code: public List<String> getParamNames() {
      if (!Strings.contains(content, ":")) { return Collections.emptyList(); }
      final List<String> params = new ArrayList<String>();
      int index = 0;
      do {
        final int colonIndex = content.indexOf(':', index);
        if (-1 == colonIndex) {
          break;
        }
        index = colonIndex + 1;
        while (index < content.length()) {
          final char c = content.charAt(index);
          if (isValidIdentifierStarter(c)) {
            index++;
          } else {
            break;
          }
        }
        final String paramName = content.substring(colonIndex + 1, index);
        if (!params.contains(paramName)) {
          params.add(paramName);
        }
      } while (index < content.length());
      return params;
    }
docs: 得到查询条件中所有的命名参数.
  
  @return a {@link java.util.List} object.