i'm actually making a plugin so it's only serverside, and i'm not using forge much, i need it only to get some player data out of another mod running on the server, everything else is handled by sponge.(yeah maybe i should use UUIDs instead of Strings - my problem is that everytime i test the code it gives me the "NoSuchMethodError" on getServer() or getConfigurationManager())
After seeing how any code i try gives me always the same error most likely my problem is that i didn't setup the project correctly (i'm not really using gradle, i just added forge jar as external dependency and works fine for other tests i did).
I'd rather not switch to gradle because for what i need to do it seems pretty time consuming to learn.