Software developped with Spring are modulars in nature. While the developper program Plain Old Java Objects (POJO), the chaining of the different objects is done by a parametrized instance of the Spring container. it is therefore easily possible to modify part of the software to accomplish customization.

The Spring framework is essentialy transparent, Java objects don't have to reference Spring itself. 

Spring is compatible with various open-source frameworks like Log4J, Hibernate, Quartz scheduler etc