package org.apache.lucene.analysis.standard;
/**
* 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.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;
/** Normalizes tokens extracted with {@link StandardTokenizer}. */
public final class StandardFilter extends TokenFilter {
/** Construct filtering <i>in</i>. */
public StandardFilter(TokenStream in) {
super(in);
}
private static final String APOSTROPHE_TYPE = StandardTokenizer.TOKEN_TYPES[StandardTokenizer.APOSTROPHE];
private static final String ACRONYM_TYPE = StandardTokenizer.TOKEN_TYPES[StandardTokenizer.ACRONYM];
// this filters uses attribute type
private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
/** Returns the next token in the stream, or null at EOS.
* <p>Removes <tt>'s</tt> from the end of words.
* <p>Removes dots from acronyms.
*/
@Override
public final boolean incrementToken() throws java.io.IOException {
if (!input.incrementToken()) {
return false;
}
final char[] buffer = termAtt.buffer();
final int bufferLength = termAtt.length();
final String type = typeAtt.type();
if (type == APOSTROPHE_TYPE && // remove 's
bufferLength >= 2 &&
buffer[bufferLength-2] == '\'' &&
(buffer[bufferLength-1] == 's' || buffer[bufferLength-1] == 'S')) {
// Strip last 2 characters off
termAtt.setLength(bufferLength - 2);
} else if (type == ACRONYM_TYPE) { // remove dots
int upto = 0;
for(int i=0;i<bufferLength;i++) {
char c = buffer[i];
if (c != '.')
buffer[upto++] = c;
}
termAtt.setLength(upto);
}
return true;
}
}