org.apache.lucene.analysis.shingle.ShingleAnalyzerWrapper.java Source code

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Here is the source code for org.apache.lucene.analysis.shingle.ShingleAnalyzerWrapper.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.shingle;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.AnalyzerWrapper;
import org.apache.lucene.analysis.standard.StandardAnalyzer;

/**
 * A ShingleAnalyzerWrapper wraps a {@link ShingleFilter} around another {@link Analyzer}.
 * <p>
 * A shingle is another name for a token based n-gram.
 * </p>
 *
 * @since 3.1
 */
public final class ShingleAnalyzerWrapper extends AnalyzerWrapper {

    private final Analyzer delegate;
    private final int maxShingleSize;
    private final int minShingleSize;
    private final String tokenSeparator;
    private final boolean outputUnigrams;
    private final boolean outputUnigramsIfNoShingles;
    private final String fillerToken;

    public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer) {
        this(defaultAnalyzer, ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
    }

    public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int maxShingleSize) {
        this(defaultAnalyzer, ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE, maxShingleSize);
    }

    public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int minShingleSize, int maxShingleSize) {
        this(defaultAnalyzer, minShingleSize, maxShingleSize, ShingleFilter.DEFAULT_TOKEN_SEPARATOR, true, false,
                ShingleFilter.DEFAULT_FILLER_TOKEN);
    }

    /**
     * Creates a new ShingleAnalyzerWrapper
     *
     * @param delegate Analyzer whose TokenStream is to be filtered
     * @param minShingleSize Min shingle (token ngram) size
     * @param maxShingleSize Max shingle size
     * @param tokenSeparator Used to separate input stream tokens in output shingles
     * @param outputUnigrams Whether or not the filter shall pass the original
     *        tokens to the output stream
     * @param outputUnigramsIfNoShingles Overrides the behavior of outputUnigrams==false for those
     *        times when no shingles are available (because there are fewer than
     *        minShingleSize tokens in the input stream)?
     *        Note that if outputUnigrams==true, then unigrams are always output,
     *        regardless of whether any shingles are available.
     * @param fillerToken filler token to use when positionIncrement is more than 1
     */
    public ShingleAnalyzerWrapper(Analyzer delegate, int minShingleSize, int maxShingleSize, String tokenSeparator,
            boolean outputUnigrams, boolean outputUnigramsIfNoShingles, String fillerToken) {
        super(delegate.getReuseStrategy());
        this.delegate = delegate;

        if (maxShingleSize < 2) {
            throw new IllegalArgumentException("Max shingle size must be >= 2");
        }
        this.maxShingleSize = maxShingleSize;

        if (minShingleSize < 2) {
            throw new IllegalArgumentException("Min shingle size must be >= 2");
        }
        if (minShingleSize > maxShingleSize) {
            throw new IllegalArgumentException("Min shingle size must be <= max shingle size");
        }
        this.minShingleSize = minShingleSize;

        this.tokenSeparator = (tokenSeparator == null ? "" : tokenSeparator);
        this.outputUnigrams = outputUnigrams;
        this.outputUnigramsIfNoShingles = outputUnigramsIfNoShingles;
        this.fillerToken = fillerToken;
    }

    /**
     * Wraps {@link StandardAnalyzer}. 
     */
    public ShingleAnalyzerWrapper() {
        this(ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE, ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
    }

    /**
     * Wraps {@link StandardAnalyzer}. 
     */
    public ShingleAnalyzerWrapper(int minShingleSize, int maxShingleSize) {
        this(new StandardAnalyzer(), minShingleSize, maxShingleSize);
    }

    /**
     * The max shingle (token ngram) size
     * 
     * @return The max shingle (token ngram) size
     */
    public int getMaxShingleSize() {
        return maxShingleSize;
    }

    /**
     * The min shingle (token ngram) size
     * 
     * @return The min shingle (token ngram) size
     */
    public int getMinShingleSize() {
        return minShingleSize;
    }

    public String getTokenSeparator() {
        return tokenSeparator;
    }

    public boolean isOutputUnigrams() {
        return outputUnigrams;
    }

    public boolean isOutputUnigramsIfNoShingles() {
        return outputUnigramsIfNoShingles;
    }

    public String getFillerToken() {
        return fillerToken;
    }

    @Override
    public final Analyzer getWrappedAnalyzer(String fieldName) {
        return delegate;
    }

    @Override
    protected TokenStreamComponents wrapComponents(String fieldName, TokenStreamComponents components) {
        ShingleFilter filter = new ShingleFilter(components.getTokenStream(), minShingleSize, maxShingleSize);
        filter.setMinShingleSize(minShingleSize);
        filter.setMaxShingleSize(maxShingleSize);
        filter.setTokenSeparator(tokenSeparator);
        filter.setOutputUnigrams(outputUnigrams);
        filter.setOutputUnigramsIfNoShingles(outputUnigramsIfNoShingles);
        filter.setFillerToken(fillerToken);
        return new TokenStreamComponents(components.getSource(), filter);
    }
}