@Override
    public void characters(char[] ch, int start, int length) throws SAXException {
        filter(ch, start, length, charactersOutput);
    }
Outputs the replacement for an invalid character. Subclasses can
override this method to use a custom replacement.

@param output where the replacement is written to
@throws SAXException if the replacement could not be written
tika-core/src/main/java/org/apache/tika/sax/SafeContentHandler.java