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Lucene example source code file (MoreLikeThisQuery.java)

This example Lucene source code file (MoreLikeThisQuery.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

analyzer, analyzer, booleanclause, booleanquery, booleanquery, io, ioexception, morelikethis, morelikethisquery, override, query, query, set, string, string, util

The Lucene MoreLikeThisQuery.java source code

/*
 * Created on 25-Jan-2006
 */
package org.apache.lucene.search.similar;

/**
 * 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.ByteArrayInputStream;
import java.io.IOException;
import java.util.Set;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.BooleanClause;
import org.apache.lucene.search.BooleanQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.similar.MoreLikeThis;

/**
 * A simple wrapper for MoreLikeThis for use in scenarios where a Query object is required eg
 * in custom QueryParser extensions. At query.rewrite() time the reader is used to construct the
 * actual MoreLikeThis object and obtain the real Query object.
 */
public class MoreLikeThisQuery extends Query
{

    
    private String likeText;
    private String[] moreLikeFields;
    private Analyzer analyzer;
    float percentTermsToMatch=0.3f;
    int minTermFrequency=1;
    int maxQueryTerms=5;
    Set<?> stopWords=null;
	int minDocFreq=-1;
    
    
    /**
     * @param moreLikeFields
     */
    public MoreLikeThisQuery(String likeText, String[] moreLikeFields, Analyzer analyzer)
    {
        this.likeText=likeText;
        this.moreLikeFields=moreLikeFields;
        this.analyzer=analyzer;
    }
    
    @Override
    public Query rewrite(IndexReader reader) throws IOException
    {
        MoreLikeThis mlt=new MoreLikeThis(reader);
        
        mlt.setFieldNames(moreLikeFields);
        mlt.setAnalyzer(analyzer);
        mlt.setMinTermFreq(minTermFrequency);
        if(minDocFreq>=0)
        {
        	mlt.setMinDocFreq(minDocFreq);
        }        
        mlt.setMaxQueryTerms(maxQueryTerms);
        mlt.setStopWords(stopWords);
        BooleanQuery bq= (BooleanQuery) mlt.like(new ByteArrayInputStream(likeText.getBytes()));        
        BooleanClause[] clauses = bq.getClauses();
        //make at least half the terms match
        bq.setMinimumNumberShouldMatch((int)(clauses.length*percentTermsToMatch));
        return bq;
    }
    /* (non-Javadoc)
     * @see org.apache.lucene.search.Query#toString(java.lang.String)
     */
    @Override
    public String toString(String field)
    {       
        return "like:"+likeText;
    }

	public float getPercentTermsToMatch() {
		return percentTermsToMatch;
	}
	public void setPercentTermsToMatch(float percentTermsToMatch) {
		this.percentTermsToMatch = percentTermsToMatch;
	}

	public Analyzer getAnalyzer()
	{
		return analyzer;
	}

	public void setAnalyzer(Analyzer analyzer)
	{
		this.analyzer = analyzer;
	}

	public String getLikeText()
	{
		return likeText;
	}

	public void setLikeText(String likeText)
	{
		this.likeText = likeText;
	}

	public int getMaxQueryTerms()
	{
		return maxQueryTerms;
	}

	public void setMaxQueryTerms(int maxQueryTerms)
	{
		this.maxQueryTerms = maxQueryTerms;
	}

	public int getMinTermFrequency()
	{
		return minTermFrequency;
	}

	public void setMinTermFrequency(int minTermFrequency)
	{
		this.minTermFrequency = minTermFrequency;
	}

	public String[] getMoreLikeFields()
	{
		return moreLikeFields;
	}

	public void setMoreLikeFields(String[] moreLikeFields)
	{
		this.moreLikeFields = moreLikeFields;
	}
    public Set<?> getStopWords()
    {
        return stopWords;
    }
    public void setStopWords(Set<?> stopWords)
    {
        this.stopWords = stopWords;
    }

	public int getMinDocFreq()
	{
		return minDocFreq;
	}

	public void setMinDocFreq(int minDocFreq)
	{
		this.minDocFreq = minDocFreq;
	}
}

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