Spring is an open source framework created to adress the complexity of enterprise application development. One of the main advantages of the Spring framework is its layered architecture, which allows you to be selective about which of its parts you use. The Spring framework consists of seven well-defined modules. The Spring modules are built on top of the core container, which defines how beans are created, configured, and managed, as shown in Figure 1.
Each of the modules that comprise the Spring framework can stand on its own or be implemented jointly with one or more of the others. The functionality of each component is as follows:
- The core container: The core container provides the essential functionality of the Spring framework. A primary component of the core container is the BeanFactory?, an implementation of the Factory pattern. The BeanFactory? applies the Inversion of Control (IOC) pattern to separate an application's configuration and dependency specification from the actual application code.
- Spring context: The Spring context is a configuration file that provides context information to the Spring framework. The Spring context includes enterprise services such as JNDI, EJB, e-mail, internalization, validation, and scheduling functionality.
- Spring AOP: The Spring AOP module integrates aspect-oriented programming functionality directly into the Spring framework, through its configuration management feature.
- Spring DAO: The Spring JDBC DAO abstraction layer offers a meaningful exception hierarchy for managing the exception handling and error messages thrown by different database vendors.
- Spring ORM: The Spring framework plugs into several ORM frameworks to provide its Object Relational tool, including JDO, Hibernate, and iBatis SQL Maps. All of these comply to Spring's generic transaction and DAO exception hierarchies.
- Spring Web module: The Web context module builds on top of the application context module, providing contexts for Web-based applications. As a result, the Spring framework supports integration with Jakarta Struts. The Web module also eases the tasks of handling multi-part requests and binding request parameters to domain objects.
- Spring MVC framework: The Model-View-Controller (MVC) framework is a full-featured MVC implementation for building Web applications.
Spring framework functionality can be used in any J2EE? server and most of it also is adaptable to non-managed environments. A central focus of Spring is to allow for reusable business and data-access objects that are not tied to specific J2EE? services. Such objects can be reused across J2EE? environments (Web or EJB), standalone applications, test environments, and so on, without any hassle.
Spring (IoC) Beans
One of most important feature of Spring core container is IoC container.