How does a large project build with small changes?

Question

Java

Hey! I'm interested in the question. Let's say we have a fairly large project (let's say Spring Boot) with a huge number of classes. We collected everything in jar / war and deployed it on the server. Everything, the application is spinning and doing its job. Now we want to change something in the Spring Boot configuration (for example, tweak security or cache) or add changes to some class due to third-party api changes. And what happens next? Should we recompile everything and deploy the project again? But what if the rebuild takes hours? And what is the advantage of the same concept of the IoC container of the same Spring when changing the configuration? The phrase "without recompiling the entire project" constantly flickers, but what does this mean purely technically?
I hope for understanding, because these questions haunt due to the lack of experience in this topic.

Answer 1

It is necessary to divide your project into different modules (different jar) files so that the assembly of various parts does not depend heavily on others. And therefore, it will be enough to rebuild certain jar modules, and not the entire project. I recommend Gradle, the ability to split the project into modules is conveniently implemented there. You still need to restart the application. Moreover, Gradle understands when it is necessary to recompile a module, and when nothing has changed in it.