Eclipse- Why module-info matters?

Question

I'm very new to java. starting from yesterday! i installed eclipse and imported spring libraries inside it. but a weird problem happened. in import statement there was an error telling The type org.springframework.context.ApplicationContext is not accessible. after running the project another error happened (related to same subject ApplicationContext cannot be resolved to a type).

Anyway! i was confused. it took one day for me. searching forums such as stackoverflow and googling didn't resolve my problem. suddenly i saw a popup message in eclipse suggesting some solutions. ignoring some worthless one of them was adding module to module-info.java file. unbelievably that solved the problem! strangest thing was that i never saw this solution in related forums! and most annoying thing is that what if i never saw that popup? where did i do a mistake? and why this solution doesn't exist on the internet?

Lots of thanks!

Answer 1

Java modules are a new feature of Java 9; they allow you to specify exactly which dependencies you need for your program, hence allowing greater control of the size of your application - no need to bring along library code you don't use. That seems to imply that you need to explicitly say what you want, I guess so that you realise that you are pulling in more modules.

So the reason that you don't see much information about modules in general is that they are comparatively new and doubt that I'm alone in being a long-standing Java developer who has never seen a module-info file!

I wonder whether Eclipse gave you some options when you were creating your project and you inadvertently took an option meaning "yes I want the extra control of doing mocules and I don't mind doing a bit more work."