code: public static String transform(final Throwable cause) {
          if (null == cause) {
              return "";
          }
          StringWriter result = new StringWriter();
          try (PrintWriter writer = new PrintWriter(result)) {
              cause.printStackTrace(writer);
          }
          return result.toString();
      }
docs: 将Throwable异常转换为字符串.
  
  @param cause 需要转换的异常
  @return 转换后的异常字符串