package org.apache.lucene.analysis.de;
// This file is encoded in UTF-8
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.
*/
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.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;
/**
* 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).
* A default set of stopwords is used unless an alternative list is specified, the
* exclusion list is empty by default.
*
* @author Gerhard Schwarz
* @version $Id: GermanAnalyzer.java 151017 2004-11-29 22:22:48Z dnaber $
*/
public class GermanAnalyzer extends Analyzer {
/**
* List of typical german stopwords.
*/
public final static String[] GERMAN_STOP_WORDS = {
"einer", "eine", "eines", "einem", "einen",
"der", "die", "das", "dass", "daß",
"du", "er", "sie", "es",
"was", "wer", "wie", "wir",
"und", "oder", "ohne", "mit",
"am", "im", "in", "aus", "auf",
"ist", "sein", "war", "wird",
"ihr", "ihre", "ihres",
"als", "für", "von", "mit",
"dich", "dir", "mich", "mir",
"mein", "sein", "kein",
"durch", "wegen", "wird"
};
/**
* 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 with the default stop words
* (<code>GERMAN_STOP_WORDS</code>).
*/
public GermanAnalyzer() {
stopSet = StopFilter.makeStopSet(GERMAN_STOP_WORDS);
}
/**
* Builds an analyzer with the given stop words.
*/
public GermanAnalyzer(String[] stopwords) {
stopSet = StopFilter.makeStopSet(stopwords);
}
/**
* Builds an analyzer with the given stop words.
*/
public GermanAnalyzer(Hashtable stopwords) {
stopSet = new HashSet(stopwords.keySet());
}
/**
* Builds an analyzer with the given stop words.
*/
public GermanAnalyzer(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 LowerCaseFilter(result);
result = new StopFilter(result, stopSet);
result = new GermanStemFilter(result, exclusionSet);
return result;
}
}