org.apache.lucene.analysis.br.BrazilianAnalyzer Maven / Gradle / Ivy
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* 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.
*/
package org.apache.lucene.analysis.br;
import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.StopwordAnalyzerBase;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.analysis.miscellaneous.SetKeywordMarkerFilter;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.util.IOUtils;
/**
* {@link Analyzer} for Brazilian Portuguese language.
*
* Supports an external list of stopwords (words that
* will not be indexed at all) and an external list of exclusions (words that will
* not be stemmed, but indexed).
*
*
* NOTE: This class uses the same {@link org.apache.lucene.util.Version}
* dependent settings as {@link StandardAnalyzer}.
*
* @since 3.1
*/
public final class BrazilianAnalyzer extends StopwordAnalyzerBase {
/** File containing default Brazilian Portuguese stopwords. */
public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
/**
* Returns an unmodifiable instance of the default stop-words set.
* @return an unmodifiable instance of the default stop-words set.
*/
public static CharArraySet getDefaultStopSet(){
return DefaultSetHolder.DEFAULT_STOP_SET;
}
private static class DefaultSetHolder {
static final CharArraySet DEFAULT_STOP_SET;
static {
try {
DEFAULT_STOP_SET = WordlistLoader.getWordSet(IOUtils.getDecodingReader(BrazilianAnalyzer.class,
DEFAULT_STOPWORD_FILE, StandardCharsets.UTF_8), "#");
} catch (IOException ex) {
// default set should always be present as it is part of the
// distribution (JAR)
throw new RuntimeException("Unable to load default stopword set");
}
}
}
/**
* Contains words that should be indexed but not stemmed.
*/
private CharArraySet excltable = CharArraySet.EMPTY_SET;
/**
* Builds an analyzer with the default stop words ({@link #getDefaultStopSet()}).
*/
public BrazilianAnalyzer() {
this(DefaultSetHolder.DEFAULT_STOP_SET);
}
/**
* Builds an analyzer with the given stop words
*
* @param stopwords
* a stopword set
*/
public BrazilianAnalyzer(CharArraySet stopwords) {
super(stopwords);
}
/**
* Builds an analyzer with the given stop words and stemming exclusion words
*
* @param stopwords
* a stopword set
*/
public BrazilianAnalyzer(CharArraySet stopwords, CharArraySet stemExclusionSet) {
this(stopwords);
excltable = CharArraySet.unmodifiableSet(CharArraySet.copy(stemExclusionSet));
}
/**
* Creates
* {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents}
* used to tokenize all the text in the provided {@link Reader}.
*
* @return {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents}
* built from a {@link StandardTokenizer} filtered with
* {@link LowerCaseFilter}, {@link StopFilter}
* , and {@link BrazilianStemFilter}.
*/
@Override
protected TokenStreamComponents createComponents(String fieldName) {
Tokenizer source = new StandardTokenizer();
TokenStream result = new LowerCaseFilter(source);
result = new StopFilter(result, stopwords);
if(excltable != null && !excltable.isEmpty())
result = new SetKeywordMarkerFilter(result, excltable);
return new TokenStreamComponents(source, new BrazilianStemFilter(result));
}
@Override
protected TokenStream normalize(String fieldName, TokenStream in) {
return new LowerCaseFilter(in);
}
}