requests to handlers, with configurable handler
mappings, view resolution like features. The default
handler is a very simple Controller interface with method,
ModelAndView handleRequest(request, response).
Spring provides a controller hierarchy that can be subclassed.

For Example if some application needs to
process user entry forms you can inherit
AbstractFormController or if Application needs to process
a multi-page entry into a single form you can inherit
AbstractWizardFormController class of framework.

Spring Architecture

Spring’s layered architecture provides a lot of flexibility
and functionality that is build on the lower levels. Spring is
a complete JEE framework and has a wellorganized
architecture consisting of seven modules:

1. Spring Core package

The Core package is the most import component of the Spring Framework. It’s primary component is the ‘BeanFactory’, an implementation of the Factory pattern. It separates the dependencies issues like initialization, creation and access of the objects from the actual program logic. The BeanFactory applies the IOC pattern to separate an application’s configuration and dependency specification from the actual application code.

2. Spring Context package

This package uses observer design pattern and provides an ability to obtain resources (for application objects through a consistent API) and it adds support for message sources. The spring context is a configuration file that provides context information to the spring framework.
The spring context supplies enterprise services such as JNDI access, EJB integration, e-mail, internalization, validation, and scheduling functionality

3. Spring DAO package

The DAO (Data Access Object) package is primarily
used for standardizing the data access work using the
technologies like JDBC, Hibernate or JDO. The Spring’s
JDBC and DAO abstraction layer offers a meaningful
Spring exception hierarchy for managing the database connection, exception handling and error messages thrown by different database vendors. The exception hierarchy simplifies error handling and greatly reduces the amount of code that we need to write, such as opening and closing connections.