Now all we have left is to save the Document to a file or write it to a String.
In order to output the Document to a more persistent format we’ll need to use the Transformer to help us with that.


/**
* Returns the document passed as a string.
* @param doc the Document to convert to string
* @param outputDocType set to true if you want to output the document type node
* @return the Document as a string
* @exception XMLException if an error occurred converting the document to a string
*/
public static String toString(Document doc, boolean outputDocType) throws XMLException
{
   StringWriter writer = new StringWriter();
   Transformer transformer;
   try
   {
     transformer = TransformerFactory.newInstance().newTransformer();
     if (outputDocType)
     {
       DocumentType type = doc.getDoctype();
       if (type != null)
       {
         String publicId = type.getPublicId();
         if (publicId != null)
         {
           transformer.setOutputProperty(DOCTYPE_PUBLIC, publicId);
         }
         String systemId = type.getSystemId();
         if (systemId != null)
         {
           transformer.setOutputProperty(DOCTYPE_SYSTEM, systemId);
         }
       }
     }
   }
   catch (TransformerConfigurationException e)
   {
     throw new XMLException("Could not create a transformer.", e);
   }
   try
   {
     transformer.transform(new DOMSource(doc), new StreamResult(writer));
   }
   catch (TransformerException e)
   {
     throw new XMLException("Could not transform document.", e);
   }
   return writer.toString();
}


We’ll use similar technic to save our Document to a file.


/**
* Writes the document passed to the file passed.
* @param fileName the name of the file to store the document to
* @param XMLdoc the source document to transform to the file
* @param XSLdoc the XSL style sheet to apply to XMLdoc
* @param outputDocType set to true if you want to output the document type node
* @exception XMLException if an error occurred writing the document to the file
*/
public static void toFile(String fileName, Document XMLdoc,Document XSLdoc, boolean outputDocType) throws XMLException
{
   Transformer transformer;
   try
   {
     transformer = TransformerFactory.newInstance().newTransformer(new DOMSource(XSLdoc));
     if (outputDocType)
     {
       DocumentType type = XMLdoc.getDoctype();
       if (type != null)
       {
         String publicId = type.getPublicId();
         if (publicId != null)
         {
           transformer.setOutputProperty(DOCTYPE_PUBLIC, publicId);
         }
         String systemId = type.getSystemId();
         if (systemId != null)
         {
           transformer.setOutputProperty(DOCTYPE_SYSTEM, systemId);
         }
       }
     }
   }
   catch (TransformerConfigurationException e)
   {
     throw new XMLException("Could not create a transformer.", e);
   }
   try
   {
     transformer.transform(new DOMSource(XMLdoc), new StreamResult(new File(fileName)));
   }
   catch (TransformerException e)
   {
     throw new XMLException("Could not transform document.", e);
   }
}


Now that you’re armed with some good utility methods working with XML files should be piece of cake.

The example I’ve brought here are limited, and it might useful to add some more methods to your utility class. If you find this tutorial helpful feel free to leave a note and maybe I’ll write another XML article where I’ll show you how to do XSL transformations and some XML schema validation with error tracking.

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