我正在研究参数化javaMap。在执行rfc查找时，代码返回的有效负载格式不正确。请找到下面的代码和堆栈跟踪。

chn = LookupService.getChannel(getBSystem(),getCChannel());
 rfc = LookupService.getRfcAccessor(chn);
 getTrace().addInfo("After LookUp");
 String req = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>"+"<ns0:OTC_NFE_MAIL_OUTPUT"+"xmlns:ns0=\"urn:sap-com:document:sap:rfc:functions\">"+"<I_ACCESS_KEY>"
    + idNFe + "<I_ACCESS_KEY></ns0:OTC_NFE_MAIL_OUTPUT>";
 getTrace().addInfo("Req value:"+req);
 InputStream inputRFC = new ByteArrayInputStream(req.getBytes());
 getTrace().addInfo("InputRFC"+inputRFC);
 XmlPayload rfcPayload = LookupService.getXmlPayload(inputRFC);
 getTrace().addInfo("rfcPayload"+rfcPayload);
 XmlPayload result = rfc.call(rfcPayload);
 getTrace().addInfo("Payload result"+result);
 InputStream resp = result.getContent();

堆栈跟踪：
查找后
 
要求value:35181204136367001755550010001002441406742916
 
输入fcjava.io。bytearrayinputstream@7ec9dfbb
 
rfcpayloadcom.sap.aii.mapping.lookup。xmlpayload@447072fe
我们需要在进行rfc调用时填充35181204136367001755550010001002441406742916值。请告诉我需要做什么改变。