In reply to Espinosa’s comment, here is a solution when “the original xml is not already (partially) indented or contain new lines“.
Background
Excerpt from the article (see References below) inspiring this solution:
Based on the DOM specification, whitespaces outside the tags are perfectly valid and they are properly preserved. To remove them, we can use XPath’s normalize-space to locate all the whitespace nodes and remove them first.
Java Code
public static String toPrettyString(String xml, int indent) {
try {
// Turn xml string into a document
Document document = DocumentBuilderFactory.newInstance()
.newDocumentBuilder()
.parse(new InputSource(new ByteArrayInputStream(xml.getBytes("utf-8"))));
// Remove whitespaces outside tags
document.normalize();
XPath xPath = XPathFactory.newInstance().newXPath();
NodeList nodeList = (NodeList) xPath.evaluate("//text()[normalize-space()='']",
document,
XPathConstants.NODESET);
for (int i = 0; i < nodeList.getLength(); ++i) {
Node node = nodeList.item(i);
node.getParentNode().removeChild(node);
}
// Setup pretty print options
TransformerFactory transformerFactory = TransformerFactory.newInstance();
transformerFactory.setAttribute("indent-number", indent);
Transformer transformer = transformerFactory.newTransformer();
transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
// Return pretty print xml string
StringWriter stringWriter = new StringWriter();
transformer.transform(new DOMSource(document), new StreamResult(stringWriter));
return stringWriter.toString();
} catch (Exception e) {
throw new RuntimeException(e);
}
}
Sample usage
String xml = "<root>" + //
"\n " + //
"\n<name>Coco Puff</name>" + //
"\n <total>10</total> </root>";
System.out.println(toPrettyString(xml, 4));
Output
<root>
<name>Coco Puff</name>
<total>10</total>
</root>
References
- Java: Properly Indenting XML String published on MyShittyCode
- Save new XML node to file