St. John was a Spanish Dominican lay brother. There's not much written about him in the sources I use. They only say that he was noted for having just two interests in life, study and prayer. He died of natural causes in 1566.
Maybe I'm being picky here, but it seems to me that if his only two natural inclinations were studying and praying, then calling him a saint is a little dodgy. After all, he was just indulging himself in the things he found most pleasant by becoming a model monk. Being naturally inclined that way gave him an inside track, and a little more should be expected of someone who has such advantages. Did his prayers fill any empty beer casks? Did they cure any lepers or keep anyone safe from wolves?