org.apache.nutch.scoring.similarity.util.LuceneAnalyzerUtil.java Source code

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Here is the source code for org.apache.nutch.scoring.similarity.util.LuceneAnalyzerUtil.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.nutch.scoring.similarity.util;

import java.util.List;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.core.LowerCaseFilter;
import org.apache.lucene.analysis.core.StopFilter;
import org.apache.lucene.analysis.en.EnglishMinimalStemFilter;
import org.apache.lucene.analysis.en.PorterStemFilter;
import org.apache.lucene.analysis.standard.ClassicTokenizer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.analysis.CharArraySet;

/**
 * Creates a custom analyzer based on user provided inputs
 *
 */
public class LuceneAnalyzerUtil extends Analyzer {

    public static enum StemFilterType {
        PORTERSTEM_FILTER, ENGLISHMINIMALSTEM_FILTER, NONE
    }

    private static StemFilterType stemFilterType;
    private static CharArraySet stopSet;

    /**
     * Creates an analyzer instance based on Lucene default stopword set if @param useStopFilter is set to true
     */
    public LuceneAnalyzerUtil(StemFilterType stemFilterType, boolean useStopFilter) {
        LuceneAnalyzerUtil.stemFilterType = stemFilterType;
        if (useStopFilter) {
            stopSet = StandardAnalyzer.STOP_WORDS_SET;
        } else {
            stopSet = null;
        }
    }

    /**
     * Creates an analyzer instance based on user provided stop words. If @param addToDefault is set to true, then 
     * user provided stop words will be added to the Lucene default stopset.
     */
    public LuceneAnalyzerUtil(StemFilterType stemFilterType, List<String> stopWords, boolean addToDefault) {
        LuceneAnalyzerUtil.stemFilterType = stemFilterType;
        if (addToDefault) {
            stopSet.addAll(stopWords);
        } else {
            stopSet = StopFilter.makeStopSet(stopWords);
        }
    }

    @Override
    protected TokenStreamComponents createComponents(String fieldName) {
        Tokenizer source = new ClassicTokenizer();
        TokenStream filter = new LowerCaseFilter(source);
        if (stopSet != null) {
            filter = new StopFilter(filter, stopSet);
        }

        switch (stemFilterType) {
        case PORTERSTEM_FILTER:
            filter = new PorterStemFilter(filter);
            break;
        case ENGLISHMINIMALSTEM_FILTER:
            filter = new EnglishMinimalStemFilter(filter);
            break;
        default:
            break;
        }
        return new TokenStreamComponents(source, filter);
    }

}