net.mumie.cocoon.search.GermanEntityAnalyzer.java Source code

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Here is the source code for net.mumie.cocoon.search.GermanEntityAnalyzer.java

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/*
 * The MIT License (MIT)
 * 
 * Copyright (c) 2010 Technische Universitaet Berlin
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package net.mumie.cocoon.search;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.de.GermanStemFilter;
import org.apache.lucene.analysis.de.WordlistLoader;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;

import java.io.File;
import java.io.IOException;
import java.io.Reader;
import java.util.HashSet;
import java.util.Hashtable;
import java.util.Set;

/**
 *  Extended Analyzer for German language. Supports an external list of stopwords (words that
 * will not be indexed at all) and an external list of exclusions (word that will
 * not be stemmed, but indexed). Additionally it replace some important XML-entities 
 * for the german language. A default set of stopwords is used unless an alternative 
 * list is specified, the exclusion list is empty by default.
 *
 * @author Gerhard Schwarz, Helmut Vieritz
 * @version $Id: GermanEntityAnalyzer.java,v 1.3 2006/11/03 10:25:19 rassy Exp $
 */
public class GermanEntityAnalyzer extends Analyzer {

    /**
     * List of typical german stopwords.
     */
    private String[] GERMAN_STOP_WORDS = { "einer", "eine", "eines", "einem", "einen", "der", "die", "das", "des",
            "dass", "da", "den", "du", "er", "sie", "es", "zu", "ich", "zur", "was", "wer", "wie", "wir", "sei",
            "ein", "und", "oder", "ohne", "mit", "seien", "am", "im", "in", "aus", "auf", "ist", "sein", "war",
            "wird", "sind", "werden", "ihr", "ihre", "ihres", "so", "auch", "dem", "kann", "als", "fr", "von",
            "mit", "nach", "dich", "dir", "mich", "mir", "mein", "sein", "kein", "vor", "durch", "wegen", "wird",
            "sodass" };

    /**
     * Contains the stopwords used with the StopFilter.
     */
    private Set stopSet = new HashSet();

    /**
     * Contains words that should be indexed but not stemmed.
     */
    private Set exclusionSet = new HashSet();

    /**
     * Builds an analyzer.
     */
    public GermanEntityAnalyzer() {
        stopSet = StopFilter.makeStopSet(GERMAN_STOP_WORDS);
    }

    /**
     * Builds an analyzer with the given stop words.
     */
    public GermanEntityAnalyzer(String[] stopwords) {
        stopSet = StopFilter.makeStopSet(stopwords);
    }

    /**
     * Builds an analyzer with the given stop words.
     */
    public GermanEntityAnalyzer(Hashtable stopwords) {
        stopSet = new HashSet(stopwords.keySet());
    }

    /**
     * Builds an analyzer with the given stop words.
     */
    public GermanEntityAnalyzer(File stopwords) throws IOException {
        stopSet = WordlistLoader.getWordSet(stopwords);
    }

    /**
     * Builds an exclusionlist from an array of Strings.
     */
    public void setStemExclusionTable(String[] exclusionlist) {
        exclusionSet = StopFilter.makeStopSet(exclusionlist);
    }

    /**
     * Builds an exclusionlist from a Hashtable.
     */
    public void setStemExclusionTable(Hashtable exclusionlist) {
        exclusionSet = new HashSet(exclusionlist.keySet());
    }

    /**
     * Builds an exclusionlist from the words contained in the given file.
     */
    public void setStemExclusionTable(File exclusionlist) throws IOException {
        exclusionSet = WordlistLoader.getWordSet(exclusionlist);
    }

    /**
     * Creates a TokenStream which tokenizes all the text in the provided Reader.
     *
     * @return A TokenStream build from a StandardTokenizer filtered with
     *         StandardFilter, LowerCaseFilter, StopFilter, GermanStemFilter
     */
    public TokenStream tokenStream(String fieldName, Reader reader) {
        TokenStream result = new StandardTokenizer(reader);
        result = new StandardFilter(result);
        result = new EntityFilter(result);
        result = new LowerCaseFilter(result);
        result = new StopFilter(result, stopSet);
        result = new GermanStemFilter(result, exclusionSet);
        return result;
    }
}