code: public int getFieldsSendTotalByteSize(Object bean, Charset charset) {
          if (!hasDynamicField()) {
              return fieldsTotalSize;
          } else {
              return getDynamicTotalFieldSize(bean, charset);
          }
      }
docs: 获取需要发送的报文长度
  
  @param bean
  @param charset
  @return
  @throws NoSuchMethodException
  @throws InvocationTargetException
  @throws IllegalAccessException