org.apache.lucene.analysis.cz.CzechAnalyzer Maven / Gradle / Ivy
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package org.apache.lucene.analysis.cz;
/**
* 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.ReusableAnalyzerBase;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.KeywordMarkerFilter;
import org.apache.lucene.analysis.LowerCaseFilter;
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.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;
import java.io.*;
import java.nio.charset.Charset;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
/**
* {@link Analyzer} for Czech language.
*
* 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.
*
*
*
*
* You must specify the required {@link Version} compatibility when creating
* CzechAnalyzer:
*
* - As of 3.1, words are stemmed with {@link CzechStemFilter}
*
- As of 2.9, StopFilter preserves position increments
*
- As of 2.4, Tokens incorrectly identified as acronyms are corrected (see
* LUCENE-1068)
*
*/
public final class CzechAnalyzer extends ReusableAnalyzerBase {
/**
* List of typical stopwords.
* @deprecated use {@link #getDefaultStopSet()} instead
*/
@Deprecated
public final static String[] CZECH_STOP_WORDS = {
"a","s","k","o","i","u","v","z","dnes","cz","t\u00edmto","bude\u0161","budem",
"byli","jse\u0161","m\u016fj","sv\u00fdm","ta","tomto","tohle","tuto","tyto",
"jej","zda","pro\u010d","m\u00e1te","tato","kam","tohoto","kdo","kte\u0159\u00ed",
"mi","n\u00e1m","tom","tomuto","m\u00edt","nic","proto","kterou","byla",
"toho","proto\u017ee","asi","ho","na\u0161i","napi\u0161te","re","co\u017e","t\u00edm",
"tak\u017ee","sv\u00fdch","jej\u00ed","sv\u00fdmi","jste","aj","tu","tedy","teto",
"bylo","kde","ke","prav\u00e9","ji","nad","nejsou","\u010di","pod","t\u00e9ma",
"mezi","p\u0159es","ty","pak","v\u00e1m","ani","kdy\u017e","v\u0161ak","neg","jsem",
"tento","\u010dl\u00e1nku","\u010dl\u00e1nky","aby","jsme","p\u0159ed","pta","jejich",
"byl","je\u0161t\u011b","a\u017e","bez","tak\u00e9","pouze","prvn\u00ed","va\u0161e","kter\u00e1",
"n\u00e1s","nov\u00fd","tipy","pokud","m\u016f\u017ee","strana","jeho","sv\u00e9","jin\u00e9",
"zpr\u00e1vy","nov\u00e9","nen\u00ed","v\u00e1s","jen","podle","zde","u\u017e","b\u00fdt","v\u00edce",
"bude","ji\u017e","ne\u017e","kter\u00fd","by","kter\u00e9","co","nebo","ten","tak",
"m\u00e1","p\u0159i","od","po","jsou","jak","dal\u0161\u00ed","ale","si","se","ve",
"to","jako","za","zp\u011bt","ze","do","pro","je","na","atd","atp",
"jakmile","p\u0159i\u010dem\u017e","j\u00e1","on","ona","ono","oni","ony","my","vy",
"j\u00ed","ji","m\u011b","mne","jemu","tomu","t\u011bm","t\u011bmu","n\u011bmu","n\u011bmu\u017e",
"jeho\u017e","j\u00ed\u017e","jeliko\u017e","je\u017e","jako\u017e","na\u010de\u017e",
};
/** File containing default Czech stopwords. */
public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
/**
* Returns a set of default Czech-stopwords
*
* @return a set of default Czech-stopwords
*/
public static final Set getDefaultStopSet(){
return DefaultSetHolder.DEFAULT_SET;
}
private static class DefaultSetHolder {
private static final Set DEFAULT_SET;
static {
try {
DEFAULT_SET = WordlistLoader.getWordSet(IOUtils.getDecodingReader(CzechAnalyzer.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 {@link StopFilter}.
*/
// TODO once loadStopWords is gone those member should be removed too in favor of StopwordAnalyzerBase
private Set stoptable;
private final Version matchVersion;
private final Set stemExclusionTable;
/**
* Builds an analyzer with the default stop words ({@link #getDefaultStopSet()}).
*
* @param matchVersion Lucene version to match See
* {@link above}
*/
public CzechAnalyzer(Version matchVersion) {
this(matchVersion, DefaultSetHolder.DEFAULT_SET);
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion Lucene version to match See
* {@link above}
* @param stopwords a stopword set
*/
public CzechAnalyzer(Version matchVersion, Set stopwords) {
this(matchVersion, 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 matchVersion Lucene version to match See
* {@link above}
* @param stopwords a stopword set
* @param stemExclusionTable a stemming exclusion set
*/
public CzechAnalyzer(Version matchVersion, Set stopwords, Set stemExclusionTable) {
this.matchVersion = matchVersion;
this.stoptable = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stopwords));
this.stemExclusionTable = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stemExclusionTable));
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion Lucene version to match See
* {@link above}
* @param stopwords a stopword set
* @deprecated use {@link #CzechAnalyzer(Version, Set)} instead
*/
@Deprecated
public CzechAnalyzer(Version matchVersion, String... stopwords) {
this(matchVersion, StopFilter.makeStopSet( matchVersion, stopwords ));
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion Lucene version to match See
* {@link above}
* @param stopwords a stopword set
* @deprecated use {@link #CzechAnalyzer(Version, Set)} instead
*/
@Deprecated
public CzechAnalyzer(Version matchVersion, HashSet stopwords) {
this(matchVersion, (Set)stopwords);
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion Lucene version to match See
* {@link above}
* @param stopwords a file containing stopwords
* @deprecated use {@link #CzechAnalyzer(Version, Set)} instead
*/
@Deprecated
public CzechAnalyzer(Version matchVersion, File stopwords ) throws IOException {
this(matchVersion, (Set)WordlistLoader.getWordSet(
IOUtils.getDecodingReader(stopwords, IOUtils.CHARSET_UTF_8), matchVersion));
}
/**
* Loads stopwords hash from resource stream (file, database...).
* @param wordfile File containing the wordlist
* @param encoding Encoding used (win-1250, iso-8859-2, ...), null for default system encoding
* @deprecated use {@link WordlistLoader#getWordSet(Reader, String, Version) }
* and {@link #CzechAnalyzer(Version, Set)} instead
*/
// TODO extend StopwordAnalyzerBase once this method is gone!
@Deprecated
public void loadStopWords( InputStream wordfile, String encoding ) {
setPreviousTokenStream(null); // force a new stopfilter to be created
if ( wordfile == null ) {
stoptable = CharArraySet.EMPTY_SET;
return;
}
try {
// clear any previous table (if present)
stoptable = CharArraySet.EMPTY_SET;
stoptable = WordlistLoader.getWordSet(IOUtils.getDecodingReader(wordfile,
encoding == null ? IOUtils.CHARSET_UTF_8 : Charset.forName(encoding)), matchVersion);
} catch ( IOException e ) {
// clear any previous table (if present)
// TODO: throw IOException
stoptable = Collections.emptySet();
}
}
/**
* Creates
* {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* used to tokenize all the text in the provided {@link Reader}.
*
* @return {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* built from a {@link StandardTokenizer} filtered with
* {@link StandardFilter}, {@link LowerCaseFilter}, {@link StopFilter}
* , and {@link CzechStemFilter} (only if version is >= LUCENE_31). If
* a version is >= LUCENE_31 and a stem exclusion set is provided via
* {@link #CzechAnalyzer(Version, Set, Set)} a
* {@link KeywordMarkerFilter} is added before
* {@link CzechStemFilter}.
*/
@Override
protected TokenStreamComponents createComponents(String fieldName,
Reader reader) {
final Tokenizer source = new StandardTokenizer(matchVersion, reader);
TokenStream result = new StandardFilter(matchVersion, source);
result = new LowerCaseFilter(matchVersion, result);
result = new StopFilter( matchVersion, result, stoptable);
if (matchVersion.onOrAfter(Version.LUCENE_31)) {
if(!this.stemExclusionTable.isEmpty())
result = new KeywordMarkerFilter(result, stemExclusionTable);
result = new CzechStemFilter(result);
}
return new TokenStreamComponents(source, result);
}
}