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https://issues.apache.org/jira/browse/WSCOMMONS-517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12796892#action_12796892
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Andreas Veithen commented on WSCOMMONS-517:
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Actually, I would expect Axiom to throw an exception in this case. The reason
is as follows:
As the name of the method implies and as explained by its Javadoc ("This will
declare a default namespace for this element explicitly"),
declareDefaultNamespace should only add a namespace declaration, but not change
the namespace of the element itself. The test case shows that the
implementation actually doesn't behave in the expected way: in that particular
example, it changes the namespace of the element from "" to
"http://someNamespace";.
That this behavior is incorrect is confirmed by two facts:
1. It seems that declareDefaultNamespace only exists because
declareNamespace(String, String) doesn't allow to declare a default namespace:
passing an empty prefix to that method has a different meaning, namely to
instruct Axiom to auto-generate a prefix. See also the Javadoc of the
declareDefaultNamespace method in the two OMElement implementations: "We use ""
to store the default namespace of this element. As one can see user can not
give "" as the prefix, when he declare a usual namespace." [sic] Since
declareNamespace never changes the namespace of the element, there is no reason
why declareDefaultNamespace would do so.
2. Only the LLOM implementation of OMElement has this behavior. DOOM's
implementation (which started as a fork of LLOM) never changes the namespace of
the element.
That means that the expected result would be as follows:
<p:outerTag xmlns="http://someNamespace"; xmlns:p="">
<p:innerTag>
<p:node1>Hello</p:node1>
<p:node2>Hello</p:node2>
</p:innerTag>
</p:outerTag>
Indeed, that would be the only way to add a default namespace declaration to
outerTag without changing its namespace (and that of its descendants). However,
xmlns:p="" is not a valid namespace declaration (at least not in XML 1.0, not
sure about XML 1.1): the empty namespace can only be used as default namespace
and can not be bound to a prefix. Thus, Axiom should trigger an error here.
More investigation is needed to understand why this particular behavior of
declareDefaultNamespace has been implemented.
> OMElement.declareDefaultNamespace() declares empty namespace for child
> element.
> -------------------------------------------------------------------------------
>
> Key: WSCOMMONS-517
> URL: https://issues.apache.org/jira/browse/WSCOMMONS-517
> Project: WS-Commons
> Issue Type: Bug
> Components: AXIOM
> Affects Versions: Axiom 1.2.8
> Environment: Microsoft Windows 2003 Server, Java 1.5.0_11. Axis2
> version 1.3 (uses AXIOM version 1.2.5).
> Reporter: Yechiel Mondrowitz
> Assignee: Andreas Veithen
>
> When calling declareDefaultNamespace() on a parent node, AXIOM assignes a
> blank namespace on the first level's child element. So if XML is passed to
> AXIOM that looks like this:
> <outerTag>
> <innerTag>
> <node1>Hello</node1>
> <node2>Hello</node2>
> </innerTag>
> </outerTag>
> And then declareDefaultNamespace() of "http://someNamespace"; is called on the
> <outerTag>, the resulting XML will be this:
> <outerTag xmlns="http://someNamespace";>
> <innerTag xmlns="">
> <node1>Hello</node1>
> <node2>Hello</node2>
> </innerTag>
> </outerTag>
> Notice the xmlns="" declared in the <innerTag>. According to my
> understanding of XML namespaces, the <innerTag> and its child nodes will no
> longer belong to the parent namespace of "http://someNamespace";, since it
> explicitly overrides it with an empty namespace. So <innerTag> and its child
> nodes will in fact not belong to any namespace! Here is a small program to
> illustrate:
> import org.apache.axiom.om.*;
> import org.apache.axiom.om.impl.llom.util.*;
> public class Test2 {
> public static void main(String [] args) {
> try {
> String xmlString =
> "<outerTag>" +
> "<innerTag>" +
> "<node1>Hello</node1>" +
> "<node2>Hello</node2>" +
> "</innerTag>" +
> "</outerTag>";
> OMElement elem = AXIOMUtil.stringToOM(xmlString);
> elem.declareDefaultNamespace("http://someNamespace";);
> System.out.println(elem.toString());
> }
> catch(Exception e) {
> e.printStackTrace();
> }
> }
> }
> The output of this program is this (I added line breaks in the XML for easier
> readability):
> <outerTag xmlns="http://someNamespace";>
> <innerTag xmlns="">
> <node1>Hello</node1>
> <node2>Hello</node2>
> </innerTag>
> </outerTag>
> As you can see, the <innerTag> was assigned xmlns="" by AXIOM.
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