How do I convert a org.w3c.dom.Document object to a String?

I want to convert a org.w3c.dom.Document object to a String. I'm using Java 6 and am open to using any (completely free) technology that is up to the task. I tried the solution from this thread -- https://stackoverflow.com/questions/315517/is-there-a-more-elegant-way-to-convert-an-xml-document-to-a-string-in-java-than, where they have

DOMImplementationLS domImplementation = (DOMImplementationLS) doc.getImplementation();
LSSerializer lsSerializer = domImplementation.createLSSerializer();
String html = lsSerializer.writeToString(doc);	

but was greeted with the following horrendous exception …

org.w3c.dom.DOMException: DOM method not supported
	at org.w3c.tidy.DOMDocumentImpl.getImplementation(DOMDocumentImpl.java:129)
	at com.myco.myproj.cleaners.JTidyCleaner.outputDocAsString(JTidyCleaner.java:74)
	at com.myco.myproj.cleaners.JTidyCleaner.parse(JTidyCleaner.java:63)
	at com.myco.myproj.util.NetUtilities.getUrlAsDocument(NetUtilities.java:51)
	at com.myco.myproj.parsers.AbstractHTMLParser.getEventFromElement(AbstractHTMLParser.java:131)
	at com.myco.myproj.parsers.AbstractHTMLParser.parsePage(AbstractHTMLParser.java:100)
	at com.myco.myproj.parsers.AbstractHTMLParser.getEvents(AbstractHTMLParser.java:63)
	at com.myco.myproj.domain.EventFeed.refresh(EventFeed.java:87)
	at com.myco.myproj.domain.EventFeed.getEvents(EventFeed.java:72)
	at com.myco.myproj.parsers.impl.ChicagoCouncilGlobalAffairsParserTest.testParser(ChicagoCouncilGlobalAffairsParserTest.java:21)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
	at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:74)
	at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:83)
	at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:72)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
	at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
	at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
	at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

use some thing like

import java.io.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

//method to convert Document to String
public String getStringFromDocument(Document doc)
{
    try
    {
       DOMSource domSource = new DOMSource(doc);
       StringWriter writer = new StringWriter();
       StreamResult result = new StreamResult(writer);
       TransformerFactory tf = TransformerFactory.newInstance();
       Transformer transformer = tf.newTransformer();
       transformer.transform(domSource, result);
       return writer.toString();
    }
    catch(TransformerException ex)
    {
       ex.printStackTrace();
       return null;
    }
} 

If you are ok to do transformation, you may try this.

DocumentBuilderFactory domFact = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = domFact.newDocumentBuilder();
Document doc = builder.parse(st);
DOMSource domSource = new DOMSource(doc);
StringWriter writer = new StringWriter();
StreamResult result = new StreamResult(writer);
TransformerFactory tf = TransformerFactory.newInstance();
Transformer transformer = tf.newTransformer();
transformer.transform(domSource, result);
System.out.println("XML IN String format is: \n" + writer.toString());

This worked for me, as documented on this page:

TransformerFactory tf = TransformerFactory.newInstance();
Transformer trans = tf.newTransformer();
StringWriter sw = new StringWriter();
trans.transform(new DOMSource(document), new StreamResult(sw));
return sw.toString();

A Scala version based on Zaz's answer.

  case class DocumentEx(document: Document) {
    def toXmlString(pretty: Boolean = false):Try[String] = {
      getStringFromDocument(document, pretty)
    }
  }

  implicit def documentToDocumentEx(document: Document):DocumentEx = {
    DocumentEx(document)
  }

  def getStringFromDocument(doc: Document, pretty:Boolean): Try[String] = {
    try
    {
      val domSource= new DOMSource(doc)
      val writer = new StringWriter()
      val result = new StreamResult(writer)
      val tf = TransformerFactory.newInstance()
      val transformer = tf.newTransformer()
      if (pretty)
        transformer.setOutputProperty(OutputKeys.INDENT, "yes")
      transformer.transform(domSource, result)
      Success(writer.toString);
    }
    catch {
      case ex: TransformerException =>
        Failure(ex)
    }
  }

With that, you can do either doc.toXmlString() or call the getStringFromDocument(doc) function.