org.apache.lucene.analysis.pl.PolishAnalyzer 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.pl;
import java.io.IOException;
import java.io.Reader;
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.analysis.stempel.StempelFilter;
import org.apache.lucene.analysis.stempel.StempelStemmer;
import org.apache.lucene.util.IOUtils;
import org.egothor.stemmer.Trie;
/**
* {@link Analyzer} for Polish.
*
* @since 3.1
*/
public final class PolishAnalyzer extends StopwordAnalyzerBase {
private final CharArraySet stemExclusionSet;
private final Trie stemTable;
/** File containing default Polish stopwords. */
public static final String DEFAULT_STOPWORD_FILE = "stopwords.txt";
/** File containing default Polish stemmer table. */
public static final String DEFAULT_STEMMER_FILE = "stemmer_20000.tbl";
/**
* Returns an unmodifiable instance of the default stop words set.
*
* @return default stop words set.
*/
public static CharArraySet getDefaultStopSet() {
return DefaultsHolder.DEFAULT_STOP_SET;
}
/** Returns an unmodifiable instance of the default stemmer table. */
public static Trie getDefaultTable() {
return DefaultsHolder.DEFAULT_TABLE;
}
/**
* Atomically loads the DEFAULT_STOP_SET in a lazy fashion once the outer class accesses the
* static final set the first time.;
*/
private static class DefaultsHolder {
static final CharArraySet DEFAULT_STOP_SET;
static final Trie DEFAULT_TABLE;
static {
try {
DEFAULT_STOP_SET =
WordlistLoader.getWordSet(
IOUtils.requireResourceNonNull(
PolishAnalyzer.class.getResourceAsStream(DEFAULT_STOPWORD_FILE),
DEFAULT_STOPWORD_FILE),
"#");
} 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", ex);
}
try {
DEFAULT_TABLE =
StempelStemmer.load(PolishAnalyzer.class.getResourceAsStream(DEFAULT_STEMMER_FILE));
} catch (IOException ex) {
// default set should always be present as it is part of the
// distribution (JAR)
throw new RuntimeException("Unable to load default stemming tables", ex);
}
}
}
/** Builds an analyzer with the default stop words: {@link #DEFAULT_STOPWORD_FILE}. */
public PolishAnalyzer() {
this(DefaultsHolder.DEFAULT_STOP_SET);
}
/**
* Builds an analyzer with the given stop words.
*
* @param stopwords a stopword set
*/
public PolishAnalyzer(CharArraySet stopwords) {
this(stopwords, CharArraySet.EMPTY_SET);
}
/**
* Builds an analyzer with the given stop words. If a non-empty stem exclusion set is provided
* this analyzer will add a {@link SetKeywordMarkerFilter} before stemming.
*
* @param stopwords a stopword set
* @param stemExclusionSet a set of terms not to be stemmed
*/
public PolishAnalyzer(CharArraySet stopwords, CharArraySet stemExclusionSet) {
super(stopwords);
this.stemTable = DefaultsHolder.DEFAULT_TABLE;
this.stemExclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(stemExclusionSet));
}
/**
* Creates a {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents} which tokenizes all
* the text in the provided {@link Reader}.
*
* @return A {@link org.apache.lucene.analysis.Analyzer.TokenStreamComponents} built from an
* {@link StandardTokenizer} filtered with {@link LowerCaseFilter}, {@link StopFilter} ,
* {@link SetKeywordMarkerFilter} if a stem exclusion set is provided and {@link
* StempelFilter}.
*/
@Override
protected TokenStreamComponents createComponents(String fieldName) {
final Tokenizer source = new StandardTokenizer();
TokenStream result = new LowerCaseFilter(source);
result = new StopFilter(result, stopwords);
if (!stemExclusionSet.isEmpty()) result = new SetKeywordMarkerFilter(result, stemExclusionSet);
result = new StempelFilter(result, new StempelStemmer(stemTable));
return new TokenStreamComponents(source, result);
}
@Override
protected TokenStream normalize(String fieldName, TokenStream in) {
return new LowerCaseFilter(in);
}
}