org.apache.lucene.analysis.cjk.CJKAnalyzer Maven / Gradle / Ivy
/*
* 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.cjk;
import java.io.IOException;
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.standard.StandardTokenizer;
/**
* An {@link Analyzer} that tokenizes text with {@link StandardTokenizer},
* normalizes content with {@link CJKWidthFilter}, folds case with
* {@link LowerCaseFilter}, forms bigrams of CJK with {@link CJKBigramFilter},
* and filters stopwords with {@link StopFilter}
*
* @since 3.1
*/
public final class CJKAnalyzer extends StopwordAnalyzerBase {
/**
* File containing default CJK stopwords.
*
* Currently it contains some common English words that are not usually
* useful for searching and some double-byte interpunctions.
*/
public final static String DEFAULT_STOPWORD_FILE = "stopwords.txt";
/**
* Returns an unmodifiable instance of the default stop-words set.
* @return an unmodifiable instance of the default stop-words set.
*/
public static CharArraySet getDefaultStopSet(){
return DefaultSetHolder.DEFAULT_STOP_SET;
}
private static class DefaultSetHolder {
static final CharArraySet DEFAULT_STOP_SET;
static {
try {
DEFAULT_STOP_SET = loadStopwordSet(false, CJKAnalyzer.class, 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");
}
}
}
/**
* Builds an analyzer which removes words in {@link #getDefaultStopSet()}.
*/
public CJKAnalyzer() {
this(DefaultSetHolder.DEFAULT_STOP_SET);
}
/**
* Builds an analyzer with the given stop words
*
* @param stopwords
* a stopword set
*/
public CJKAnalyzer(CharArraySet stopwords){
super(stopwords);
}
@Override
protected TokenStreamComponents createComponents(String fieldName) {
final Tokenizer source = new StandardTokenizer();
// run the widthfilter first before bigramming, it sometimes combines characters.
TokenStream result = new CJKWidthFilter(source);
result = new LowerCaseFilter(result);
result = new CJKBigramFilter(result);
return new TokenStreamComponents(source, new StopFilter(result, stopwords));
}
@Override
protected TokenStream normalize(String fieldName, TokenStream in) {
TokenStream result = new CJKWidthFilter(in);
result = new LowerCaseFilter(result);
return result;
}
}