// Add participants
String primaryParticipant = "http://primary.participant/";
String secondaryParticipant = "http://secondary.participant/";
ParticipantType primary = new ParticipantType();
Document doc = DOMUtils.newDocument();
primary.setAny(createEndpointReference(doc, primaryParticipant));
ParticipantType secondary = new ParticipantType();
secondary.setAny(createEndpointReference(doc, secondaryParticipant));
ParticipantsType participants = new ParticipantsType();
participants.setPrimary(primary);
participants.getParticipant().add(secondary);