Pretty print an XML document in Java

This post is older than a year. Consider some information might not be accurate anymore.

If you want to have a pretty printed output of a XML tree, following snippet may be of interest to you.

import java.io.StringWriter;
import java.nio.charset.StandardCharsets;
import org.w3c.dom.DOMConfiguration;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.ls.DOMImplementationLS;
import org.w3c.dom.ls.LSOutput;
import org.w3c.dom.ls.LSSerializer;
/**
 * Test util for debugging and handling of {@link Document}}
 */
public final class DocumentUtils {
    private static final String FORMAT_PRETTY_PRINT = "format-pretty-print";
    /**
     * prevent instantiation
     */
    private DocumentUtils() {
        //nth.
    }
    /**
     * Prints a DOM document to XML using DOM Load and Save's LSSerializer.
     * @param doc
     * @return xml output
     * @see LSSerializer
     */
    public static final String getStringFromDoc(org.w3c.dom.Document doc) {
        DOMImplementationLS domImplementation = (DOMImplementationLS) doc.getImplementation();
        LSSerializer lsSerializer = domImplementation.createLSSerializer();
        return lsSerializer.writeToString(doc);
    }
    /**
     * Pretty-prints a DOM document to XML using DOM Load and Save's LSSerializer.
     * Note that the "format-pretty-print" DOM configuration parameter can only be set in JDK 1.6+.
     * @param doc
     * @return formatted xml output
     * @see LSSerializer
     * @see LSOutput
     * @see DOMConfiguration
     */
    public static final String getPrettyPrintedStringFromDoc(org.w3c.dom.Document doc) {
        DOMImplementation domImplementation = doc.getImplementation();
        if (domImplementation.hasFeature("LS", "3.0") && domImplementation.hasFeature("Core", "2.0")) {
            DOMImplementationLS domImplementationLS = (DOMImplementationLS) domImplementation.getFeature("LS", "3.0");
            LSSerializer lsSerializer = domImplementationLS.createLSSerializer();
            DOMConfiguration domConfiguration = lsSerializer.getDomConfig();
            if (domConfiguration.canSetParameter(FORMAT_PRETTY_PRINT, Boolean.TRUE)) {
                lsSerializer.getDomConfig().setParameter(FORMAT_PRETTY_PRINT, Boolean.TRUE);
                LSOutput lsOutput = domImplementationLS.createLSOutput();
                lsOutput.setEncoding(StandardCharsets.UTF_8.name());
                StringWriter stringWriter = new StringWriter();
                lsOutput.setCharacterStream(stringWriter);
                lsSerializer.write(doc, lsOutput);
                return stringWriter.toString();
            } else {
                throw new UnsupportedOperationException("DOMConfiguration 'format-pretty-print' parameter isn't settable.");
            }
        } else {
            throw new UnsupportedOperationException("DOM 3.0 LS and/or DOM 2.0 Core not supported.");
        }
    }
}

Can be used like this:

@Test
public void testGetStringFromDoc() throws Exception {
	// arrange
	Document document = DocumentUtils.createEmptyDocument();
	// act
	Element customer = document.createElement("id");
	customer.setTextContent("4711");
	document.appendChild(customer);
	String actual = DocumentUtils.getPrettyPrintedStringFromDoc(document);
	// assert
	assertEquals("Generated xml is equals.", "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<id>4711</id>", actual.trim());
}