Don't insist on writeStartDocument

Interesting. I will need to have a look at the problem. A very quick work-around (in case you need to make it work before fixes, or fow older version) is to disable structural checks (there's a property in WstxOutputProperties, or so), which are on by default. Disabling these checks should prevent the particular exception.

I was wondering if it would be necessary to implementing something similar to what input side does (allow 3 modes: standard tree, fragment, or multi-doc ["forest"]) on output side as well, but thought I'll wait until someone needs such a feature. Sounds like you do.

Anyway, I will need to have a look at sources: it may be that it's not so much related to writeStartDocument(), but to missing writeStartElement() call: or put another way, writer's preference to write well-formed output and prevent non-whitespace stuff outside of main document tree. If so, "fragment mode" is probably needed.

This needs to be fixed for 4.0; I think there is no point in requiring that call, considering that currently there is no way to avoid generating the xml declaration.

It took a while, but I started looking into this issue again. Turns out that indeed problem is not missing writeStartDocument() call, but rather writing of content that is not legal outside of xml document.
While this would not be valid when writing pure xml content, it does make sense if one is to write xml fragments.

I am not yet sure if it should be enough that one can disable structural checks, which does allow such writes. The problem is that this also removes all the other structural checks which may not be optimal.