Boost Spring Boot Development with Just: A Zero‑Config CLI for Fast Builds

Just is a command‑line tool that automatically reloads changed source code, build files, or Docker compose files, improving the Java development experience for Spring Boot applications. It also supports generating native applications and native Docker images.

Developed by freelance architect and developer Maciej Walkowiak, Just was released a month after its first code commit. The native binary Spring Boot application is built with picocli, uses Testcontainers for JUnit tests, integrates Sentry for error monitoring, and employs JReleaser for releases.

Just can detect source changes and, after a rebuild, reload the application using Spring Boot DevTools. Modifying pom.xml or build.gradle triggers a pause and restart after the build files are refreshed. Unlike Spring Boot DevTools, running the run sub‑command also starts databases and other infrastructure services defined in Docker compose. Executing just automatically triggers application build‑configuration detection. Just supports both Maven and Gradle wrappers, including Maven Daemon. A single run command handles all changes.

Compared with the run sub‑command, the build sub‑command translates to the appropriate Maven or Gradle command based on the build target:

just build [--quick] [--skip-test] <buildTarget>

Using the quick option skips tests, documentation generation, formatting checks, and static analysis. Just provides jar, native, image, and native native-image build targets to create (native) applications or Docker images. The format sub‑command formats the codebase according to project defaults, Spring Java format, and Spotless rules. The running process can be terminated with the kill sub‑command; the default port 8080 can be changed with -p, and -9 forces a kill.

In IntelliJ IDEA, Just can be run via the init idea sub‑command to add a run configuration, after which the “Shell script” option can be set to execute just run.

Installation: on macOS use Homebrew brew install maciejwalkowiak/brew/just; on Windows use Scoop

scoop bucket add maciejwalkowiak https://github.com/maciejwalkowiak/scoop-just.git

and scoop install just; or download the Linux zip, unzip, make executable, and move to /usr/local/bin/just. The help sub‑command verifies the installation.

Just is not open‑source; the GitHub repository contains only binaries, release notes, and issue tracking. It is currently in Alpha, free to use, but each release includes an embedded expiration time that may require purchasing or updating later.

For more details, see the “Getting Started” documentation.