Namespace repairing generates xmlns definitions for xml: prefix (which is implicit)

[mvysny]

Saving this class:

data class StdTitle(@field:JacksonXmlProperty(isAttribute = true, namespace = "http://www.w3.org/XML/1998/namespace", localName = "lang") var lang: String = "")

will produce the following XML when namespace repairing is true:

<StdTitle xmlns:wstxns1="http://www.w3.org/XML/1998/namespace" wstxns1:lang="en"/>

However, the xml: prefix and the http://www.w3.org/XML/1998/namespace namespace is implicitly defined on all XMLs and there is no need to generate xmlns for that.

[mvysny]

Workaround is to disable namespace repairing and explicitly set xml prefix. Sample code:

        val mapper: XmlMapper = XmlMapper().apply {
            enable(SerializationFeature.INDENT_OUTPUT)
            enable(ToXmlGenerator.Feature.WRITE_XML_DECLARATION)
            setSerializationInclusion(JsonInclude.Include.NON_NULL)
            factory.xmlOutputFactory.setProperty(WstxOutputProperties.P_USE_DOUBLE_QUOTES_IN_XML_DECL, true)
            factory.xmlOutputFactory.setProperty(XMLOutputFactory.IS_REPAIRING_NAMESPACES, false)
            factory.xmlOutputFactory.setProperty(WstxInputProperties.P_RETURN_NULL_FOR_DEFAULT_NAMESPACE, true)
        }
        file.outputStream().buffered().use { fout ->
            val writer: XMLStreamWriter = mapper.factory.xmlOutputFactory.createXMLStreamWriter(fout)
            writer.setPrefix("xml", "http://www.w3.org/XML/1998/namespace")
            mapper.writeValue(writer, this)
            writer.close()
        }

[cowtowncoder]

If this is for actual Woodstox bug, test should only use Woodstox API, and not rely on Jackson XML format module.
Would it be simple enough to change test in that way?

Alternatively I can transfer this to jackson-dataformat-xml if this is more likely to be due to the way XML module uses stax(2) API.

[cowtowncoder]

Interesting. I can reproduce this -- I am surprised Woodstox does try to output this as it shouldn't (as per XML specification). Will need to see what gives.

[cowtowncoder]

Fix will be included in 2.10.5 (which will take a while to release) and 2.11.1 (probably released earlier, in 1-2 months)