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Lucene example source code file (QueryScorer.java)

This example Lucene source code file (QueryScorer.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

hashset, indexreader, indexreader, io, ioexception, positionincrementattribute, queryscorer, queryscorer, set, string, string, tokenstream, util, weightedspanterm, weightedspanterm, weightedspantermextractor

The Lucene QueryScorer.java source code

package org.apache.lucene.search.highlight;

/**
 * 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 java.io.IOException;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import org.apache.lucene.analysis.CachingTokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.memory.MemoryIndex;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.spans.SpanQuery;
import org.apache.lucene.util.StringHelper;

/**
 * {@link Scorer} implementation which scores text fragments by the number of
 * unique query terms found. This class converts appropriate {@link Query}s to
 * {@link SpanQuery}s and attempts to score only those terms that participated in
 * generating the 'hit' on the document.
 */
public class QueryScorer implements Scorer {
  private float totalScore;
  private Set<String> foundTerms;
  private Map<String,WeightedSpanTerm> fieldWeightedSpanTerms;
  private float maxTermWeight;
  private int position = -1;
  private String defaultField;
  private CharTermAttribute termAtt;
  private PositionIncrementAttribute posIncAtt;
  private boolean expandMultiTermQuery = true;
  private Query query;
  private String field;
  private IndexReader reader;
  private boolean skipInitExtractor;
  private boolean wrapToCaching = true;
  private int maxCharsToAnalyze;

  /**
   * @param query Query to use for highlighting
   */
  public QueryScorer(Query query) {
    init(query, null, null, true);
  }

  /**
   * @param query Query to use for highlighting
   * @param field Field to highlight - pass null to ignore fields
   */
  public QueryScorer(Query query, String field) {
    init(query, field, null, true);
  }

  /**
   * @param query Query to use for highlighting
   * @param field Field to highlight - pass null to ignore fields
   * @param reader {@link IndexReader} to use for quasi tf/idf scoring
   */
  public QueryScorer(Query query, IndexReader reader, String field) {
    init(query, field, reader, true);
  }


  /**
   * @param query to use for highlighting
   * @param reader {@link IndexReader} to use for quasi tf/idf scoring
   * @param field to highlight - pass null to ignore fields
   * @param defaultField
   */
  public QueryScorer(Query query, IndexReader reader, String field, String defaultField) {
    this.defaultField = StringHelper.intern(defaultField);
    init(query, field, reader, true);
  }

  /**
   * @param defaultField - The default field for queries with the field name unspecified
   */
  public QueryScorer(Query query, String field, String defaultField) {
    this.defaultField = StringHelper.intern(defaultField);
    init(query, field, null, true);
  }

  /**
   * @param weightedTerms an array of pre-created {@link WeightedSpanTerm}s
   */
  public QueryScorer(WeightedSpanTerm[] weightedTerms) {
    this.fieldWeightedSpanTerms = new HashMap<String,WeightedSpanTerm>(weightedTerms.length);

    for (int i = 0; i < weightedTerms.length; i++) {
      WeightedSpanTerm existingTerm = fieldWeightedSpanTerms.get(weightedTerms[i].term);

      if ((existingTerm == null) ||
            (existingTerm.weight < weightedTerms[i].weight)) {
        // if a term is defined more than once, always use the highest
        // scoring weight
        fieldWeightedSpanTerms.put(weightedTerms[i].term, weightedTerms[i]);
        maxTermWeight = Math.max(maxTermWeight, weightedTerms[i].getWeight());
      }
    }
    skipInitExtractor = true;
  }

  /*
   * (non-Javadoc)
   *
   * @see org.apache.lucene.search.highlight.Scorer#getFragmentScore()
   */
  public float getFragmentScore() {
    return totalScore;
  }

  /**
   *
   * @return The highest weighted term (useful for passing to
   *         GradientFormatter to set top end of coloring scale).
   */
  public float getMaxTermWeight() {
    return maxTermWeight;
  }

  /*
   * (non-Javadoc)
   *
   * @see org.apache.lucene.search.highlight.Scorer#getTokenScore(org.apache.lucene.analysis.Token,
   *      int)
   */
  public float getTokenScore() {
    position += posIncAtt.getPositionIncrement();
    String termText = termAtt.toString();

    WeightedSpanTerm weightedSpanTerm;

    if ((weightedSpanTerm = fieldWeightedSpanTerms.get(
              termText)) == null) {
      return 0;
    }

    if (weightedSpanTerm.positionSensitive &&
          !weightedSpanTerm.checkPosition(position)) {
      return 0;
    }

    float score = weightedSpanTerm.getWeight();

    // found a query term - is it unique in this doc?
    if (!foundTerms.contains(termText)) {
      totalScore += score;
      foundTerms.add(termText);
    }

    return score;
  }

  /* (non-Javadoc)
   * @see org.apache.lucene.search.highlight.Scorer#init(org.apache.lucene.analysis.TokenStream)
   */
  public TokenStream init(TokenStream tokenStream) throws IOException {
    position = -1;
    termAtt = tokenStream.addAttribute(CharTermAttribute.class);
    posIncAtt = tokenStream.addAttribute(PositionIncrementAttribute.class);
    if(!skipInitExtractor) {
      if(fieldWeightedSpanTerms != null) {
        fieldWeightedSpanTerms.clear();
      }
      return initExtractor(tokenStream);
    }
    return null;
  }
  
  /**
   * Retrieve the {@link WeightedSpanTerm} for the specified token. Useful for passing
   * Span information to a {@link Fragmenter}.
   *
   * @param token to get {@link WeightedSpanTerm} for
   * @return WeightedSpanTerm for token
   */
  public WeightedSpanTerm getWeightedSpanTerm(String token) {
    return fieldWeightedSpanTerms.get(token);
  }

  /**
   */
  private void init(Query query, String field, IndexReader reader, boolean expandMultiTermQuery) {
    this.reader = reader;
    this.expandMultiTermQuery = expandMultiTermQuery;
    this.query = query;
    this.field = field;
  }
  
  private TokenStream initExtractor(TokenStream tokenStream) throws IOException {
    WeightedSpanTermExtractor qse = defaultField == null ? new WeightedSpanTermExtractor()
        : new WeightedSpanTermExtractor(defaultField);
    qse.setMaxDocCharsToAnalyze(maxCharsToAnalyze);
    qse.setExpandMultiTermQuery(expandMultiTermQuery);
    qse.setWrapIfNotCachingTokenFilter(wrapToCaching);
    if (reader == null) {
      this.fieldWeightedSpanTerms = qse.getWeightedSpanTerms(query,
          tokenStream, field);
    } else {
      this.fieldWeightedSpanTerms = qse.getWeightedSpanTermsWithScores(query,
          tokenStream, field, reader);
    }
    if(qse.isCachedTokenStream()) {
      return qse.getTokenStream();
    }
    
    return null;
  }

  /*
   * (non-Javadoc)
   *
   * @see org.apache.lucene.search.highlight.Scorer#startFragment(org.apache.lucene.search.highlight.TextFragment)
   */
  public void startFragment(TextFragment newFragment) {
    foundTerms = new HashSet<String>();
    totalScore = 0;
  }
  
  /**
   * @return true if multi-term queries should be expanded
   */
  public boolean isExpandMultiTermQuery() {
    return expandMultiTermQuery;
  }

  /**
   * Controls whether or not multi-term queries are expanded
   * against a {@link MemoryIndex} {@link IndexReader}.
   * 
   * @param expandMultiTermQuery true if multi-term queries should be expanded
   */
  public void setExpandMultiTermQuery(boolean expandMultiTermQuery) {
    this.expandMultiTermQuery = expandMultiTermQuery;
  }
  
  /**
   * By default, {@link TokenStream}s that are not of the type
   * {@link CachingTokenFilter} are wrapped in a {@link CachingTokenFilter} to
   * ensure an efficient reset - if you are already using a different caching
   * {@link TokenStream} impl and you don't want it to be wrapped, set this to
   * false.
   * 
   * @param wrap
   */
  public void setWrapIfNotCachingTokenFilter(boolean wrap) {
    this.wrapToCaching = wrap;
  }

  public void setMaxDocCharsToAnalyze(int maxDocCharsToAnalyze) {
    this.maxCharsToAnalyze = maxDocCharsToAnalyze;
  }
}

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