Spring is not monolithic. You can use a part of it, or only some of the features. You can include some of the modules of Spring that you need and leave out others. Some modules depend on some others, but Gradle, Maven, or some other build tool handles that.

The following image shows you the modules of the Spring framework for version 4:

Spring is constantly developing since its first release, and it is still considered as a modern framework. The core of the framework is a dependency injection container similar to the one we saw in the previous chapter. As the framework developed, it also supported AOP and many other enterprise functionalities, such as message oriented patterns and web programming with an implementation of Model View Controller, supporting not only servlets but also portlets and WebSockets. Since Spring targets the enterprise application arena, it also supports database handling in many different ways. It supports JDBC using templates, Object Relational Mapping (ORM), and transaction management.

In the sample program, we use a fairly recent module: Spring boot. This module makes it extremely easy to start writing and running applications, assuming a lot of configurations that are usually the same for many programs. It contains an embedded servlet container that it configures for default settings and configures Spring wherever it is possible, so we can focus on the programming aspect rather than on the Spring configuration.