"Empire" executive producer Danny Strong is directing the script, he adapted based on the Kenneth Slawenski biography "JD Salinger: A Life", reported Deadline.
Hoult, 26, was set last fall to play Salinger as he progressed toward writing the seminal novel of the 20th Century.
Spacey, 56, will play Whit Burnett, a professor at Columbia and editor of Story magazine.
He became a mentor and was the first to challenge the young Salinger, inspiring him to grow as a storyteller.