home | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Lucene example source code file (LikeThisQueryBuilder.java)

This example Lucene source code file (LikeThisQueryBuilder.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, chartermattribute, dom, hashset, io, ioexception, likethisquerybuilder, likethisquerybuilder, parserexception, parserexception, set, string, string, stringreader, tokenstream, tokenstream, util

The Lucene LikeThisQueryBuilder.java source code

/*
 * Created on 25-Jan-2006
 */
package org.apache.lucene.xmlparser.builders;

import java.io.IOException;
import java.io.StringReader;
import java.util.HashSet;
import java.util.Set;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.search.similar.MoreLikeThisQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.xmlparser.DOMUtils;
import org.apache.lucene.xmlparser.ParserException;
import org.apache.lucene.xmlparser.QueryBuilder;
import org.w3c.dom.Element;
/**
 * 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.
 */

/**
 * 
 */
public class LikeThisQueryBuilder implements QueryBuilder {

	private Analyzer analyzer;
	String defaultFieldNames [];
	int defaultMaxQueryTerms=20;
	int defaultMinTermFrequency=1;
	float defaultPercentTermsToMatch=30; //default is a 3rd of selected terms must match

	public LikeThisQueryBuilder(Analyzer analyzer,String [] defaultFieldNames)
	{
		this.analyzer=analyzer;
		this.defaultFieldNames=defaultFieldNames;
	}
	
	/* (non-Javadoc)
	 * @see org.apache.lucene.xmlparser.QueryObjectBuilder#process(org.w3c.dom.Element)
	 */
	public Query getQuery(Element e) throws ParserException {
		String fieldsList=e.getAttribute("fieldNames"); //a comma-delimited list of fields
		String fields[]=defaultFieldNames;
		if((fieldsList!=null)&&(fieldsList.trim().length()>0))
		{
			fields=fieldsList.trim().split(",");
			//trim the fieldnames
			for (int i = 0; i < fields.length; i++) {
				fields[i]=fields[i].trim();
			}
		}
		
		//Parse any "stopWords" attribute
		//TODO MoreLikeThis needs to ideally have per-field stopWords lists - until then 
		//I use all analyzers/fields to generate multi-field compatible stop list
		String stopWords=e.getAttribute("stopWords");
		Set<String> stopWordsSet=null;
		if((stopWords!=null)&&(fields!=null))
		{
		    stopWordsSet=new HashSet<String>();
		    for (int i = 0; i < fields.length; i++)
            {
                try
                {
                  TokenStream ts = analyzer.reusableTokenStream(fields[i],new StringReader(stopWords));
                  CharTermAttribute termAtt = ts.addAttribute(CharTermAttribute.class);
                  ts.reset();
	                while(ts.incrementToken()) {
	                    stopWordsSet.add(termAtt.toString());
	                }
	                ts.end();
	                ts.close();
                }
                catch(IOException ioe)
                {
                    throw new ParserException("IoException parsing stop words list in "
                            +getClass().getName()+":"+ioe.getLocalizedMessage());
                }
            }
		}
		
		
		MoreLikeThisQuery mlt=new MoreLikeThisQuery(DOMUtils.getText(e),fields,analyzer);
		mlt.setMaxQueryTerms(DOMUtils.getAttribute(e,"maxQueryTerms",defaultMaxQueryTerms));
		mlt.setMinTermFrequency(DOMUtils.getAttribute(e,"minTermFrequency",defaultMinTermFrequency));
		mlt.setPercentTermsToMatch(DOMUtils.getAttribute(e,"percentTermsToMatch",defaultPercentTermsToMatch)/100);
		mlt.setStopWords(stopWordsSet);
		int minDocFreq=DOMUtils.getAttribute(e,"minDocFreq",-1);
		if(minDocFreq>=0)
		{
			mlt.setMinDocFreq(minDocFreq);
		}

		mlt.setBoost(DOMUtils.getAttribute(e,"boost",1.0f));

		return mlt;
	}



}

Other Lucene examples (source code examples)

Here is a short list of links related to this Lucene LikeThisQueryBuilder.java source code file:



my book on functional programming

 

new blog posts

 

Copyright 1998-2019 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.