Pretty Print XML with Java Dom and XSLT

By mkyong | Updated: May 16, 2021

Viewed: 7,017 (+67 pv/w)

Tags: dom java xml pretty print read xml transform xml xslt

This article shows how to use Java DOM Parser + XSLT to format or pretty print a XML document.

Table of contents

• 1. An XML file
• 2. Pretty Print XML via Transformer
• 3. Pretty Print XML via XSLT
• 4. Download Source Code
• 5. References

P.S Tested with Java 11

1. An XML file

<?xml version="1.0" encoding="utf-8"?>
<company>
    <staff id="1001">
        <name>mkyong</name>
        <role>support</role>
    </staff>
    <staff id="1002">
        <name>yflow</name>
        <role>admin</role>
    </staff>
</company>

2. Pretty Print XML via Transformer

In javax.xml.transform.Transformer, we can configure the OutputKeys.INDENT property to pretty print the XML documents.

  private static void transform(Document doc, OutputStream output)
          throws TransformerException {

      TransformerFactory transformerFactory = TransformerFactory.newInstance();
      Transformer transformer = transformerFactory.newTransformer();

      // pretty print
      transformer.setOutputProperty(OutputKeys.INDENT, "yes");

      transformer.transform(new DOMSource(doc), new StreamResult(output));

  }

Output

<?xml version="1.0" encoding="utf-8" standalone="no"?>
<company>

  <staff id="1001">

      <name>mkyong</name>

      <role>support</role>

  </staff>

  <staff id="1002">

      <name>yflow</name>

      <role>admin</role>

  </staff>

</company>

However, the Transformer will add many empty newlines (tested in Java 11) in the output, Not sure why?

3. Pretty Print XML via XSLT

3.1 To solve the above extra empty newlines problem, we can add an xslt file for the pretty print transformation.

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output indent="yes" cdata-section-elements="cdata-other-elements"/>
    <xsl:strip-space elements="*"/>

    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()"/>
        </xsl:copy>
    </xsl:template>

</xsl:stylesheet>

3.2 DOM parser example for the XSLT transformation.

package com.mkyong.xml.dom.xslt;

import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import java.io.*;

public class XsltPrettyPrintDomParser {

  private static final String XML_FILENAME
                          = "src/main/resources/staff-simple.xml";
  private static final String XSLT_FILENAME
                          = "src/main/resources/xslt/staff-format.xslt";

  public static void main(String[] args) {

      DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

      try (InputStream is = new FileInputStream(XML_FILENAME)) {

          DocumentBuilder db = dbf.newDocumentBuilder();

          Document doc = db.parse(is);

          transform(doc, System.out);


      } catch (IOException | ParserConfigurationException |
              SAXException | TransformerException e) {
          e.printStackTrace();
      }

  }

  private static void transform(Document doc, OutputStream output)
          throws TransformerException {

      TransformerFactory transformerFactory = TransformerFactory.newInstance();

      //Transformer transformer = transformerFactory.newTransformer();

      // add XSLT for pretty print
      Transformer transformer = transformerFactory.newTransformer(
              new StreamSource(new File(XSLT_FILENAME)));

      // pretty print, this will add extra new lines
      // transformer.setOutputProperty(OutputKeys.INDENT, "yes");

      // add extra standalone to break the root node to a new line
      transformer.setOutputProperty(OutputKeys.STANDALONE, "no");

      transformer.transform(new DOMSource(doc), new StreamResult(output));

  }

}

Output

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<company>
  <staff id="1001">
      <name>mkyong</name>
      <role>support</role>
  </staff>
  <staff id="1002">
      <name>yflow</name>
      <role>admin</role>
  </staff>
</company>

4. Download Source Code

5. References

• Wikipedia – Document Object Model
• Wikipedia – XSLT
• Oracle – Document Object Model
• Java DOM Parser XML and XSLT examples
• How to read XML file in Java – (DOM Parser)
• How to write XML file in Java – (DOM Parser)
• How to modify XML file in Java – (DOM Parser)