JKube maven plugin can't find jar file when building docker image using mvn k8s:build

Question

I'm trying to use JKube for building and deploying APIs to my K8S cluster but when I do mvn k8s:build I'm getting this error:

[INFO] --- kubernetes-maven-plugin:1.1.1:build (default-cli) @ trips-api ---
[INFO] k8s: Running in Kubernetes mode
[INFO] k8s: Building Docker image in Kubernetes mode
[INFO] k8s: [carpooling/trips-api:latest]: Created docker-build.tar in 2 seconds 
[ERROR] k8s: Failed to execute the build [Error while trying to build the image: Unable to build image [carpooling/trips-api:latest] : "COPY failed: no source files were specified" ]

This is the content of my Dockerfile :

FROM adoptopenjdk/openjdk11:latest
VOLUME /tmp
COPY target/*.jar app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

NB: I'm ensuring that under my target/ directory I have the right jar file.

Does anyone have an idea about why I'm getting this error?

Answer 1

Eclipse JKube has an assembly mechanism for adding files to your container images. When using zero configuration Dockerfile mode, assembly name is set to maven . You would need to prefix your project files with maven to be able to access it. So your Dockerfile should look like this:

FROM adoptopenjdk/openjdk11:latest
VOLUME /tmp
COPY maven/target/*.jar app.jar
ENTRYPOINT ["java","-jar","/app.jar"]

I tested this with a simple demo project with your Dockerfile contents: https://github.com/r0haaaan/eclipse-jkube-spring-boot-simple-dockerfile and it seemed to work okay for me.