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, DefaultListableBeanFactory, StaticListableBeanFactory, StaticWebApplicationContext, XmlWebApplicationContext

public interface BeanFactory

Interface to be implemented by objects that hold a number of bean definitions, each uniquely identified by a String name. An independent instance of any of these objects can be obtained (the Prototype design pattern), or a single shared instance can be obtained (a superior alternative to the Singleton design pattern). Which type of instance will be returned depends on the bean factory configuration - the API is the same. The Singleton approach is much 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 the configuring 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.

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 factories are supposed to 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. ApplicationContextAware's setApplicationContext (only applicable if running in an application context)
4. postProcessBeforeInitialization methods of BeanPostProcessors
5. InitializingBean's afterPropertiesSet
6. a custom init-method definition
7. 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

Version:

$Revision: 1.7 $

Author:

Rod Johnson, Juergen Hoeller

See Also:

BeanNameAware.setBeanName(java.lang.String), BeanFactoryAware.setBeanFactory(org.springframework.beans.factory.BeanFactory), InitializingBean.afterPropertiesSet(), DisposableBean.destroy(), BeanPostProcessor.postProcessBeforeInitialization(java.lang.Object, java.lang.String), BeanPostProcessor.postProcessAfterInitialization(java.lang.Object, java.lang.String), RootBeanDefinition.getInitMethodName(), RootBeanDefinition.getDestroyMethodName(), ApplicationContextAware.setApplicationContext(org.springframework.context.ApplicationContext)

Method Summary

boolean	containsBean(java.lang.String name) Does this bean factory contain a bean with the given name?
java.lang.String[]	getAliases(java.lang.String name) Return the aliases for the given bean name, if defined.
java.lang.Object	getBean(java.lang.String name) Return an instance (possibly shared or independent) of the given bean name.
java.lang.Object	getBean(java.lang.String name, java.lang.Class requiredType) Return an instance (possibly shared or independent) of the given bean name.
boolean	isSingleton(java.lang.String name) Is this bean a singleton? That is, will getBean() always return the same object?

Method Detail

getBean

public java.lang.Object getBean(java.lang.String name)
                         throws BeansException

Return an instance (possibly shared or independent) of the given bean name. This method allows a bean factory to be used as a replacement for the Singleton or Prototype design pattern.

Note that callers should retain references to returned objects. There is no guarantee that this method will be implemented to be efficient. For example, it may be synchronized, or may need to run an RDBMS query.

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

Parameters:

name - name of the bean to return

Returns:

the instance of the bean

Throws:

NoSuchBeanDefinitionException - if there's no such bean definition

BeansException - if the bean could not be created

getBean

public java.lang.Object getBean(java.lang.String name,
                                java.lang.Class requiredType)
                         throws BeansException

Return an instance (possibly shared or independent) of the given bean name. Provides a measure of type safety by throwing an exception if the bean is not of the required type.

Note that callers should retain references to returned objects. There is no guarantee that this method will be implemented to be efficient. For example, it may be synchronized, or may need to run an RDBMS query.

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

Parameters:

name - name of the bean to return

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

Returns:

the instance of the bean

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

public boolean containsBean(java.lang.String name)

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

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

Parameters:

name - name of the bean to query

Returns:

whether a bean with the given name is defined

isSingleton

public boolean isSingleton(java.lang.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 - name of the bean to query

Returns:

is this bean a singleton

Throws:

NoSuchBeanDefinitionException - if there is no bean with the given name

getAliases

public java.lang.String[] getAliases(java.lang.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