Some Spring Boot questions, access to files?

Just getting started with Render, free tier, and was looking for some guidance about deploying a Spring Boot REST API that my REACT static front end needs to work.

From my googling and YouTubing, it sounds like spring boot APIs have to run in a docker container to work on Render. Is this right?

My Spring boot REST API currently doesn’t have a database, but will eventually. However it does need read access to data files not stored in a database but on the local file system. I’m very unsure how I would go about accessing files from a docker container running on render? I currently access with them with Java’s file api, and they’re on my local file system, so how would I do that from a docker container on Render? I don’t know a lot about docker either, could I include read only data files in my docker image and access them there?

Eventually I’d like to have read only access to around 15GB of data files from the spring boot API, although much smaller at first as I do the POC on Render.