soap serialize / digital signature question

[Paul Tomsic <pt...@yahoo.com>]

I'm trying to serialize a bean to send in my soap
envelope (the bean is merely a wrapper for a
org.w3c.dom.Document containing a single getter method
that returns a org.w3c.dom.Document)
 
I can do this just fine, but I can't seem to figure
out how to sign the soap.
There's an example that ships w/ AXIS in the security
folder that contains a class classed
SignedSOAPEnvelope
but the demo for it doesn't deal with serialization.

Here's the code that I've got.  Could someone offer a
suggestion as to where in my code, I'd get the
envelope to sign it? 
Thanks in advance.. 
-- code --

MyBean mybean = new MyBean();
mybean.setDoc(this.xml_document);

Call call = (Call)service.createCall();
QName qn = new QName("urn:SoapService", "Map");
call.registerTypeMapping(MyBean.class, qn, new
BeanSerializerFactory(MyBean.class, qn), new
BeanDeserializerFactory(MyBean.class, qn));
call.setTargetEndpointAddress(new
java.net.URL(this.endPoint));
 
call.setOperationName(new QName(SERVICE_NAME,
REMOTE_METHOD_NAME));
 
call.addParameter("arg1", qn, ParameterMode.IN);
 
call.setReturnType(XMLType.XSD_STRING);
this.strResult = (String)call.invoke(new Object[] {mybean});