title: ResponseEntity got null body when using DeferredResult
body: <p>I am using SpringBoot 1.4.4 to create an async RESTful api. Everything works fine except when request is successfully processed, DeferredResult&lt;ResponseEntity&lt;String>> always has null body and 200 OK status code even though i explicitly set string value to the result object.The code looks like this:</p>
  
  <p>RestController impl:</p>
  
  <pre><code> @Async
    public DeferredResult&lt;ResponseEntity&lt;String&gt;&gt; parseWithLongDelay(    
       @RequestBody MyRequestObject req){
       DeferredResult&lt;ResponseEntity&lt;String&gt;&gt; result = new DeferredResult&lt;&gt;();
       :
       :
       result.setResult(new ResponseEntity&lt;String&gt;("That big zip file successfully parsed.", HttpStatus.OK));
       return result;
    }
  </code></pre>
  
  <p>Client side:</p>
  
  <pre><code> @Test
   public void test(){
      ListenableFuture&lt;ResponseEntity&lt;String&gt;&gt; futureEntity = new AsyncRestTemplate().postForEntity(url, requestEntity,
      String.class);
      futureEntity.addCallback(new MyFutureCallback());
      :
    }
    class MyFutureCallback implements ListenableFutureCallback&lt;ResponseEntity&lt;String&gt;&gt; {
    @Override
    public void onSuccess(ResponseEntity&lt;String&gt; entity) {
     String body = entity.getBody();
     log.info("response content: " + body);
     //always get null body, there is no server side exception or error
     //when callback happens
   }
  }  
  </code></pre>
  
  <p>I am expecting string "That big zip file successfully parsed." as body get return instead of null? Any clue? Please help!</p>