code: static String parseContentType(String contentType) throws IOException {
          if (contentType.indexOf(System.getProperty("line.separator")) > 0) {
              BufferedReader reader = new BufferedReader(new StringReader(contentType));
  
              try {
                  String plainContentType = reader.readLine();
                  if (plainContentType != null && plainContentType.trim().endsWith(";")) {
                      plainContentType = plainContentType.trim().substring(0, plainContentType.length() - 1);
                  }
  
                  return plainContentType;
              } finally {
                  try {
                      reader.close();
                  } catch (IOException e) {
                      log.warn("Failed to close reader", e);
                  }
              }
          }
  
          return contentType;
      }
docs: When content type has multiple lines this method just returns plain content type information in first line.
  This is the case when multipart mixed content type has boundary information in next line.
  @param contentType
  @return
  @throws IOException