Java: How to Indent XML Generated by Transformer

Question

I'm using Java's built in XML transformer to take a DOM document and print out the resulting XML. The problem is that it isn't indenting the text at all despite having set the parameter "indent" explicitly.

sample code

public class TestXML {

 public static void main(String args[]) throws Exception {
  ByteArrayOutputStream s;

  Document d = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
  Transformer t = TransformerFactory.newInstance().newTransformer();

  Element a,b;

  a = d.createElement("a");
  b = d.createElement("b");

  a.appendChild(b);

  d.appendChild(a);

  t.setParameter(OutputKeys.INDENT, "yes");

  s = new ByteArrayOutputStream();

  t.transform(new DOMSource(d),new StreamResult(s));

  System.out.println(new String(s.toByteArray()));

 }
}

result

<?xml version="1.0" encoding="UTF-8" standalone="no"?><a><b/></a>

desired result

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<a>
 <b/>
</a>

Thoughts?

Answer 1

You need to enable 'INDENT' and set the indent amount for the transformer:

t.setOutputProperty(OutputKeys.INDENT, "yes");
t.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");

Update:

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Reference : How to strip whitespace-only text nodes from a DOM before serialization?

(Many thanks to all members especially @marc-novakowski, @james-murty and @saad):