How can we get Output SOAP message with XML transformer

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.soap.MessageFactory;
import javax.xml.soap.Name;
import javax.xml.soap.SOAPBody;
import javax.xml.soap.SOAPBodyElement;
import javax.xml.soap.SOAPEnvelope;
import javax.xml.soap.SOAPHeader;
import javax.xml.soap.SOAPHeaderElement;
import javax.xml.soap.SOAPMessage;
import javax.xml.soap.SOAPPart;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.xml.sax.InputSource;

public class MainClass {

public static void main(String[] args) throws Exception {
SOAPMessage soapMessage = MessageFactory.newInstance().createMessage();
SOAPPart soapPart = soapMessage.getSOAPPart();
SOAPEnvelope soapEnvelope = soapPart.getEnvelope();

SOAPHeader soapHeader = soapEnvelope.getHeader();
SOAPHeaderElement headerElement = soapHeader.addHeaderElement(soapEnvelope.createName(
"Signature", "SOAP-SEC", "http://schemas.xmlsoap.org/soap/security/2000-12"));

SOAPBody soapBody = soapEnvelope.getBody();
soapBody.addAttribute(soapEnvelope.createName("id", "SOAP-SEC",
"http://schemas.xmlsoap.org/soap/security/2000-12"), "Body");
Name bodyName = soapEnvelope.createName("FooBar", "z", "http://example.com");
SOAPBodyElement gltp = soapBody.addBodyElement(bodyName);

Source source = soapPart.getContent();

Node root = null;
if (source instanceof DOMSource) {
root = ((DOMSource) source).getNode();
} else if (source instanceof SAXSource) {
InputSource inSource = ((SAXSource) source).getInputSource();
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
DocumentBuilder db = null;

db = dbf.newDocumentBuilder();

Document doc = db.parse(inSource);
root = (Node) doc.getDocumentElement();
}

Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.transform(new DOMSource(root), new StreamResult(System.out));
}
}