jib

Jib is an open-source tool from Google that packages Java applications into container images without requiring Docker to be installed or running on the developer's machine. A container image is a standardized bundle that includes your application and everything it needs to run, making it easy to deploy consistently across different computers and cloud environments.

Traditionally, packaging a Java application into a container meant writing a special configuration file called a Dockerfile, then using Docker's own command-line tools to build and push the image. Jib removes all of those steps. Instead, it plugs directly into Maven or Gradle, which are the standard build tools that Java developers already use. You run your normal build command and Jib handles creating and uploading the container image automatically.

One of Jib's main advantages is speed. A typical approach puts the entire application into a single layer inside the container. Jib instead splits the application into separate layers: one for the external libraries your code depends on, and another for the code you actually wrote. Because libraries change far less often than your own code, only the changed layer needs to be re-uploaded when you redeploy. This can dramatically cut down the time between making a change and having it live.

Jib also produces reproducible builds. Given the same source code and dependencies, it will always produce an identical container image, down to the byte. This means you can be confident that rebuilding does not introduce hidden differences.

The tool is available as a Maven plugin, a Gradle plugin, a Java library called Jib Core for more customized use cases, and a standalone command-line tool. It works with any container registry that accepts standard Docker or OCI images, which are two widely supported image formats. Google developed it primarily to work well with their own cloud build and deployment services, but it is not limited to the Google ecosystem.