org.apache.lucene.analysis.standard.StandardAnalyzer.java Source code

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Here is the source code for org.apache.lucene.analysis.standard.StandardAnalyzer.java

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/*
 * 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.standard;

import java.io.IOException;
import java.io.Reader;

import org.apache.lucene.analysis.CharArraySet;
import org.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.StopwordAnalyzerBase;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.WordlistLoader;

/**
 * Filters {@link StandardTokenizer} with {@link LowerCaseFilter} and
 * {@link StopFilter}, using a configurable list of stop words.
 *
 * @since 3.1
 */
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;

    /** Builds an analyzer with the given stop words.
     * @param stopWords stop words */
    public StandardAnalyzer(CharArraySet stopWords) {
        super(stopWords);
    }

    /** Builds an analyzer with no stop words.
     */
    public StandardAnalyzer() {
        this(CharArraySet.EMPTY_SET);
    }

    /** Builds an analyzer with the stop words from the given reader.
     * @see WordlistLoader#getWordSet(Reader)
     * @param stopwords Reader to read stop words from */
    public StandardAnalyzer(Reader stopwords) throws IOException {
        this(loadStopwordSet(stopwords));
    }

    /**
     * Set the max allowed token length.  Tokens larger than this will be chopped
     * up at this token length and emitted as multiple tokens.  If you need to
     * skip such large tokens, you could increase this max length, and then
     * use {@code LengthFilter} to remove long tokens.  The default is
     * {@link StandardAnalyzer#DEFAULT_MAX_TOKEN_LENGTH}.
     */
    public void setMaxTokenLength(int length) {
        maxTokenLength = length;
    }

    /** Returns the current maximum token length
     * 
     *  @see #setMaxTokenLength */
    public int getMaxTokenLength() {
        return maxTokenLength;
    }

    @Override
    protected TokenStreamComponents createComponents(final String fieldName) {
        final StandardTokenizer src = new StandardTokenizer();
        src.setMaxTokenLength(maxTokenLength);
        TokenStream tok = new LowerCaseFilter(src);
        tok = new StopFilter(tok, stopwords);
        return new TokenStreamComponents(r -> {
            src.setMaxTokenLength(StandardAnalyzer.this.maxTokenLength);
            src.setReader(r);
        }, tok);
    }

    @Override
    protected TokenStream normalize(String fieldName, TokenStream in) {
        return new LowerCaseFilter(in);
    }
}