AHMET ARSLAN wrote:
--- On Sat, 9/12/09, Paul Taylor <paul_t...@fastmail.fm> wrote:
From: Paul Taylor <paul_t...@fastmail.fm>
Subject: Filter before tokenize ?
To: java-user@lucene.apache.org
Date: Saturday, September 12, 2009, 9:39 PM
Is it possible to filter before
tokenize, or is that not a good idea.
I want to convert '&' to 'and' , so they are dealt with
the same way, but the StandardTokenizer I am using removes
the &, I could change the tokenizer but because
I'm not too clear on jflex syntax it would seem easier to
just apply a CharFilter before tokenizing, but is that
possible
May be you can use WhitespaceTokenizer that won't remove &?
Why and's (&) are import for you? Do you need to search them?
Replacing &'s before indexing (by preprocessing) can be a option?
Filter before tokenizer can be simulated by using:
1-)KeywordTokenizer
2-)Your CharFilter
3-)A token filter that tokenizes input token's text using StandardTokenizer
But i think this is not a good idea.
Hope this helps.
Yes, I want to search them and I want to be able to search using either
'&' or 'and' and get the same results. Ive just been playing with this
and using a CharFilter before the Tokenizer did work, the only problem
was modifications required for reusableTokenStream because CharFilter
doesn't have a reset(Reader) method like tokenizer, so I guess I
recreate this bit and then reset tokenizer, seems to work okay so thats
what Im going with, if this is wronmg please someone let me know.
Because of this problem I also tried modifying the StandardTokenizer
jflex file so that it didn't remove &s, but then realised CharFilter HAS
to be before a tokenizer it cant work on a tokenizers output. I then
tried making a modiofication to StandardFilter, but because this only
removes characters it wasnt clear how tro add a case for adding characters.
Paul
public class StandardUnaccentAnalyzer extends Analyzer {
private NormalizeCharMap charConvertMap;
private void setCharConvertMap() {
charConvertMap = new NormalizeCharMap();
charConvertMap.add("&","and");
}
public StandardUnaccentAnalyzer() {
setCharConvertMap();
}
public TokenStream tokenStream(String fieldName, Reader reader) {
CharFilter mappingCharFilter = new MappingCharFilter(charConvertMap,reader);
StandardTokenizer tokenStream = new StandardTokenizer(mappingCharFilter);
TokenStream result = new ICUTransformFilter(tokenStream,
Transliterator.getInstance("[ー[:Script=Katakana:]]Katakana-Hiragana"));
result = new StandardFilter(result);
result = new AccentFilter(result);
result = new LowerCaseFilter(result);
return result;
}
private static final class SavedStreams {
CharFilter preFilter;
StandardTokenizer tokenStream;
TokenStream filteredTokenStream;
}
public TokenStream reusableTokenStream(String fieldName, Reader reader)
throws IOException {
SavedStreams streams = (SavedStreams)getPreviousTokenStream();
if (streams == null) {
streams = new SavedStreams();
setPreviousTokenStream(streams);
streams.preFilter = new MappingCharFilter(charConvertMap,reader);
streams.tokenStream = new StandardTokenizer(streams.preFilter);
streams.filteredTokenStream = new
ICUTransformFilter(streams.tokenStream, Transliterator.getInstance("[ー
[:Script=Katakana:]]Katakana-Hiragana"));
streams.filteredTokenStream = new
StandardFilter(streams.filteredTokenStream);
streams.filteredTokenStream = new AccentFilter(streams.filteredTokenStream);
streams.filteredTokenStream = new
LowerCaseFilter(streams.filteredTokenStream);
}
else {
streams.preFilter = new MappingCharFilter(charConvertMap,reader);
streams.tokenStream.reset(streams.preFilter);
}
return streams.filteredTokenStream;
}
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