Output Attachment is null in Operation Mapping only while working fine in Message Mapping

Hi Eperts,

I have written this piece of code to create an output attachment in Message Mapping (not UDF), see screen. It's running fine in Message mapping. But it is getting failed in Operation mapping. See the reults and sample code below.

Message mapping Result:

DN File Attached

Operation Mapping Result:

outAtt is null

Error in Operation mapping:

com.sap.aii.mapping.api.StreamTransformationException: while trying to invoke the method com.sap.aii.mapping.api.OutputAttachments.create(java.lang.String, byte[]) of a null object loaded

Code:

public void transform(TransformationInput in, TransformationOutput out) throws StreamTransformationException {

try{

OutputStream os = out.getOutputPayload().getOutputStream();

//creating output attachment

OutputAttachments outAtt = out.getOutputAttachments();

if (outAtt==null)

getTrace().addInfo("outAtt is null");

//File Names

String dnFileName="001DN.txt";

String CRLF = "\r\n";

String df="test attachment";

// Forming attachment for DN file

Attachment attDN = outAtt.create(dnFileName, df.getBytes());

if (attDN!=null)

{

outAtt.setAttachment(attDN);

getTrace().addInfo("DN File Attached");

}

else

getTrace().addInfo("DN File NOT Attached");

// forming Email Package

String emailPackage=

"<?xml version=\"1.0\" encoding=\"UTF-8\"?>"+CRLF+ "<ns:Mail xmlns:ns=\"http://sap.com/xi/XI/Mail/30\">"+CRLF+ "<Subject>Delivery notes of CORUS</Subject>"+CRLF+ "<From>test.com</From>"+CRLF+ "<To>test.com</To>"+CRLF+ "<Reply_To />"+CRLF+ "<Content_Type>text/plain</Content_Type>"+CRLF+ "<Content></Content>"+CRLF+ "</ns:Mail>";

// writing Email Package

getTrace().addInfo("Writing Email Package");

os.write(emailPackage.getBytes());

os.flush();

os.close();

}

catch (Exception e)

{

throw new StreamTransformationException(e.getMessage());

}

}

Can someone explain to me, why it's happening. Why outAtt is not null in Message mapping and null in Operation Mapping?