Spring旗下有若干子项目，整个spring工程中其实包含了若干个子项目，这些子项目种类丰富，分别适用于不同的应用领域。开发者可以根据自己的project的功能特色选取spring中某些特定的子项目集成到自己的project中，避免重复造车轮，从而加快自己的project的build的速度。（spring官网documentation：From configuration to security, web apps to big data – whatever the infrastructure【基础设施】 needs of your application may be, there is a Spring Project to help you build it. Start small and use just what you need – Spring is modular by design.
