It's not blackbox in that you can't look inside... it's blackbox in that you can choose to ignore it and be just fine.

Springboot takes an opinionated approach to a lot of things, but always lets you override it and do whatever you want wherever you want.

I suppose that's more of a greybox...

ah, yes! point taken.

You can use Spring without all that magic. I, personally, hate Spring Boot and would never use it, exactly because of all that magic. But Spring itself is perfectly fine and I can control every single bit of it with explicit configurations.

For us, springboot gave about 90% of what we wanted out of the box. The 10% that we wanted customized (special authentication related things or transparent multitenant database switching with repositories etc), it let us override and do what we wanted it to do. It certainly is a lot of magic, but nothing that cannot be deduced if you are familiar with Spring, and/or look at the source.

I used to be opposed to all the "magic"... but after you write a few MVC projects with Hibernate backends, etc... why keep having to do that all from scratch each time?

You end up making your own framework that has all that in it, so that you just change a few things here and there and can start getting to the business logic that much quicker.

Then you realize you're maintaining all of that code... when you'd much rather maintain the business logic bits...

Which leads to using Spring Boot and letting them maintain everything else.