Container Image

Build container images with tools and best practices.


git clone
cd jvm-helloworld-by-example/helloworld-springboot-tomcat


./mvnw package

Enable API

Enable Container Registry API to push your container images to the Container Registry.

gcloud services enable


Typically, tutorials teach you how to write a Dockerfile to containerize a Java application. A Dockerfile can be error prone and it's hard to implement all the best practices. Rather than writing a Dockerfile, use tools such as Jib and Buildpacks to automatically create optimized container images.

Build and Push

Most tools can build and push directly into a container registry. In case of Jib, this step does not require a Docker daemon at all, and it can push changed layers directly into a remote registry. This is great for automated CI/CD pipelines.

Jib can containerize any Java application easily, without a Dockerfile nor docker installed. Jib will push the container image directly to the remote registry.

PROJECT_ID=$(gcloud config get-value project)
./mvnw compile \${PROJECT_ID}/helloworld

You can configure Jib Maven plugin or Jib Gradle plugin directly in the build file to run the Jib easier, such as ./mvnw jib:build.

Build Locally

If you are running a local Docker daemon and you do not want to push straight to a remote registry, then you can build container images without pushing:

PROJECT_ID=$(gcloud config get-value project)
./mvnw compile \${PROJECT_ID}/helloworld

Run Locally

If you have Docker installed locally, you can run the docker container locally to ensure everything works. This command will run the container locally and forward localhost's port 8080 to the container instance's port 8080.

PROJECT_ID=$(gcloud config get-value project)

docker pull${PROJECT_ID}/helloworld
docker run -ti --rm -p 8080:8080${PROJECT_ID}/helloworld

The -ti flag means allocate a TTY, and expect interaction via STDIN. The --rm flag means delete the container completely upon exit.

Connect Locally

You can connect to the container that's running locally

curl localhost:8080

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