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avelino

16 days ago

I built a tool to solve a problem I kept hitting: deploying Clojure apps without requiring Java on the target machine.23:20:00 [3/101]

The usual answer is GraalVM native-image, but in practice it means dealing with reflection configs, library incompatibilities, long build times, and a complex toolchain. For many projects it's more friction than it's worth.

clj-pack takes a different approach: it bundles a minimal JVM runtime (via jlink) with your uberjar into a single executable. The result is a binary that runs anywhere with zero external dependencies and full JVM compatibility — no reflection configs, no unsupported libraries, your app runs exactly as it does in development.

clj-pack build --input ./my-project --output ./dist/my-app ./dist/my-app # no Java needed How it works:

Detects your build system (deps.edn or project.clj)

Compiles the uberjar

Downloads a JDK from Adoptium (cached locally)

Uses jdeps + jlink to create a minimal runtime (~30-50 MB)

Packs everything into a single binary

The binary extracts on first run (cached by content hash), subsequent runs are instant.

Trade-off is honest: binaries are slightly larger than GraalVM output (~30-50 MB vs ~20-40 MB), and first execution has extraction overhead. But you get full compatibility and a simple build process in return.

Written in Rust, supports Linux and macOS (x64/aarch64).

Feedback and contributions welcome

geokon

15 days ago

whats the advantage over just manually making a uberjar and using jlink/jpackage?

Do you have the ability to crosscompile to other architectures/OS?

Do you have the ability to generate a plain executable? the jlink/jpackage route ends up generating an "installers" for each system, which i find hard/annoying to test and people are reluctant to install a program you send them

In the past ive ended up distributing an uberjar bc i didnt have the setup to test all the resulting bundles (esp MacOS which requires buying a separate machine). I also found JavaFX to be a bit inconsistent.. though its been a few years and maybe the situation has improved

avelino

14 days ago

Advantage over manual uberjar + jlink/jpackage:

The main pain point jbundle solves is that jpackage generates installers (.deb, .rpm, .dmg, .msi), not plain executables. jbundle produces a single self-contained binary — just a shell stub concatenated with a compressed payload. You chmod +x it, distribute it, and the user runs ./app. No installation step, no system-level changes.

It also automates the full pipeline (detect build system → build uberjar → download JDK → jdeps → jlink → pack) so you don't need a JDK installed on the build machine — it fetches the exact version from Adoptium. Plus it includes startup optimizations like AppCDS (auto-created on first run, JDK 19+), CRaC checkpoints, and profile-tuned JVM flags for CLI vs server workloads.

Cross-compilation:

Yes — jbundle build --target linux-x64 (or linux-aarch64, macos-x64, macos-aarch64). Since the JAR is platform-independent, it just downloads the appropriate JDK runtime for the target OS/arch from Adoptium and bundles it. You can build a Linux binary from macOS and vice-versa.

Plain executable (not an installer):

That's exactly what jbundle produces. The output is a single file you can scp to a server or hand to someone. On first run it extracts the runtime and jar to ~/.jbundle/cache/ (keyed by content hash), so subsequent runs are instant. No .deb, no .dmg, no "install this first" — just a binary.

For the macOS testing concern: since it's a CLI binary (not a .app bundle), it doesn't require signing/notarization to run. And with --target macos-aarch64 you can build it from a Linux CI without needing a Mac.