Output XML with indentation...

Question

I've not found an answer to this on the forums so was hoping someone might have discovered what's up since...
Using the Transformation API with the default JAXP 1.1 transformer (Xalan) and setting the output property "indent" to "yes", the resulting XML contains carriage returns but no indentation as hoped.
I don't think that indentation is required for the transformer to adhere to the specification but it seems like quite an omission nonetheless.
Does anyone know how to output indented XML without going to the trouble of adding whitespace text nodes into the document tree?
Many thanks,
K.
Transformer transformer = TransformerFactory.newInstance().newTransformer();
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
transformer.transform(new DOMSource(doc), new StreamResult(out));

Answer 1

We did it this way:
import java.util.Map;
import java.util.HashMap;
import java.util.Properties;
import java.io.*;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.InputSource;
import org.apache.xml.serialize.XMLSerializer;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xerces.parsers.SAXParser;
public class XmlPrettyPrinter extends XMLSerializer {
  private Map mapping = new HashMap();
  public XmlPrettyPrinter(StringWriter out, OutputFormat format) {
    super(out, format);
  public static String beautify(String xml) {
    if (xml == null || xml.trim().length() == 0) {
      return "";
    Reader reader = new StringReader(xml);
    XMLReader parser = new SAXParser();
    try {
      parser.setFeature("http://xml.org/sax/features/validation", false);
      OutputFormat format = new OutputFormat();
      format.setIndenting(true);
      format.setIndent(2);
      format.setLineWidth(80);
      StringWriter out = new StringWriter();
      XmlPrettyPrinter serializer = new XmlPrettyPrinter(out, format);
      parser.setContentHandler(serializer.asContentHandler());
      parser.parse(new InputSource(reader));
      return out.toString();
    } catch (Exception e) {
      // do something about this Exception
    return xml;
  public void characters(char[] chars, int offset, int length) throws SAXException {
    String s = new String(chars, offset, length).trim();
    char[] array = s.toCharArray();
    super.characters(array, 0, array.length);
}Maybe you get an idea what to change in your code.
Regards,
hedtfeld