Why is Spring Framework popular?

The first version of Spring Framework was released in March 2004. In the subsequent decade and a half, the use and popularity of Spring Framework only grew.

The important reasons behind the popularity of Spring Framework are as follows:

• Simplified unit testing--because of dependency injection
• Reduction in plumbing code
• Architectural flexibility
• Keeping up with changing times

Let's discuss each of these in detail.

Simplified unit testing

Earlier versions of EJBs were very difficult to unit test. In fact, it was difficult to run EJBs outside the container (as of version 2.1). The only way to test them was to deploy them in a container.

Spring Framework brought in the concept of Dependency...