Just, a New CLI for Spring Boot Applications

Published on Jan 10, 2023

A command line tool called Just, which requires no configuration, enhances the Java development experience when building Spring Boot applications. When source code, build files, or Docker compose files are changed, Just automatically reloads the application. In addition, the project supports the creation of (native) applications and (native) Docker images.

Just exactly eleven months after the first commit, Maciej Walkowiak, Freelance Architect & Developer, released the project. This is a Spring Boot application compiled to a native binary that uses: picocli to create a command line application; Testcontainers to run containers in JUnit tests; Sentry for error monitoring; and JReleaser for releasing the application.

Uses Spring Boot Devtools to reload the application after the source code has been changed and the build has been initiated. In addition to Spring Boot Devtools, Just automatically detects and compiles source code changes. Furthermore, whenever the contents of pom.xml or build.gradle change, the application is stopped, the build file is refreshed, and the application is re-started. As opposed to Spring Boot Devtools, Just also starts infrastructure services such as databases and Docker Compose services whenever the run sub-command is executed. The just command detects the build configuration automatically and uses it whenever it is executed. Maven and Gradle are supported, as well as their wrappers and the Maven Daemon. You only need to execute the run sub-command once, and the application will be updated accordingly.

Tests, document generation, and checks such as formatting and static analysis are not included in the quick option. Several buildTarget options are available to create a (native) application or a (native) Docker image: jar, native, image, and native-image.

The format sub-command formats the codebase according to the settings specified in the project configuration, such as the Spring Java Format or Spotless settings.

A running process may be terminated by using the kill subcommand. By default, the process running on port 8080 is terminated. A port may also be specified using the -p argument, and the kill sub-command can be forced by using the -9 argument.

Just can be executed from the command line or from IntelliJ IDEA by adding a run configuration by running the init idea subcommand. Alternatively, the run configuration may be added manually by opening the configuration via the Run menu option and selecting Edit Configurations. Add a Shell Script and specify its name. The Execute option should be set to Shell Script and the Script Text should be set to just run. You can apply the configuration after unchecking Execute in the terminal. Run now shows the name of the new shell script that can be used to start Just.

Verify the installation using the help subcommand.

It is not an open source project. Binaries, release notes, and issue trackers are available on GitHub, but not source code. Currently, the project is in alpha status and is free. Upon expiration, the application can either be purchased or updated to the latest release.