I am using Guidewire PolicyCenter On-Prem version 10, and we have two options for consuming REST API services:
1)Using the REST API client provided by Guidewire, where we define a JSON service definition file to generate a JAR and include it in the PolicyCenter shared lib folder. 2)Using the conventional java.net.http.HttpClient.newBuilder class for making HTTP requests.
I would like to know which option is recommended and compatible with Guidewire Cloud releases.
I would say the REST API Client is the way to go. The Guidewire documentation for 10.2.4 (latest on-premise release) and Las Lenas (latest GWCP release) point to the exact same REST API Client documentation. Link below (GW partner/customer login required).
So using the REST API Client provided by Guidewire is the best option if you want your development effort on-premise to be able to move to GWCP. Setting up and using the REST API Client takes a bit more of time initially, but should be easier to maintain over the long run. Good luck!