XML namespace parsing

[Nathan Bruning]

We are using a custom XSD schema with a namespace to define our own XMPP extension.

JAXB is correctly adding xsi:type attributes where necessary:

<ns2:iq xmlns:ns4="urn:ietf:params:xml:ns:xmpp-stanzas" xmlns:ns3="http://mynamespace" xmlns:ns2="jabber:client" id="..." to="[e-mail]" type="set">
   <ns3:notification xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns3:queueUpdateNotification">
      ...
   </ns3:notification>
</ns2:iq>

But when Babbler pushes the XML through the PrefixFreeCanonicalizationWriter, it results in:

<iq id="..." to="[e-mail]" type="set">
   <notification xmlns="http://mynamespace" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns3:queueUpdateNotification">
      ...
   </notification>
</iq>

Note that the resulting XML contains a "ns3" prefix which is unbound. Actually, when the same XML is later received by Babblet, a parser error is thrown.

I guess the root cause if that xsi:type is a QName but writeAttribute of the PrefixFreeCanonicalizationWriter does no rewrite attributes.

Any suggestions?

[Christian Schudt]

Do you have a piece of code for reproduction? Afaik xsi:type is only is only required in the XSD, but not in the XML, so maybe the solution is to omit it.

[Nathan Bruning]

I'll see if I can come up with a minimal reproduction scenario.

The xsi:type is definately required in the generated XML, as it's the only way for a parser to determine the actual type of an element when subtyping (polymorphism) is used in XSD.

[Nathan Bruning]

Given this XSD:

<xs:schema targetNamespace="http://testnamespace.com"
           xmlns:xs="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified"
           xmlns="http://testnamespace.com" xmlns:jxb="http://java.sun.com/xml/ns/jaxb"
           jxb:version="1.0">
    <xs:element name="myElement" type="parentType">
    </xs:element>

    <xs:complexType name="parentType">
    </xs:complexType>

    <xs:complexType name="childType">
        <xs:complexContent>
            <xs:extension base="parentType">
                <xs:sequence>
                    <xs:element name="prop" type="xs:string"/>
                </xs:sequence>
            </xs:extension>
        </xs:complexContent>
    </xs:complexType>

</xs:schema>

And this code:

        Writer writer = new StringWriter();
        XMLStreamWriter xmlStreamWriter = XMLOutputFactory.newFactory().createXMLStreamWriter(writer);
        XMLStreamWriter xmppStreamWriter = XmppUtils.createXmppStreamWriter(
                xmlStreamWriter,
                "jabber:client",
                true);

        JAXBContext jaxbContext = JAXBContext.newInstance(ClientIQ.class, ObjectFactory.class);
        Marshaller marshaller = jaxbContext.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FRAGMENT, true);

        ObjectFactory factory = new ObjectFactory();
        JAXBElement<ParentType> childElem = factory.createMyElement(new ChildType());

        IQ iq = new IQ(Jid.of("[e-mail]"), IQ.Type.SET, childElem);
        marshaller.marshal(ClientIQ.from(iq), xmppStreamWriter);
        xmppStreamWriter.flush();
        System.out.println(writer.toString());

Results in the following (incorrect) XML:

<iq id="6549cbb8-d2e4-4018-8b99-f29e9305eef4" to="[e-mail]" type="set">
    <myElement xmlns="http://testnamespace.com" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns3:childType">
    </myElement>
</iq>

[Christian Schudt]

What about the most interesting part here, the ChildType class?

[Nathan Bruning]

It's generated by XJC. Just a POJO class, extending ParentType, having one field (prop), a getter and a setter.

[Christian Schudt]

Ensure that xsi:type values have a known namespace prefix

Fixes issue #137

→ <<cset 5a745ee6c46b>>

[Christian Schudt]

I've hopefully fixed this issue. If an "xsi:type" is written with a "prefix:namespace", it ensures, that there's also a "xmlns:prefix="namespace" somewhere. Unless the namespace is already the default namespace.

[Nathan Bruning]

Thanks, this indeed solves my issues. When are you planning to release this?

[Christian Schudt]

Fix version 0.8.0