Single property support for JSON based values of GCP Secret Manager integration about spring-boot

[wilkinsona]

Thanks for the proposal, @thecanadianroot.

I'm afraid I disagree with @meltsufin here as I think this should be implemented alongside the support for sm: in Spring Cloud GCP. To Spring Boot, a value like ${sm://my-database/json/username} is almost completely opaque. All it knows is that the sm: prefix means that the remainder of the string (my-database/json/username) should be handled by Spring Cloud GCP.

We do have CloudFoundryVcapEnvironmentPostProcessor in Boot that takes a JSON payload from Cloud Foundry's VCAP_APPLICATION and VCAP_SERVICE environment variables and maps it to several properties in the environment. This logic is specific to CloudFoundry and the structure of its JSON. I would expect similar functionality that's specific to GCP's Secret Manager and how it uses JSON to be part of Spring Cloud GCP rather than Spring Boot itself.

Perhaps there's an opportunity for some lower-level helper classes in Spring Boot that can establish some conventions for extracting a single value from some JSON and assigning it to a property or mapping a whole JSON document to configuration properties but I think we'd need to see multiple implementations doing similar things before we'd be in a position where it made sense to add such functionality to Boot.

[meltsufin]

@wilkinsona Thanks for the feedback. Cloud Secret Manager doesn't have any JSON format. It simply allows storage and retrieval of secrets of type byte[]. So, support for interpreting the byte[] as JSON and extracting properties from it doesn't seem to be specific to Cloud Secret Manager. That being said, as this FR seems to be just in spring-cloud-gcp right now, we can keep it scoped to our repo.

[wilkinsona]

Thanks, @meltsufin. I'll close this one for now then. If this becomes something of a theme and we see the same requirement from other areas we can look at adding some common infrastructure to Spring Boot at that point.