Spring is a lightweight framework. Most of your Java classes will have nothing about Spring in their source code. This means that you can easily transition your application from the Spring framework to something else. It also means that transferring an existing application to use the Spring framework doesn’t have to mean a complete code rewrite.
All Java applications that consist of multiple classes have inter-dependencies or coupling between classes. Spring helps us develop applications that minimize the negative effects of coupling and encourages the use of interfaces in application development. Using interfaces in our applications to specify type helps make our applications easier to maintain and enhance later.
The Spring framework helps developers clearly separate responsibilities. Many Java applications suffer from class bloat – that is a class that has too many responsibilities. For example a service class that is also logging information about what its doing. Think of two situations – one is you’ve been told by your supervisor to do your normal work but also to write down everything you do and how long it takes you. You’d be even busier and less responsive.
A better situation would be you do your normal work, but another person observers what you’re doing and records it and measures how long it took. Even better would be if you were totally unaware of that other person and that other person was able to also observe and record other people’s work and time.
