Do you tarnish your Clojure with the occasional hint of Java? Have you become indescribably tired of reloading your REPL every time you change anything with a .java suffix? Look no further.

Virgil is a library for live-recompiling Java classes from the REPL. This can be done either manually or by starting a process that watches your source directories for changes in Java files and triggering recompilation when that happens.

Usage

Add com.clojure-goes-fast/virgil dependency to your project.clj or deps.edn. Since this is a devtime dependency, you probably want to a profile/alias that you enable only during development.

(require 'virgil)
;; To recompile once, manually:
(virgil/compile-java ["src"])

;; To recompile automatically when files change:
(virgil/watch-and-recompile ["src"])

The main argument to these functions is a list of directories where Java source files are located. Both functions can accept a list of string :options that is passed to Java compiler, e.g. :options ["-Xlint:all"] to print compilation warnings, and a :verbose flag to print all classnames that got compiled.

watch-and-recompile accepts an optional :post-hook function. You can use it to, e.g., trigger tools.namespace refresh after the classes get recompiled.

Check example directory for a sample project.

Happy tarnishing.

Should I use Virgil in production?

Even though it is possible to dynamically compile Java classes with Virgil in the production builds of your project, it is not advised. Virgil is primarily a dev-time tool. For the release, it is preferable to use javac task of your build tool to generate real .class files that you will later pack into the JAR or put onto the classpath in some other way.

Migration from 0.1.9

From version 0.3.0, Virgil no longer provides lein-virgil plugin for Leiningen. Instead, you should add virgil it as a regular dependency to your project (but preferably only during the development) and call its functions from the REPL.

Supported versions

Virgil makes sure to support Clojure 1.10+ and JDK 8, 11, 17, 21, 22 (see CI job. Supporting future versions of Java so far required only bumping ASM library dependency, so that shouldn't take long. Please, create an issue if you run into any compatibility problems.

License

Copyright © 2016-2019 Zachary Tellman, 2022-2024 Oleksandr Yakushev

Distributed under the MIT License