queryscorer.java

lucene2.2.0版本

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.util.HashMap;
import java.util.HashSet;

import org.apache.lucene.analysis.Token;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Query;

/**
 * {@link Scorer} implementation which scores text fragments by the number of unique query terms found.
 * This class uses the {@link QueryTermExtractor} class to process determine the query terms and 
 * their boosts to be used. 
 * @author [e-mail]
 */
//TODO: provide option to boost score of fragments near beginning of document 
// based on fragment.getFragNum()
public class QueryScorer implements Scorer
{
	TextFragment currentTextFragment=null;
	HashSet uniqueTermsInFragment;
	float totalScore=0;
	float maxTermWeight=0;
	private HashMap termsToFind;
	

	/**
	 * 
	 * @param query a Lucene query (ideally rewritten using query.rewrite 
	 * before being passed to this class and the searcher)
	 */
	public QueryScorer(Query query)
	{
		this(QueryTermExtractor.getTerms(query));
	}
	
	/**
	 * 
	 * @param query a Lucene query (ideally rewritten using query.rewrite 
	 * before being passed to this class and the searcher)
	 * @param fieldName the Field name which is used to match Query terms
	 */
	public QueryScorer(Query query, String fieldName)
	{
		this(QueryTermExtractor.getTerms(query, false,fieldName));
	}	

	/**
	 * 
	 * @param query a Lucene query (ideally rewritten using query.rewrite 
	 * before being passed to this class and the searcher)
	 * @param reader used to compute IDF which can be used to a) score selected fragments better 
	 * b) use graded highlights eg set font color intensity
	 * @param fieldName the field on which Inverse Document Frequency (IDF) calculations are based
	 */
	public QueryScorer(Query query, IndexReader reader, String fieldName)
	{
		this(QueryTermExtractor.getIdfWeightedTerms(query, reader, fieldName)); 
	}

	public QueryScorer(WeightedTerm []weightedTerms	)
	{
		termsToFind = new HashMap();
		for (int i = 0; i < weightedTerms.length; i++)
		{
			WeightedTerm existingTerm=(WeightedTerm) termsToFind.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
				termsToFind.put(weightedTerms[i].term,weightedTerms[i]);
				maxTermWeight=Math.max(maxTermWeight,weightedTerms[i].getWeight());
			}
		}
	}
	

	/* (non-Javadoc)
	 * @see org.apache.lucene.search.highlight.FragmentScorer#startFragment(org.apache.lucene.search.highlight.TextFragment)
	 */
	public void startFragment(TextFragment newFragment)
	{
		uniqueTermsInFragment = new HashSet();
		currentTextFragment=newFragment;
		totalScore=0;
		
	}
	
	/* (non-Javadoc)
	 * @see org.apache.lucene.search.highlight.FragmentScorer#scoreToken(org.apache.lucene.analysis.Token)
	 */
	public float getTokenScore(Token token)
	{
		String termText=token.termText();
		
		WeightedTerm queryTerm=(WeightedTerm) termsToFind.get(termText);
		if(queryTerm==null)
		{
			//not a query term - return
			return 0;
		}
		//found a query term - is it unique in this doc?
		if(!uniqueTermsInFragment.contains(termText))
		{
			totalScore+=queryTerm.getWeight();
			uniqueTermsInFragment.add(termText);
		}
		return queryTerm.getWeight();
	}
	
	
	/* (non-Javadoc)
	 * @see org.apache.lucene.search.highlight.FragmentScorer#endFragment(org.apache.lucene.search.highlight.TextFragment)
	 */
	public float getFragmentScore()
	{
		return totalScore;		
	}


	/* (non-Javadoc)
	 * @see org.apache.lucene.search.highlight.FragmentScorer#allFragmentsProcessed()
	 */
	public void allFragmentsProcessed()
	{
		//this class has no special operations to perform at end of processing
	}

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