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 API is the same. Since Spring 2.0, further scopes are available depending on the concrete application context (e.g. "request" and "session" scopes in a web environment).

The point of this approach is that the BeanFactory is a central registry of application components, and centralizes configuration of application components (no more do individual objects need to read properties files, for example). See chapters 4 and 11 of "Expert One-on-One J2EE Design and Development" for a discussion of the benefits of this approach.

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 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 ListableBeanFactory , all of the operations in this interface will also check parent factories if this is a 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:
1. BeanNameAware's setBeanName
2. BeanClassLoaderAware's setBeanClassLoader
3. BeanFactoryAware's setBeanFactory
4. ResourceLoaderAware's setResourceLoader (only applicable when running in an application context)
5. ApplicationEventPublisherAware's setApplicationEventPublisher (only applicable when running in an application context)
6. MessageSourceAware's setMessageSource (only applicable when running in an application context)
7. ApplicationContextAware's setApplicationContext (only applicable when running in an application context)
8. ServletContextAware's setServletContext (only applicable when running in a web application context)
9. postProcessBeforeInitialization methods of BeanPostProcessors
10. InitializingBean's afterPropertiesSet
11. a custom init-method definition
12. postProcessAfterInitialization methods of BeanPostProcessors

On shutdown of a bean factory, the following lifecycle methods apply:
1. DisposableBean's destroy
2. a custom destroy-method definition

Also see:

BeanNameAware#setBeanName
BeanClassLoaderAware#setBeanClassLoader
BeanFactoryAware#setBeanFactory
org.springframework.context.ResourceLoaderAware#setResourceLoader
org.springframework.context.ApplicationEventPublisherAware#setApplicationEventPublisher
org.springframework.context.MessageSourceAware#setMessageSource
org.springframework.context.ApplicationContextAware#setApplicationContext
org.springframework.web.context.ServletContextAware#setServletContext
org.springframework.beans.factory.config.BeanPostProcessor#postProcessBeforeInitialization
InitializingBean#afterPropertiesSet
org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization
DisposableBean#destroy
org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName
author: Rod - Johnson

author: Juergen - Hoeller

since: 13 - April 2001

 public boolean containsBean(String name)
Does this bean factory contain a bean with the given name? More specifically,
is #getBean  able to obtain a bean instance for the given name?
Translates aliases back to the corresponding canonical bean name.
Will ask the parent factory if the bean cannot be found in this factory instance.

 public String[] getAliases(String name)
Return the aliases for the given bean name, if any.
All of those aliases point to the same bean when used in a #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.

 public Object getBean(String name) throws BeansException
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.

 public Object getBean(String name,
    Class requiredType) throws BeansException
Return an instance, which may be shared or independent, of the specified bean.
Behaves the same as #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 #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.

 public Object getBean(String name,
    Object[] args) 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.

 public Class getType(String name) throws NoSuchBeanDefinitionException
Determine the type of the bean with the given name. More specifically,
determine the type of object that #getBean  would return for the given name.
For a FactoryBean , return the type of object that the FactoryBean creates,
as exposed by 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.

 public boolean isPrototype(String name) throws NoSuchBeanDefinitionException
Is this bean a prototype? That is, will #getBean  always return
independent instances?
Note: This method returning false does not clearly indicate
a singleton object. It indicates non-independent instances, which may correspond
to a scoped bean as well. Use the #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.

 public boolean isSingleton(String name) throws NoSuchBeanDefinitionException
Is this bean a shared singleton? That is, will #getBean  always
return the same instance?
Note: This method returning false does not clearly indicate
independent instances. It indicates non-singleton instances, which may correspond
to a scoped bean as well. Use the #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.

 public boolean isTypeMatch(String name,
    Class targetType) throws NoSuchBeanDefinitionException
Check whether the bean with the given name matches the specified type.
More specifically, check whether a #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.