package org.apache.lucene.analysis.miscellaneous;
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.io.IOException;
import java.util.Map;
import org.apache.lucene.analysis.CharArrayMap;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.util.Version;
/**
* Provides the ability to override any {@link KeywordAttribute} aware stemmer
* with custom dictionary-based stemming.
*/
public final class StemmerOverrideFilter extends TokenFilter {
private final CharArrayMap<String> dictionary;
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final KeywordAttribute keywordAtt = addAttribute(KeywordAttribute.class);
/**
* Create a new StemmerOverrideFilter, performing dictionary-based stemming
* with the provided <code>dictionary</code>.
* <p>
* Any dictionary-stemmed terms will be marked with {@link KeywordAttribute}
* so that they will not be stemmed with stemmers down the chain.
* </p>
*/
public StemmerOverrideFilter(Version matchVersion, TokenStream input,
Map<?,String> dictionary) {
super(input);
this.dictionary = dictionary instanceof CharArrayMap ?
(CharArrayMap<String>) dictionary : CharArrayMap.copy(matchVersion, dictionary);
}
@Override
public boolean incrementToken() throws IOException {
if (input.incrementToken()) {
if (!keywordAtt.isKeyword()) { // don't muck with already-keyworded terms
String stem = dictionary.get(termAtt.buffer(), 0, termAtt.length());
if (stem != null) {
termAtt.setEmpty().append(stem);
keywordAtt.setKeyword(true);
}
}
return true;
} else {
return false;
}
}
}