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《深入理解Spring系列之一：开篇》中提到在Spring容器启动的过程中，会将类解析成Spring内部的BeanDefinition结构，并将BeanDefinition存储到一个叫DefaultListableBeanFactory中，本篇将深入分析BeanFactory

首先，看一下DefaultListableBeanFactory的类图，

可以看到 DefaultListableBeanFactory 间接实现了BeanFactory接口，先来分析一下这个BeanFactory，直接查看BeanFactory源代码，

public interface BeanFactory {	/**	 * Used to dereference a {@link FactoryBean} instance and distinguish it from	 * beans created by the FactoryBean. For example, if the bean named	 * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}	 * will return the factory, not the instance returned by the factory.	 */	String FACTORY_BEAN_PREFIX = "&";	/**	 * Return an instance, which may be shared or independent, of the specified bean.	 * 
This method allows a Spring BeanFactory to be used as a replacement for the	 * Singleton or Prototype design pattern. Callers may retain references to	 * returned objects in the case of Singleton beans.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to retrieve	 * @return an instance of the bean	 * @throws NoSuchBeanDefinitionException if there is no bean definition	 * with the specified name	 * @throws BeansException if the bean could not be obtained	 */	Object getBean(String name) throws BeansException;	/**	 * Return an instance, which may be shared or independent, of the specified bean.	 * 
Behaves the same as {@link #getBean(String)}, but provides a measure of type	 * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the	 * required type. This means that ClassCastException can't be thrown on casting	 * the result correctly, as can happen with {@link #getBean(String)}.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to retrieve	 * @param requiredType type the bean must match. Can be an interface or superclass	 * of the actual class, or {@code null} for any match. For example, if the value	 * is {@code Object.class}, this method will succeed whatever the class of the	 * returned instance.	 * @return an instance of the bean	 * @throws NoSuchBeanDefinitionException if there is no such bean definition	 * @throws BeanNotOfRequiredTypeException if the bean is not of the required type	 * @throws BeansException if the bean could not be created	 */	
     
       T getBean(String name, Class
      
        requiredType) throws BeansException;	/**	 * Return an instance, which may be shared or independent, of the specified bean.	 * 
      
     
Allows for specifying explicit constructor arguments / factory method arguments,	 * overriding the specified default arguments (if any) in the bean definition.	 * @param name the name of the bean to retrieve	 * @param args arguments to use when creating a bean instance using explicit arguments	 * (only applied when creating a new instance as opposed to retrieving an existing one)	 * @return an instance of the bean	 * @throws NoSuchBeanDefinitionException if there is no such bean definition	 * @throws BeanDefinitionStoreException if arguments have been given but	 * the affected bean isn't a prototype	 * @throws BeansException if the bean could not be created	 * @since 2.5	 */	Object getBean(String name, Object... args) throws BeansException;	/**	 * Return the bean instance that uniquely matches the given object type, if any.	 * 
This method goes into {@link ListableBeanFactory} by-type lookup territory	 * but may also be translated into a conventional by-name lookup based on the name	 * of the given type. For more extensive retrieval operations across sets of beans,	 * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.	 * @param requiredType type the bean must match; can be an interface or superclass.	 * {@code null} is disallowed.	 * @return an instance of the single bean matching the required type	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found	 * @throws BeansException if the bean could not be created	 * @since 3.0	 * @see ListableBeanFactory	 */	
     
       T getBean(Class
      
        requiredType) throws BeansException;	/**	 * Return an instance, which may be shared or independent, of the specified bean.	 * 
      
     
Allows for specifying explicit constructor arguments / factory method arguments,	 * overriding the specified default arguments (if any) in the bean definition.	 * 
This method goes into {@link ListableBeanFactory} by-type lookup territory	 * but may also be translated into a conventional by-name lookup based on the name	 * of the given type. For more extensive retrieval operations across sets of beans,	 * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.	 * @param requiredType type the bean must match; can be an interface or superclass.	 * {@code null} is disallowed.	 * @param args arguments to use when creating a bean instance using explicit arguments	 * (only applied when creating a new instance as opposed to retrieving an existing one)	 * @return an instance of the bean	 * @throws NoSuchBeanDefinitionException if there is no such bean definition	 * @throws BeanDefinitionStoreException if arguments have been given but	 * the affected bean isn't a prototype	 * @throws BeansException if the bean could not be created	 * @since 4.1	 */	
     
       T getBean(Class
      
        requiredType, Object... args) throws BeansException;	/**	 * Does this bean factory contain a bean definition or externally registered singleton	 * instance with the given name?	 * 
      
     
If the given name is an alias, it will be translated back to the corresponding	 * canonical bean name.	 * 
If this factory is hierarchical, will ask any parent factory if the bean cannot	 * be found in this factory instance.	 * 
If a bean definition or singleton instance matching the given name is found,	 * this method will return {@code true} whether the named bean definition is concrete	 * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}	 * return value from this method does not necessarily indicate that {@link #getBean}	 * will be able to obtain an instance for the same name.	 * @param name the name of the bean to query	 * @return whether a bean with the given name is present	 */	boolean containsBean(String name);	/**	 * Is this bean a shared singleton? That is, will {@link #getBean} always	 * return the same instance?	 * 
Note: This method returning {@code false} does not clearly indicate	 * independent instances. It indicates non-singleton instances, which may correspond	 * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly	 * check for independent instances.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to query	 * @return whether this bean corresponds to a singleton instance	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name	 * @see #getBean	 * @see #isPrototype	 */	boolean isSingleton(String name) throws NoSuchBeanDefinitionException;	/**	 * Is this bean a prototype? That is, will {@link #getBean} always return	 * independent instances?	 * 
Note: This method returning {@code false} does not clearly indicate	 * a singleton object. It indicates non-independent instances, which may correspond	 * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly	 * check for a shared singleton instance.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to query	 * @return whether this bean will always deliver independent instances	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name	 * @since 2.0.3	 * @see #getBean	 * @see #isSingleton	 */	boolean isPrototype(String name) throws NoSuchBeanDefinitionException;	/**	 * Check whether the bean with the given name matches the specified type.	 * More specifically, check whether a {@link #getBean} call for the given name	 * would return an object that is assignable to the specified target type.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to query	 * @param typeToMatch the type to match against (as a {@code ResolvableType})	 * @return {@code true} if the bean type matches,	 * {@code false} if it doesn't match or cannot be determined yet	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name	 * @since 4.2	 * @see #getBean	 * @see #getType	 */	boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;	/**	 * Check whether the bean with the given name matches the specified type.	 * More specifically, check whether a {@link #getBean} call for the given name	 * would return an object that is assignable to the specified target type.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to query	 * @param typeToMatch the type to match against (as a {@code Class})	 * @return {@code true} if the bean type matches,	 * {@code false} if it doesn't match or cannot be determined yet	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name	 * @since 2.0.1	 * @see #getBean	 * @see #getType	 */	boolean isTypeMatch(String name, Class
      typeToMatch) throws NoSuchBeanDefinitionException;	/**	 * Determine the type of the bean with the given name. More specifically,	 * determine the type of object that {@link #getBean} would return for the given name.	 * 
For a {@link FactoryBean}, return the type of object that the FactoryBean creates,	 * as exposed by {@link FactoryBean#getObjectType()}.	 * 
Translates aliases back to the corresponding canonical bean name.	 * Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the name of the bean to query	 * @return the type of the bean, or {@code null} if not determinable	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name	 * @since 1.1.2	 * @see #getBean	 * @see #isTypeMatch	 */	Class
      getType(String name) throws NoSuchBeanDefinitionException;	/**	 * Return the aliases for the given bean name, if any.	 * All of those aliases point to the same bean when used in a {@link #getBean} call.	 * 
If the given name is an alias, the corresponding original bean name	 * and other aliases (if any) will be returned, with the original bean name	 * being the first element in the array.	 * 
Will ask the parent factory if the bean cannot be found in this factory instance.	 * @param name the bean name to check for aliases	 * @return the aliases, or an empty array if none	 * @see #getBean	 */	String[] getAliases(String name);}复制代码

从接口中的方法名可以很容易的理解每个方法的意图，最常用或者最常见的就是getBean方法，用于获取Bean的实例。BeanFactory是用于访问Spring Bean容器的根接口，是一个单纯的Bean工厂，也就是常说的IOC容器的顶层定义，各种IOC容器是在其基础上为了满足不同需求而扩展的，包括经常使用的ApplicationContext。

DefaultListableBeanFactory是整个Bean加载的核心部分，是Spring注册及加载Bean的默认实现。下面列出了DefaultListableBeanFactory源代码中两个重要的属性，

/** Map of bean definition objects, keyed by bean name */	private final Map
    
      beanDefinitionMap = new ConcurrentHashMap
     
      (256);	/** List of bean definition names, in registration order */	private volatile List
      
        beanDefinitionNames = new ArrayList
       
        (256);复制代码
       
      
     
    

其中，bean的定义被解析成 BeanDefinition，同时解析得到 beanName，将beanName和BeanDefinition存储到beanDefinitionMap中，同时会将beanName存储到beanDefinitionNames中。