What is Spring?

Spring is grate framework for development of Enterprise grade applications. Spring is a light-weight framework for the development of enterprise-ready applications. Spring can be used to configure declarative transaction management, remote access to your logic using RMI or web services, mailing facilities and various options in persisting your data to a database. Spring framework can be used in modular fashion, it allows to use in parts and leave the other components which is not required by the application.

Features of Spring Framework:

• Transaction Management: Spring framework provides a generic abstraction layer for transaction management. This allowing the developer to add the pluggable transaction managers, and making it easy to demarcate transactions without dealing with low-level issues. Spring's transaction support is not tied to J2EE environments and it can be also used in container less environments.
     
• JDBC Exception Handling: The JDBC abstraction layer of the Spring offers a meaningful exception hierarchy, which simplifies the error handling strategy
   
• Integration with Hibernate, JDO, and iBATIS: Spring provides best Integration services with Hibernate, JDO and iBATIS.
   
• AOP Framework: Spring is best AOP framework
     
• MVC Framework: Spring comes with MVC web application framework, built on core Spring functionality. This framework is highly configurable via strategy interfaces, and accommodates multiple view technologies like JSP, Velocity, Tiles, iText, and POI. But other frameworks can be easily used instead of Spring MVC Framework..

Spring Architecture

Spring is well-organized architecture consisting  of seven modules. Modules in the Spring framework are:

1. Spring AOP
   One of the key components of Spring is the AOP framework. AOP is used in Spring:

   • To provide declarative enterprise services, especially as a replacement for EJB declarative services. The most important such service is declarative transaction management, which builds on Spring's transaction abstraction.

   • To allow users to implement custom aspects, complementing their use of OOP with AOP

2. Spring ORM
   The ORM package is related to the database access. It provides integration layers for popular object-relational mapping APIs, including JDO, Hibernate and iBatis.
     
3. Spring Web
   The Spring Web module is part of Spring’s web application development stack, which includes Spring MVC.
      
4. Spring DAO
   The DAO (Data Access Object) support in Spring is primarily for standardizing the data access work using the technologies like JDBC, Hibernate or JDO.
      
5. Spring Context
   This package builds on the beans package to add support for message sources and for the Observer design pattern, and the ability for application objects to obtain resources using a consistent API.
     
6. Spring Web MVC
   This is the Module which provides the MVC implementations for the web applications.
     
7. Spring Core
   The Core package is the most import component of the Spring Framework.
   This component provides the Dependency Injection features. The BeanFactory  provides a factory pattern which separates the dependencies like initialization, creation and access of the objects from your actual program logic.

The following diagram represents the Spring Framework Architecture

Spring Framework Architecture