/*
* Created on 25-Jan-2006
*/
package org.apache.lucene.queryparser.xml.builders;
import java.io.IOException;
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.queries.mlt.MoreLikeThisQuery;
import org.apache.lucene.queryparser.xml.QueryBuilder;
import org.apache.lucene.search.Query;
import org.apache.lucene.util.IOUtils;
import org.apache.lucene.queryparser.xml.DOMUtils;
import org.apache.lucene.queryparser.xml.ParserException;
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.
*/
/**
* Builder for {@link MoreLikeThisQuery}
*/
public class LikeThisQueryBuilder implements QueryBuilder {
private static final int DEFAULT_MAX_QUERY_TERMS = 20;
private static final int DEFAULT_MIN_TERM_FREQUENCY = 1;
private static final float DEFAULT_PERCENT_TERMS_TO_MATCH = 30; //default is a 3rd of selected terms must match
private final Analyzer analyzer;
private final String defaultFieldNames[];
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)
*/
@Override
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 (String field : fields) {
TokenStream ts = null;
try {
ts = analyzer.tokenStream(field, stopWords);
CharTermAttribute termAtt = ts.addAttribute(CharTermAttribute.class);
ts.reset();
while (ts.incrementToken()) {
stopWordsSet.add(termAtt.toString());
}
ts.end();
} catch (IOException ioe) {
throw new ParserException("IoException parsing stop words list in "
+ getClass().getName() + ":" + ioe.getLocalizedMessage());
} finally {
IOUtils.closeWhileHandlingException(ts);
}
}
}
MoreLikeThisQuery mlt = new MoreLikeThisQuery(DOMUtils.getText(e), fields, analyzer, fields[0]);
mlt.setMaxQueryTerms(DOMUtils.getAttribute(e, "maxQueryTerms", DEFAULT_MAX_QUERY_TERMS));
mlt.setMinTermFrequency(DOMUtils.getAttribute(e, "minTermFrequency", DEFAULT_MIN_TERM_FREQUENCY));
mlt.setPercentTermsToMatch(DOMUtils.getAttribute(e, "percentTermsToMatch", DEFAULT_PERCENT_TERMS_TO_MATCH) / 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;
}
}