I'm curious in which languages I can actually write plugins? I found Kotlin and Groovy in the docs. I'm fairly used to Java but not at all to the other two.
Which on is easier to learn/will feel more natural for a Java and mainly web development guy? Are there any advantages/disadvantages in using one over the other despite the languages itself? I mean are there APIs I can't use with Kotlin/Groovy or sth? What would you recommend?
Is there a good reference project using Gradle/Groovy resp. Kotlin? I guess it will be beneficial to have a gradle build, right?