Allow specifying encodings other than UTF-8 in XML declaration written

[cassiomolin]

The UTF-8 encoding is hard coded in the ToXmlGenerator source code:

if (Feature.WRITE_XML_1_1.enabledIn(_formatFeatures)) {
    _xmlWriter.writeStartDocument("UTF-8", "1.1");
} else if (Feature.WRITE_XML_DECLARATION.enabledIn(_formatFeatures)) {
    _xmlWriter.writeStartDocument("UTF-8", "1.0");
} else {
    return;
}

Once ToXmlGenerator is final, there might not be an easy way to have other encodings such as ISO-8859-1:

<?xml version="1.0" encoding="ISO-8859-1"?>

See this question in Stack Overflow for reference.

[cowtowncoder]

Ah. Yes, I see. So although underlying writer may actually use different encoding, xml declaration claims it is UTF-8. That's not good.

[saimonsez]

Additionaly, XmlFactory outputs utf-8 only:

protected XMLStreamWriter _createXmlWriter(IOContext ctxt, OutputStream out) throws IOException
    {
     XMLStreamWriter sw;
     try {
         sw = _xmlOutputFactory.createXMLStreamWriter(_decorate(ctxt, out), "UTF-8");
     } catch (Exception e) {
         throw new JsonGenerationException(e.getMessage(), e, null);
     }
     return _initializeXmlWriter(sw);
}

[cowtowncoder]

@saimonsez That is intentional however (partly since there is no mechanism to pass non-Unicode encodings); caller is expected to create Writer for alternate encodings.

However, I hope to introduce a mechanism to allow users to create document "header" (xml declaration and/or DOCTYPE declaration) via XMLStreamWriter, which would allow adding encoding in xml declaration.

[saimonsez]

I see, thank you for clarification. In my case, the caller is spring-web (AbstractJackson2HttpMessageConverter) without a chance to configure an enocding other than unicode, so I am stuck again. Are you by chance involved with springs integration of jackson?

[saimonsez]

I just created spring-projects/spring-framework#25076 which is related to this issue (if jackson is used with spring).

[cowtowncoder]

I am only involved whenever Spring folks file bugs, but do not know their code base (and they don't use, I think, Jackson JAX-RS provider).
Their involvement would be needed even if new functionality / endpoints were added, for what that is worth.

[kromit]

This is still moved for 2 years from 2.10 to 2.11 to 2.12. So next is2.13?

Any stupid workaround would be great.

[cowtowncoder]

@kromit You are absolutely welcome to provide a fix as you seem to need it.