Arjen, I realize that ":" is just the separation between prefix and localname. Perhaps I didnt clearly explain what I am doing.
Here is my code:
When tracing, I can see that both elements have the prefix set properly, but already in the SoapEndpointIntercoptor's handleResponse, those elements are missing the prefix. So somehow, somewhere soap's parser removes this prefix, but I really need it to be there.
private static final String NAMESPACE ="http.../tst";
private static final String PREFIX = "tst";
Element element = doc.createElementNS(NAMESPACE, "Element");
Element idElement = doc.createElementNS(NAMESPACE, PREFIX + ":" + "id");
Hope its a little clearer whats happening.
And thanks again for your help.