In SOAPMessageComposer#decompose there is an error in this line:
218: Node messageNodeImport = soapMessage.getSOAPBody().getOwnerDocument().importNode(messageNode, true);
Although messageNode is retrived like this:
Node messageNode = message.getContent(Node.class);
it is possible, that messageNode is from type Document (because it is inhearted fom Node).
This produces the following exception: "org.w3c.dom.DOMException: NOT_SUPPORTED_ERR", because Document#importNode ist not allowd for nodes of type DOCUMENT_NODE, see here: http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/core.html#Core-Document-importNode

I think somthing like this should be added:
if (messageNode.getNodeType() == Node.DOCUMENT_NODE)