[java] Base image for spring-boot

[cbeauchesne]

Motivation

Changes

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes (if something not related to your task is failing, you can ignore it)
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner. We're working on refining the codeowners file quickly.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• If PR title starts with [<language>], double-check that only <language> is impacted by the change
• No system-tests internal is modified. Otherwise, I have the approval from R&P team
• CI is green, or failing jobs are not related to this change (and you are 100% sure about this statement)
• A docker base image is modified?
  • the relevant build-XXX-image label is present
• A scenario is added (or removed)?
  • Get a review from R&P team

[smola]

Yes, it does. Unfortunately some things are only fetched once the sources are available and all build stages run. But at least what is fetched does not depend on sources' contents except pom.xml, so it would be ok to include them in the base image for build (perhaps deleting them later?).

[cbeauchesne]

IIUC, we could preload them in the base image, and so this command won't have to download it, but would pick it from the base image? If yes, that's perfect.

[smola]

Yes, I think the main aspect to consider here is not mix old with new sources. I'm not sure what's COPY behavior if you do it over an existing directory. If it fully replaces the directory, then it's fine to include the sources as is and run package in the base image. Otherwise, it's just the same but deleting the sources from base image before finishing.

[cbeauchesne]

let's zoom when we'll be back !