XApps can be written using the RIC utility libraries (RMR, SDL, logging, etc) directly or by utilizing the xApp frameworks (in go, C++, and Python). The xApp frameworks are described in
https://docs.o-ran-sc.org/projects/o-ran-sc-ric-plt-xapp-frame-cpp/en/latest/user-guide.html
For RIC xApps to be deployable, they need to have a proper docker image generated and available in a accessible docker registry, and a valid xApp descriptor,