IntelliJ Can't resolve Q Class(QueryDSL) // 인텔리J, QClass(QueryDSL)을 못 찾을때 -- Java Developing environment

IntelliJ Can't resolve Q Class(QueryDSL). (Cannot import, Cannot build)

I use IntelliJ, and it can't resolve(import) Q Class in my projects, even though Classes are generated by gradle. My thing can't find it. 

I spent a lot of hours for solving this problem. Finally I solved it.

At IntelliJ, Right mouse click on your QueryDSL generated directory.(Ex: /src/main/generated)
then, chose "Mark directory as" >> click "Mark Generated source root"
(Caution: If you clean and build your project after do this, you have to set this again)

(I'm not sure how to set this at Eclipse)