title: STOMP header on @MessageMapping return
body: <p>In my Spring Boot 1.5 application with Spring Websocket, I'd like to set a custom STOMP header on the return value of a <code>@MessageMapping</code> method, but I don't know how to do this. For example:</p>
  
  <pre><code>@Controller
  public class ChannelController {
  
      @MessageMapping("/books/{id}")
      public Book receive(@DestinationVariable("id") Long bookId) {
          return findBook(bookId);
      }
  
      private Book findBook(Long bookId) {
          return //...
      }
  }
  </code></pre>
  
  <p>When <code>receive</code> is triggered from a client's <code>STOMP SEND</code>, I'd like the <code>STOMP MESSAGE</code> reply frame with the book body to have a custom header: <code>message-type:BOOK</code> like this:</p>
  
  <pre><code>MESSAGE
  message-type:BOOK
  destination:/topic/books/1
  content-type:application/json;charset=UTF-8
  subscription:sub-0
  message-id:0-7
  content-length:1868
  
  { 
    "createdDate" : "2017-08-10T10:40:39.256", 
    "lastModifiedDate" : "2017-08-10T10:42:57.976", 
    "id" : 1, 
    "name" : "The big book", 
    "description" : null 
  }
  ^@
  </code></pre>
  
  <p>How do I set a STOMP header for the reply return value in a <code>@MessageMapping</code>?</p>