XOM API for Processing XML with Java

[Regier Avery J <RegierAveryJ AT JohnDeere.com>]

Here's as simple a test case as I can muster.

import java.io.IOException;
import java.io.StringReader;

import nu.xom.Builder;
import nu.xom.Document;
import nu.xom.Nodes;
import nu.xom.ParsingException;
import nu.xom.ValidityException;
import nu.xom.XPathContext;

import org.junit.Test;
import static org.junit.Assert.assertEquals;


public class ERHTest {
        // This test succeeds
        @Test
        public void testNot() throws ValidityException, ParsingException, 
IOException {
                Document doc = new Builder().build(new StringReader("<hi/>"));
                Nodes query = doc.query("//*[not(self::human)]", 
XPathContext.makeNamespaceContext(doc.getRootElement()));
                assertEquals(1, query.size());
        }
        
        // This test fails with 
        // nu.xom.XPathException: XPath error: No Such Function 
{there://mr.space/alien}:not
        @Test
        public void testNotWithNamespace() throws ValidityException, 
ParsingException, IOException {
                Document doc = new Builder().build(new StringReader("<hi 
xmlns='there://mr.space/alien'/>"));
                XPathContext context = 
XPathContext.makeNamespaceContext(doc.getRootElement());
                context.addNamespace("a", 
doc.getRootElement().getNamespaceURI());
                Nodes query = doc.query("//*[not(self::a:human)]", context);
                assertEquals(1, query.size());
        }

        // This test succeeds
        @Test
        public void testNotWithNamespaceWorkaround() throws 
ValidityException, ParsingException, IOException {
                Document doc = new Builder().build(new StringReader("<hi 
xmlns='there://mr.space/alien'/>"));
                XPathContext context = 
XPathContext.makeNamespaceContext(doc.getRootElement());
                context.addNamespace("a", 
doc.getRootElement().getNamespaceURI());
                context.addNamespace("f", "");
                Nodes query = doc.query("//*[f:not(self::a:human)]", context);
                assertEquals(1, query.size());
        }
}

nu.xom.XPathException: XPath error: No Such Function 
{there://mr.space/alien}:not
        at nu.xom.Node.query(Unknown Source)
        at ERHTest.testNotWithNamespace(ERHTest.java:30)
<snip>
Caused by: nu.xom.jaxen.UnresolvableException: No Such Function 
{there://mr.space/alien}:not
        at nu.xom.jaxen.SimpleFunctionContext.getFunction(Unknown Source)
        at nu.xom.jaxen.ContextSupport.getFunction(Unknown Source)
        at nu.xom.jaxen.Context.getFunction(Unknown Source)
        at nu.xom.jaxen.expr.DefaultFunctionCallExpr.evaluate(Unknown Source)
        at nu.xom.jaxen.expr.DefaultPredicate.evaluate(Unknown Source)
        at nu.xom.jaxen.expr.PredicateSet.applyPredicate(Unknown Source)
        at nu.xom.jaxen.expr.PredicateSet.evaluatePredicates(Unknown Source)
        at nu.xom.jaxen.expr.DefaultNameStep.evaluate(Unknown Source)
        at nu.xom.jaxen.expr.DefaultLocationPath.evaluate(Unknown Source)
        at nu.xom.jaxen.expr.DefaultAbsoluteLocationPath.evaluate(Unknown 
Source)
        at nu.xom.jaxen.expr.DefaultXPathExpr.asList(Unknown Source)
        at nu.xom.jaxen.BaseXPath.selectNodesForContext(Unknown Source)
        at nu.xom.jaxen.BaseXPath.selectNodes(Unknown Source)
        at nu.xom.JaxenConnector.selectNodes(Unknown Source)
        ... 24 more

While debugging I can see that the SimpleFunctionContext object has a 
function list that includes not, but it has an empty namespace.  It appears 
the namespace of the root node of the XML document doesn't match the 
namespace of the 'not' function, resulting in the 'not' function not being 
found.  

Why should I have to declare a namespace for functions?  Does the XPath spec 
require this? 

Would specifying a namespace for the not() function work across other XPath 
implementations?

Avery J. Regier 
RegierAveryJ AT JohnDeere.com