Enterprise Application Integration (EAI)Fundamentals

ERP applications like SAP, PeopleSoft, and JD Edwards, and customer relationship management systems (CRMs) like Clarify and Siebel quickly became enterprise data silos, and it became increasingly important to reuse the data and functionality in those systems.

Spring Framework Components

 

 Figure 1.0 (Spring Framework Modules)

*list all the modules coming with Spring 3.1

Most of the modules have a dependency on some other module in the Spring Framework. The core module is an exception to this rule. Figure 1.1 gives an overview of the commonly used modules and their dependencies on other modules. Notice that the instrumentation, aspect, and test modules are missing from the figure; this is because their dependencies depend on the project and what other modules are used. The Spring Framework has only one required dependency: commons-logging, a logging abstraction framework. The other dependencies differ based on the needs of the project.

Dependency Injection

The concept of dependency injection (DI), objects are given their dependencies at construction time, is one of the foundations of the Spring Framework.

Application Context

To be able to do dependency injection in Spring, we need an application context. In Spring, this is an instance of the org.spring framework.context. Application-Context interface. The application context is responsible for managing the beans defined in it. It also enables more elaborate things like applying AOP to the beans defined in it.The Application-Context interface can be configured in different ways. The most well-known way is to use one or more XML files; however, we could also use a properties file or Java classes. We could even mix-and-match different configuration approaches. In general, it is best to stick with a single approach. Doing so makes it easier to understand and figure out what your configuration is. This also removes the need to hunt down Java, XML, and properties files.Spring provides several different Application-Context implementations . Each of these implementations provides the same features, but differs in how it loads the application context configuration.