Docker cannot find the jar file

No, that won’t work. The contents of an image cannot directly be injected into the filesystem of a container created from another image.

Try this:

  1. Build an image which, when run, simply copies the jar to a path and exits.
  2. Use that image as as InitContainer in whichever pods need the jar. Mount a volume to the path to which the jar is copied.
  3. Now, mount the same volume in the container(s) defined in your main application podspecs, and ensure that the main application picks up the jar from there.