Lucene example source code file (ChineseTokenizer.java)

This example Lucene source code file (ChineseTokenizer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

chartermattribute, chinesetokenizer, chinesetokenizer, deprecated, io, io_buffer_size, ioexception, ioexception, max_word_len, offsetattribute, override, override, reader, reader, tokenizer

The Lucene ChineseTokenizer.java source code

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.IOException;
import java.io.Reader;

import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.util.AttributeSource;


/**
 * Tokenize Chinese text as individual chinese characters.
 * 
 * <p>
 * The difference between ChineseTokenizer and
 * CJKTokenizer is that they have different
 * token parsing logic.
 * </p>
 * <p>
 * For example, if the Chinese text
 * "C1C2C3C4" is to be indexed:
 * <ul>
 * <li>The tokens returned from ChineseTokenizer are C1, C2, C3, C4. 
 * <li>The tokens returned from the CJKTokenizer are C1C2, C2C3, C3C4.
 * </ul>
 * </p>
 * <p>
 * Therefore the index created by CJKTokenizer is much larger.
 * </p>
 * <p>
 * The problem is that when searching for C1, C1C2, C1C3,
 * C4C2, C1C2C3 ... the ChineseTokenizer works, but the
 * CJKTokenizer will not work.
 * </p>
 * @version 1.0
 * @deprecated Use {@link StandardTokenizer} instead, which has the same functionality.
 * This filter will be removed in Lucene 5.0
 */
@Deprecated
public final class ChineseTokenizer extends Tokenizer {


    public ChineseTokenizer(Reader in) {
      super(in);
    }

    public ChineseTokenizer(AttributeSource source, Reader in) {
      super(source, in);
    }

    public ChineseTokenizer(AttributeFactory factory, Reader in) {
      super(factory, 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 CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
    private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
    
    private final void push(char c) {

        if (length == 0) start = offset-1;            // start of token
        buffer[length++] = Character.toLowerCase(c);  // buffer it

    }

    private final boolean flush() {

        if (length>0) {
            //System.out.println(new String(buffer, 0,
            //length));
          termAtt.copyBuffer(buffer, 0, length);
          offsetAtt.setOffset(correctOffset(start), correctOffset(start+length));
          return true;
        }
        else
            return false;
    }

    @Override
    public boolean incrementToken() throws IOException {
        clearAttributes();

        length = 0;
        start = offset;


        while (true) {

            final char c;
            offset++;

            if (bufferIndex >= dataLen) {
                dataLen = input.read(ioBuffer);
                bufferIndex = 0;
            }

            if (dataLen == -1) {
              offset--;
              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;
            }
        }
    }
    
    @Override
    public final void end() {
      // set final offset
      final int finalOffset = correctOffset(offset);
      this.offsetAtt.setOffset(finalOffset, finalOffset);
    }

    @Override
    public void reset() throws IOException {
      super.reset();
      offset = bufferIndex = dataLen = 0;
    }
    
    @Override
    public void reset(Reader input) throws IOException {
      super.reset(input);
      reset();
    }
}