

            //根据beanName取其根Bean定义
            final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
            checkMergedBeanDefinition(mbd, beanName, args);

            String[] dependsOn = mbd.getDependsOn();//得到这个根定义的所有依赖
            if (dependsOn != null) {
                for (String dependsOnBean : dependsOn) {
                    getBean(dependsOnBean);//注册这个Bean
                    //注册一个Bean和依赖于它的Bean（后参数依赖前参数）
                    registerDependentBean(dependsOnBean, beanName);
                }
            }

            // 如果Bean定义是单例，就在返回单例
            if (mbd.isSingleton()) {
                sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                    public Object getObject() throws BeansException {
                        try {
                            return createBean(beanName, mbd, args);
                        }
                        catch (BeansException ex) {
                            destroySingleton(beanName);
                            throw ex;
                        }
                    }
                });
                //根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
                bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
            }
            //如果是原型
            else if (mbd.isPrototype()) {
                // It's a prototype -> create a new instance.
                Object prototypeInstance = null;
                try {
                    beforePrototypeCreation(beanName);//原型创建前，与当前线程绑定
                    prototypeInstance = createBean(beanName, mbd, args);
                }
                finally {
                    afterPrototypeCreation(beanName);//原型创建后，与当前线程解除绑定
                }
                bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
            }

            else {//既不是单例又不是原型的情况
                String scopeName = mbd.getScope();
                final Scope scope = this.scopes.get(scopeName);//得到范围
                if (scope == null) {
                    throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
                }
                try {//根据范围创建实例
                    Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                        public Object getObject() throws BeansException {
                            beforePrototypeCreation(beanName);
                            try {
                                return createBean(beanName, mbd, args);//原型创建前，与当前线程绑定
                            }
                            finally {
                                ////原型创建后，与当前线程解除绑定
                                afterPrototypeCreation(beanName);
                            }
                        }
                    });
                    //根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
                    bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                }
                catch (IllegalStateException ex) {
                    throw new BeanCreationException(beanName,
                            "Scope '" + scopeName + "' is not active for the current thread; " +
                            "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                            ex);
                }
            }
        }

        //判断要求的类型是否和Bean实例的类型正在匹配
        if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
            try {
                return getTypeConverter().convertIfNecessary(bean, requiredType);//转换类型，不抛出异常就说明类型匹配
            }
            catch (TypeMismatchException ex) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Failed to convert bean '" + name + "' to required type [" +
                            ClassUtils.getQualifiedName(requiredType) + "]", ex);
                }
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
    }
    
    //判断本容器是否包含指定bean
    public boolean containsBean(String name) {
        String beanName = transformedBeanName(name);
        //    （如果是否包含单例 或 包含Bean定义）且 （为工厂Bean的产物 或 本身就是工厂bean），就返回true
        if (containsSingleton(beanName) || containsBeanDefinition(beanName)) {
            return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(name));
        }
        // 如果不包含单例且不包含Bean定义，就从父类去查找
        BeanFactory parentBeanFactory = getParentBeanFactory();
        return (parentBeanFactory != null && parentBeanFactory.containsBean(originalBeanName(name)));
    }

    //判断指定Bean是否为单例
    public boolean isSingleton(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        Object beanInstance = getSingleton(beanName, false);//首先从单例集合中取
        if (beanInstance != null) {//取不到，就判断它是不是FactoryBean的实例
            if (beanInstance instanceof FactoryBean) {    //    如果是，要求它是工厂Bean产生的实例或这个工厂bean是单例
                return (BeanFactoryUtils.isFactoryDereference(name) || ((FactoryBean<?>) beanInstance).isSingleton());
            }
            else {//    如果不是，要求它不是工厂Bean产生的实例
                return !BeanFactoryUtils.isFactoryDereference(name);
            }
        }//若虽然取不到，但是单例集合中包含它的名字，说明它是单例
        else if (containsSingleton(beanName)) {
            return true;
        }

        else {
            //从父工厂中去查询Bean定义
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                //父工厂找不到Bean定义，那就在父工厂根据原始名去查是否为单例
                return parentBeanFactory.isSingleton(originalBeanName(name));
            }
            //返回一个合并后的根Bean定义
            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            // In case of FactoryBean, return singleton status of created object if not a dereference.
            //若该根定义是单例
            if (mbd.isSingleton()) {
                if (isFactoryBean(beanName, mbd)) {    //若该根定义为工厂Bean
                    if (BeanFactoryUtils.isFactoryDereference(name)) {//判断是否为工厂产生的实例
                        return true;
                    }
                    //取对应的工厂，判断该工厂Bean是否为单例
                    FactoryBean<?> factoryBean = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                    return factoryBean.isSingleton();
                }
                else {    //    是否不为工厂Bean产生的实例（此时，即，该根定义不为工厂Bean，且不为工厂Bean产生的实例的时候，由于根定义是单例，那么它就是单例）
                    return !BeanFactoryUtils.isFactoryDereference(name);
                }
            }
            else {
                return false;
            }
        }
    }

    //判断是否为原型
    public boolean isPrototype(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        BeanFactory parentBeanFactory = getParentBeanFactory();//得到父工厂
        //若父工厂中的定义为原型，就为原型
        if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
            return parentBeanFactory.isPrototype(originalBeanName(name));
        }

        //若合并后的根定义为原型，且不是工厂Bean产生的实例、或本身是工厂Bean，那么就为原型
        RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
        if (mbd.isPrototype()) {
            return (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(beanName, mbd));
        }
        else {
            if (BeanFactoryUtils.isFactoryDereference(name)) {//若为工厂Bean产生的实例
                return false;
            }
            if (isFactoryBean(beanName, mbd)) {//若为工厂Bean，取它产生的Bean，判断SmartFactoryBean
                final FactoryBean<?> factoryBean = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
                if (System.getSecurityManager() != null) {
                    return AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
                        public Boolean run() {
                            return ((factoryBean instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factoryBean).isPrototype()) ||
                                    !factoryBean.isSingleton());
                        }
                    }, getAccessControlContext());
                }
                else {
                    return ((factoryBean instanceof SmartFactoryBean && ((SmartFactoryBean<?>) factoryBean).isPrototype()) ||
                            !factoryBean.isSingleton());
                }
            }
            else {
                return false;
            }
        }
    }

    //判断类型是否匹配
    public boolean isTypeMatch(String name, Class<?> targetType) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);
        Class<?> typeToMatch = (targetType != null ? targetType : Object.class);

        Object beanInstance = getSingleton(beanName, false);//取name对应的单例
        if (beanInstance != null) {
            if (beanInstance instanceof FactoryBean) {//若为工厂Bean
                //若不是工厂Bean产生的实例
                if (!BeanFactoryUtils.isFactoryDereference(name)) {
                    //取工厂Bean的类型与targetType进行对比
                    Class<?> type = getTypeForFactoryBean((FactoryBean<?>) beanInstance);
                    return (type != null && ClassUtils.isAssignable(typeToMatch, type));
                }
                else {
                    return ClassUtils.isAssignableValue(typeToMatch, beanInstance);
                }
            }
            //不是工厂Bean，那就直接判断
            else {
                return !BeanFactoryUtils.isFactoryDereference(name) &&
                        ClassUtils.isAssignableValue(typeToMatch, beanInstance);
            }
        }
        //单例表中，对应的Key没有值，也不包含Bean定义，说明没有注册，返回false
        else if (containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            return false;
        }
        //以下是包含Bean定义的情况
        else {
            //先查父类的Bean定义
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // No bean definition found in this factory -> delegate to parent.
                return parentBeanFactory.isTypeMatch(originalBeanName(name), targetType);
            }
            
            //直接查合并后的根定义
            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            //构建类型数组
            Class[] typesToMatch = (FactoryBean.class.equals(typeToMatch) ?
                    new Class[] {typeToMatch} : new Class[] {FactoryBean.class, typeToMatch});

            // Check decorated bean definition, if any: We assume it'll be easier
            // to determine the decorated bean's type than the proxy's type.
            //得到Bean定义的持有者
            BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
            if (dbd != null && !BeanFactoryUtils.isFactoryDereference(name)) {//若为Bean工厂生成的实例，先得到根定义
                RootBeanDefinition tbd = getMergedBeanDefinition(dbd.getBeanName(), dbd.getBeanDefinition(), mbd);
                Class<?> targetClass = predictBeanType(dbd.getBeanName(), tbd, typesToMatch);//得到预测的根定义
                if (targetClass != null && !FactoryBean.class.isAssignableFrom(targetClass)) {
                    return typeToMatch.isAssignableFrom(targetClass);
                }
            }

            Class<?> beanType = predictBeanType(beanName, mbd, typesToMatch);//预测后的类型
            if (beanType == null) {
                return false;
            }

            if (FactoryBean.class.isAssignableFrom(beanType)) {//BeanFactory是否为其子类
                if (!BeanFactoryUtils.isFactoryDereference(name)) {//若不为工厂Bean的产物
                    // If it's a FactoryBean, we want to look at what it creates, not the factory class.
                    beanType = getTypeForFactoryBean(beanName, mbd);
                    if (beanType == null) {
                        return false;
                    }
                }
            }
            else if (BeanFactoryUtils.isFactoryDereference(name)) {//若为工厂类Bean的产物
                beanType = predictBeanType(beanName, mbd, FactoryBean.class);//预测类型
                if (beanType == null || !FactoryBean.class.isAssignableFrom(beanType)) {
                    return false;
                }
            }

            return typeToMatch.isAssignableFrom(beanType);
        }
    }

    //返回类型
    public Class<?> getType(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        // Check manually registered singletons.
        Object beanInstance = getSingleton(beanName, false);
        if (beanInstance != null) {
            if (beanInstance instanceof FactoryBean && !BeanFactoryUtils.isFactoryDereference(name)) {
                return getTypeForFactoryBean((FactoryBean<?>) beanInstance);
            }
            else {
                return beanInstance.getClass();
            }
        }
        else if (containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            // null instance registered
            return null;
        }

        else {
            // No singleton instance found -> check bean definition.
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
                // No bean definition found in this factory -> delegate to parent.
                return parentBeanFactory.getType(originalBeanName(name));
            }

            RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);

            // Check decorated bean definition, if any: We assume it'll be easier
            // to determine the decorated bean's type than the proxy's type.
            BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
            if (dbd != null && !BeanFactoryUtils.isFactoryDereference(name)) {
                RootBeanDefinition tbd = getMergedBeanDefinition(dbd.getBeanName(), dbd.getBeanDefinition(), mbd);
                Class<?> targetClass = predictBeanType(dbd.getBeanName(), tbd);
                if (targetClass != null && !FactoryBean.class.isAssignableFrom(targetClass)) {
                    return targetClass;
                }
            }

            Class<?> beanClass = predictBeanType(beanName, mbd);

            // Check bean class whether we're dealing with a FactoryBean.
            if (beanClass != null && FactoryBean.class.isAssignableFrom(beanClass)) {
                if (!BeanFactoryUtils.isFactoryDereference(name)) {
                    // If it's a FactoryBean, we want to look at what it creates, not at the factory class.
                    return getTypeForFactoryBean(beanName, mbd);
                }
                else {
                    return beanClass;
                }
            }
            else {
                return (!BeanFactoryUtils.isFactoryDereference(name) ? beanClass : null);
            }
        }
    }

    //重写了，得到别名的方法。
    @Override
    public String[] getAliases(String name) {
        String beanName = transformedBeanName(name);
        List<String> aliases = new ArrayList<String>();
        boolean factoryPrefix = name.startsWith(FACTORY_BEAN_PREFIX);
        String fullBeanName = beanName;
        if (factoryPrefix) {
            fullBeanName = FACTORY_BEAN_PREFIX + beanName;
        }
        if (!fullBeanName.equals(name)) {
            aliases.add(fullBeanName);
        }
        String[] retrievedAliases = super.getAliases(beanName);
        for (String retrievedAlias : retrievedAliases) {
            String alias = (factoryPrefix ? FACTORY_BEAN_PREFIX : "") + retrievedAlias;
            if (!alias.equals(name)) {
                aliases.add(alias);
            }
        }
        if (!containsSingleton(beanName) && !containsBeanDefinition(beanName)) {
            BeanFactory parentBeanFactory = getParentBeanFactory();
            if (parentBeanFactory != null) {
                aliases.addAll(Arrays.asList(parentBeanFactory.getAliases(fullBeanName)));
            }
        }
        return StringUtils.toStringArray(aliases);
    }


    //---------------------------------------------------------------------
    // Implementation of HierarchicalBeanFactory interface
    //---------------------------------------------------------------------

    //返回本Bean工厂的父Bean工厂
    public BeanFactory getParentBeanFactory() {
        return this.parentBeanFactory;
    }

    //是否在本容器中（就是说，并不是工厂bean生产出来的）
    public boolean containsLocalBean(String name) {
        String beanName = transformedBeanName(name);    //    转换后的名字
        //（是否为单例或有对应的Bean定义） 且（不是工厂Bean生产出来的 或 本身就是工厂bean）
        return ((containsSingleton(beanName) || containsBeanDefinition(beanName)) &&
                (!BeanFactoryUtils.isFactoryDereference(name) || isFactoryBean(beanName)));
    }


    //---------------------------------------------------------------------
    // Implementation of ConfigurableBeanFactory interface
    //---------------------------------------------------------------------

    public void setParentBeanFactory(BeanFactory parentBeanFactory) {
        if (this.parentBeanFactory != null && this.parentBeanFactory != parentBeanFactory) {
            throw new IllegalStateException("Already associated with parent BeanFactory: " + this.parentBeanFactory);
        }
        this.parentBeanFactory = parentBeanFactory;
    }

    public void setBeanClassLoader(ClassLoader beanClassLoader) {
        this.beanClassLoader = (beanClassLoader != null ? beanClassLoader : ClassUtils.getDefaultClassLoader());
    }

    public ClassLoader getBeanClassLoader() {
        return this.beanClassLoader;
    }

    public void setTempClassLoader(ClassLoader tempClassLoader) {
        this.tempClassLoader = tempClassLoader;
    }

    public ClassLoader getTempClassLoader() {
        return this.tempClassLoader;
    }

    public void setCacheBeanMetadata(boolean cacheBeanMetadata) {
        this.cacheBeanMetadata = cacheBeanMetadata;
    }

    public boolean isCacheBeanMetadata() {
        return this.cacheBeanMetadata;
    }

    public void setBeanExpressionResolver(BeanExpressionResolver resolver) {
        this.beanExpressionResolver = resolver;
    }

    public BeanExpressionResolver getBeanExpressionResolver() {
        return this.beanExpressionResolver;
    }

    public void setConversionService(ConversionService conversionService) {
        this.conversionService = conversionService;
    }

    public ConversionService getConversionService() {
        return this.conversionService;
    }

    public void addPropertyEditorRegistrar(PropertyEditorRegistrar registrar) {
        Assert.notNull(registrar, "PropertyEditorRegistrar must not be null");
        this.propertyEditorRegistrars.add(registrar);
    }

    /**
     * Return the set of PropertyEditorRegistrars.
     */
    public Set<PropertyEditorRegistrar> getPropertyEditorRegistrars() {
        return this.propertyEditorRegistrars;
    }

    public void registerCustomEditor(Class<?> requiredType, Class<? extends PropertyEditor> propertyEditorClass) {
        Assert.notNull(requiredType, "Required type must not be null");
        Assert.isAssignable(PropertyEditor.class, propertyEditorClass);
        this.customEditors.put(requiredType, propertyEditorClass);
    }

    public void copyRegisteredEditorsTo(PropertyEditorRegistry registry) {
        registerCustomEditors(registry);
    }

    /**
     * Return the map of custom editors, with Classes as keys and PropertyEditor classes as values.
     */
    public Map<Class<?>, Class<? extends PropertyEditor>> getCustomEditors() {
        return this.customEditors;
    }

    public void setTypeConverter(TypeConverter typeConverter) {
        this.typeConverter = typeConverter;
    }

    //得到通用的类型转换器
    protected TypeConverter getCustomTypeConverter() {
        return this.typeConverter;
    }

    //得到类型转换器
    public TypeConverter getTypeConverter() {
        TypeConverter customConverter = getCustomTypeConverter();
        if (customConverter != null) {
            return customConverter;
        }
        else {//若本容器未注册类型转换器，就创建一个简单的类型转换器
            SimpleTypeConverter typeConverter = new SimpleTypeConverter();
            typeConverter.setConversionService(getConversionService());
            registerCustomEditors(typeConverter);
            return typeConverter;
        }
    }

    public void addEmbeddedValueResolver(StringValueResolver valueResolver) {
        Assert.notNull(valueResolver, "StringValueResolver must not be null");
        this.embeddedValueResolvers.add(valueResolver);
    }

    public String resolveEmbeddedValue(String value) {
        String result = value;
        for (StringValueResolver resolver : this.embeddedValueResolvers) {
            if (result == null) {
                return null;
            }
            result = resolver.resolveStringValue(result);
        }
        return result;
    }

    public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
        Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
        this.beanPostProcessors.remove(beanPostProcessor);
        this.beanPostProcessors.add(beanPostProcessor);
        if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
            this.hasInstantiationAwareBeanPostProcessors = true;
        }
        if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
            this.hasDestructionAwareBeanPostProcessors = true;
        }
    }

    public int getBeanPostProcessorCount() {
        return this.beanPostProcessors.size();
    }

    /**
     * Return the list of BeanPostProcessors that will get applied
     * to beans created with this factory.
     */
    public List<BeanPostProcessor> getBeanPostProcessors() {
        return this.beanPostProcessors;
    }

    /**
     * Return whether this factory holds a InstantiationAwareBeanPostProcessor
     * that will get applied to singleton beans on shutdown.
     * @see #addBeanPostProcessor
     * @see org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor
     */
    protected boolean hasInstantiationAwareBeanPostProcessors() {
        return this.hasInstantiationAwareBeanPostProcessors;
    }

    /**
     * Return whether this factory holds a DestructionAwareBeanPostProcessor
     * that will get applied to singleton beans on shutdown.
     * @see #addBeanPostProcessor
     * @see org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor
     */
    protected boolean hasDestructionAwareBeanPostProcessors() {
        return this.hasDestructionAwareBeanPostProcessors;
    }

    public void registerScope(String scopeName, Scope scope) {
        Assert.notNull(scopeName, "Scope identifier must not be null");
        Assert.notNull(scope, "Scope must not be null");
        if (SCOPE_SINGLETON.equals(scopeName) || SCOPE_PROTOTYPE.equals(scopeName)) {
            throw new IllegalArgumentException("Cannot replace existing scopes 'singleton' and 'prototype'");
        }
        this.scopes.put(scopeName, scope);
    }

    public String[] getRegisteredScopeNames() {
        return StringUtils.toStringArray(this.scopes.keySet());
    }

    public Scope getRegisteredScope(String scopeName) {
        Assert.notNull(scopeName, "Scope identifier must not be null");
        return this.scopes.get(scopeName);
    }

    /**
     * Set the security context provider for this bean factory. If a security manager
     * is set, interaction with the user code will be executed using the privileged
     * of the provided security context.
     */
    public void setSecurityContextProvider(SecurityContextProvider securityProvider) {
        this.securityContextProvider = securityProvider;
    }

    /**
     * Delegate the creation of the access control context to the
     * {@link #setSecurityContextProvider SecurityContextProvider}.
     */
    @Override
    public AccessControlContext getAccessControlContext() {
        return (this.securityContextProvider != null ?
                this.securityContextProvider.getAccessControlContext() :
                AccessController.getContext());
    }

    public void copyConfigurationFrom(ConfigurableBeanFactory otherFactory) {
        Assert.notNull(otherFactory, "BeanFactory must not be null");
        setBeanClassLoader(otherFactory.getBeanClassLoader());
        setCacheBeanMetadata(otherFactory.isCacheBeanMetadata());
        setBeanExpressionResolver(otherFactory.getBeanExpressionResolver());
        if (otherFactory instanceof AbstractBeanFactory) {
            AbstractBeanFactory otherAbstractFactory = (AbstractBeanFactory) otherFactory;
            this.customEditors.putAll(otherAbstractFactory.customEditors);
            this.propertyEditorRegistrars.addAll(otherAbstractFactory.propertyEditorRegistrars);
            this.beanPostProcessors.addAll(otherAbstractFactory.beanPostProcessors);
            this.hasInstantiationAwareBeanPostProcessors = this.hasInstantiationAwareBeanPostProcessors ||
                    otherAbstractFactory.hasInstantiationAwareBeanPostProcessors;
            this.hasDestructionAwareBeanPostProcessors = this.hasDestructionAwareBeanPostProcessors ||
                    otherAbstractFactory.hasDestructionAwareBeanPostProcessors;
            this.scopes.putAll(otherAbstractFactory.scopes);
            this.securityContextProvider = otherAbstractFactory.securityContextProvider;
        }
        else {
            setTypeConverter(otherFactory.getTypeConverter());
        }
    }

    //返回合并后的bean定义（父Bean定义和子Bean定义合并）
    public BeanDefinition getMergedBeanDefinition(String name) throws BeansException {
        String beanName = transformedBeanName(name);

        // Efficiently check whether bean definition exists in this factory.
        //若Bean定义不存在，且本容器父工厂为ConfigurableBeanFactory的实例，让父工厂来调用这个方法
        if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
            return ((ConfigurableBeanFactory) getParentBeanFactory()).getMergedBeanDefinition(beanName);
        }
        //否则直接从本地合并后的Bean定义中取
        return getMergedLocalBeanDefinition(beanName);
    }

    public boolean isFactoryBean(String name) throws NoSuchBeanDefinitionException {
        String beanName = transformedBeanName(name);

        Object beanInstance = getSingleton(beanName, false);
        if (beanInstance != null) {
            return (beanInstance instanceof FactoryBean);
        }
        else if (containsSingleton(beanName)) {
            // null instance registered
            return false;
        }

        // No singleton instance found -> check bean definition.
        if (!containsBeanDefinition(beanName) && getParentBeanFactory() instanceof ConfigurableBeanFactory) {
            // No bean definition found in this factory -> delegate to parent.
            return ((ConfigurableBeanFactory) getParentBeanFactory()).isFactoryBean(name);
        }

        return isFactoryBean(beanName, getMergedLocalBeanDefinition(beanName));
    }

    @Override
    public boolean isActuallyInCreation(String beanName) {
        return isSingletonCurrentlyInCreation(beanName) || isPrototypeCurrentlyInCreation(beanName);
    }

    //    判断指定的原型是否正在被创建
    protected boolean isPrototypeCurrentlyInCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        return (curVal != null &&
                (curVal.equals(beanName) || (curVal instanceof Set && ((Set<?>) curVal).contains(beanName))));
    }

    //原型创建前回调，需要子类重写
    @SuppressWarnings("unchecked")
    protected void beforePrototypeCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        if (curVal == null) {//原型创建状态与当前线程绑定
            this.prototypesCurrentlyInCreation.set(beanName);
        }
        else if (curVal instanceof String) {
            Set<String> beanNameSet = new HashSet<String>(2);
            beanNameSet.add((String) curVal);
            beanNameSet.add(beanName);
            this.prototypesCurrentlyInCreation.set(beanNameSet);
        }
        //这里多余了。。。
        else {
            Set<String> beanNameSet = (Set<String>) curVal;
            beanNameSet.add(beanName);
        }
    }

    //创建原型后，从当前线程解除绑定
    @SuppressWarnings("unchecked")
    protected void afterPrototypeCreation(String beanName) {
        Object curVal = this.prototypesCurrentlyInCreation.get();
        if (curVal instanceof String) {
            this.prototypesCurrentlyInCreation.remove();
        }
        else if (curVal instanceof Set) {
            Set<String> beanNameSet = (Set<String>) curVal;
            beanNameSet.remove(beanName);
            if (beanNameSet.isEmpty()) {
                this.prototypesCurrentlyInCreation.remove();
            }
        }
    }

    public void destroyBean(String beanName, Object beanInstance) {
        destroyBean(beanName, beanInstance, getMergedLocalBeanDefinition(beanName));
    }

    /**
     * Destroy the given bean instance (usually a prototype instance
     * obtained from this factory) according to the given bean definition.
     * @param beanName the name of the bean definition
     * @param beanInstance the bean instance to destroy
     * @param mbd the merged bean definition
     */
    protected void destroyBean(String beanName, Object beanInstance, RootBeanDefinition mbd) {
        new DisposableBeanAdapter(beanInstance, beanName, mbd, getBeanPostProcessors(), getAccessControlContext()).destroy();
    }

    public void destroyScopedBean(String beanName) {
        RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
        if (mbd.isSingleton() || mbd.isPrototype()) {
            throw new IllegalArgumentException(
                    "Bean name '" + beanName + "' does not correspond to an object in a mutable scope");
        }
        String scopeName = mbd.getScope();
        Scope scope = this.scopes.get(scopeName);
        if (scope == null) {
            throw new IllegalStateException("No Scope SPI registered for scope '" + scopeName + "'");
        }
        Object bean = scope.remove(beanName);
        if (bean != null) {
            destroyBean(beanName, bean, mbd);
        }
    }


    //---------------------------------------------------------------------
    // Implementation methods
    //---------------------------------------------------------------------

    //变换后的Bean名称（先去掉BeanFactory前缀，然后在aliasMap中取标准名）
    protected String transformedBeanName(String name) {
        return canonicalName(BeanFactoryUtils.transformedBeanName(name));
    }

    //返回原始的Bean名
    protected String originalBeanName(String name) {
        String beanName = transformedBeanName(name);
        if (name.startsWith(FACTORY_BEAN_PREFIX)) {
            beanName = FACTORY_BEAN_PREFIX + beanName;
        }
        return beanName;
    }

    /**
     * Initialize the given BeanWrapper with the custom editors registered
     * with this factory. To be called for BeanWrappers that will create
     * and populate bean instances.
     * <p>The default implementation delegates to {@link #registerCustomEditors}.
     * Can be overridden in subclasses.
     * @param bw the BeanWrapper to initialize
     */
    protected void initBeanWrapper(BeanWrapper bw) {
        bw.setConversionService(getConversionService());
        registerCustomEditors(bw);
    }

    /**
     * Initialize the given PropertyEditorRegistry with the custom editors
     * that have been registered with this BeanFactory.
     * <p>To be called for BeanWrappers that will create and populate bean
     * instances, and for SimpleTypeConverter used for constructor argument
     * and factory method type conversion.
     * @param registry the PropertyEditorRegistry to initialize
     */
    protected void registerCustomEditors(PropertyEditorRegistry registry) {
        PropertyEditorRegistrySupport registrySupport =
                (registry instanceof PropertyEditorRegistrySupport ? (PropertyEditorRegistrySupport) registry : null);
        if (registrySupport != null) {
            registrySupport.useConfigValueEditors();
        }
        if (!this.propertyEditorRegistrars.isEmpty()) {
            for (PropertyEditorRegistrar registrar : this.propertyEditorRegistrars) {
                try {
                    registrar.registerCustomEditors(registry);
                }
                catch (BeanCreationException ex) {
                    Throwable rootCause = ex.getMostSpecificCause();
                    if (rootCause instanceof BeanCurrentlyInCreationException) {
                        BeanCreationException bce = (BeanCreationException) rootCause;
                        if (isCurrentlyInCreation(bce.getBeanName())) {
                            if (logger.isDebugEnabled()) {
                                logger.debug("PropertyEditorRegistrar [" + registrar.getClass().getName() +
                                        "] failed because it tried to obtain currently created bean '" +
                                        ex.getBeanName() + "': " + ex.getMessage());
                            }
                            onSuppressedException(ex);
                            continue;
                        }
                    }
                    throw ex;
                }
            }
        }
        if (!this.customEditors.isEmpty()) {
            for (Map.Entry<Class<?>, Class<? extends PropertyEditor>> entry : this.customEditors.entrySet()) {
                Class<?> requiredType = entry.getKey();
                Class<? extends PropertyEditor> editorClass = entry.getValue();
                registry.registerCustomEditor(requiredType, BeanUtils.instantiateClass(editorClass));
            }
        }
    }

    //返回一个合并后的根Bean定义（父Bean定义和子Bean定义合并）（从当前容器取）
    protected RootBeanDefinition getMergedLocalBeanDefinition(String beanName) throws BeansException {
        // Quick check on the concurrent map first, with minimal locking.
        RootBeanDefinition mbd = this.mergedBeanDefinitions.get(beanName);//首先直接从合并根定义集合中取
        if (mbd != null) {
            return mbd;
        }
        //根据bean名和其对应的Bean定义，取其根Bean根定义
        return getMergedBeanDefinition(beanName, getBeanDefinition(beanName));
    }

    //根据Bean名和Bean定义取其Bean根定义
    protected RootBeanDefinition getMergedBeanDefinition(String beanName, BeanDefinition bd)
            throws BeanDefinitionStoreException {

        return getMergedBeanDefinition(beanName, bd, null);//调用重载方法
    }

    //根据Bean名称返回根定义（若给定的Bean定义为子Bean定义，那么合并它的父Bean定义）
    protected RootBeanDefinition getMergedBeanDefinition(
            String beanName, BeanDefinition bd, BeanDefinition containingBd)
            throws BeanDefinitionStoreException {

        synchronized (this.mergedBeanDefinitions) {
            RootBeanDefinition mbd = null;

            //若给定的Bean定义并没有包含子Bean定义，那么直接根据Bean名取根定义
            if (containingBd == null) {
                mbd = this.mergedBeanDefinitions.get(beanName);
            }

            if (mbd == null) {//若取不到
                if (bd.getParentName() == null) {//若Bean定义没有父类，就很简单了
                    if (bd instanceof RootBeanDefinition) {//若Bean定义是RootBeanDefinition的实例，克隆、强转后返回
                        mbd = ((RootBeanDefinition) bd).cloneBeanDefinition();
                    }
                    else {//否则，根据Bean定义，来构造一个根Bean定义
                        mbd = new RootBeanDefinition(bd);
                    }
                }
                else {//若Bean定义有父类
                    // Child bean definition: needs to be merged with parent.
                    BeanDefinition pbd;
                    try {
                        String parentBeanName = transformedBeanName(bd.getParentName());//取其父Bean定义的名字
                        if (!beanName.equals(parentBeanName)) {//若Bean名字并不是bd的父Bean的名字
                            pbd = getMergedBeanDefinition(parentBeanName);//根据父Bean定义名称来返回合并后的bean定义
                        }
                        else {//如果beanName对应的Bean就是bd的父Bean
                            if (getParentBeanFactory() instanceof ConfigurableBeanFactory) {//若父Bean工厂为ConfigurableBeanFactory的实例
                                //    那么强转成ConfigurableBeanFactory后再调用合并方法
                                pbd = ((ConfigurableBeanFactory) getParentBeanFactory()).getMergedBeanDefinition(parentBeanName);
                            }
                            else {//若父Bean工厂不是ConfigurableBeanFactory的实例，就抛出异常
                                throw new NoSuchBeanDefinitionException(bd.getParentName(),
                                        "Parent name '" + bd.getParentName() + "' is equal to bean name '" + beanName +
                                        "': cannot be resolved without an AbstractBeanFactory parent");
                            }
                        }
                    }
                    catch (NoSuchBeanDefinitionException ex) {
                        throw new BeanDefinitionStoreException(bd.getResourceDescription(), beanName,
                                "Could not resolve parent bean definition '" + bd.getParentName() + "'", ex);
                    }
                    // 深度复制
                    mbd = new RootBeanDefinition(pbd);//根据Bean定义生成一个根Bean定义
                    mbd.overrideFrom(bd);//将Bean定义的属性复制进自己的定义（根Bean定义）中
                }

                if (!StringUtils.hasLength(mbd.getScope())) {//如果根Bean定义未设置范围
                    mbd.setScope(RootBeanDefinition.SCOPE_SINGLETON);//那么设置其范围为单例
                }

                //    若本根Bean定义包含Bean定义、本根Bean定义为单例且包含的Bean定义并不是单例
                if (containingBd != null && !containingBd.isSingleton() && mbd.isSingleton()) {
                    mbd.setScope(containingBd.getScope());//    那么将本根Bean定义的范围设置为包含的Bean定义的范围
                }

                //若本根Bean定义不包含Bean定义，且是缓存Bean元数据（重写前均为true）且Bean定义是否有资格缓存（默认实现是，这个Bean已经创建便有资格）
                if (containingBd == null && isCacheBeanMetadata() && isBeanEligibleForMetadataCaching(beanName)) {
                    this.mergedBeanDefinitions.put(beanName, mbd);//放进mergedBeanDefinitions中
                }
            }

            return mbd;
        }
    }

    //检查Bean定义，抛出异常
    protected void checkMergedBeanDefinition(RootBeanDefinition mbd, String beanName, Object[] args)
            throws BeanDefinitionStoreException {

        if (mbd.isAbstract()) {
            throw new BeanIsAbstractException(beanName);
        }

        if (args != null && !mbd.isPrototype()) {
            throw new BeanDefinitionStoreException(
                    "Can only specify arguments for the getBean method when referring to a prototype bean definition");
        }
    }

    /**
     * Remove the merged bean definition for the specified bean,
     * recreating it on next access.
     * @param beanName the bean name to clear the merged definition for
     */
    protected void clearMergedBeanDefinition(String beanName) {
        this.mergedBeanDefinitions.remove(beanName);
    }

    //解析类型，处理异常
    protected Class<?> resolveBeanClass(final RootBeanDefinition mbd, String beanName, final Class<?>... typesToMatch)
            throws CannotLoadBeanClassException {
        try {
            if (mbd.hasBeanClass()) {
                return mbd.getBeanClass();
            }
            if (System.getSecurityManager() != null) {
                return AccessController.doPrivileged(new PrivilegedExceptionAction<Class<?>>() {
                    public Class<?> run() throws Exception {
                        return doResolveBeanClass(mbd, typesToMatch);
                    }
                }, getAccessControlContext());
            }
            else {
                return doResolveBeanClass(mbd, typesToMatch);
            }
        }
        catch (PrivilegedActionException pae) {
            ClassNotFoundException ex = (ClassNotFoundException) pae.getException();
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        }
        catch (ClassNotFoundException ex) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
        }
        catch (LinkageError err) {
            throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
        }
    }

    // 真正的解析类型
    private Class<?> doResolveBeanClass(RootBeanDefinition mbd, Class<?>... typesToMatch) throws ClassNotFoundException {
        if (!ObjectUtils.isEmpty(typesToMatch)) {
            ClassLoader tempClassLoader = getTempClassLoader();//找到临时的类加载器
            if (tempClassLoader != null) {
                if (tempClassLoader instanceof DecoratingClassLoader) {//若为装饰类加载器
                    DecoratingClassLoader dcl = (DecoratingClassLoader) tempClassLoader;
                    for (Class<?> typeToMatch : typesToMatch) {
                        dcl.excludeClass(typeToMatch.getName());
                    }
                }
                String className = mbd.getBeanClassName();
                return (className != null ? ClassUtils.forName(className, tempClassLoader) : null);
            }
        }
        return mbd.resolveBeanClass(getBeanClassLoader());
    }

    /**
     * Evaluate the given String as contained in a bean definition,
     * potentially resolving it as an expression.
     * @param value the value to check
     * @param beanDefinition the bean definition that the value comes from
     * @return the resolved value
     * @see #setBeanExpressionResolver
     */
    protected Object evaluateBeanDefinitionString(String value, BeanDefinition beanDefinition) {
        if (this.beanExpressionResolver == null) {
            return value;
        }
        Scope scope = (beanDefinition != null ? getRegisteredScope(beanDefinition.getScope()) : null);
        return this.beanExpressionResolver.evaluate(value, new BeanExpressionContext(this, scope));
    }

    //预测类型
    protected Class<?> predictBeanType(String beanName, RootBeanDefinition mbd, Class<?>... typesToMatch) {
        //若根Bena定义的工厂方法名存在，说明它是工厂Bean创建的，无法预测类型？
        if (mbd.getFactoryMethodName() != null) {
            return null;
        }
        //否则，解析Bean的Class
        return resolveBeanClass(mbd, beanName, typesToMatch);
    }

    /**
     * Check whether the given bean is defined as a {@link FactoryBean}.
     * @param beanName the name of the bean
     * @param mbd the corresponding bean definition
     */
    protected boolean isFactoryBean(String beanName, RootBeanDefinition mbd) {
        Class<?> beanType = predictBeanType(beanName, mbd, FactoryBean.class);
        return (beanType != null && FactoryBean.class.isAssignableFrom(beanType));
    }

    //返回工厂Bean的类型
    protected Class<?> getTypeForFactoryBean(String beanName, RootBeanDefinition mbd) {
        if (!mbd.isSingleton()) {
            return null;
        }
        try {
            FactoryBean<?> factoryBean = doGetBean(FACTORY_BEAN_PREFIX + beanName, FactoryBean.class, null, true);
            return getTypeForFactoryBean(factoryBean);
        }
        catch (BeanCreationException ex) {
            // Can only happen when getting a FactoryBean.
            if (logger.isDebugEnabled()) {
                logger.debug("Ignoring bean creation exception on FactoryBean type check: " + ex);
            }
            onSuppressedException(ex);
            return null;
        }
    }

    //标记这个Bean已经被创建
    protected void markBeanAsCreated(String beanName) {
        this.alreadyCreated.put(beanName, Boolean.TRUE);
    }

    /**
     * Determine whether the specified bean is eligible for having
     * its bean definition metadata cached.
     * @param beanName the name of the bean
     * @return {@code true} if the bean's metadata may be cached
     * at this point already
     */
    //若本根Bean定义包含Bean元定义作为缓存，这个方法应被之类覆盖，这里仅判断Bean是否已经被创建
    protected boolean isBeanEligibleForMetadataCaching(String beanName) {
        return this.alreadyCreated.containsKey(beanName);
    }

    /**
     * Remove the singleton instance (if any) for the given bean name,
     * but only if it hasn't been used for other purposes than type checking.
     * @param beanName the name of the bean
     * @return {@code true} if actually removed, {@code false} otherwise
     */
    protected boolean removeSingletonIfCreatedForTypeCheckOnly(String beanName) {
        if (!this.alreadyCreated.containsKey(beanName)) {
            removeSingleton(beanName);
            return true;
        }
        else {
            return false;
        }
    }

    //根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
    protected Object getObjectForBeanInstance(
            Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

        //如果这个Bean是工厂Bean创建的 且 这个Bean实例并不是FactoryBean实例，抛异常
        if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
            throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
        }

        //如果这个Bean实例并不是FactoryBean实例 或 这个Bean是工厂Bean创建的，直接返回
        if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
            return beanInstance;
        }

        //——————————以下都是 这个Bean实例是FactoryBean实例的情况
        Object object = null;
        if (mbd == null) {//若根Bean定义为空，取这个BeanFactory所生产的实例
            object = getCachedObjectForFactoryBean(beanName);
        }
        if (object == null) {//若取不到，那么手动取
            FactoryBean<?> factory = (FactoryBean<?>) beanInstance;//把这个实例转化成一个FactoryBean
            // Caches object obtained from FactoryBean if it is a singleton.
            if (mbd == null && containsBeanDefinition(beanName)) {//若根Bean定义为空，但是容器内有Bean定义
                mbd = getMergedLocalBeanDefinition(beanName);//返回合并后的Bean定义
            }
            boolean synthetic = (mbd != null && mbd.isSynthetic());//标记这个Bean定义是合并的
            object = getObjectFromFactoryBean(factory, beanName, !synthetic);//从工厂Bean中取
        }
        return object;
    }

    //判断给定的Bean是否被使用过
    public boolean isBeanNameInUse(String beanName) {
        //若是别名 或 并非工厂bean生产出来的 或 被其他某个bean所依赖，那么判断其被使用过
        return isAlias(beanName) || containsLocalBean(beanName) || hasDependentBean(beanName);
    }

    /**
     * Determine whether the given bean requires destruction on shutdown.
     * <p>The default implementation checks the DisposableBean interface as well as
     * a specified destroy method and registered DestructionAwareBeanPostProcessors.
     * @param bean the bean instance to check
     * @param mbd the corresponding bean definition
     * @see org.springframework.beans.factory.DisposableBean
     * @see AbstractBeanDefinition#getDestroyMethodName()
     * @see org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor
     */
    protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {
        return (bean != null &&
                (DisposableBeanAdapter.hasDestroyMethod(bean, mbd) || hasDestructionAwareBeanPostProcessors()));
    }

    /**
     * Add the given bean to the list of disposable beans in this factory,
     * registering its DisposableBean interface and/or the given destroy method
     * to be called on factory shutdown (if applicable). Only applies to singletons.
     * @param beanName the name of the bean
     * @param bean the bean instance
     * @param mbd the bean definition for the bean
     * @see RootBeanDefinition#isSingleton
     * @see RootBeanDefinition#getDependsOn
     * @see #registerDisposableBean
     * @see #registerDependentBean
     */
    protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
        AccessControlContext acc = (System.getSecurityManager() != null ? getAccessControlContext() : null);
        if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
            if (mbd.isSingleton()) {
                // Register a DisposableBean implementation that performs all destruction
                // work for the given bean: DestructionAwareBeanPostProcessors,
                // DisposableBean interface, custom destroy method.
                registerDisposableBean(beanName,
                        new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
            }
            else {
                // A bean with a custom scope...
                Scope scope = this.scopes.get(mbd.getScope());
                if (scope == null) {
                    throw new IllegalStateException("No Scope registered for scope '" + mbd.getScope() + "'");
                }
                scope.registerDestructionCallback(beanName,
                        new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors(), acc));
            }
        }
    }


    //---------------------------------------------------------------------
    // Abstract methods to be implemented by subclasses
    //---------------------------------------------------------------------

    //标记是否包含Bean定义的方法
    protected abstract boolean containsBeanDefinition(String beanName);

    //根据Bean名返回其BeanDefinition
    protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;

    //根据指定的bean定义和bean名、参数，创建对象
    protected abstract Object createBean(String beanName, RootBeanDefinition mbd, Object[] args)
            throws BeanCreationException;

}

FactoryBeanRegistrySupport，并且实现了BeanFactory重要的第三级接口——ConfigurableBeanFactory。需要具体了解这个接口，可以去看我之前的接口分析——Spring源码分析——BeanFactory体系之接口详细分析 。ConfigurableBeanFactory是一个非常复杂的接口，继承了HierarchicalBeanFactory和SingletonBeanRegistry，主要实现了工厂创建、注册Bean、单例类注册等各种功能。

　　AbstractBeanFactory实现了ConfigurableBeanFactory接口的绝大多数方法，实现了Bean工厂的许多重要功能，如BeanDefinition、RootBeanDefinition、原型、单例相关的各种操作。

　　下面列出一些主要方法实现，其他的方法说明，可具体参照上文我贴出的大部分注释过的源码。

（1）、从容器中获取bean的方法——doGetBean：

@SuppressWarnings("unchecked")
    protected <T> T doGetBean(
            final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
            throws BeansException {

        final String beanName = transformedBeanName(name);//在aliasMap中取得的标准名
        Object bean;

        // Eagerly check singleton cache for manually registered singletons.
        Object sharedInstance = getSingleton(beanName);//首先在单例集合中取
        if (sharedInstance != null && args == null) {//如果取得到，没有指定参数
            if (logger.isDebugEnabled()) {//若Log允许调试
                if (isSingletonCurrentlyInCreation(beanName)) {//若正准备创建，输出日志
                    logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
                            "' that is not fully initialized yet - a consequence of a circular reference");
                }
                else {
                    logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
                }
            }
            ////根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
            bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
        }

        else {
            if (isPrototypeCurrentlyInCreation(beanName)) {//如果正在被创建，就抛出异常
                throw new BeanCurrentlyInCreationException(beanName);
            }

            BeanFactory parentBeanFactory = getParentBeanFactory();//取本容器的父容器
            if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {//若存在父容器，且本容器不存在对应的Bean定义
                String nameToLookup = originalBeanName(name);//取原始的Bean名
                if (args != null) {//若参数列表存在
                    // 那么用父容器根据原始Bean名和参数列表返回
                    return (T) parentBeanFactory.getBean(nameToLookup, args);
                }
                else {
                    // 参数列表不要求，那就直接根据原始名称和要求的类型返回
                    return parentBeanFactory.getBean(nameToLookup, requiredType);
                }
            }

            //如果不需要类型检查，标记其已经被创建
            if (!typeCheckOnly) {
                markBeanAsCreated(beanName);
            }

            //根据beanName取其根Bean定义
            final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
            checkMergedBeanDefinition(mbd, beanName, args);

            String[] dependsOn = mbd.getDependsOn();//得到这个根定义的所有依赖
            if (dependsOn != null) {
                for (String dependsOnBean : dependsOn) {
                    getBean(dependsOnBean);//注册这个Bean
                    //注册一个Bean和依赖于它的Bean（后参数依赖前参数）
                    registerDependentBean(dependsOnBean, beanName);
                }
            }

            // 如果Bean定义是单例，就在返回单例
            if (mbd.isSingleton()) {
                sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
                    public Object getObject() throws BeansException {
                        try {
                            return createBean(beanName, mbd, args);
                        }
                        catch (BeansException ex) {
                            destroySingleton(beanName);
                            throw ex;
                        }
                    }
                });
                //根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
                bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
            }
            //如果是原型
            else if (mbd.isPrototype()) {
                // It's a prototype -> create a new instance.
                Object prototypeInstance = null;
                try {
                    beforePrototypeCreation(beanName);//原型创建前，与当前线程绑定
                    prototypeInstance = createBean(beanName, mbd, args);
                }
                finally {
                    afterPrototypeCreation(beanName);//原型创建后，与当前线程解除绑定
                }
                bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
            }

            else {//既不是单例又不是原型的情况
                String scopeName = mbd.getScope();
                final Scope scope = this.scopes.get(scopeName);//得到范围
                if (scope == null) {
                    throw new IllegalStateException("No Scope registered for scope '" + scopeName + "'");
                }
                try {//根据范围创建实例
                    Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
                        public Object getObject() throws BeansException {
                            beforePrototypeCreation(beanName);
                            try {
                                return createBean(beanName, mbd, args);//原型创建前，与当前线程绑定
                            }
                            finally {
                                ////原型创建后，与当前线程解除绑定
                                afterPrototypeCreation(beanName);
                            }
                        }
                    });
                    //根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例
                    bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
                }
                catch (IllegalStateException ex) {
                    throw new BeanCreationException(beanName,
                            "Scope '" + scopeName + "' is not active for the current thread; " +
                            "consider defining a scoped proxy for this bean if you intend to refer to it from a singleton",
                            ex);
                }
            }
        }

        //判断要求的类型是否和Bean实例的类型正在匹配
        if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
            try {
                return getTypeConverter().convertIfNecessary(bean, requiredType);//转换类型，不抛出异常就说明类型匹配
            }
            catch (TypeMismatchException ex) {
                if (logger.isDebugEnabled()) {
                    logger.debug("Failed to convert bean '" + name + "' to required type [" +
                            ClassUtils.getQualifiedName(requiredType) + "]", ex);
                }
                throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
            }
        }
        return (T) bean;
    }

下面对这个方法进行简要的解释：

　　<1>、这个方法形参为final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly，分别表示Bean的名称、要求返回的Bean的类型、取Bean时提供的参数数组 以及 是否需要类型检查。哦

　　<2>、final String beanName = transformedBeanName(name); 这个方法是从aliasMap中取得对应的标准名。方法实现是，首先去掉name的 FACTORY_BEAN_PREFIX 前缀（如果是工厂Bean本身，那么Bean名有这个前缀），然后调用SimpleAliasRegistry的canonicalName方法。上篇博客已经介绍过SimpleAliasRegistry了，这里贴一下这个方法的源码：

/*
* 根据name这个Key，在aliasMap中不断循环的取对应的value，如果取得到，就继续根据这个value取值，不断循环继续。
* 直到取不到，就把这个在aliasMap中无对应值的key返回。这个动作，叫规范名
*/

public String canonicalName(String name) {
    String canonicalName = name;    //规范名
    // Handle aliasing...
    String resolvedName;//已解析名
    do {
        resolvedName = this.aliasMap.get(canonicalName);//aliasMap中规范名对应的值赋值给已解析名
        if (resolvedName != null) {//如果已解析名存在（即规范名在aliasMap中有对应的值）
            canonicalName = resolvedName;   // 这个已解析名赋值给标准名
        }
    } while (resolvedName != null);//不断循环，直到已解析名不存在
    return canonicalName;
}

　　<3>、首先根据标准名beanName，在单例缓存中取对应的Bean：Object sharedInstance = getSingleton(beanName);

　　<4>、如果取得到，且args为空，根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例：bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);然后结束整个方法。这个方法源码如下：

//根据给定的实例是否为工厂Bean，返回它自己或工厂Bean创建的实例

protected Object getObjectForBeanInstance(
            Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

        //如果这个Bean是工厂Bean创建的 且 这个Bean实例并不是FactoryBean实例，抛异常
        if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
            throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
        }

        //如果这个Bean实例并不是FactoryBean实例 或 这个Bean是工厂Bean创建的，直接返回
        if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
            return beanInstance;
        }

        //——————————以下都是 这个Bean实例是FactoryBean实例的情况
        Object object = null;
        if (mbd == null) {//若根Bean定义为空，取这个BeanFactory所生产的实例
            object = getCachedObjectForFactoryBean(beanName);
        }
        if (object == null) {//若取不到，那么手动取
            FactoryBean<?> factory = (FactoryBean<?>) beanInstance;//把这个实例转化成一个FactoryBean
            // Caches object obtained from FactoryBean if it is a singleton.
            if (mbd == null && containsBeanDefinition(beanName)) {//若根Bean定义为空，但是容器内有Bean定义
                mbd = getMergedLocalBeanDefinition(beanName);//返回合并后的Bean定义
            }
            boolean synthetic = (mbd != null && mbd.isSynthetic());//标记这个Bean定义是合并的
            object = getObjectFromFactoryBean(factory, beanName, !synthetic);//从工厂Bean中取
        }
        return object;

　　<5>、如果取不到、或 args 不为空（下面都是基于这个条件）：

（如果对应的Bean正在被创建，就抛出异常）首先用父容器（如果本容器有的话）根据给出的形参取对应的Bean。

　　<6>、此时，判断，如果不需要类型检查，标记其已经被创建。

　　<7>、根据beanName取本地合并后的RootBeanDefinition（这个方法getMergedLocalBeanDefinition涉及到多层BeanDefinition相关的调用），然后检查一下。然后根据这个RootBeanDefinition，注册这个Bean和它的所有依赖。

　　<8>、如果这个RootBeanDefinition是单例，先根据beanName从单例缓存中取，取不到就创建一个匿名内部Bean工厂，创建一个单例，直接结束方法。

　　<9>、如果这个RootBeanDefinition是原型，就直接创建一个Bean返回，并在创建前把beanName与当前线程绑定，创建后解绑。

　　<10>、如果这个RootBeanDefinition既不是单例，又不是原型，那么根据这个RootBeanDefinition定义的范围Scope，直接创建一个scopedInstance。

　　<11>、若这个scopedInstance为工厂Bean，就得到它创建的实例，否则得到它自身。

　　<12>、对<9>或<11>中最后产生的Bean就进行一次检查，要求这个产生的Bean的类型是否和Bean实例的类型匹配，不匹配就抛出异常。

　　以上就是这个doGetBean方法了。