Issues with xpath in java

Question

I'm currently having an issue with my xpath expressions in java. I'm trying to get a list of shopNames!

I got the following XML;

<?xml version="1.0" encoding="UTF-8"?>
<w:shops xmlns:w="namespace">
    <w:shop>
        <w:shopID>1</w:shopID>
        <w:shopName>ShopName</w:shopName>
        <w:shopURL>ShopUrl</w:shopURL>
    </w:shop>
    <w:shop>
        <w:shopID>2</w:shopID>
        <w:shopName>ShopNames</w:shopName>
        <w:shopURL>ShopUrl</w:shopURL>
    </w:shop>
</w:shops>

And I'm feeding this in a Document to a function alike this:

List<String> getShops(Document d)
    throws Exception
{
    List<String> shopnames = new ArrayList<String>();

    XPath xpath = XPathFactory.newInstance().newXPath();

    XPathExpression expr = xpath.compile("/descendant::w:shop/descendant::w:shopName");
    NodeList nodes = (NodeList) expr.evaluate(d, XPathConstants.NODESET);

    for(int x=0; x<nodes.getLength(); x++)
    {
        shopnames.add("" + nodes.item(x).getNodeValue());
    }
    return shopnames;
}

However the issue is that it simply returns an empty list, I'm suspecting it to be my xpath expression, but I'm not sure about it.

Anyone see the issue here?

Answer 1

The root Element is not shop but shops. I think, you have to compile this expression:

xpath.compile("/descendant::w:shops/descendant::w:shop/descendant::w:shopName");

---

You may have to set a namespace context:

xpath.setNamespaceContext(new NamespaceContext() {

   public String getNamespaceURI(String prefix) {
    if (prefix.equals("w")) return "namespace";
    else return XMLConstants.NULL_NS_URI;
   }

   public String getPrefix(String namespace) {
    if (namespace.equals("namespace")) return "w";
    else return null;
   }

   public Iterator getPrefixes(String namespace) {return null;}

});

and parse so that the document is aware of namespaces

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);  // <----
DocumentBuilder db = dbf.newDocumentBuilder();
Document xmlDom = db.parse("./shops.xml");

Answer 2

This one also works: //w:shopName/text() is not as "selective", but I think it's more readable. And returns a list of strings, rather than a list of nodes, which might be better or not, depending what you need.