code: public static String retrieveDataPost(String sUrl, String encoding, String postRequestBody, String contentType, int timeout) throws IOException {
          return retrieveStringInternalPost(sUrl, encoding, postRequestBody, contentType, timeout, null);
      }
docs: Download data from an URL with a POST request, if necessary converting from a character encoding.
  
  @param sUrl The full URL used to download the content.
  @param encoding An encoding, e.g. UTF-8, ISO-8859-15. Can be null.
  @param postRequestBody the body of the POST request, e.g. request parameters; must not be null
  @param contentType the content-type of the POST request; may be null
  @param timeout The timeout in milliseconds that is used for both connection timeout and read timeout.
  @return The response from the HTTP POST call.
  @throws IOException If accessing the resource fails.