Lỗi ServletContext cannot be resolved to a type
https://hocdelamduocviec.blogspot.com/2014/03/loi-servletcontext-cannot-be-resolved.html
- Click chuột phải lên project bị lỗi đó ->Build Path->Configure Build Path...->Libraries->Add Library...->Server Runtime->Next->Chọn server->Finish->Ok
