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https://issues.apache.org/jira/browse/AXIOM-441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13496332#comment-13496332
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Paul Millar commented on AXIOM-441:
-----------------------------------
It turns out the bug is in axiom-api's StAXOMBuilder#processNamespaceData
method. The bug is that this method assumes the parser's getNamespaceURI
method will always returns a non-null String.
The Oracle and Woodstox JavaDoc are clear that this method may return null.
The getNamespaceURI method in the StAX implementation that comes with Java 7
returns null for the element 'bar' in the above example. This results in an
attempt to create a namespace object with a null namespace, triggering the
exception.
The patch fixes this by converting the null value to an empty String. From the
org.apache.axiom.om.impl.llom.OMElementImpl#getDefaultNamespace method, an
empty String seems the expected way of expressing "outside a namespace". A
prefix of an empty String is how the default namespace is represented.
Therefore, adding a namespace declaration of an empty String URI to an empty
String prefix achieves the desired result of taking the element outside of a
defined namespace.
It would be good if someone with more familiarity with the code-base could
double-check that this is OK.
After applying the patch, the existing tests continue to pass ("mvn clean
verify") and the above XML is parsed correctly and builds the correct XML
output.
NB. I've not added unit- or functional- tests for this patch as I'm not sure
where such a test would fit in with the existing test infrastructure. There
doesn't seem to be existing unit tests for StAXOMBuilder and I'm not sure which
of the more function-orientated tests would be the most appropriate place.
Cheers,
Paul.
> Fails to parse XML with empty default namespace attribute value
> ---------------------------------------------------------------
>
> Key: AXIOM-441
> URL: https://issues.apache.org/jira/browse/AXIOM-441
> Project: Axiom
> Issue Type: Bug
> Components: API, LLOM
> Affects Versions: 1.2.13
> Reporter: Paul Millar
> Priority: Critical
> Labels: patch
> Attachments: patch-fix-StAXOMBuilder.diff
>
>
> From:
> http://www.w3.org/TR/2009/REC-xml-names-20091208/
> "The attribute value in a default namespace declaration MAY be empty. This
> has the same effect, within the scope of the declaration, of there being no
> default namespace."
> Here is a document that demonstrates this:
> <?xml version='1.0' encoding='UTF-8'?>
> <foo xmlns='http://example.org/'>
> <bar xmlns=''>value</bar>
> </foo>
> The following code snippet (slightly modified from Axiom documentation) uses
> Axiom to parse a String variable xmlData:
> InputStream in =
> new
> ByteArrayInputStream(xmlData.getBytes(Charset.forName("UTF-8")));
> OMXMLParserWrapper builder = OMXMLBuilderFactory.createOMBuilder(in);
> OMElement documentElement = builder.getDocumentElement();
> documentElement.serialize(System.out);
> System.out.println();
> When given the above XML example, an IllegalArgumentException is thrown:
> Exception in thread "main" java.lang.IllegalArgumentException: Namespace URI
> may not be null
> at
> org.apache.axiom.om.impl.llom.OMNamespaceImpl.<init>(OMNamespaceImpl.java:38)
> at
> org.apache.axiom.om.impl.llom.OMElementImpl.addNamespaceDeclaration(OMElementImpl.java:430)
> at
> org.apache.axiom.om.impl.builder.StAXOMBuilder.processNamespaceData(StAXOMBuilder.java:608)
> at
> org.apache.axiom.om.impl.builder.StAXOMBuilder.populateOMElement(StAXOMBuilder.java:430)
> at
> org.apache.axiom.om.impl.builder.StAXOMBuilder.createOMElement(StAXOMBuilder.java:461)
> at
> org.apache.axiom.om.impl.builder.StAXOMBuilder.createNextOMElement(StAXOMBuilder.java:318)
> at
> org.apache.axiom.om.impl.builder.StAXOMBuilder.next(StAXOMBuilder.java:249)
> at
> org.apache.axiom.om.impl.llom.OMElementImpl.buildNext(OMElementImpl.java:709)
> at
> org.apache.axiom.om.impl.llom.OMNodeImpl.getNextOMSibling(OMNodeImpl.java:121)
> at
> org.apache.axiom.om.impl.traverse.OMChildrenIterator.getNextNode(OMChildrenIterator.java:36)
> at
> org.apache.axiom.om.impl.traverse.OMAbstractIterator.hasNext(OMAbstractIterator.java:69)
> at
> org.apache.axiom.om.impl.util.OMSerializerUtil.serializeChildren(OMSerializerUtil.java:555)
> at
> org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:846)
> at
> org.apache.axiom.om.impl.llom.OMSerializableImpl.serialize(OMSerializableImpl.java:120)
> at
> org.apache.axiom.om.impl.llom.OMSerializableImpl.serialize(OMSerializableImpl.java:108)
> at
> org.apache.axiom.om.impl.llom.OMSerializableImpl.serialize(OMSerializableImpl.java:127)
> This looks like a bug.
> Cheers,
> Paul.
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