How can I build a Docker image that is based on a multi-staged build process?

I know that Kaniko can perform the job. How can I use that from within a Maven file?

Q2: Paketo build are getting more popular. Is there a way to build with a Dockerfile? I know that Paketo tries to do the heavy lifting without any Dockerfile.

Let me give a simplistic (old) example: build a Spring Boot app consisting of both Angular frontend and a Java backend. Building maven allows running first ‘npm’ to build the frontend part and add it to the resources path. Then compile the Spring Boot app taking the frontend from the resources path.

Can you give a working example?