code: @SuppressWarnings("unchecked")
      public void finishJson(final JsonConvert convert, final CompletableFuture future) {
          finish(convert, (Type) null, future);
      }
docs: 将CompletableFuture的结果对象以JSON格式输出
  
  @param convert 指定的JsonConvert
  @param future  输出对象的句柄