| /* |
| * 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.lucene.analysis.en; |
| |
| import java.io.IOException; |
| import org.apache.lucene.analysis.TokenFilter; |
| import org.apache.lucene.analysis.TokenStream; |
| import org.apache.lucene.analysis.tokenattributes.CharTermAttribute; |
| import org.apache.lucene.analysis.tokenattributes.KeywordAttribute; |
| |
| /** |
| * A high-performance kstem filter for english. |
| * |
| * <p>See <a href="http://ciir.cs.umass.edu/pubfiles/ir-35.pdf">"Viewing Morphology as an Inference |
| * Process"</a> (Krovetz, R., Proceedings of the Sixteenth Annual International ACM SIGIR Conference |
| * on Research and Development in Information Retrieval, 191-203, 1993). |
| * |
| * <p>All terms must already be lowercased for this filter to work correctly. |
| * |
| * <p>Note: This filter is aware of the {@link KeywordAttribute}. To prevent certain terms from |
| * being passed to the stemmer {@link KeywordAttribute#isKeyword()} should be set to <code>true |
| * </code> in a previous {@link TokenStream}. |
| * |
| * <p>Note: For including the original term as well as the stemmed version, see {@link |
| * org.apache.lucene.analysis.miscellaneous.KeywordRepeatFilterFactory} |
| */ |
| public final class KStemFilter extends TokenFilter { |
| private final KStemmer stemmer = new KStemmer(); |
| private final CharTermAttribute termAttribute = addAttribute(CharTermAttribute.class); |
| private final KeywordAttribute keywordAtt = addAttribute(KeywordAttribute.class); |
| |
| public KStemFilter(TokenStream in) { |
| super(in); |
| } |
| |
| /** |
| * Returns the next, stemmed, input Token. |
| * |
| * @return The stemmed form of a token. |
| * @throws IOException If there is a low-level I/O error. |
| */ |
| @Override |
| public boolean incrementToken() throws IOException { |
| if (!input.incrementToken()) return false; |
| |
| char[] term = termAttribute.buffer(); |
| int len = termAttribute.length(); |
| if ((!keywordAtt.isKeyword()) && stemmer.stem(term, len)) { |
| termAttribute.setEmpty().append(stemmer.asCharSequence()); |
| } |
| |
| return true; |
| } |
| } |