Problem while returning a ResponseEntity<byte[]> from REST API. Why?

Question

When, I return ResponseEntity<byte[]>(new ResponseEntity<byte[]>(sb.toString().getBytes(), headers, HttpStatus.OK)) from REST API, it takes about 6 seconds but when I return responseEntity.getBody(), it takes about 1 seconds. How ?

ResponseEntity<byte[]> responseEntity = configTemplateService.getConfigTemplateExample(type);
// This need very long time
return responseEntity;

ResponseEntity<byte[]> responseEntity = configTemplateService.getConfigTemplateExample(type);
// This need less time
return responseEntity.getBody();

Answer 1

Data type of responseEntity.getBody() is String (1).

Data type of responseEntity is binary data (2) including Body and another parts those are not Body (such as Header).

(2) = (1) + (another parts)

therefore, (2) > (1)