None I'm aware of. We're doing a lot of unit tests which consist of
feeding example data into the template using createDocument() and
see if the resulting document can still be read using Simple Java
API for ODF [1]. We also have a few test support classes which might
be a candidate to release as OSS. This way, we catch all the
problems that might occurr due to FTL templates creating ill-formed
XML.
One of my colleague is currently pushing the Jetbrains guys to fix
IDEA's 'IntelliLang' feature, so that it will be possible to have
some form of syntax checking inside the content.xml contained in
your ODF document from inside IDEA. Build 108.944 of IDEA has this
fix in (but is not released yet AFAICS). This would however mean
you'd have to find some way to extract the content.xml file from
your ODF template file and re-pack it if you want to use it as a
template. IIRC, JODReports can also work with unpacked directories
as templates, but you'd be on your own to make this work in your IDE
for the time being.
Hope this helps a bit.
Ansgar
[1]
http://odftoolkit.org/projects/simple/pages/Home