title: Polymorphic serialization using Jackson when return type is marker interface
body: <p>I have a rest service which returns marker interface and this interface have multiple implementations and don't have any common property in the implementations.</p>
  
  <pre><code>    @RequestMapping(value = "/users/{userName}", method = RequestMethod.GET)
      public User getUser(@PathVariable("userName") String userName) {
          return userService.getUser(userName);
      }
  </code></pre>
  
  <p>User and its implementations.Note : User is marker interface.</p>
  
  <pre><code>public interface User {}
  
  public AdminUser implements User { // some properties &amp; its setters &amp; getters } 
  
  public SupportUser implements User { // some properties &amp; its setters &amp; getters } 
  </code></pre>
  
  <p>I use Jackson 1.9.1 to serialize and deserialize.</p>
  
  <p>When I hit above service, I am getting below response</p>
  
  <pre><code>{}
  </code></pre>
  
  <p>When I debug it, I see user implementation object is prepared and sent back to Jackson for serialization.But jackson is sending empty response to browser.Can anyone suggest how to use serialize when return type is marker interface.</p>