Unbound namespace URI '' when using isAttribute=true on JacksonXmlProperty

[fredrik-rambris]

When streaming beans and producing XML I get an exception saying Unbound namespace URI '' when I am using @JacksonXmlProperty(isAttribute=true).

@JacksonXmlProperty(isAttribute = true)
private String source="ECOM";
private Member member;

Using Jackson 2.9.7 with woodstox 5.0.3.

If I set
xmlOutputFactory.setProperty(XMLOutputFactory.IS_REPAIRING_NAMESPACES, true);
The code works but then the produced document has no xmlns.

A gist displaying the failing code

[cowtowncoder]

Interesting. You are right, there is an exception, and unexpected one at that.
I would have thought that works fine, and it should I think. I'll see if I can figure out what causes it, fix.

[cowtowncoder]

Also interesting: fails on 2.x, but passes on 3.0.0-SNAPSHOT for some reason. Hmmh.

[cowtowncoder]

Oh, actually... so, exception is weird, but one thing to note is that you MUST NOT turn off namespace repairing. Jackson XML module absolutely expects and requires it be enabled; I'll probably add a check so that attempting to use one without will fail when constructing XmlMapper. I can't think of valid reasons for needing to disable it, but I think you are attempting to use it as workaround for a problem.

I also wonder if you might be misunderstanding how XML namespaces, and in particular default namespace works with attributes: it is different from elements. That is, "default namespace" only ever applies to elements, and never to attributes: attribute without prefix always has namespace of "". To have attribute in a different namespace requires use of namespace bound to explicit prefix.
So it may make sense for you to read XML namespace specification (or an article that explains it) -- there are some subtleties there which are not necessarily intuitive, such as above-mentioned difference between attributes and elements wrt default namespace binding.

[cowtowncoder]

Filed #326 as replacement.