Based on Hideaki Sorachi's manga of the same name, the film is written and directed by Yuichi Fukuda (Hentai Kamen). This isn't the first time the series had a movie as it previously inspired two anime movies, including the "final" Gintama movie, Gintama: Forever Odd Jobs.
Gintama is set for a July 14 release.
[Source: Anime News Network (link 2)]