org.lukhnos.lucenestudy.HighlightingHelper.java Source code

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Here is the source code for org.lukhnos.lucenestudy.HighlightingHelper.java

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package org.lukhnos.lucenestudy;

/**
 * Copyright (c) 2015 Lukhnos Liu
 *
 * Licensed under the MIT License.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.highlight.Encoder;
import org.apache.lucene.search.highlight.Formatter;
import org.apache.lucene.search.highlight.Fragmenter;
import org.apache.lucene.search.highlight.Highlighter;
import org.apache.lucene.search.highlight.InvalidTokenOffsetsException;
import org.apache.lucene.search.highlight.QueryScorer;
import org.apache.lucene.search.highlight.SimpleHTMLFormatter;
import org.apache.lucene.search.highlight.SimpleSpanFragmenter;

import java.io.IOException;
import java.util.regex.Pattern;

class HighlightingHelper {
    // For removing any leading spaces or punctuations except "<" since <B> is used for highlights.
    static final Pattern cleanUpPattern = Pattern.compile("^[\\s\\p{Punct}&&[^<]]+",
            Pattern.UNICODE_CHARACTER_CLASS);

    // For concatenating paragraphes separated by \n.
    static final Pattern replaceLFPattern = Pattern.compile("\\n");

    static final int DEFAULT_FRAGMENT_LENGTH = 120;

    final QueryScorer scorer;
    final Highlighter highlighter;
    final Analyzer analyzer;
    int fragmentLength;

    HighlightingHelper(Query query, Analyzer analyzer) {
        this.analyzer = analyzer;

        Formatter formatter = new SimpleHTMLFormatter();
        Encoder encoder = new MinimalHTMLEncoder();
        scorer = new QueryScorer(query);
        highlighter = new Highlighter(formatter, encoder, scorer);

        fragmentLength = DEFAULT_FRAGMENT_LENGTH;
        Fragmenter fragmenter = new SimpleSpanFragmenter(scorer, fragmentLength);
        highlighter.setTextFragmenter(fragmenter);
    }

    int getFragmentLength() {
        return fragmentLength;
    }

    void setFragmentLength(int length) {
        if (length < 1) {
            throw new AssertionError("length must be at least 1");
        }

        // Create a new fragmenter if the length is different.
        if (fragmentLength != length) {
            Fragmenter fragmenter = new SimpleSpanFragmenter(scorer, length);
            highlighter.setTextFragmenter(fragmenter);
            fragmentLength = length;
        }
    }

    String highlightOrOriginal(String fieldName, String text) {
        if (text == null) {
            return null;
        }

        String highlighted = highlight(fieldName, text);
        if (highlighted != null) {
            return highlighted;
        }

        // The text has no highlights. We count the codepoints for the fallback substring.
        int cpCount = text.codePointCount(0, text.length());
        if (cpCount < fragmentLength) {
            return text;
        }

        int index = text.offsetByCodePoints(0, fragmentLength - 1);
        return text.substring(0, index) + "";
    }

    String highlight(String fieldName, String text) {
        if (text == null) {
            return null;
        }

        try {
            String highlighted = highlighter.getBestFragment(analyzer, fieldName, text);
            if (highlighted == null) {
                return null;
            }

            highlighted = cleanUpPattern.matcher(highlighted).replaceAll("");
            highlighted = replaceLFPattern.matcher(highlighted).replaceAll(" ");
            if (highlighted.isEmpty()) {
                highlighted = null;
            }

            return highlighted;
        } catch (InvalidTokenOffsetsException | IOException e) {
            return null;
        }
    }
}