MonkeyCI uses the Clojure CLI in order to execute the build scripts. This CLI allows to configure dependencies to include other libraries in your code, and so it's also possible to do this in your build scripts. These dependencies are configured in a file called deps.edn which should be put next to your build.clj, in the .monkeyci/ directory. Although the CLI provides a lot of functionality with this file, we use it mainly to declare dependencies, like so:

;; Example deps.edn file
;; Add the maven plugin library
{:deps {com.monkeyci/plugin-mvn {:mvn/version "1.0.0"}}}

The file format is EDN, short for extenisble data notation. It's to Clojure what JSON is to JavaScript.

This is required if you want to use any plugins in your build script. But you can also use it to include any 3rd party library in your script, which you can then use in action jobs. These libraries can be native Clojure, but also Java libraries, so the entire Java ecosystem is available in your builds!

MonkeyCI will automatically include a reference to itself in the dependencies, so you don't need to do that yourself. This is necessary to be able to access the basic core functionality of MonkeyCI. But apart from that you're free to add any Java or Clojure library in your build script, as long as they don't require any native dependencies.