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.core.LowerCaseFilter;
import org.apache.lucene.analysis.miscellaneous.KeywordMarkerFilter; // for javadoc
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.KeywordAttribute;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.ru.RussianStemmer;//javadoc @link
import org.apache.lucene.analysis.snowball.SnowballFilter; // 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 LowerCaseFilter} before passing it to RussianStemFilter ,
* because RussianStemFilter only works with lowercase characters.
* </p>
* <p>
* To prevent terms from being stemmed use an instance of
* {@link KeywordMarkerFilter} or a custom {@link TokenFilter} that sets
* the {@link KeywordAttribute} before this {@link TokenStream}.
* </p>
* @see KeywordMarkerFilter
* @deprecated Use {@link SnowballFilter} with
* {@link org.tartarus.snowball.ext.RussianStemmer} instead, which has the
* same functionality. This filter will be removed in Lucene 4.0
*/
@Deprecated
public final class RussianStemFilter extends TokenFilter
{
/**
* The actual token in the input stream.
*/
private RussianStemmer stemmer = new RussianStemmer();
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private final KeywordAttribute keywordAttr = addAttribute(KeywordAttribute.class);
public RussianStemFilter(TokenStream in)
{
super(in);
}
/**
* Returns the next token in the stream, or null at EOS
*/
@Override
public final boolean incrementToken() throws IOException
{
if (input.incrementToken()) {
if(!keywordAttr.isKeyword()) {
final String term = termAtt.toString();
final String s = stemmer.stem(term);
if (s != null && !s.equals(term))
termAtt.setEmpty().append(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;
}
}
}