How do you return your REST API result to java cli?

I've developed before with node.js and spray.io to receive and throw REST API to front-end and back-end server vice versa, but I'm having a hard time to return a value to just java cli (like terminal) using plain java. I thought this could be a good practice for me to understand but it's more difficult than I thought it would be. I was able to reproduce echo servers on here https://www.cs.uic.edu/~troy/spring05/cs450/sockets/socket.html But what I want to do is to take a string parameter, and send it to the spring framework and process it in the back, then throw it out to the cli but just can't find an example for that. Could anyone direct me to a good project sample that does this? Thanks!