/**
* 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 com.mozilla.grouperfish.lucene.analysis.en;
import java.io.Reader;
import java.util.Set;
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.PorterStemFilter;
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.en.EnglishPossessiveFilter;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.util.Version;
/**
* {@link Analyzer} for English.
*/
public final class EnglishAnalyzer extends StopwordAnalyzerBase {
private final boolean stem;
private final Set<?> stemExclusionSet;
/**
* Returns an unmodifiable instance of the default stop words set.
*
* @return default stop words set.
*/
public static Set<?> getDefaultStopSet() {
return DefaultSetHolder.DEFAULT_STOP_SET;
}
/**
* 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 DefaultSetHolder {
static final Set<?> DEFAULT_STOP_SET = StandardAnalyzer.STOP_WORDS_SET;
}
/**
* Builds an analyzer with the default stop words:
* {@link #getDefaultStopSet}.
*/
public EnglishAnalyzer(Version matchVersion) {
this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET, false);
}
/**
* @param matchVersion
* @param stem
*/
public EnglishAnalyzer(Version matchVersion, boolean stem) {
this(matchVersion, DefaultSetHolder.DEFAULT_STOP_SET, stem);
}
/**
* Builds an analyzer with the given stop words.
*
* @param matchVersion
* lucene compatibility version
* @param stopwords
* a stopword set
*/
public EnglishAnalyzer(Version matchVersion, Set<?> stopwords, boolean stem) {
this(matchVersion, stopwords, stem, 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 KeywordMarkerFilter} before stemming.
*
* @param matchVersion
* lucene compatibility version
* @param stopwords
* a stopword set
* @param stemExclusionSet
* a set of terms not to be stemmed
*/
public EnglishAnalyzer(Version matchVersion, Set<?> stopwords, boolean stem, Set<?> stemExclusionSet) {
super(matchVersion, stopwords);
this.stem = stem;
this.stemExclusionSet = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion, stemExclusionSet));
}
/**
* Creates a
* {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* which tokenizes all the text in the provided {@link Reader}.
*
* @return A
* {@link org.apache.lucene.analysis.ReusableAnalyzerBase.TokenStreamComponents}
* built from an {@link StandardTokenizer} filtered with
* {@link StandardFilter}, {@link LowerCaseFilter},
* {@link StopFilter} , {@link KeywordMarkerFilter} if a stem
* exclusion set is provided and {@link PorterStemFilter}.
*/
@Override
protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
final Tokenizer source = new StandardTokenizer(matchVersion, reader);
TokenStream result = new StandardFilter(matchVersion, source);
// prior to this we get the classic behavior, standardfilter does it for
// us.
if (matchVersion.onOrAfter(Version.LUCENE_31)) {
result = new EnglishPossessiveFilter(result);
}
result = new LowerCaseFilter(matchVersion, result);
result = new StopFilter(matchVersion, result, stopwords);
if (stem) {
if (!stemExclusionSet.isEmpty())
result = new KeywordMarkerFilter(result, stemExclusionSet);
result = new PorterStemFilter(result);
result = new StopFilter(matchVersion, result, stopwords);
}
return new TokenStreamComponents(source, result);
}
}