Problem

Maybe when you execute a message mappping with the character & the error  “Unable to display tree view; Error when parsing an XML document (The entity name must immediately follow the ‘&’ in the entity reference.)” is returned.

The solution for this problem is simple, just develop the java mapping for change the character & by &. 

Solution

In your Message Mapping, in the tab Functions copy and past the code below int the area Attributes and Methods, (or if you prefer, create a java mapping in NWDS with the same code, works the same way).

public void transform(TransformationInput transformationInput, TransformationOutput transformationOutput) throws StreamTransformationException {
	try {
		InputStream inputstream = transformationInput.getInputPayload().getInputStream();
		OutputStream outputstream = transformationOutput.getOutputPayload().getOutputStream();

		byte[] b = new byte[inputstream.available()];
		inputstream.read(b);
		String encoding ="UTF-8";
		String inputXML=new String(b);

		inputXML = inputXML.replaceAll("&(?!amp;)", "&");
		outputstream.write(inputXML.getBytes(encoding));

	} catch (Exception exception) {
		getTrace().addDebugMessage(exception.getMessage());
		throw new StreamTransformationException(exception.toString());
	}
}

Test

Open your Message Mapping (or operation mapping if you create a jar in NWDS), in Text View, fill the field with the & and run a test.

I hope I have collaborated with the community, and I await your feedback.