Hi Aashish,
RestExpress uses Netty as its server instead of Tomcat. So those procedures won't work.
Most often, when an API is hosted, it's behind a proxy or load balancer of some sort (HAProxy, Linkerd, NGINX, etc.) and it's that proxy that hosts the certificates. Using non-SSL/TLS behind that load balancer is usually OK because the API is behind your firewall.
Optionally, you can choose to run an HAProxy on the same box as your API, using the HAProxy to host the cert and perform API traffic on the loopback interface (127.0.0.1).
I hope this helps!
--Todd