All namespaces that you intend to select from in the source XML must be associated with a prefix in the host language. In Java/JAXP this is done by specifying the URI for each namespace prefix using an instance of javax.xml.namespace.NamespaceContext. Unfortunately, there is no implementation of NamespaceContext provided in the SDK.
Fortunately, it's very easy to write your own:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.xml.namespace.NamespaceContext;
public class SimpleNamespaceContext implements NamespaceContext {
private final Map<String, String> PREF_MAP = new HashMap<String, String>();
public SimpleNamespaceContext(final Map<String, String> prefMap) {
PREF_MAP.putAll(prefMap);
}
public String getNamespaceURI(String prefix) {
return PREF_MAP.get(prefix);
}
public String getPrefix(String uri) {
throw new UnsupportedOperationException();
}
public Iterator getPrefixes(String uri) {
throw new UnsupportedOperationException();
}
}
Use it like this:
XPathFactory factory = XPathFactory.newInstance();
XPath xpath = factory.newXPath();
HashMap<String, String> prefMap = new HashMap<String, String>() {{
put("main", "http://schemas.openxmlformats.org/spreadsheetml/2006/main");
put("r", "http://schemas.openxmlformats.org/officeDocument/2006/relationships");
}};
SimpleNamespaceContext namespaces = new SimpleNamespaceContext(prefMap);
xpath.setNamespaceContext(namespaces);
XPathExpression expr = xpath
.compile("/main:workbook/main:sheets/main:sheet[1]");
Object result = expr.evaluate(doc, XPathConstants.NODESET);
Note that even though the first namespace does not specify a prefix in the source document (i.e. it is the default namespace) you must associate it with a prefix anyway. Your expression should then reference nodes in that namespace using the prefix you've chosen, like this:
/main:workbook/main:sheets/main:sheet[1]
The prefix names you choose to associate with each namespace are arbitrary; they do not need to match what appears in the source XML. This mapping is just a way to tell the XPath engine that a given prefix name in an expression correlates with a specific namespace in the source document.
