code: protected String performGetRequest(String requestString) throws IOException {
      HttpGet request = new HttpGet(getBaseUrl() + requestString);
      if (USER != null && !USER.isEmpty()) {
        request.setHeader("Authorization", USER + ":" + TOKEN);
      }
  
      String json = null;
      CloseableHttpClient httpClient = HttpClients.createDefault();
      try {
        logger.debug("------------------------------------------------");
        logger.debug("OSS Index GET: " + getBaseUrl() + requestString);
        logger.debug("------------------------------------------------");
  
        CloseableHttpResponse response = httpClient.execute(request);
        int code = response.getStatusLine().getStatusCode();
        if(code < 200 || code > 299) {
          throw new ConnectException(response.getStatusLine().getReasonPhrase() + " (" + code + ")");
        }
        json = EntityUtils.toString(response.getEntity(), "UTF-8");
      } catch(ParseException e) {
        throw new IOException(e);
      } finally {
        httpClient.close();
      }
      return json;
    }
docs: Perform a get request
  
  @param requestString
  @return
  @throws IOException