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Lucene example source code file (WordTokenFilter.java)

This example Lucene source code file (WordTokenFilter.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, io, ioexception, ioexception, iterator, list, offsetattribute, override, override, tokenfilter, typeattribute, util, wordsegmenter, wordsegmenter, wordtokenfilter, wordtokenfilter

The Lucene WordTokenFilter.java source code

/**
 * 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.cn.smart;

import java.io.IOException;
import java.util.Iterator;
import java.util.List;

import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.cn.smart.hhmm.SegToken;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.TypeAttribute;

/**
 * A {@link TokenFilter} that breaks sentences into words.
 * @lucene.experimental
 */
public final class WordTokenFilter extends TokenFilter {

  private WordSegmenter wordSegmenter;

  private Iterator<SegToken> tokenIter;

  private List<SegToken> tokenBuffer;
  
  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
  private final TypeAttribute typeAtt = addAttribute(TypeAttribute.class);

  /**
   * Construct a new WordTokenizer.
   * 
   * @param in {@link TokenStream} of sentences 
   */
  public WordTokenFilter(TokenStream in) {
    super(in);
    this.wordSegmenter = new WordSegmenter();
  }
  
  @Override
  public boolean incrementToken() throws IOException {   
    if (tokenIter == null || !tokenIter.hasNext()) {
      // there are no remaining tokens from the current sentence... are there more sentences?
      if (input.incrementToken()) {
        // a new sentence is available: process it.
        tokenBuffer = wordSegmenter.segmentSentence(termAtt.toString(), offsetAtt.startOffset());
        tokenIter = tokenBuffer.iterator();
        /* 
         * it should not be possible to have a sentence with 0 words, check just in case.
         * returning EOS isn't the best either, but its the behavior of the original code.
         */
        if (!tokenIter.hasNext())
          return false;
      } else {
        return false; // no more sentences, end of stream!
      }
    } 
    // WordTokenFilter must clear attributes, as it is creating new tokens.
    clearAttributes();
    // There are remaining tokens from the current sentence, return the next one. 
    SegToken nextWord = tokenIter.next();
    termAtt.copyBuffer(nextWord.charArray, 0, nextWord.charArray.length);
    offsetAtt.setOffset(nextWord.startOffset, nextWord.endOffset);
    typeAtt.setType("word");
    return true;
  }

  @Override
  public void reset() throws IOException {
    super.reset();
    tokenIter = null;
  }
}

Other Lucene examples (source code examples)

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