title: How to reply to unauthenticated user in Spring 4 STOMP over WebSocket configuration?
body: <p>I'm experimenting with Spring 4 WebSocket STOMP application. Is there a way to reply to a <em>single unauthenticated</em> user on condition that each user has unique session ID? Right now I can only either broadcast a message or send it directly to an <em>authenticated</em> user.</p>
  
  <pre><code>@Controller
  public class ProductController {
  
      @MessageMapping("/products/{id}")
      @SendTo("/topic") // This line makes return value to be broadcasted to every connected user.
      public String getProduct(@DestinationVariable int id) {
          return "Product " + id;
      }
  }
  </code></pre>