package org.apache.lucene.analysis.ru;
/**
* 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.
*/
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.TermAttribute;
import org.apache.lucene.analysis.ru.RussianStemmer;//javadoc @link
import java.io.IOException;
/**
* A {@link TokenFilter} that stems Russian words.
* <p>
* The implementation was inspired by GermanStemFilter.
* The input should be filtered by {@link RussianLowerCaseFilter} before passing it to RussianStemFilter ,
* because RussianStemFilter only works with lowercase part of any "russian" charset.
* </p>
*
* @version $Id: RussianStemFilter.java 808427 2009-08-27 14:28:22Z hossman $
*/
public final class RussianStemFilter extends TokenFilter
{
/**
* The actual token in the input stream.
*/
private RussianStemmer stemmer = null;
private TermAttribute termAtt;
/**
* @deprecated Use {@link #RussianStemFilter(TokenStream)} instead.
*/
public RussianStemFilter(TokenStream in, char[] charset)
{
super(in);
stemmer = new RussianStemmer(charset);
termAtt = (TermAttribute) addAttribute(TermAttribute.class);
}
public RussianStemFilter(TokenStream in)
{
this(in, RussianCharsets.UnicodeRussian);
}
/**
* Returns the next token in the stream, or null at EOS
*/
public final boolean incrementToken() throws IOException
{
if (input.incrementToken()) {
String term = termAtt.term();
String s = stemmer.stem(term);
if (s != null && !s.equals(term))
termAtt.setTermBuffer(s);
return true;
} else {
return false;
}
}
/**
* Set a alternative/custom {@link RussianStemmer} for this filter.
*/
public void setStemmer(RussianStemmer stemmer)
{
if (stemmer != null)
{
this.stemmer = stemmer;
}
}
}