/*
* 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.Token;
import org.apache.lucene.analysis.TokenStream;
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.
*/
/**
* @author maharwood
*/
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 stopWordsSet=null;
if((stopWords!=null)&&(fields!=null))
{
stopWordsSet=new HashSet();
for (int i = 0; i < fields.length; i++)
{
TokenStream ts = analyzer.tokenStream(fields[i],new StringReader(stopWords));
try
{
Token stopToken=ts.next();
while(stopToken!=null)
{
stopWordsSet.add(stopToken.termText());
stopToken=ts.next();
}
}
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;
}
}