Grails download file

I'v used this method to copy a file to a folder in my project(first method), and I have edited it so the location is stored on my 'Location' in class Submissions (see below).

Now I want to be able to, after clicking on an image in my view, download that file. How can I do that ?

class Submissions {

    Date dateSub
    String Location
    String fileName

}