| /* |
| * 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.cz; |
| |
| 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.StandardTokenizer; |
| import org.apache.lucene.util.IOUtils; |
| |
| /** |
| * {@link Analyzer} for Czech language. |
| * |
| * <p>Supports an external list of stopwords (words that will not be indexed at all). A default set |
| * of stopwords is used unless an alternative list is specified. |
| * |
| * @since 3.1 |
| */ |
| public final class CzechAnalyzer extends StopwordAnalyzerBase { |
| /** File containing default Czech stopwords. */ |
| public static final String DEFAULT_STOPWORD_FILE = "stopwords.txt"; |
| |
| /** |
| * Returns a set of default Czech-stopwords |
| * |
| * @return a set of default Czech-stopwords |
| */ |
| public static final CharArraySet getDefaultStopSet() { |
| return DefaultSetHolder.DEFAULT_SET; |
| } |
| |
| private static class DefaultSetHolder { |
| private static final CharArraySet DEFAULT_SET; |
| |
| static { |
| try { |
| DEFAULT_SET = |
| WordlistLoader.getWordSet( |
| IOUtils.getDecodingReader( |
| CzechAnalyzer.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"); |
| } |
| } |
| } |
| |
| private final CharArraySet stemExclusionTable; |
| |
| /** Builds an analyzer with the default stop words ({@link #getDefaultStopSet()}). */ |
| public CzechAnalyzer() { |
| this(DefaultSetHolder.DEFAULT_SET); |
| } |
| |
| /** |
| * Builds an analyzer with the given stop words. |
| * |
| * @param stopwords a stopword set |
| */ |
| public CzechAnalyzer(CharArraySet stopwords) { |
| this(stopwords, CharArraySet.EMPTY_SET); |
| } |
| |
| /** |
| * Builds an analyzer with the given stop words and a set of work to be excluded from the {@link |
| * CzechStemFilter}. |
| * |
| * @param stopwords a stopword set |
| * @param stemExclusionTable a stemming exclusion set |
| */ |
| public CzechAnalyzer(CharArraySet stopwords, CharArraySet stemExclusionTable) { |
| super(stopwords); |
| this.stemExclusionTable = CharArraySet.unmodifiableSet(CharArraySet.copy(stemExclusionTable)); |
| } |
| |
| /** |
| * 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 |
| * CzechStemFilter} (only if version is >= LUCENE_31). If a stem exclusion set is provided |
| * via {@link #CzechAnalyzer(CharArraySet, CharArraySet)} a {@link SetKeywordMarkerFilter} is |
| * added before {@link CzechStemFilter}. |
| */ |
| @Override |
| protected TokenStreamComponents createComponents(String fieldName) { |
| final Tokenizer source = new StandardTokenizer(); |
| TokenStream result = new LowerCaseFilter(source); |
| result = new StopFilter(result, stopwords); |
| if (!this.stemExclusionTable.isEmpty()) |
| result = new SetKeywordMarkerFilter(result, stemExclusionTable); |
| result = new CzechStemFilter(result); |
| return new TokenStreamComponents(source, result); |
| } |
| |
| @Override |
| protected TokenStream normalize(String fieldName, TokenStream in) { |
| return new LowerCaseFilter(in); |
| } |
| } |