package org.apache.lucene.analysis.cn;
/**
* 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 java.io.Reader;
import org.apache.lucene.analysis.*;
/**
* Title: ChineseTokenizer
* Description: Extract tokens from the Stream using Character.getType()
* Rule: A Chinese character as a single token
* Copyright: Copyright (c) 2001
* Company:
*
* The difference between thr ChineseTokenizer and the
* CJKTokenizer (id=23545) is that they have different
* token parsing logic.
*
* Let me use an example. If having a Chinese text
* "C1C2C3C4" to be indexed, the tokens returned from the
* ChineseTokenizer are C1, C2, C3, C4. And the tokens
* returned from the CJKTokenizer are C1C2, C2C3, C3C4.
*
* Therefore the index the CJKTokenizer created is much
* larger.
*
* The problem is that when searching for C1, C1C2, C1C3,
* C4C2, C1C2C3 ... the ChineseTokenizer works, but the
* CJKTokenizer will not work.
*
* @author Yiyi Sun
* @version 1.0
*
*/
public final class ChineseTokenizer extends Tokenizer {
public ChineseTokenizer(Reader in) {
input = in;
}
private int offset = 0, bufferIndex=0, dataLen=0;
private final static int MAX_WORD_LEN = 255;
private final static int IO_BUFFER_SIZE = 1024;
private final char[] buffer = new char[MAX_WORD_LEN];
private final char[] ioBuffer = new char[IO_BUFFER_SIZE];
private int length;
private int start;
private final void push(char c) {
if (length == 0) start = offset-1; // start of token
buffer[length++] = Character.toLowerCase(c); // buffer it
}
private final Token flush() {
if (length>0) {
//System.out.println(new String(buffer, 0, length));
return new Token(new String(buffer, 0, length), start, start+length);
}
else
return null;
}
public final Token next() throws java.io.IOException {
length = 0;
start = offset;
while (true) {
final char c;
offset++;
if (bufferIndex >= dataLen) {
dataLen = input.read(ioBuffer);
bufferIndex = 0;
}
if (dataLen == -1) return flush();
else
c = ioBuffer[bufferIndex++];
switch(Character.getType(c)) {
case Character.DECIMAL_DIGIT_NUMBER:
case Character.LOWERCASE_LETTER:
case Character.UPPERCASE_LETTER:
push(c);
if (length == MAX_WORD_LEN) return flush();
break;
case Character.OTHER_LETTER:
if (length>0) {
bufferIndex--;
offset--;
return flush();
}
push(c);
return flush();
default:
if (length>0) return flush();
break;
}
}
}
}
/////////////////////////////////////////
package org.apache.lucene.analysis.cn;
/**
* 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 java.util.Hashtable;
import org.apache.lucene.analysis.*;
/**
* Title: ChineseFilter
* Description: Filter with a stop word table
* Rule: No digital is allowed.
* English word/token should larger than 1 character.
* One Chinese character as one Chinese word.
* TO DO:
* 1. Add Chinese stop words, such as /ue400
* 2. Dictionary based Chinese word extraction
* 3. Intelligent Chinese word extraction
*
* Copyright: Copyright (c) 2001
* Company:
* @author Yiyi Sun
* @version 1.0
*
*/
public final class ChineseFilter extends TokenFilter {
// Only English now, Chinese to be added later.
public static final String[] STOP_WORDS = {
"and", "are", "as", "at", "be", "but", "by",
"for", "if", "in", "into", "is", "it",
"no", "not", "of", "on", "or", "such",
"that", "the", "their", "then", "there", "these",
"they", "this", "to", "was", "will", "with"
};
private Hashtable stopTable;
public ChineseFilter(TokenStream in) {
super(in);
stopTable = new Hashtable(STOP_WORDS.length);
for (int i = 0; i < STOP_WORDS.length; i++)
stopTable.put(STOP_WORDS[i], STOP_WORDS[i]);
}
public final Token next() throws java.io.IOException {
for (Token token = input.next(); token != null; token = input.next()) {
String text = token.termText();
// why not key off token type here assuming ChineseTokenizer comes first?
if (stopTable.get(text) == null) {
switch (Character.getType(text.charAt(0))) {
case Character.LOWERCASE_LETTER:
case Character.UPPERCASE_LETTER:
// English word/token should larger than 1 character.
if (text.length()>1) {
return token;
}
break;
case Character.OTHER_LETTER:
// One Chinese character as one Chinese word.
// Chinese word extraction to be added later here.
return token;
}
}
}
return null;
}
}
/////////////////////////
package org.apache.lucene.analysis.cn;
/**
* 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 java.io.Reader;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
/**
* Title: ChineseAnalyzer
* Description:
* Subclass of org.apache.lucene.analysis.Analyzer
* build from a ChineseTokenizer, filtered with ChineseFilter.
* Copyright: Copyright (c) 2001
* Company:
* @author Yiyi Sun
* @version 1.0
*
*/
public class ChineseAnalyzer extends Analyzer {
public ChineseAnalyzer() {
}
/**
* Creates a TokenStream which tokenizes all the text in the provided Reader.
*
* @return A TokenStream build from a ChineseTokenizer filtered with ChineseFilter.
*/
public final TokenStream tokenStream(String fieldName, Reader reader) {
TokenStream result = new ChineseTokenizer(reader);
result = new ChineseFilter(result);
return result;
}
}