While developing a "Spring Cloud Data Flow" sample, a question came to mind. Once my applications are registered, is it possible to retrieve/ customize their code through the UI or Shell?
Also, is it possible to access the code of the predefined applications of Spring Cloud Data Flow?
No, you cannot alter it from SCDF GUI/Shell.
Any custom application you'd author would likely go through a CI/CD pipeline in a typical deployment environment. An uber-jar or a container image would then have to be generated.
SCDF provides a metadata footprint to host where those artifacts are hosted in what registry etc.
On subsequent updates to your code, you probably want to unit-level/IT test it locally and then feed it into the CI/CD supply chain to generate another new version of the same application artifact.
However, to consume net-new versions in an already running stream/task data pipeline, users can automatically rolling-upgrade or rolling-rollback to a version using the SCDF APIs and GUI wizards (see: docs).
The code for the applications that we ship out-of-the-box in SCDF is in GitHub repo here - feel free to fork/customize them per your needs. Contributions welcome, of course, too!