StandardAnalyzer.java

package mj.ocraptor.database;

/**
 * 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.File;
import java.io.IOException;
import java.io.Reader;
import java.util.Set;

import org.apache.lucene.analysis.CharReader;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.MappingCharFilter;
import org.apache.lucene.analysis.NormalizeCharMap;
import org.apache.lucene.analysis.StopAnalyzer;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.StopwordAnalyzerBase;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.WordlistLoader;
import org.apache.lucene.analysis.standard.ClassicAnalyzer;
import org.apache.lucene.analysis.standard.ClassicTokenizer;
import org.apache.lucene.analysis.standard.StandardFilter;
import org.apache.lucene.analysis.standard.StandardTokenizer;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.util.Version;

/**
 * Filters {@link StandardTokenizer} with {@link StandardFilter},
 * {@link LowerCaseFilter} and {@link StopFilter}, using a list of English stop
 * words.
 *
 * <a name="version"/>
 * <p>
 * You must specify the required {@link Version} compatibility when creating
 * StandardAnalyzer:
 * <ul>
 * <li>As of 3.4, Hiragana and Han characters are no longer wrongly split from
 * their combining characters. If you use a previous version number, you get the
 * exact broken behavior for backwards compatibility.
 * <li>As of 3.1, StandardTokenizer implements Unicode text segmentation, and
 * StopFilter correctly handles Unicode 4.0 supplementary characters in
 * stopwords. {@link ClassicTokenizer} and {@link ClassicAnalyzer} are the
 * pre-3.1 implementations of StandardTokenizer and StandardAnalyzer.
 * <li>As of 2.9, StopFilter preserves position increments
 * <li>As of 2.4, Tokens incorrectly identified as acronyms are corrected (see
 * <a href="https://issues.apache.org/jira/browse/LUCENE-1068">LUCENE-1068</a>)
 * </ul>
 */
public final class StandardAnalyzer extends StopwordAnalyzerBase {

  /** Default maximum allowed token length */
  public static final int DEFAULT_MAX_TOKEN_LENGTH = 255;

  private int maxTokenLength = DEFAULT_MAX_TOKEN_LENGTH;

  final static NormalizeCharMap map = new NormalizeCharMap();
  static {
    // ------------------------------------------------ //
    map.add(".", " ");
    map.add(":", " ");
    map.add(",", " ");
    map.add("_", " ");
    map.add("=", " ");
    map.add("-", " ");
    map.add("&", " ");
    // ------------------------------------------------ //
  }

  /**
   * An unmodifiable set containing some common English words that are usually
   * not useful for searching.
   */
  public static final Set<?> STOP_WORDS_SET = StopAnalyzer.ENGLISH_STOP_WORDS_SET;

  /**
   * Builds an analyzer with the given stop words.
   *
   * @param matchVersion
   *          Lucene version to match See {@link <a href="#version">above</a>}
   * @param stopWords
   *          stop words
   */
  public StandardAnalyzer(Version matchVersion, Set<?> stopWords) {
    super(matchVersion, stopWords);
    // replaceInvalidAcronym = matchVersion.onOrAfter(Version.LUCENE_24);
  }

  /**
   * Builds an analyzer with the default stop words ({@link #STOP_WORDS_SET}).
   *
   * @param matchVersion
   *          Lucene version to match See {@link <a href="#version">above</a>}
   */
  public StandardAnalyzer(Version matchVersion) {
    this(matchVersion, STOP_WORDS_SET);
  }

  /**
   * Builds an analyzer with the stop words from the given file.
   *
   * @see WordlistLoader#getWordSet(Reader, Version)
   * @param matchVersion
   *          Lucene version to match See {@link <a href="#version">above</a>}
   * @param stopwords
   *          File to read stop words from
   * @deprecated Use {@link #StandardAnalyzer(Version, Reader)} instead.
   */
  @Deprecated
  public StandardAnalyzer(Version matchVersion, File stopwords) throws IOException {
    this(matchVersion, WordlistLoader.getWordSet(IOUtils.getDecodingReader(stopwords,
        IOUtils.CHARSET_UTF_8), matchVersion));
  }

  /**
   * Builds an analyzer with the stop words from the given reader.
   *
   * @see WordlistLoader#getWordSet(Reader, Version)
   * @param matchVersion
   *          Lucene version to match See {@link <a href="#version">above</a>}
   * @param stopwords
   *          Reader to read stop words from
   */
  public StandardAnalyzer(Version matchVersion, Reader stopwords) throws IOException {
    this(matchVersion, WordlistLoader.getWordSet(stopwords, matchVersion));
  }

  /**
   * Set maximum allowed token length. If a token is seen that exceeds this
   * length then it is discarded. This setting only takes effect the next time
   * tokenStream or reusableTokenStream is called.
   */
  public void setMaxTokenLength(int length) {
    maxTokenLength = length;
  }

  /**
   * @see #setMaxTokenLength
   */
  public int getMaxTokenLength() {
    return maxTokenLength;
  }

  @Override
  protected TokenStreamComponents createComponents(final String fieldName, final Reader reader) {
    final StandardTokenizer src = new StandardTokenizer(matchVersion, reader);
    src.setMaxTokenLength(maxTokenLength);
    TokenStream tok = new StandardFilter(matchVersion, src);
    tok = new LowerCaseFilter(matchVersion, tok);
    tok = new StopFilter(matchVersion, tok, stopwords);

    return new TokenStreamComponents(src, tok) {
      @Override
      protected boolean reset(final Reader reader) throws IOException {
        Reader reader2 = new MappingCharFilter(map, CharReader.get(reader));
        src.setMaxTokenLength(StandardAnalyzer.this.maxTokenLength);
        return super.reset(reader2);
      }
    };
  }
}