Spring Framework

org.springframework.beans.factory
Interface BeanFactory

All Known Subinterfaces:
ApplicationContext, AutowireCapableBeanFactory, ConfigurableApplicationContext, ConfigurableBeanFactory, ConfigurableListableBeanFactory, ConfigurablePortletApplicationContext, ConfigurableWebApplicationContext, HierarchicalBeanFactory, ListableBeanFactory, WebApplicationContext
All Known Implementing Classes:
AbstractApplicationContext, AbstractAutowireCapableBeanFactory, AbstractBeanFactory, AbstractRefreshableApplicationContext, AbstractRefreshableConfigApplicationContext, AbstractRefreshablePortletApplicationContext, AbstractRefreshableWebApplicationContext, AbstractXmlApplicationContext, AnnotationConfigApplicationContext, AnnotationConfigWebApplicationContext, ClassPathXmlApplicationContext, DefaultListableBeanFactory, FileSystemXmlApplicationContext, GenericApplicationContext, GenericWebApplicationContext, GenericXmlApplicationContext, ResourceAdapterApplicationContext, SimpleJndiBeanFactory, StaticApplicationContext, StaticListableBeanFactory, StaticPortletApplicationContext, StaticWebApplicationContext, XmlBeanFactory, XmlPortletApplicationContext, 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. 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

Since:
13 April 2001
Author:
Rod Johnson, Juergen Hoeller, Chris Beams
See Also:
BeanNameAware.setBeanName(java.lang.String), BeanClassLoaderAware.setBeanClassLoader(java.lang.ClassLoader), 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 java.lang.String FACTORY_BEAN_PREFIX
          Used to dereference a FactoryBean instance and distinguish it from beans created by the FactoryBean.
 
Method Summary
 boolean containsBean(java.lang.String name)
          Does this bean factory contain a bean definition or externally registered singleton instance with the given name?
 java.lang.String[] getAliases(java.lang.String name)
          Return the aliases for the given bean name, if any.
<T> T
getBean(java.lang.Class<T> requiredType)
          Return the bean instance that uniquely matches the given object type, if any.
 java.lang.Object getBean(java.lang.String name)
          Return an instance, which may be shared or independent, of the specified bean.
<T> T
getBean(java.lang.String name, java.lang.Class<T> requiredType)
          Return an instance, which may be shared or independent, of the specified bean.
 java.lang.Object getBean(java.lang.String name, java.lang.Object... args)
          Return an instance, which may be shared or independent, of the specified bean.
 java.lang.Class<?> getType(java.lang.String name)
          Determine the type of the bean with the given name.
 boolean isPrototype(java.lang.String name)
          Is this bean a prototype? That is, will getBean(java.lang.String) always return independent instances?
 boolean isSingleton(java.lang.String name)
          Is this bean a shared singleton? That is, will getBean(java.lang.String) always return the same instance?
 boolean isTypeMatch(java.lang.String name, java.lang.Class<?> targetType)
          Check whether the bean with the given name matches the specified type.
 

Field Detail

FACTORY_BEAN_PREFIX

static final java.lang.String FACTORY_BEAN_PREFIX
Used to dereference a FactoryBean instance and distinguish it from beans created by the FactoryBean. For example, if the bean named myJndiObject is a FactoryBean, getting &myJndiObject will return the factory, not the instance returned by the factory.

See Also:
Constant Field Values
Method Detail

getBean

java.lang.Object getBean(java.lang.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.

Parameters:
name - the name of the bean to retrieve
Returns:
an 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

<T> T getBean(java.lang.String name,
              java.lang.Class<T> 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.

Parameters:
name - the name of the bean to retrieve
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
Throws:
NoSuchBeanDefinitionException - if there's no such bean definition
BeanNotOfRequiredTypeException - if the bean is not of the required type
BeansException - if the bean could not be created

getBean

<T> T getBean(java.lang.Class<T> requiredType)
          throws BeansException
Return the bean instance that uniquely matches the given object type, if any.

Parameters:
requiredType - type the bean must match; can be an interface or superclass. null is disallowed.

This method goes into 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 ListableBeanFactory and/or BeanFactoryUtils.

Returns:
an instance of the single bean matching the required type
Throws:
NoSuchBeanDefinitionException - if there is not exactly one matching bean found
BeansException
Since:
3.0
See Also:
ListableBeanFactory

getBean

java.lang.Object getBean(java.lang.String name,
                         java.lang.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.

Parameters:
name - the name of the bean to retrieve
args - arguments to use if creating a prototype using explicit arguments to a static factory method. It is invalid to use a non-null args value in any other case.
Returns:
an instance of the bean
Throws:
NoSuchBeanDefinitionException - if there's no such bean definition
BeanDefinitionStoreException - if arguments have been given but the affected bean isn't a prototype
BeansException - if the bean could not be created
Since:
2.5

containsBean

boolean containsBean(java.lang.String name)
Does this bean factory contain a bean definition or externally registered singleton instance with the given name?

If the given name is an alias, it will be translated back to the corresponding canonical bean name.

If this factory is hierarchical, will ask any parent factory if the bean cannot be found in this factory instance.

If a bean definition or singleton instance matching the given name is found, this method will return true whether the named bean definition is concrete or abstract, lazy or eager, in scope or not. Therefore, note that a true return value from this method does not necessarily indicate that getBean(java.lang.String) will be able to obtain an instance for the same name.

Parameters:
name - the name of the bean to query
Returns:
whether a bean with the given name is present

isSingleton

boolean isSingleton(java.lang.String name)
                    throws NoSuchBeanDefinitionException
Is this bean a shared singleton? That is, will getBean(java.lang.String) 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(java.lang.String) 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.

Parameters:
name - the name of the bean to query
Returns:
whether this bean corresponds to a singleton instance
Throws:
NoSuchBeanDefinitionException - if there is no bean with the given name
See Also:
getBean(java.lang.String), isPrototype(java.lang.String)

isPrototype

boolean isPrototype(java.lang.String name)
                    throws NoSuchBeanDefinitionException
Is this bean a prototype? That is, will getBean(java.lang.String) 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(java.lang.String) 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.

Parameters:
name - the name of the bean to query
Returns:
whether this bean will always deliver independent instances
Throws:
NoSuchBeanDefinitionException - if there is no bean with the given name
Since:
2.0.3
See Also:
getBean(java.lang.String), isSingleton(java.lang.String)

isTypeMatch

boolean isTypeMatch(java.lang.String name,
                    java.lang.Class<?> targetType)
                    throws NoSuchBeanDefinitionException
Check whether the bean with the given name matches the specified type. More specifically, check whether a getBean(java.lang.String) 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.

Parameters:
name - the name of the bean to query
targetType - the type to match against
Returns:
true if the bean type matches, 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 Also:
getBean(java.lang.String), getType(java.lang.String)

getType

java.lang.Class<?> getType(java.lang.String name)
                           throws NoSuchBeanDefinitionException
Determine the type of the bean with the given name. More specifically, determine the type of object that getBean(java.lang.String) 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.

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), isTypeMatch(java.lang.String, java.lang.Class)

getAliases

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

Parameters:
name - the bean name to check for aliases
Returns:
the aliases, or an empty array if none
See Also:
getBean(java.lang.String)

Spring Framework