title: How to write ResponseEntity to HttpServletResponse?
body: <p>How to write ResponseEntity to HttpServletResponse (as it makes @ResponseBody)?</p>
  
  <p>For example I have authentication success handler:</p>
  
  <pre><code>@Override
  public void onAuthenticationSuccess(HttpServletRequest request, HttpServletResponse response, Authentication authentication) throws IOException, ServletException {
      Map responseMap = new HashMap();
      responseMap.put("user", "my_user_name");
      ResponseEntity responseEntity = new ResponseEntity(response, HttpStatus.OK);
  }
  </code></pre>
  
  <p>If use MappingJackson2HttpMessageConverter I have error: "Could not write content: not in non blocking mode."</p>
  
  <p>Code:</p>
  
  <pre><code>HttpOutputMessage outputMessage = new ServletServerHttpResponse(response);
  messageConverter.write(responseEntity, null, outputMessage);
  </code></pre>
  
  <p>What are the best practices of implementation handlers with HttpServletResponse?</p>