Execute Sevlet class from java main

I have a requirement to process custom code in a sepparate server.

We have some node js code which process these custom code. Custom code can be a java class , servlet , sql statement or a js code. I am able call simple java code from node js and pass back the results. But how can I call a servlet? I want to return the result of it as an html string. is it possible to execute a servlet from a java main?
I have only the servlet class available with me. My servlets accept small parameters like int or String.

The context here is to keep a sepparate machine to process custom code, something like server less computing. Is it suggested to use frame works like AWS Lamda to acheive this? Does it take care of servlets also

via Xiao