code: private static String getUpType(String path) {
          if (path == null || !path.startsWith("/")) {
              return "";
          }
          if ("/".equals(path)) {
              return "form";
          }
          int l = path.indexOf('/', 1);
          if (l < 1) {
              return "";
          }
          String m = path.substring(1, l);
          switch (m) {
              case "mkblk":
                  return "mkblk";
              case "bput":
                  return "bput";
              case "mkfile":
                  return "mkfile";
              case "put":
                  return "put";
              default:
                  return "";
          }
      }
docs: 通过path ，解析出是 form, mkblk, bput, mkfile