Spring bean container 的根接口，也是一个bean容器的基本功能，更深一步的接口像ListableBeanFactory 和 ConfigurableBeanFactory 都是 为特殊目标设计的
这个接口的实现将维护一定属性的的bean定义，每个bean用一个唯一的字符串名字来识别。
This interface is implemented by objects that hold a number of bean definitions,each uniquely identified by a String name. Depending on the bean definition,the factory will return either an independent instance of a contained object (the Prototype design pattern), or a single shared instance (a superior alternative to the Singleton design pattern, in which the instance is a singleton in the scope of the factory). Which type of instance will be returned depends on the bean factory configuration
The point of this approach is that the BeanFactory is a central registry of application components, and centralizes configuration of application components
Note that it is generally better to rely on Dependency Injection("push" configuration) to configure application objects through setters or constructors, rather than use any form of "pull" configuration like a BeanFactory lookup. Spring‘s Dependency Injection functionality is implemented using this BeanFactory interface and its subinterfaces.
Normally a BeanFactory will load bean definitions stored in a configuration source (such as an XML document), and use the {@code org.springframework.beans} package to configure the beans. However, an implementation could simply return Java objects it creates as necessary directly in Java code. There are no constraints on how the definitions could be stored: LDAP, RDBMS, XML,properties file, etc. Implementations are encouraged to support references amongst beans (Dependency Injection).
In contrast to the methods in {@link ListableBeanFactory}, all of the operations in this interface will also check parent factories if this is a {@link HierarchicalBeanFactory}. If a bean is not found in this factory instance,the immediate parent factory will be asked. Beans in this factory instance are supposed to override beans of the same name in any parent factory.
Bean factory implementations should support the standard bean lifecycle interfaces as far as possible. The full set of initialization methods and their standard order is:<br>
* 1. BeanNameAware‘s {@code setBeanName}<br>
* 2. BeanClassLoaderAware‘s {@code setBeanClassLoader}<br>
* 3. BeanFactoryAware‘s {@code setBeanFactory}<br>
* 4. ResourceLoaderAware‘s {@code setResourceLoader}
* (only applicable when running in an application context)<br>
* 5. ApplicationEventPublisherAware‘s {@code setApplicationEventPublisher}
* (only applicable when running in an application context)<br>
* 6. MessageSourceAware‘s {@code setMessageSource}
* (only applicable when running in an application context)<br>
* 7. ApplicationContextAware‘s {@code setApplicationContext}
* (only applicable when running in an application context)<br>
* 8. ServletContextAware‘s {@code setServletContext}
* (only applicable when running in a web application context)<br>
* 9. {@code postProcessBeforeInitialization} methods of BeanPostProcessors<br>
* 10. InitializingBean‘s {@code afterPropertiesSet}<br>
* 11. a custom init-method definition<br>
* 12. {@code postProcessAfterInitialization} methods of BeanPostProcessors
On shutdown of a bean factory, the following lifecycle methods apply: 1. DisposableBean‘s {@code destroy}2. a custom destroy-method definition
ClassPathXmlApplicationContext 和FileSystemXmlApplicationContext的区别
ClassPathXmlApplicationContext: 前缀是不需要的，默认就是指项目的classpath路径下面;如果要使用绝对路径，需要加上file:前缀表示这是绝对路径；
new ClassPathResource("appcontext.xml");
new ClassPathXmlApplicationContext("classpath:appcontext.xml");
对于FileSystemXmlApplicationContext: 默认表示的是两种：
1，没有盘符的是项目工作路径，即项目的根目录；
2，有盘符表示的是文件绝对路径。
new FileSystemXmlApplicationContext("src/appcontext.xml");
new FileSystemXmlApplicationContext("classpath:appcontext.xml");
("file:G:/java/Spring/Jar/workspace/appcontext.xml");
("G:/java/Spring/Jar/workspace/appcontext.xml");
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 = "&";
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;
<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 targetType the type to match against
* @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<?> targetType) 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);
}