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Lucene example source code file (StandardAnalyzer.java)

This example Lucene source code file (StandardAnalyzer.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

default_max_token_length, file, io, ioexception, ioexception, override, reader, reader, set, standardanalyzer, standardanalyzer, standardtokenizer, standardtokenizer, stop_words_set, tokenstreamcomponents, util

The Lucene StandardAnalyzer.java source code

package org.apache.lucene.analysis.standard;

/**
 * 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.util.Version;

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

/**
 * 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 3.1, 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)
 * </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;

  /**
   * Specifies whether deprecated acronyms should be replaced with HOST type.
   * See {@linkplain "https://issues.apache.org/jira/browse/LUCENE-1068"}
   */
  private final boolean replaceInvalidAcronym;

  /** 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}
   * @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}
   */
  public StandardAnalyzer(Version matchVersion) {
    this(matchVersion, STOP_WORDS_SET);
  }

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

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

  /**
   * 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);
    src.setReplaceInvalidAcronym(replaceInvalidAcronym);
    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 {
        src.setMaxTokenLength(StandardAnalyzer.this.maxTokenLength);
        return super.reset(reader);
      }
    };
  }
}

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