Lucene example source code file (ReversePathHierarchyTokenizer.java)

This example Lucene source code file (ReversePathHierarchyTokenizer.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

arraylist, default_buffer_size, default_buffer_size, default_delimiter, default_delimiter, default_skip, default_skip, io, ioexception, offsetattribute, override, reversepathhierarchytokenizer, reversepathhierarchytokenizer, stringbuilder, tokenizer, util

The Lucene ReversePathHierarchyTokenizer.java source code

package org.apache.lucene.analysis.path;
/**
 * 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 java.util.ArrayList;
import java.util.List;

import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;

/**
 *
 * Take something like:
 *
 * <pre>
 * www.site.co.uk
 * </pre>
 *
 * and make:
 *
 * <pre>
 * www.site.co.uk
 * site.co.uk
 * co.uk
 * uk
 * </pre>
 *
 */
public class ReversePathHierarchyTokenizer extends Tokenizer {

  public ReversePathHierarchyTokenizer(Reader input) {
    this(input, DEFAULT_BUFFER_SIZE, DEFAULT_DELIMITER, DEFAULT_DELIMITER, DEFAULT_SKIP);
  }

  public ReversePathHierarchyTokenizer(Reader input, int skip) {
    this(input, DEFAULT_BUFFER_SIZE, DEFAULT_DELIMITER, DEFAULT_DELIMITER, skip);
  }

  public ReversePathHierarchyTokenizer(Reader input, int bufferSize, char delimiter) {
    this(input, bufferSize, delimiter, delimiter, DEFAULT_SKIP);
  }

  public ReversePathHierarchyTokenizer(Reader input, char delimiter, char replacement) {
    this(input, DEFAULT_BUFFER_SIZE, delimiter, replacement, DEFAULT_SKIP);
  }

  public ReversePathHierarchyTokenizer(Reader input, int bufferSize, char delimiter, char replacement) {
    this(input, bufferSize, delimiter, replacement, DEFAULT_SKIP);
  }

  public ReversePathHierarchyTokenizer(Reader input, char delimiter, int skip) {
    this(input, DEFAULT_BUFFER_SIZE, delimiter, delimiter, skip);
  }

  public ReversePathHierarchyTokenizer(Reader input, char delimiter, char replacement, int skip) {
    this(input, DEFAULT_BUFFER_SIZE, delimiter, replacement, skip);
  }

  public ReversePathHierarchyTokenizer(Reader input, int bufferSize, char delimiter, char replacement, int skip) {
    super(input);
    termAtt.resizeBuffer(bufferSize);
    this.delimiter = delimiter;
    this.replacement = replacement;
    this.skip = skip;
    resultToken = new StringBuilder(bufferSize);
    resultTokenBuffer = new char[bufferSize];
    delimiterPositions = new ArrayList<Integer>(bufferSize/10);
  }

  private static final int DEFAULT_BUFFER_SIZE = 1024;
  public static final char DEFAULT_DELIMITER = '/';
  public static final int DEFAULT_SKIP = 0;

  private final char delimiter;
  private final char replacement;
  private final int skip;

  private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
  private final OffsetAttribute offsetAtt = addAttribute(OffsetAttribute.class);
  private final PositionIncrementAttribute posAtt = addAttribute(PositionIncrementAttribute.class);
  
  private int endPosition = 0;
  private int finalOffset = 0;
  private int skipped = 0;
  private StringBuilder resultToken;

  private List<Integer> delimiterPositions;
  private int delimitersCount = -1;
  private char[] resultTokenBuffer;

  @Override
  public final boolean incrementToken() throws IOException {
    clearAttributes();
    if(delimitersCount == -1){
      int length = 0;
      delimiterPositions.add(0);
      while (true) {
        int c = input.read();
        if( c < 0 ) {
          break;
        }
        length++;
        if( c == delimiter ) {
          delimiterPositions.add(length);
          resultToken.append(replacement);
        }
        else{
          resultToken.append((char)c);
        }
      }
      delimitersCount = delimiterPositions.size();
      if( delimiterPositions.get(delimitersCount-1) < length ){
        delimiterPositions.add(length);
        delimitersCount++;
      }
      if( resultTokenBuffer.length < resultToken.length() ){
        resultTokenBuffer = new char[resultToken.length()];
      }
      resultToken.getChars(0, resultToken.length(), resultTokenBuffer, 0);
      resultToken.setLength(0);
      endPosition = delimiterPositions.get(delimitersCount-1 - skip);
      finalOffset = correctOffset(length);
      posAtt.setPositionIncrement(1);
    }
    else{
      posAtt.setPositionIncrement(0);
    }

    while( skipped < delimitersCount-skip-1 ){
      int start = delimiterPositions.get(skipped);
      termAtt.copyBuffer(resultTokenBuffer, start, endPosition - start);
      offsetAtt.setOffset(correctOffset(start), correctOffset(endPosition));
      skipped++;
      return true;
    }

    return false;
  }

  @Override
  public final void end() {
    // set final offset
    offsetAtt.setOffset(finalOffset, finalOffset);
  }

  @Override
  public void reset(Reader input) throws IOException {
    super.reset(input);
    resultToken.setLength(0);
    finalOffset = 0;
    skipped = 0;
    delimitersCount = -1;
    delimiterPositions.clear();
  }
}