Is AbstractDocumentBuilder actually an SPI type, i.e. are we expecting others to extend it and build their own document builder types (given all the types in *.spi it may be though that I'm having another definition of "SPI" in mind than the one used here)?

Regarding the getter, if it is not intended to be used by integrators, who is the intended user then? Maybe it just could be removed? Or if required internally, moved to an internally-used extension of AbstractDocumentBuilder?

Should we ever want to OSGi-ify SEARCH (or restrict the public packages of the JBoss module) such leakage of non-exported types via public signatures would cause some trouble.