title: How to implement not-real time chat between clients in Spring
body: <p>I would like to understand what's the best way to implement a very simple message exchange system between two clients, using Spring Boot as back-end and AngularJS as front-end. </p>
  
  <p>I'm new to Spring, I'm studying it and using it for a University project.</p>
  
  <p>Let's say that my project is a kind of a simplified e-commerce. I want to create a "conversation" between two clients (for example, something like the messaging system on eBay) based on the exchange of simple text messages. If one of the clients is not connected, he has to be able to retrieve the messages received while he was offline. </p>
  
  <p>I came across several tutorials and guides but most of them explain how to create a real time "chat room" which is not what I'm looking for. </p>
  
  <p>I would like to have some suggestions on what would be the best path to follow (JMS, WebSocket...) and why. </p>
  
  <p>Thanks in advance!</p>