Xpath cannot request namespace tag

Question

I have xml as shown below (Google API) but cannot get the value of the gphoto:id element. How to do it? Note. When I use domFactory.setNamespaceAware(true); , /feed/entry xpath stops working.

 <?xml version="1.0" encoding="UTF-8"?> <feed xmlns="http://www.w3.org/2005/Atom" xmlns:gphoto="http://schemas.google.com/photos/2007" xmlns:media="http://search.yahoo.com/mrss/" xmlns:openSearch="http://a9.com/-/spec/opensearchrss/1.0/"> <entry> <title type="text">Test</title> <author> <name>username</name> <uri>https://picasaweb.google.com/113422203255202384532</uri> </author> <gphoto:id>57060151229174417</gphoto:id> </entry> </feed> 

Java

 NodeList nodes = (NodeList) path(body, "/feed/entry", XPathConstants.NODESET); for (int i = 0; i < nodes.getLength(); i++) { Node n = nodes.item(i); XPath xpath = XPathFactory.newInstance().newXPath(); // empty :( System.out.println( xpath.evaluate("id[namespace-uri()='http://schemas.google.com/photos/2007']",n) ); // empty too :( System.out.println( xpath.evaluate("gphoto:id",n) ); // ok System.out.println( xpath.evaluate("author",n) ); l.add(new Album("", "", "")); } 

way method

 private Object path(String content, String path, QName returnType) { try { DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = domFactory.newDocumentBuilder(); Document doc = builder.parse(new InputSource(new StringReader(content))); XPath xpath = XPathFactory.newInstance().newXPath(); XPathExpression expr = xpath.compile(path); return expr.evaluate(doc, returnType); } catch (Exception e) { e.printStackTrace(); } return null; } 

SOLVED according to @gioele path() answer now looks like this:

 private Object path(String content, String path, QName returnType) { try { domFactory.setNamespaceAware(true); DocumentBuilder builder = domFactory.newDocumentBuilder(); Document doc = builder.parse(new InputSource(new StringReader(content))); XPath xpath = XPathFactory.newInstance().newXPath(); NamespaceContext nsContext = new NamespaceContext() { @Override public Iterator getPrefixes(String namespaceURI) { return null; } @Override public String getPrefix(String namespaceURI) { return null; } @Override public String getNamespaceURI(String prefix) { if ("gphoto".equals(prefix)) return "http://schemas.google.com/photos/2007"; if ("media".equals(prefix)) return "http://search.yahoo.com/mrss/"; if("".equals(prefix)) return "http://www.w3.org/2005/Atom"; throw new IllegalArgumentException(prefix); } }; xpath.setNamespaceContext(nsContext); XPathExpression expr = xpath.compile(path); return expr.evaluate(doc, returnType); } catch (Exception e) { e.printStackTrace(); } return null; } 

Answer 1

Before compiling xpath, you need to register a NamespaceContext .

Look at the code at https://github.com/gioele/xpathapi-jaxp/blob/master/src/main/java/it/svario/xpathapi/jaxp/NodeNamespaceContext.java .

If you want to avoid all these complications, you can use the XPathAPI library :

 Map<String, String> nsMap = new HashMap<String, String>(); nsMap.put(XMLConstants.DEFAULT_NS_PREFIX, "http://www.w3.org/2005/Atom"); nsMap.put("gphoto", "http://schemas.google.com/photos/2007"); List<Node> entries = XPathAPI.selectListOfNodes(doc, "/feed/entry", nsMap); for (Node entry : entries) { String id = XPathAPI.selectSingleNodeAsString(entry, "gphoto:id", nsMap); // or, if you prefer a Node // Node id = XPathAPI.selectSingleNode(entry, "gphoto:id", nsMap); } 

Disclaimer: I am the creator of XPathAPI-JAXP.

Answer 2

An easier way to deal with the namespace problem is to simply redirect the call from the NamespaceContext to the lookupNamespaceURI () method of the document. This will be returned "http://search.yahoo.com/mrss/" when called from "media", etc.

 xPath.setNamespaceContext(new NamespaceContext() { @Override public String getNamespaceURI(String prefix) { return doc.lookupNamespaceURI(prefix); } @Override public Iterator<?> getPrefixes(String arg0) { return null; } @Override public String getPrefix(String arg0) { return null; } });