I have multiple java projects which all build independently but most of which depend on one or more of the others to build. This is very basic stuff for anyone using Java with a build server, I hope there a standard solution for this?
Yes, this is quite standard. I think the standard solution would be a dependency management tool like Maven or Gradle to publish the dependencies to a repository with can then be loaded as needed by downstream projects. Maven and gradle are supported by all our JDK based images.
Alternately you could checkout the additional dependencies and build from scratch, but in my opinion it feels cleaner to delegate the packaging and release lifecycle to the individual projects.