Comment by jauntywundrkind

That's something DI does sure, but Spring for example is a fully managed way of talking about stuff in your app. It exposes universal APIs to talk about all the things, and the ways of making things, and config for things. It lets you see what stuff is made.

I've found there to be something radically compelling about all the hooks Spring allows into it's runtime. The sub-interfaces of Aware offer all sorts of ways to see what is in your runtime, see things getting constructed, see other parts of the lifetime of things.

Asking the container for a thing is the most well known use case, but there's so so much we can learn about our environment at runtime by having these managed containers. Programming used to hint at "Meta-Object Protocols", more expansive forms of objects, and Spring for example delivered us something like that: a higher level better modeled object (and factory and other pieces) than what the runtimes gave us.