javafx is a component not available in openjdk, easiest way around is to download a linux build on Oracle's homepage and extract the zip somewhere.
using this separate JRE is quite easy, something like this works.
JAVA_HOME="/path/to/extracted/oracle/jre/" /path/to/extracted/oracle/jre/java -jar DISpurity.jar
but I only get a grey window and the console throws this warnings:
[INFO] Application starting ...
[WARN] Media player (id = 'player1') cannot use 'mediaView' as view of media content.
[WARN] Media player (id = 'player') cannot use 'mediaView' as view of media content.
when I tried dispurity some time ago I solved this somehow, but I forgot how :)