code: public HttpServerExchange setMaxEntitySize(final long maxEntitySize) {
          if (!isRequestChannelAvailable()) {
              throw UndertowMessages.MESSAGES.requestChannelAlreadyProvided();
          }
          this.maxEntitySize = maxEntitySize;
          connection.maxEntitySizeUpdated(this);
          return this;
      }
docs: Sets the max entity size for this exchange. This cannot be modified after the request channel has been obtained.
  
  @param maxEntitySize The max entity size