org.apache.lucene.analysis.fr.FrenchAnalyzer.java Source code

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Here is the source code for org.apache.lucene.analysis.fr.FrenchAnalyzer.java

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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.fr;

import java.io.IOException;
import java.io.Reader;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;

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.snowball.SnowballFilter;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.util.ElisionFilter;
import org.apache.lucene.util.IOUtils;

/**
 * {@link Analyzer} for French language. 
 * <p>
 * Supports an external list of stopwords (words that
 * will not be indexed at all) and an external list of exclusions (word that will
 * not be stemmed, but indexed).
 * A default set of stopwords is used unless an alternative list is specified, but the
 * exclusion list is empty by default.
 * </p>
 *
 * <p><b>NOTE</b>: This class uses the same {@link org.apache.lucene.util.Version}
 * dependent settings as {@link StandardAnalyzer}.</p>
 *
 * @since 3.1
 */
public final class FrenchAnalyzer extends StopwordAnalyzerBase {

    /** File containing default French stopwords. */
    public final static String DEFAULT_STOPWORD_FILE = "french_stop.txt";

    /** Default set of articles for ElisionFilter */
    public static final CharArraySet DEFAULT_ARTICLES = CharArraySet.unmodifiableSet(new CharArraySet(
            Arrays.asList("l", "m", "t", "qu", "n", "s", "j", "d", "c", "jusqu", "quoiqu", "lorsqu", "puisqu"),
            true));

    /**
     * Contains words that should be indexed but not stemmed.
     */
    private final CharArraySet excltable;

    /**
     * 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.getSnowballWordSet(IOUtils.getDecodingReader(SnowballFilter.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");
            }
        }
    }

    /**
     * Builds an analyzer with the default stop words ({@link #getDefaultStopSet}).
     */
    public FrenchAnalyzer() {
        this(DefaultSetHolder.DEFAULT_STOP_SET);
    }

    /**
     * Builds an analyzer with the given stop words
     * 
     * @param stopwords
     *          a stopword set
     */
    public FrenchAnalyzer(CharArraySet stopwords) {
        this(stopwords, CharArraySet.EMPTY_SET);
    }

    /**
     * Builds an analyzer with the given stop words
     * 
     * @param stopwords
     *          a stopword set
     * @param stemExclutionSet
     *          a stemming exclusion set
     */
    public FrenchAnalyzer(CharArraySet stopwords, CharArraySet stemExclutionSet) {
        super(stopwords);
        this.excltable = CharArraySet.unmodifiableSet(CharArraySet.copy(stemExclutionSet));
    }

    /**
     * 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 ElisionFilter},
     *         {@link LowerCaseFilter}, {@link StopFilter},
     *         {@link SetKeywordMarkerFilter} if a stem exclusion set is
     *         provided, and {@link FrenchLightStemFilter}
     */
    @Override
    protected TokenStreamComponents createComponents(String fieldName) {
        final Tokenizer source = new StandardTokenizer();
        TokenStream result = new ElisionFilter(source, DEFAULT_ARTICLES);
        result = new LowerCaseFilter(result);
        result = new StopFilter(result, stopwords);
        if (!excltable.isEmpty())
            result = new SetKeywordMarkerFilter(result, excltable);
        result = new FrenchLightStemFilter(result);
        return new TokenStreamComponents(source, result);
    }

    @Override
    protected TokenStream normalize(String fieldName, TokenStream in) {
        TokenStream result = new ElisionFilter(in, DEFAULT_ARTICLES);
        result = new LowerCaseFilter(result);
        return result;
    }
}