public void characters(char[] ch, int start, int length) {
        buffer.append(ch, start, length);
    }
This adds a Metadata entry for a given node.
The textual content of the node is used as the
value, and the Metadata name is taken from
an attribute, with a prefix if required.
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-xml-module/src/main/java/org/apache/tika/parser/xml/AttributeDependantMetadataHandler.java