The Spring Framework consists of features organized into about 20 modules. These modules are grouped into Core Container, Data Access/Integration, Web, AOP (Aspect Oriented Programming), Instrumentation, and Test, as shown in the following diagram.
Overview of the Spring Framework
The Core Container consists of the Core, Beans, Context, and Expression Language modules.
The Core and
Beans modules provide the fundamental parts of the
framework, including the IoC and Dependency Injection features. The
BeanFactory is a sophisticated implementation of
the factory pattern. It removes the need for programmatic singletons and
allows you to decouple the configuration and specification of
dependencies from your actual program logic.
The Context
module builds on the solid base provided by the Core and Beans
modules: it is a means to access objects in a framework-style manner
that is similar to a JNDI registry. The Context module inherits its
features from the Beans module and adds support for internationalization
(using, for example, resource bundles), event-propagation,
resource-loading, and the transparent creation of contexts by, for
example, a servlet container. The Context module also supports Java EE
features such as EJB, JMX ,and basic remoting. The
ApplicationContext interface is the focal point
of the Context module.
The Expression Language module provides a powerful expression language for querying and manipulating an object graph at runtime. It is an extension of the unified expression language (unified EL) as specified in the JSP 2.1 specification. The language supports setting and getting of property values, property assignment, method invocation, accessing the context of arrays, collections and indexers, logical and arithmetic operators, named variables, and retrieval of objects by name from Spring's IoC container. It also supports list projection and selection, as well as common list aggregations.
The Data Access/Integration layer consists of the JDBC, ORM, OXM, JMS and Transaction modules.
The JDBC module provides a JDBC-abstraction layer that removes the need to do tedious JDBC coding and parsing of database-vendor specific error codes.
The ORM module provides integration layers for popular object-relational mapping APIs, including JPA, JDO, Hibernate, and iBatis. Using the ORM package you can use all those O/R-mappers in combination with all the other features Spring offers, such as the simple declarative transaction management feature mentioned previously.
The OXM module provides an abstraction layer that supports Object/XML mapping implementations for JAXB, Castor, XMLBeans, JiBX and XStream.
The Java Messaging Service (JMS )module contains features for producing and consuming messages.
The Transaction module supports programmatic and declarative transaction management for classes that implement special interfaces and for all your POJOs (plain old Java objects).
The Web layer consists of the Web, Web-Servlet, and Web-Portlet modules.
Spring's Web module provides basic web-oriented integration features such as multipart file-upload functionality and the initialization of the IoC container using servlet listeners and a web-oriented application context. It also contains the web-related parts of Spring's remoting support.
The Web-Servlet module contains Spring's model-view-controller (MVC) implementation for web applications. Spring's MVC framework provides a clean separation between domain model code and web forms, and integrates with all the other features of the Spring Framework.
The Web-Portlet module provides the MVC implementation to be used in a portlet environment and mirrors the functionality of Web-Servlet module.
Spring's AOP module provides an AOP Alliance-compliant aspect-oriented programming implementation allowing you to define, for example, method-interceptors and pointcuts to cleanly decouple code that implements functionality that should be separated. Using source-level metadata functionality, you can also incorporate behavioral information into your code, in a manner similar to that of .NET attributes.
The separate Aspects module provides integration with AspectJ.
The Instrumentation module provides class instrumentation support and classloader implementations to be used in certain application servers.