Fieldable[] fields = aDoc.getFieldables(FieldNames.PROPERTIES);
Token t = new Token();
for (int k = 0; k < fields.length; k++) {
Fieldable field = fields[k];
// assume properties fields use SingleTokenStream
t = field.tokenStreamValue().next(t);
String value = new String(t.termBuffer(), 0, t.termLength());
if (value.startsWith(namePrefix)) {
// extract value
value = value.substring(namePrefix.length());
// create new named value