title: Spring @RestController won't product application/xml
body: <p>I have a <code>@RestController</code> with the following method</p>
  
  <pre><code>@RequestMapping(path = "/thing", method = RequestMethod.GET, 
      produces = { MediaType.APPLICATION_XML_VALUE })
  public List&lt;Thing&gt; listThings() {
      return thingMapper.listThings();
  }
  </code></pre>
  
  <p>But when I make a GET request with <code>Accept:application/xml</code> in the header, the Content-Length of the response is 0 and it doesn't produce anything. I know that data is being returned by my query and if I remove the <code>produces</code> attribute and make a plain get request it returns the data as json....I just cant get it to produce xml. Any ideas?</p>
  
  <p><strong>EDIT:</strong> I should mention that I am using the Spring Boot web starter</p>