org.springframework.beans.factory
Interface BeanFactory

All Known Subinterfaces:

ApplicationContext, AutowireCapableBeanFactory, ConfigurableApplicationContext, ConfigurableBeanFactory, ConfigurableListableBeanFactory, ConfigurableWebApplicationContext, HierarchicalBeanFactory, ListableBeanFactory, WebApplicationContext

All Known Implementing Classes:

AbstractApplicationContext, AbstractAutowireCapableBeanFactory, AbstractBeanFactory, AbstractRefreshableApplicationContext, AbstractRefreshableWebApplicationContext, AbstractXmlApplicationContext, ClassPathXmlApplicationContext, DefaultListableBeanFactory, FileSystemXmlApplicationContext, GenericApplicationContext, GenericWebApplicationContext, StaticApplicationContext, StaticListableBeanFactory, StaticWebApplicationContext, XmlBeanFactory, XmlWebApplicationContext

public interface BeanFactory

The root interface for accessing a Spring bean container. This is the basic client view of a bean container; further interfaces such as ListableBeanFactory and ConfigurableBeanFactory are available for specific purposes.

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. The Singleton approach is more useful and more common in practice.

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 BeanFactory 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, to either Singletons or Prototypes.

In contrast to the methods in ListableBeanFactory, all of the methods 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 is 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 maximum set of initialization methods and their standard order is:
1. BeanNameAware's setBeanName
2. BeanFactoryAware's setBeanFactory
3. ResourceLoaderAware's setResourceLoader (only applicable when running in an application context)
4. ApplicationEventPublisherAware's setApplicationEventPublisher (only applicable when running in an application context)
5. MessageSourceAware's setMessageSource (only applicable when running in an application context)
6. ApplicationContextAware's setApplicationContext (only applicable when running in an application context)
7. ServletContextAware's setServletContext (only applicable when running in a web application context)
8. postProcessBeforeInitialization methods of BeanPostProcessors
9. InitializingBean's afterPropertiesSet
10. a custom init-method definition
11. 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

Since:

13 April 2001

Author:

Rod Johnson, Juergen Hoeller

See Also:

ListableBeanFactory, ConfigurableBeanFactory, BeanNameAware.setBeanName(java.lang.String), BeanFactoryAware.setBeanFactory(org.springframework.beans.factory.BeanFactory), ResourceLoaderAware.setResourceLoader(org.springframework.core.io.ResourceLoader), ApplicationEventPublisherAware.setApplicationEventPublisher(org.springframework.context.ApplicationEventPublisher), MessageSourceAware.setMessageSource(org.springframework.context.MessageSource), ApplicationContextAware.setApplicationContext(org.springframework.context.ApplicationContext), ServletContextAware.setServletContext(javax.servlet.ServletContext), BeanPostProcessor.postProcessBeforeInitialization(java.lang.Object, java.lang.String), InitializingBean.afterPropertiesSet(), AbstractBeanDefinition.getInitMethodName(), BeanPostProcessor.postProcessAfterInitialization(java.lang.Object, java.lang.String), DisposableBean.destroy(), AbstractBeanDefinition.getDestroyMethodName()

Field Summary

static String

FACTORY_BEAN_PREFIX Used to dereference a FactoryBean and distinguish it from beans created by the FactoryBean.

Method Summary

boolean	containsBean(String name) Does this bean factory contain a bean definition with the given name?
String[]	getAliases(String name) Return the aliases for the given bean name, if defined.
Object	getBean(String name) Return an instance, which may be shared or independent, of the given bean name.
Object	getBean(String name, Class requiredType) Return an instance (possibly shared or independent) of the given bean name.
Class	getType(String name) Determine the type of the bean with the given name.
boolean	isSingleton(String name) Is this bean a singleton?

Field Detail

FACTORY_BEAN_PREFIX

static final String FACTORY_BEAN_PREFIX

Used to dereference a FactoryBean and distinguish it from beans created by the FactoryBean. For example, if the bean named myEjb is a FactoryBean, getting &myEjb will return the factory, not the instance returned by the factory.

See Also:

Constant Field Values

Method Detail

getBean

Object getBean(String name)
               throws BeansException

Return an instance, which may be shared or independent, of the given bean name. 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.

Parameters:

name - the name of the bean to return

Returns:

the instance of the bean

Throws:

NoSuchBeanDefinitionException - if there is no bean definition with the specified name

BeansException - if the bean could not be obtained

getBean

Object getBean(String name,
               Class requiredType)
               throws BeansException

Return an instance (possibly shared or independent) of the given bean name.

Behaves the same as getBean(String), but provides a measure of type safety by throwing a Spring BeansException 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).

Parameters:

name - the name of the bean to return

requiredType - type the bean must match. Can be an interface or superclass of the actual class, or null for any match. For example, if the value is Object.class, this method will succeed whatever the class of the returned instance.

Returns:

an instance of the bean (never null)

Throws:

BeanNotOfRequiredTypeException - if the bean is not of the required type

NoSuchBeanDefinitionException - if there's no such bean definition

BeansException - if the bean could not be created

containsBean

boolean containsBean(String name)

Does this bean factory contain a bean definition with the given name?

Will ask the parent factory if the bean cannot be found in this factory instance.

Parameters:

name - the name of the bean to query

Returns:

whether a bean with the given name is defined

isSingleton

boolean isSingleton(String name)
                    throws NoSuchBeanDefinitionException

Is this bean a singleton? That is, will getBean always return the same object?

Will ask the parent factory if the bean cannot be found in this factory instance.

Parameters:

name - the name of the bean to query

Returns:

is this bean a singleton

Throws:

NoSuchBeanDefinitionException - if there is no bean with the given name

See Also:

getBean(java.lang.String)

getType

Class getType(String name)
              throws NoSuchBeanDefinitionException

Determine the type of the bean with the given name. More specifically, checks the type of object that getBean would return. For a FactoryBean, returns the type of object that the FactoryBean creates.

Parameters:

name - the name of the bean to query

Returns:

the type of the bean, or null if not determinable

Throws:

NoSuchBeanDefinitionException - if there is no bean with the given name

Since:

1.1.2

See Also:

getBean(java.lang.String), FactoryBean.getObjectType()

getAliases

String[] getAliases(String name)
                    throws NoSuchBeanDefinitionException

Return the aliases for the given bean name, if defined.

Will ask the parent factory if the bean cannot be found in this factory instance.

Parameters:

name - the bean name to check for aliases

Returns:

the aliases, or an empty array if none

Throws:

NoSuchBeanDefinitionException - if there's no such bean definition