org.apache.lucene.analysis.ja.JapaneseAnalyzer.java Source code

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Here is the source code for org.apache.lucene.analysis.ja.JapaneseAnalyzer.java

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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.ja;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

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.cjk.CJKWidthFilter;
import org.apache.lucene.analysis.ja.JapaneseTokenizer.Mode;
import org.apache.lucene.analysis.ja.dict.UserDictionary;

/**
 * Analyzer for Japanese that uses morphological analysis.
 * @see JapaneseTokenizer
 *
 * @since 3.6.0
 */
public class JapaneseAnalyzer extends StopwordAnalyzerBase {
    private final Mode mode;
    private final Set<String> stoptags;
    private final UserDictionary userDict;

    public JapaneseAnalyzer() {
        this(null, JapaneseTokenizer.DEFAULT_MODE, DefaultSetHolder.DEFAULT_STOP_SET,
                DefaultSetHolder.DEFAULT_STOP_TAGS);
    }

    public JapaneseAnalyzer(UserDictionary userDict, Mode mode, CharArraySet stopwords, Set<String> stoptags) {
        super(stopwords);
        this.userDict = userDict;
        this.mode = mode;
        this.stoptags = stoptags;
    }

    public static CharArraySet getDefaultStopSet() {
        return DefaultSetHolder.DEFAULT_STOP_SET;
    }

    public static Set<String> getDefaultStopTags() {
        return DefaultSetHolder.DEFAULT_STOP_TAGS;
    }

    /**
     * Atomically loads DEFAULT_STOP_SET, DEFAULT_STOP_TAGS in a lazy fashion once the 
     * outer class accesses the static final set the first time.
     */
    private static class DefaultSetHolder {
        static final CharArraySet DEFAULT_STOP_SET;
        static final Set<String> DEFAULT_STOP_TAGS;

        static {
            try {
                DEFAULT_STOP_SET = loadStopwordSet(true, JapaneseAnalyzer.class, "stopwords.txt", "#"); // ignore case
                final CharArraySet tagset = loadStopwordSet(false, JapaneseAnalyzer.class, "stoptags.txt", "#");
                DEFAULT_STOP_TAGS = new HashSet<>();
                for (Object element : tagset) {
                    char chars[] = (char[]) element;
                    DEFAULT_STOP_TAGS.add(new String(chars));
                }
            } 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 or stoptag set");
            }
        }
    }

    @Override
    protected TokenStreamComponents createComponents(String fieldName) {
        Tokenizer tokenizer = new JapaneseTokenizer(userDict, true, mode);
        TokenStream stream = new JapaneseBaseFormFilter(tokenizer);
        stream = new JapanesePartOfSpeechStopFilter(stream, stoptags);
        stream = new CJKWidthFilter(stream);
        stream = new StopFilter(stream, stopwords);
        stream = new JapaneseKatakanaStemFilter(stream);
        stream = new LowerCaseFilter(stream);
        return new TokenStreamComponents(tokenizer, stream);
    }

    @Override
    protected TokenStream normalize(String fieldName, TokenStream in) {
        TokenStream result = new CJKWidthFilter(in);
        result = new LowerCaseFilter(result);
        return result;
    }
}