@Override
    public void setDocumentLocator(final Locator locator) {
        handler.setDocumentLocator(locator);
        super.setDocumentLocator(locator);
    }
@param locator an object that can return the location of any SAX document
               event
@see Locator
@see AbstractXMLFilter#setDocumentLocator(Locator)
stroom-pipeline/src/main/java/stroom/pipeline/filter/AbstractSamplingFilter.java