Spring Packaging for Development

The Spring modules, shown in Figure 6.1, are essentially conceptual groups of functionality provided by the extensive list of Spring's Java packages and underlying classes.

Figure 6.2 shows the various top-level Spring packages. (Note:The shaded packages are ones we will use for our sample application, again demonstrating that Spring does not take an all-or-nothing approach.)

Figure 6.2. Spring's top-level Java packages under org.springframework.

Overwhelmed by the Size of the Spring Framework?

The Spring Framework contains something along the lines of 130+ Java packages and 1,200+ Java classes. However, do not be overwhelmed by this number; here is why.

First, you may want to use only Spring's IoC features, so you could essentially ignore most of the APIs. Second, although there are lots of classes and there's lots of Javadoc, many of these classes are for internal use by the framework itself. Third, Spring enables you to select the modules you want to use and ignore the rest. For example, we will use only a handful of these for our sample application, Time Expressionthis is proof that Spring's design is highly modular.