The Spring framework’s philosophy is to make enterprise Java simpler to use, more flexible, and less susceptible to vendor specifics or external API
dependencies. This approach manifests itself by advocating and ensuring that all objects in the system are simple Java objects (POJOs). By following
this approach, we ensure that it’s very easy to develop unit tests for any component since we can control its lifecycle and invocation and ensure that it does not contain infrastructure-dependent code that cannot be easily tested or simulated.

Spring框架的哲学是让企业级Java开发变更容易、更灵活、更少依赖于供应商的特性、更少依赖于外部的API。这样就导致了它提倡并确保系统中的所有对象都是简单的Java对象（POJO）。通过这种方式，我们可以确保很容易为任何组件开发单元测试，因为我们可以控制它的生命周期和调用，我们也可以确保它没有包含依赖于基础设施的代码，因为这样的代码不能够简单地测试或模拟。