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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 <i>created</i> 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.
* <p>This method allows a Spring BeanFactory to be used as a replacement for the
* Singleton or Prototype design pattern. Callers may retain references to
* returned objects in the case of Singleton beans.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to retrieve
* @return an instance of the bean
* @throws NoSuchBeanDefinitionException if there is no bean 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.
* <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
* safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
* required type. This means that ClassCastException can't be thrown on casting
* the result correctly, as can happen with {@link #getBean(String)}.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to retrieve
* @param requiredType type the bean must match. Can be an interface or superclass
* 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> T getBean(String name, Class<T> requiredType) throws BeansException;
/**
* Return an instance, which may be shared or independent, of the specified bean.
* <p>Allows for specifying explicit constructor arguments / factory method arguments,
* overriding the specified default arguments (if any) in the bean definition.
* @param name the name of the bean to retrieve
* @param args arguments to use when creating a bean instance using explicit arguments
* (only applied when creating a new instance as opposed to retrieving an existing one)
* @return an instance of the bean
* @throws NoSuchBeanDefinitionException if there is no such bean definition
* @throws BeanDefinitionStoreException if arguments have been given but
* the affected bean isn't a prototype
* @throws BeansException if the bean could not be created
* @since 2.5
*/
Object getBean(String name, Object... args) throws BeansException;
/**
* Return the bean instance that uniquely matches the given object type, if any.
* <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
* but may also be translated into a conventional by-name lookup based on the name
* of the given type. For more extensive retrieval operations across sets of beans,
* use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
* @param requiredType type the bean must match; can be an interface or superclass.
* {@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> T getBean(Class<T> requiredType) throws BeansException;
/**
* Return an instance, which may be shared or independent, of the specified bean.
* <p>Allows for specifying explicit constructor arguments / factory method arguments,
* overriding the specified default arguments (if any) in the bean definition.
* <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
* but may also be translated into a conventional by-name lookup based on the name
* of the given type. For more extensive retrieval operations across sets of beans,
* use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
* @param requiredType type the bean must match; can be an interface or superclass.
* {@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> T getBean(Class<T> requiredType, Object... args) throws BeansException;
/**
* Does this bean factory contain a bean definition or externally registered singleton
* instance with the given name?
* <p>If the given name is an alias, it will be translated back to the corresponding
* canonical bean name.
* <p>If this factory is hierarchical, will ask any parent factory if the bean cannot
* be found in this factory instance.
* <p>If a bean definition or singleton instance matching the given name is found,
* this method will return {@code true} whether the named bean definition is concrete
* or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}
* return value from this method does not necessarily indicate that {@link #getBean}
* will be able to obtain an instance for the same name.
* @param name the name of the bean to query
* @return whether a bean with the given name is present
*/
boolean containsBean(String name);
/**
* Is this bean a shared singleton? That is, will {@link #getBean} always
* return the same instance?
* <p>Note: This method returning {@code false} does not clearly indicate
* independent instances. It indicates non-singleton instances, which may correspond
* to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly
* check for independent instances.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to query
* @return whether this bean corresponds to a singleton instance
* @throws NoSuchBeanDefinitionException if there is no bean with the given name
* @see #getBean
* @see #isPrototype
*/
boolean isSingleton(String name) throws NoSuchBeanDefinitionException;
/**
* Is this bean a prototype? That is, will {@link #getBean} always return
* independent instances?
* <p>Note: This method returning {@code false} does not clearly indicate
* a singleton object. It indicates non-independent instances, which may correspond
* to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly
* check for a shared singleton instance.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to query
* @return whether this bean will always deliver independent instances
* @throws NoSuchBeanDefinitionException if there is no bean with the given name
* @since 2.0.3
* @see #getBean
* @see #isSingleton
*/
boolean isPrototype(String name) throws NoSuchBeanDefinitionException;
/**
* Check whether the bean with the given name matches the specified type.
* More specifically, check whether a {@link #getBean} call for the given name
* would return an object that is assignable to the specified target type.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to query
* @param typeToMatch the type to match against (as a {@code ResolvableType})
* @return {@code true} if the bean type matches,
* {@code false} if it doesn't match or cannot be determined yet
* @throws NoSuchBeanDefinitionException if there is no bean with the given name
* @since 4.2
* @see #getBean
* @see #getType
*/
boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;
/**
* Check whether the bean with the given name matches the specified type.
* More specifically, check whether a {@link #getBean} call for the given name
* would return an object that is assignable to the specified target type.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to query
* @param typeToMatch the type to match against (as a {@code Class})
* @return {@code true} if the bean type matches,
* {@code false} if it doesn't match or cannot be determined yet
* @throws NoSuchBeanDefinitionException if there is no bean with the given name
* @since 2.0.1
* @see #getBean
* @see #getType
*/
boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;
/**
* Determine the type of the bean with the given name. More specifically,
* determine the type of object that {@link #getBean} would return for the given name.
* <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
* as exposed by {@link FactoryBean#getObjectType()}.
* <p>Translates aliases back to the corresponding canonical bean name.
* Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the name of the bean to query
* @return the type of the bean, or {@code null} if not determinable
* @throws NoSuchBeanDefinitionException if there is no bean with the given name
* @since 1.1.2
* @see #getBean
* @see #isTypeMatch
*/
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.
* <p>If the given name is an alias, the corresponding original bean name
* and other aliases (if any) will be returned, with the original bean name
* being the first element in the array.
* <p>Will ask the parent factory if the bean cannot be found in this factory instance.
* @param name the bean name to check for aliases
* @return the aliases, or an empty array if none
* @see #getBean
*/
String[] getAliases(String name);
}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<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<String, BeanDefinition>(256);
/** List of bean definition names, in registration order */
private volatile List<String> beanDefinitionNames = new ArrayList<String>(256);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。