AbstractDOMOutputProcessor doesn't explicitly set namespace of xmlns attributes

[petergeneric]

Hello,

The default implementation of DOMOutputProcessor generates xmlns attributes without setting the namespace. On the JAXP in Oracle Java 1.7 this means the generated Attrs have a null Namespace URI. This is causing us problems when serialising these Elements as part of a JAXB object (using EclipseLink MOXy - the Metro implementation is able to cope with it).

I'm not entirely sure if this is strictly a bug in JDOM or if the fault lies with JAXP for not inferring the Namespace URI on an element prefixed with "xmlns" - but it does mean the Documents coming from DOMOutputter don't look the same as a document coming from the built-in DocumentBuilderFactory.

Here's a JUnit test to reproduce the issue.

import org.jdom2.Element;
import org.jdom2.JDOMConstants;
import org.jdom2.input.DOMBuilder;
import org.jdom2.input.SAXBuilder;
import org.jdom2.output.DOMOutputter;
import org.junit.Test;
import org.w3c.dom.Document;
import org.xml.sax.InputSource;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.StringReader;

import static org.junit.Assert.assertEquals;

public class DOMOutputterNamespaceTest
{
    /**
     * The XML document to test - this document
     */
    private static final String XML = "<el xmlns:test=\"urn:test\" />";


    /**
     * Parse the XML using DOM
     *
     * @throws Exception
     */
    @Test
    public void testDocumentBuilderSource() throws Exception
    {
        org.w3c.dom.Element element = parseDOM(XML);

        final String namespace = element.getAttributeNode("xmlns:test").getNamespaceURI();

        assertEquals("DocumentBuilder output", JDOMConstants.NS_URI_XMLNS, namespace);
    }


    /**
     * Parse the XML using JDOM, convert to DOM
     *
     * @throws Exception
     */
    @Test
    public void testJdomToDom() throws Exception
    {
        org.w3c.dom.Element element = jdomToDom(parseJDOM(XML)); // load JDOM and convert to DOM

        final String namespace = element.getAttributeNode("xmlns:test").getNamespaceURI();

        assertEquals("SAXBuilder->DOMOutputter output", JDOMConstants.NS_URI_XMLNS, namespace);
    }


    /**
     * Parse the XML using DOM, then convert to JDOM and then finally back to DOM
     *
     * @throws Exception
     */

    @Test
    public void testDomToJdomToDom() throws Exception
    {
        org.w3c.dom.Element element = jdomToDom(domToJdom(parseDOM(XML))); // load DOM, convert to JDOM and back to DOM

        final String namespace = element.getAttributeNode("xmlns:test").getNamespaceURI();

        assertEquals("DocumentBuilder->DOMBuilder->DOMOutputter output", JDOMConstants.NS_URI_XMLNS, namespace);
    }


    private Element parseJDOM(String xml) throws Exception
    {
        final StringReader src = new StringReader(xml);

        return new SAXBuilder().build(src).getRootElement();
    }


    private org.w3c.dom.Element parseDOM(String xml) throws Exception
    {
        InputSource src = new InputSource(new StringReader(xml));

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        factory.setNamespaceAware(true);

        DocumentBuilder documentBuilder = factory.newDocumentBuilder();

        Document result = documentBuilder.parse(src);

        return result.getDocumentElement();
    }


    /**
     * Converts a JDOM Element to a DOM Element
     *
     * @param element
     *
     * @return
     *
     * @throws Exception
     */
    private org.w3c.dom.Element jdomToDom(org.jdom2.Element element) throws Exception
    {
        return new DOMOutputter().output(element);
    }


    /**
     * Converts a DOM Element to a JDOM Element
     *
     * @param element
     *
     * @return
     *
     * @throws Exception
     */
    private org.jdom2.Element domToJdom(org.w3c.dom.Element element) throws Exception
    {
        final DOMBuilder builder = new DOMBuilder();

        return builder.build(element);
    }
}

On our machines (Oracle Java 1.7, JDOM 2.0.4) the output is as follows:

testDocumentBuilderSource: pass
testJdomToDom: fail
    java.lang.AssertionError: SAXBuilder->DOMOutputter output expected:<http://www.w3.org/2000/xmlns/> but was:<null>
testDomToJdomToDom: fail
    java.lang.AssertionError: DocumentBuilder->DOMBuilder->DOMOutputter output expected:<http://www.w3.org/2000/xmlns/> but was:<null>

[rolfl]

Well, that's a comprehensive issue report, and a suprising problem. Thanks. I will look in to it shortly.

[petergeneric]

I've got a patch to AbstractDOMOutputProcessor that should work at petergeneric@c27a4fc and a unit test as part of petergeneric@2c32cc5 (it doesn't use the same structure as the other jdom unit tests though - added it in a separate commit for clarity)

[rolfl]

I pulled your fixes right in - b174b37 and 25153ea . Thanks