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Lucene QueryParsers module

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/*
 * 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.
 */
package org.apache.lucene.queryparser.xml.builders;

import org.apache.lucene.queries.BoostingQuery;
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.apache.lucene.queryparser.xml.QueryBuilder;
import org.w3c.dom.Element;
/**
 * Builder for {@link BoostingQuery}
 */
public class BoostingQueryBuilder implements QueryBuilder {

  private static float DEFAULT_BOOST = 0.01f;
  
  private final QueryBuilder factory;

  public BoostingQueryBuilder(QueryBuilder factory) {
    this.factory = factory;
  }

  @Override
  public Query getQuery(Element e) throws ParserException {
    Element mainQueryElem = DOMUtils.getChildByTagOrFail(e, "Query");
    mainQueryElem = DOMUtils.getFirstChildOrFail(mainQueryElem);
    Query mainQuery = factory.getQuery(mainQueryElem);

    Element boostQueryElem = DOMUtils.getChildByTagOrFail(e, "BoostQuery");
    float boost = DOMUtils.getAttribute(boostQueryElem, "boost", DEFAULT_BOOST);
    boostQueryElem = DOMUtils.getFirstChildOrFail(boostQueryElem);
    Query boostQuery = factory.getQuery(boostQueryElem);

    Query bq = new BoostingQuery(mainQuery, boostQuery, boost);

    boost = DOMUtils.getAttribute(e, "boost", 1.0f);
    if (boost != 1f) {
      return new BoostQuery(bq, boost);
    }
    return bq;
  }
}