How do http requests work in deployed Spring Boot app?

Question

Can someone explain how hosting works? in my spring boot app there'ss embedded tomcat server. as I understand the spring app runs with tomcat, tomcat takes some port, 8080 for example, and listens to requests coming to that port (when deployed locally at least) localhost:8080. I can make requests from my front end app, which runs on localhost:3000 and tomcat will take the requests, find controllers mapped to the urls that front request is directed to "/user" or "/myposts" or whatever, that controller runs code, talks to db inserts data into response and tomcat sends it back to front end.

If I deploy my app to some hosting service, like Google cloud, does the spring app still run with tomcat? in that case which port will tomcat run on, where would my front end send requests to? to the subdomain that google cloud has set up for my project? Where would i need to configure SSL/https? Would my front end send secure requests to google subdomain over https endpoints and it would relay those requests to deployed spring app through http(unsecured, inside hosting server)? Or how?

Answer 1

One of the most straightforward way to do this is to spin up an instance, ssh into the that instance and run your spring boot app the same way you would run it on your machine. Everything works the same as it would on that cloud instance. Your spring boot app still runs within tomcat and it still listens to port 8080. The only difference is now the hostname is no longer localhost and it will be the DNS name of that instance. You can find the DNS name on the console.

You need to get a SSL certificate if you wanna enable https "natively" in your spring boot app. Alternatively, you can set up a load balancer or an API gateway in front of your cloud instance to do the SSL termination for you. In this case, your frontend will send request to the load balancer or API gateway instead of your spring boot app. They accept https requests and transform them to http request and send it to your spring boot app.