There is a relevant question, but I could not get the answer clearly.
I would like to POST a short xml code
You can get the content of the response using:
String responseXml = EntityUtils.toString(httpResponse.getEntity());
You can then write this to a file using something like this.
there is something wrong with receiving the response
Since you havn't said what is wrong with receiving the response it's somewhat difficult to help you with this point.