Asciidoctor is a Ruby tool, but luckily we can use AsciidoctorJ to use Asciidoctor in Java code. The Asciidoctor Gradle plugin relies on AsciidoctorJ to run. AsciidoctorJ allows us to write custom extensions in Java (or Groovy), but we can still use Asciidoctor extensions written in Ruby with the Gradle plugin.

In the following example we use the emoji-inline-macro from Asciidoctor extensions lab. This is an extension written in Ruby. We create a new directory for our sample and create a lib folder. Inside the lib directory we copy the file emoji-inline-macro.rb and the supporting directory emoji-inline-macro. These files are all in the Asciidoctor extensions lab repository. After we have copied the files we should have the following structure:

$ tree lib/
├── emoji-inline-macro
│   ├── extension.rb
│   ├── sample.adoc
│   └── twemoji-awesome.css
└── emoji-inline-macro.rb

1 directory, 4 files

In our build file we configure the asciidoctor task and use the requires method to define a dependency on the Ruby emoji-inline-macro.rb file:

// File: build.gradle
plugins {
    id 'org.asciidoctor.convert' version '1.5.3'

asciidoctor {
    // Add requirement on Ruby extension.
    requires './lib/emoji-inline-macro.rb'

We are done. Next we create a sample Asciidoc markup document with the following content:

= Asciidoctor is awesome!

Writing with Asciidoctor makes me feel emoji:sunny[5x]

This sample is written while Devoxx BE is in progress, so
@DevoxxPeople: Enjoy your emoji:beers[]

We get the following HTML5 output when we run the asciidoctor task:

Written with Asciidoctor Gradle plugin 1.5.3.

Original blog post