title: @GetMapping not produces response content type application/json
body: <p>I'm developing an API Rest with Spring 4 and annotations swagger. Until now I was using<br>
  <code>'@RequestMapping(value = "/myapi/{id}", method = RequestMethod.GET, produces = "application/json; charset=UTF-8")'</code>, but I want to use the reduced version with GET:
  <code>@GetMapping("/myapi/{id}")</code>.
  The problem is that swagger is not showing correctly the response content type:
  Instead of it, I get the following:</p>
  
  <blockquote>
    <p>response content type <em>/</em></p>
  </blockquote>
  
  <p>I have tried adding an HttpHeaders object to the response entity but not works.</p>
  
  <p>Can you help me?</p>