/*
 * 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
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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.BoostQuery;
import org.apache.lucene.search.Query;
import org.apache.lucene.queryparser.xml.DOMUtils;
import org.apache.lucene.queryparser.xml.ParserException;
import org.w3c.dom.Element;

Builder for MoreLikeThisQuery
/** * 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<>(); for (String field : fields) { try (TokenStream 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()); } } } 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); } Query q = mlt; float boost = DOMUtils.getAttribute(e, "boost", 1.0f); if (boost != 1f) { q = new BoostQuery(mlt, boost); } return q; } }