@Override
    public void characters(final char[] ch, final int start, final int length) throws SAXException {
        if (!buffer) {
            super.characters(ch, start, length);
        }
    }
This method will fire character events if the current element depth is
greater than the split depth, i.e. no content is output for elements that
are lower in the element hierarchy than the split depth.

@param ch     An array of characters.
@param start  The starting position in the array.
@param length The number of characters to use from the array.
@throws org.xml.sax.SAXException The client may throw an exception during processing.
@see stroom.pipeline.filter.AbstractXMLFilter#characters(char[],
int, int)
stroom-pipeline/src/main/java/stroom/pipeline/filter/SplitFilter.java