lucene/contrib/analyzers/common/src/java/org/apache/lucene/analysis/snowball/SnowballAnalyzer.java

package org.apache.lucene.analysis.snowball;

/**
 * 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 org.apache.lucene.analysis.*;
import org.apache.lucene.analysis.standard.*;
import org.apache.lucene.analysis.tr.TurkishLowerCaseFilter;
import org.apache.lucene.util.Version;

import java.io.IOException;
import java.io.Reader;
import java.util.Set;

/** Filters {@link StandardTokenizer} with {@link StandardFilter}, {@link
 * LowerCaseFilter}, {@link StopFilter} and {@link SnowballFilter}.
 *
 * Available stemmers are listed in org.tartarus.snowball.ext.  The name of a
 * stemmer is the part of the class name before "Stemmer", e.g., the stemmer in
 * {@link org.tartarus.snowball.ext.EnglishStemmer} is named "English".
 *
 * <p><b>NOTE</b>: This class uses the same {@link Version}
 * dependent settings as {@link StandardAnalyzer}, with the following addition:
 * <ul>
 *   <li> As of 3.1, uses {@link TurkishLowerCaseFilter} for Turkish language.
 * </ul>
 * </p>
 * @deprecated Use the language-specific analyzer in contrib/analyzers instead. 
 * This analyzer will be removed in Lucene 4.0
 */
@Deprecated
public final class SnowballAnalyzer extends Analyzer {
  private String name;
  private Set<?> stopSet;
  private final Version matchVersion;

  /** Builds the named analyzer with no stop words. */
  public SnowballAnalyzer(Version matchVersion, String name) {
    this.name = name;
    this.matchVersion = matchVersion;
  }

  /** 
   * Builds the named analyzer with the given stop words.
   * @deprecated Use {@link #SnowballAnalyzer(Version, String, Set)} instead.  
   */
  @Deprecated
  public SnowballAnalyzer(Version matchVersion, String name, String[] stopWords) {
    this(matchVersion, name);
    stopSet = StopFilter.makeStopSet(matchVersion, stopWords);
  }
  
  /** Builds the named analyzer with the given stop words. */
  public SnowballAnalyzer(Version matchVersion, String name, Set<?> stopWords) {
    this(matchVersion, name);
    stopSet = CharArraySet.unmodifiableSet(CharArraySet.copy(matchVersion,
        stopWords));
  }

  /** Constructs a {@link StandardTokenizer} filtered by a {@link
      StandardFilter}, a {@link LowerCaseFilter}, a {@link StopFilter},
      and a {@link SnowballFilter} */
  @Override
  public TokenStream tokenStream(String fieldName, Reader reader) {
    TokenStream result = new StandardTokenizer(matchVersion, reader);
    result = new StandardFilter(result);
    // Use a special lowercase filter for turkish, the stemmer expects it.
    if (matchVersion.onOrAfter(Version.LUCENE_31) && name.equals("Turkish"))
      result = new TurkishLowerCaseFilter(result);
    else
      result = new LowerCaseFilter(matchVersion, result);
    if (stopSet != null)
      result = new StopFilter(matchVersion,
                              result, stopSet);
    result = new SnowballFilter(result, name);
    return result;
  }
  
  private class SavedStreams {
    Tokenizer source;
    TokenStream result;
  }
  
  /** Returns a (possibly reused) {@link StandardTokenizer} filtered by a 
   * {@link StandardFilter}, a {@link LowerCaseFilter}, 
   * a {@link StopFilter}, and a {@link SnowballFilter} */
  @Override
  public TokenStream reusableTokenStream(String fieldName, Reader reader)
      throws IOException {
    SavedStreams streams = (SavedStreams) getPreviousTokenStream();
    if (streams == null) {
      streams = new SavedStreams();
      streams.source = new StandardTokenizer(matchVersion, reader);
      streams.result = new StandardFilter(streams.source);
      // Use a special lowercase filter for turkish, the stemmer expects it.
      if (matchVersion.onOrAfter(Version.LUCENE_31) && name.equals("Turkish"))
        streams.result = new TurkishLowerCaseFilter(streams.result);
      else
        streams.result = new LowerCaseFilter(matchVersion, streams.result);
      if (stopSet != null)
        streams.result = new StopFilter(matchVersion,
                                        streams.result, stopSet);
      streams.result = new SnowballFilter(streams.result, name);
      setPreviousTokenStream(streams);
    } else {
      streams.source.reset(reader);
    }
    return streams.result;
  }
}