What is Jib? A Complete Guide to Java Containerization Without Dockerfiles

Introduction When I joined PayPay, one of the first things I tried to understand was how our services were containerized. A common exercise when joining a new backend team is to look at the Dockerfiles used across services as they often reveal interesting patterns: Which base images are used Whether the builds are optimized If multi-stage builds are implemented Opportunities for reducing image size or improving caching So naturally, I went looking for the Dockerfile. But to my surprise… I couldn't find one. After digging a bit deeper, I realized something interesting. The project wasn’t using a Dockerfile at all. Instead, it was using Jib . 📦 Enter Jib Imagine shipping a Java microservice where changing a single line of code doesn’t force your CI pipeline to rebuild a massive container image. That’s exactly what Jib enables. Jib is an open-source container image builder for Java applications that: Eliminates the need for a Dockerfile Does not require a Docker daemon Integrates directly