Locating XML element anywhere in the document with Java

Question

Given the following XML (example):

<?xml version="1.0" encoding="UTF-8"?>
<rsb:VersionInfo xmlns:atom="http://www.w3.org/2005/Atom" xmlns:rsb="http://ws.rsb.de/v2">
    <rsb:Variant>Windows</rsb:Variant>
    <rsb:Version>10</rsb:Version>
</rsb:VersionInfo>

I need to get the values of Variant and Version. My current approach is using XPath as I cannnot rely on the given structure. All I know is that there is an element rsb:Version somewhere in the document.

XPath xpath = XPathFactory.newInstance().newXPath();
String expression = "//Variant";
InputSource inputSource = new InputSource("test.xml");
String result = (String) xpath.evaluate(expression, inputSource, XPathConstants.STRING);
System.out.println(result);

This however does not output anything. I have tried the following XPath expressions:

//Variant
//Variant/text()
//rsb:Variant
//rsb:Variant/text()

What is the correct XPath expression? Or is there an even simpler way getting to this element?

The XPathFactory needs to be created with a NamespaceContext. Once you have the figured out, the `•//rsb:Variant` XPath should work. — JerryM, Oct 28 '15 at 21:29
also please see this question. https://stackoverflow.com/questions/2811001/how-to-read-xml-using-xpath-in-java — Michael Queue, Oct 28 '15 at 21:34

Michael Queue · Answer 1 · 2015-10-28T21:23:53.117

I would suggest just looping through the document to find the given tag

public static void main(String[] args) throws SAXException, IOException,ParserConfigurationException, TransformerException {

    DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory
            .newInstance();
    DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
    Document document = docBuilder.parse(new File("test.xml"));

    NodeList nodeList = document.getElementsByTagName("rsb:VersionInfo");
    for (int i = 0; i < nodeList.getLength(); i++) {
        Node node = nodeList.item(i);
        if (node.getNodeType() == Node.ELEMENT_NODE) {
            // do something with the current element
            System.out.println(node.getNodeName());
        }
    }
}

Edit: Yassin pointed out that it won't get child nodes. This should point you in the right direction for getting the children.

private static List<Node> getChildren(Node n)
  {
    List<Node> children = asList(n.getChildNodes());
    Iterator<Node> it = children.iterator();
    while (it.hasNext())
      if (it.next().getNodeType() != Node.ELEMENT_NODE)
        it.remove();
    return children;
  }

Thanks, @michael-quatrani. Your answer is very helpful and I have implemented your mechanism for other methods. However I have chosen another comment as my preferred answer. — Robert Strauch, Oct 30 '15 at 08:29

Locating XML element anywhere in the document with Java

1 Answers1