Spring offers the following benefits:
Spring is famous for its great flexibility. You can customize and integrate nearly everything.
While JEE application servers including very expensive commercial products turned out to be a dead-end, spring has guided projects through the changing trends of IT throughout decades. It may be the framework with the longest history track and popularity. As a result you can easily find developers, experts, books, articles, etc. about spring.
non-invasive and not biased
Spring became famous for its non-invasive coding based on patterns instead of hard dependencies. It gives you a lot of freedom and avoids tight coupling of your (business) code.
See Why Spring? for details.