org.apache.lucene.analysis.nl.DutchAnalyzer Maven / Gradle / Ivy
package org.apache.lucene.analysis.nl;
/**
* 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 org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.CharArrayMap;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.KeywordMarkerFilter;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.ReusableAnalyzerBase;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.analysis.miscellaneous.StemmerOverrideFilter;
import org.apache.lucene.analysis.snowball.SnowballFilter;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.standard.StandardAnalyzer; // for javadoc
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;
import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;
import java.util.Map;
/**
* {@link Analyzer} for Dutch language.
*
* Supports an external list of stopwords (words that
* will not be indexed at all), an external list of exclusions (word that will
* not be stemmed, but indexed) and an external list of word-stem pairs that overrule
* the algorithm (dictionary stemming).
* A default set of stopwords is used unless an alternative list is specified, but the
* exclusion list is empty by default.
*
*
*
* You must specify the required {@link Version}
* compatibility when creating DutchAnalyzer:
*
* - As of 3.1, Snowball stemming is done with SnowballFilter,
* LowerCaseFilter is used prior to StopFilter, and Snowball
* stopwords are used by default.
*
- As of 2.9, StopFilter preserves position
* increments
*
*
* NOTE: This class uses the same {@link Version}
* dependent settings as {@link StandardAnalyzer}.
*/
public final class DutchAnalyzer extends ReusableAnalyzerBase {
/**
* List of typical Dutch stopwords.
* @deprecated use {@link #getDefaultStopSet()} instead
*/
@Deprecated
public final static String[] DUTCH_STOP_WORDS;
/** File containing default Dutch stopwords. */
public final static String DEFAULT_STOPWORD_FILE = "dutch_stop.txt";
static {
Set defaultStopSet = getDefaultStopSet();
DUTCH_STOP_WORDS = new String[defaultStopSet.size()];
int i = 0;
for (Object object: defaultStopSet) {
DUTCH_STOP_WORDS[i++] = new String((char[])object);
} // what a hack!
}
/**
* Returns an unmodifiable instance of the default stop-words set.
* @return an unmodifiable instance of the default stop-words set.
*/
public static Set getDefaultStopSet(){
return DefaultSetHolder.DEFAULT_STOP_SET;
}
private static class DefaultSetHolder {
static final Set DEFAULT_STOP_SET;
static {
try {
DEFAULT_STOP_SET = WordlistLoader.getSnowballWordSet(IOUtils.getDecodingReader(SnowballFilter.class,
DEFAULT_STOPWORD_FILE, IOUtils.CHARSET_UTF_8), Version.LUCENE_CURRENT);
} 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 the stopwords used with the StopFilter.
*/
private final Set stoptable;
/**
* Contains words that should be indexed but not stemmed.
*/
private Set excltable = Collections.emptySet();
private Map stemdict = CharArrayMap.emptyMap();
private final Version matchVersion;
/**
* Builds an analyzer with the default stop words ({@link #getDefaultStopSet()})
* and a few default entries for the stem exclusion table.
*
*/
public DutchAnalyzer(Version matchVersion) {
this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET);
stemdict = new CharArrayMap(matchVersion, 16, false);
stemdict.put("fiets", "fiets"); //otherwise fiet
stemdict.put("bromfiets", "bromfiets"); //otherwise bromfiet
stemdict.put("ei", "eier");
stemdict.put("kind", "kinder");
}
public DutchAnalyzer(Version matchVersion, Set stopwords){
this(matchVersion, stopwords, CharArraySet.EMPTY_SET);
}
public DutchAnalyzer(Version matchVersion, Set stopwords, Set stemExclusionTable){
stoptable = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stopwords));
excltable = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stemExclusionTable));
this.matchVersion = matchVersion;
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion
* @param stopwords
* @deprecated use {@link #DutchAnalyzer(Version, Set)} instead
*/
@Deprecated
public DutchAnalyzer(Version matchVersion, String... stopwords) {
this(matchVersion, StopFilter.makeStopSet(matchVersion, stopwords));
}
/**
* Builds an analyzer with the given stop words.
*
* @param stopwords
* @deprecated use {@link #DutchAnalyzer(Version, Set)} instead
*/
@Deprecated
public DutchAnalyzer(Version matchVersion, HashSet stopwords) {
this(matchVersion, (Set)stopwords);
}
/**
* Builds an analyzer with the given stop words.
*
* @param stopwords
* @deprecated use {@link #DutchAnalyzer(Version, Set)} instead
*/
@Deprecated
public DutchAnalyzer(Version matchVersion, File stopwords) {
// this is completely broken!
try {
stoptable = WordlistLoader.getWordSet(IOUtils.getDecodingReader(stopwords,
IOUtils.CHARSET_UTF_8), matchVersion);
} catch (IOException e) {
// TODO: throw IOException
throw new RuntimeException(e);
}
this.matchVersion = matchVersion;
}
/**
* Builds an exclusionlist from an array of Strings.
*
* @param exclusionlist
* @deprecated use {@link #DutchAnalyzer(Version, Set, Set)} instead
*/
@Deprecated
public void setStemExclusionTable(String... exclusionlist) {
excltable = StopFilter.makeStopSet(matchVersion, exclusionlist);
setPreviousTokenStream(null); // force a new stemmer to be created
}
/**
* Builds an exclusionlist from a Hashtable.
* @deprecated use {@link #DutchAnalyzer(Version, Set, Set)} instead
*/
@Deprecated
public void setStemExclusionTable(HashSet exclusionlist) {
excltable = exclusionlist;
setPreviousTokenStream(null); // force a new stemmer to be created
}
/**
* Builds an exclusionlist from the words contained in the given file.
* @deprecated use {@link #DutchAnalyzer(Version, Set, Set)} instead
*/
@Deprecated
public void setStemExclusionTable(File exclusionlist) {
try {
excltable = WordlistLoader.getWordSet(IOUtils.getDecodingReader(exclusionlist,
IOUtils.CHARSET_UTF_8), matchVersion);
setPreviousTokenStream(null); // force a new stemmer to be created
} catch (IOException e) {
// TODO: throw IOException
throw new RuntimeException(e);
}
}
/**
* Reads a stemdictionary file , that overrules the stemming algorithm
* This is a textfile that contains per line
* word\tstem, i.e: two tab seperated words
* @deprecated This prevents reuse of TokenStreams. If you wish to use a custom
* stem dictionary, create your own Analyzer with {@link StemmerOverrideFilter}
*/
@Deprecated
public void setStemDictionary(File stemdictFile) {
try {
stemdict = WordlistLoader.getStemDict(IOUtils.getDecodingReader(stemdictFile,
IOUtils.CHARSET_UTF_8), new CharArrayMap(matchVersion, 16, false));
setPreviousTokenStream(null); // force a new stemmer to be created
} catch (IOException e) {
// TODO: throw IOException
throw new RuntimeException(e);
}
}
/**
* Returns a (possibly reused) {@link TokenStream} which tokenizes all the
* text in the provided {@link Reader}.
*
* @return A {@link TokenStream} built from a {@link StandardTokenizer}
* filtered with {@link StandardFilter}, {@link LowerCaseFilter},
* {@link StopFilter}, {@link KeywordMarkerFilter} if a stem exclusion set is provided,
* {@link StemmerOverrideFilter}, and {@link SnowballFilter}
*/
@Override
protected TokenStreamComponents createComponents(String fieldName,
Reader aReader) {
if (matchVersion.onOrAfter(Version.LUCENE_31)) {
final Tokenizer source = new StandardTokenizer(matchVersion, aReader);
TokenStream result = new StandardFilter(matchVersion, source);
result = new LowerCaseFilter(matchVersion, result);
result = new StopFilter(matchVersion, result, stoptable);
if (!excltable.isEmpty())
result = new KeywordMarkerFilter(result, excltable);
if (!stemdict.isEmpty())
result = new StemmerOverrideFilter(matchVersion, result, stemdict);
result = new SnowballFilter(result, new org.tartarus.snowball.ext.DutchStemmer());
return new TokenStreamComponents(source, result);
} else {
final Tokenizer source = new StandardTokenizer(matchVersion, aReader);
TokenStream result = new StandardFilter(matchVersion, source);
result = new StopFilter(matchVersion, result, stoptable);
if (!excltable.isEmpty())
result = new KeywordMarkerFilter(result, excltable);
result = new DutchStemFilter(result, stemdict);
return new TokenStreamComponents(source, result);
}
}
}
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