Hi Davide
as far as I know, in an import directive you should specify a class, or all the classes in a package. When you state "import com.fasterxml.jackson.core", you are addressing a java package, not a Class.
Try to import each class you really need, I mean:
import com.fasterxml.jackson.core.YourClass
(substitute YourClass with the actual one), or all the classes in that package with:
import com.fasterxml.jackson.core.*
This should be correct. Let me know.