Andreas Veithen created XERCESJ-1586:
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Summary: lookupNamespaceURI may return unexpected result when
looking up default namespace
Key: XERCESJ-1586
URL: https://issues.apache.org/jira/browse/XERCESJ-1586
Project: Xerces2-J
Issue Type: Bug
Components: DOM (Level 3 Core)
Affects Versions: 2.9.1
Reporter: Andreas Veithen
Priority: Minor
Consider the following XML document:
<root xmlns="urn:test"><child xmlns=""/></root>
Assume that the document is constructed programmatically without explicitly
adding the namespace declarations:
Document document =
DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
Element root = document.createElementNS("urn:test", "root");
document.appendChild(root);
Element child = document.createElementNS(null, "child");
root.appendChild(child);
The expectation is that when looking up the default namespace on the child
element, the result is null. However, this is not the case, as demonstrated by
the following code:
System.out.println("uri=" + child.lookupNamespaceURI(null));
In fact, the output is:
uri=urn:test
Moreover, the result changes after normalizing the document:
document.normalizeDocument();
System.out.println("uri=" + child.lookupNamespaceURI(null));
The output with Xerces 2.9.1 is now (Note that the result is still not correct
because one would expect uri=null, but this has been fixed in recent Xerces
versions; see XERCESJ-1394):
uri=
The reason is that normalizeDocument adds xmlns="" to the child node (as
expected).
Actually, the behavior of lookupNamespaceURI shown here strictly conforms to
the DOM Level 3 Core specification, as described in appendix B.4. That is
because of the namespace != null condition in the following part of the pseudo
code:
if ( Element's namespace != null and Element's prefix == prefix )
{
// Note: prefix could be "null" in this case we are looking for
default namespace
return (Element's namespace);
}
However, if one strictly follows the specification, then normalizeDocument
should also not add xmlns="" to the child element. In fact, the action taken by
normalizeDocument to fixup the namespace of that element is described by the
following part of the pseudo code in appendix B.1:
// Element has no pseudo-prefix
if ( there's a conflicting local default namespace declaration
already present )
{
==> change its value to use this empty namespace.
}
// NOTE that this may break other nodes within this Element's
// subtree, if they're already using the default namespaces.
// They will be repaired when we reach them.
Since there is no conflicting _local_ default namespace declaration on the
child element, according to the specification, nothing should be done. This is
obviously not what one wants in this case, and Xerces ignores that aspect of
the specification. However, for consistency, Xerces should then also ignore the
namespace != null condition in appendix B.4.
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