final XMLStreamWriter xmlOut = _writer.getStreamWriter();
xmlOut.setPrefix(csq(ENVELOPE_PREFIX), csq(ENVELOPE_URI));
xmlOut.writeStartElement(csq(ENVELOPE_URI), csq("Envelope"));
xmlOut.writeNamespace(csq(ENVELOPE_PREFIX), csq(ENVELOPE_URI));
xmlOut.writeStartElement(csq(ENVELOPE_URI), csq("Header"));
xmlOut.writeEndElement();
xmlOut.writeStartElement(csq(ENVELOPE_URI), csq("Body"));
writeRequest(_writer);
_writer.close();
// Sends the request.