The org.springframework.beans and org.springframework.context packages
are the two most important and fundamental packages in Spring. These packages
provides the basis for Spring's Inversion of Control (Dependency Injection) features.
The BeanFactory provides configuration mechanism which is capable of managing
beans (objects). The ApplicationContext is build on top of the BeanFactory which adds other functionality
such as message resource handling (for use in internationalization), event
propagation, easier integration with Springs AOP features, declarative
mechanisms.
The BeanFactory provides the configuration framework and basic functionality,
while the ApplicationContext adds enhanced capabilities to it, some of
them perhaps more J2EE and enterprise-centric. ApplicationContext is a superset
of a BeanFactory, and BeanFactory capabilities and behavior apply to
ApplicationContexts as well.
At times we often face the question as whether a BeanFactory or an
ApplicationContext are best suited for use in a particular situation. Normally
when building most applications in a J2EE-environment, the best option is to use the
ApplicationContext, since it
offers all the features of the BeanFactory and adds on to it in terms of features,
while also allowing a more declarative approach to use of some functionality,
which is desirable. In certain cases where memory usage is concerned one might
prefer to use BeanFactory over Application Context.
The BeanFactory
The BeanFactory is the container which instantiates, configures, and
manages a number of beans. These beans typically collaborate with one another.
A BeanFactory is represented by the interface
org.springframework.beans.factory.BeanFactory, for which there are multiple implementations. The most
commonly used simple BeanFactory implementation is org.springframework.beans.factory.xml.XmlBeanFactory.
The BeanFactory is instantiated as below for different
implementation:
Resource res = new FileSystemResource("beans.xml");
XmlBeanFactory factory = new XmlBeanFactory(res);
or
ClassPathResource res = new ClassPathResource("beans.xml");
XmlBeanFactory factory = new XmlBeanFactory(res);
or
ClassPathXmlApplicationContext appContext = new ClassPathXmlApplicationContext(
new String[] {"applicationContext.xml", "applicationContext-part2.xml"});
BeanFactory factory = (BeanFactory) appContext;
The ApplicationContext
The ApplicationContext, enhances BeanFactory functionality in a
more framework-oriented style.
The ApplicationContext interface, is
located in the org.springframework.context package. Its is derived from the BeanFactory interface, and
provides all the functionality of BeanFactory. To allow working in a more
framework-oriented fashion, using layering and hierarchical contexts, the
context package also provides the following:
- MessageSource: providing access to messages in,
i18n-style
- Access to resources: such as URLs and files
- Event
propagation: to
beans implementing the ApplicationListener interface
- Loading of multiple (hierarchical) contexts: allowing each to be focused
on one particular layer.
As the ApplicationContext
includes all functionality of the BeanFactory, it is generally recommended that
it be used over the BeanFactory, except for a few limited situations where
memory consumption might be critical, and a few extra kilobytes might make a
difference.
ApplicationContext |