Spring started out as a ‘small’ Dependency Injection container, which gave the Java world a whole new direction. Especially on the area of Java Enterprise, it offered innovations which allowed for faster and easier development of new Java applications.
In the last few years, Spring has grown enormously as a framework. The basics are still relatively simple, but due to the large number of different extensions it can be hard to start a new project. The people at Spring are familiar with this situation and are trying to remedy it with its newest addition: Spring Boot.