Spring Modules

As mentioned previously, one advantage of Spring is to be modular. Its layers are:

• Core Container
• Data Access
• Web
• Aop
• Test

The Core layer container is formed by the modules: Core, Beans, Context, and Expression Language. Core modules and Beans form the main structure of the framework, including the capabilities of IoC and DI, which are implemented through the BeanFactory, which is a sophisticated implementation of the Factory Method Pattern . The BeanFactory enables the decoupling between the definition and configuration of the application logic and dependencies.
The Context module, based on Form Beans, acts as a conduit for access to objects through its main interface specification: ApplicationContext. The ApplicationContext inherits all the functionality of the BeanFactory, adding others such as support for internationalization, the propagation of events, loading resources, support for J2EE.
The Expression Language layer provides a powerful expression language for manipulating objects at runtime.

The Layer Data Access / Integration consists of the sub-modules: JDBC, ORM, OXM, and JMS Transaction. The module provides an abstraction of JDBC JDBC API, designed to make it less tedious programming through the same. The module ORM provides a level of integration with popular frameworks O \ R mapping, such as JPA , Hibernate, iBatis . Spring allows the use of all the potential of these frameworks, making it possible to intergrate with its own peculiarities, such as transaction management.
The OXM layer provides an abstraction layer for the Object / XML mapping to JAXB , XMLBeans and more. The module contains funzinalità JMS for sending and receiving messages, while the module provides a Transaction Manager transaction for all types of classes.

The web layer is formed by the modules: Web, Web Servlets, Struts-Web and Web portlets. The Web module contains basic functionality for creating Enterprise Applications on, such as support for upload files, also offering the initialization of the IoC container via a Servlet Listener. The Web module contains a Servlet-part of the MVC framework, whereas the module contains classes for Web-Struts integration with Struts2 , however, is not recommended in that version 3 of Spring. Finally, the Web form-portlet provides identical functionality to the Web form-Servlet, but oriented to applications that make use of portlets .

Aop layer provides an adherent to the AOP Alliance , allowing aspect-oriented programming. This layer allows you to create code that has to be decoupled from the other features, even if related to the general flow of the application (the part relating to the AOP will be discussed in later sections). This layer also has a module Aspects for integration with AspectJ , and Instrumentantions a module that allows monitoring of classes, offering a ClassLoader that can be used in some Application Server.

The layer provides possbiltà Test to test the components of Spring using JUnit or TestNG . This module provides the possibility of practicing to initialize and cache ApplicationContexts for testing purposes, fornerndo also possible to use mock objects to test the code in isolation.

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