BEAN FACTORY supports two object modes.

Singleton mode provides a shared instance of the object with a particular name, which can be retrieved on lookup. Singleton is the default and most often used object mode. It is ideal for stateless service objects.

Prototype mode ensures that each retrieval will result in the creation of an independent object. Prototype mode would be best used in a case where each user needed to have his or her own object. The bean factory concept is the foundation of Spring as an IOC container. IOC moves the responsibility for making things happen into the framework and away from application code. The Spring framework uses JavaBean properties and configuration data to figure out which dependencies must be set.

There are several implementation of BeanFactory like “org.springframework.beans.factory.xml. XmlBeanFactory” which loads its beans based on the definition contained in an XML file.

APPLICATION CONTEXT:

The Application Context is spring’s more advanced container. Like ‘BeanFactory’ it can load bean definitions, wire beans together and dispense beans upon request. Additonally, It also provides:

1. A means for resolving text messages, including support for internationalization ie. i18n messages
2. A generic way to load file resources.
3. Events to notify beans that are registered as listeners.

Because of additional functionality, ‘Application Context’ is preferred over a BeanFactory. BeanFactory is used for simple applications and when the resource is scarce like mobile devices.

III Service Abstraction Layers

Spring provides consistent integration with various standard and 3rd party APIs through its various Service abstraction layers. Few of them are:

Benefits of the Service Abstraction Layers in spring framework:

1. There is no implicit contract with JNDI, etc.
2. It separates the user from the underlying APIs.
3. It enhances the reusability to a great extent.
4. Spring abstractions always consist of inter faces.
5. Testing is kept simpler than ever before.
6. For data access, Spring uses a generic transaction infrastructure and DAO exception hierarchy that is ommon across all sup ported platforms.