BoostQueryNodeBuilder.java

/**
 * Copyright 2014 National University of Ireland, Galway.
 *
 * This file is part of the SIREn project. Project and contact information:
 *
 *  https://github.com/rdelbru/SIREn
 *
 * Licensed 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.sindice.siren.qparser.keyword.builders;

import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.core.builders.QueryTreeBuilder;
import org.apache.lucene.queryparser.flexible.core.nodes.BoostQueryNode;
import org.apache.lucene.queryparser.flexible.core.nodes.QueryNode;
import org.apache.lucene.search.Query;

/**
 * This builder basically reads the {@link Query} object set on the
 * {@link BoostQueryNode} child using
 * {@link QueryTreeBuilder#QUERY_TREE_BUILDER_TAGID} and applies the boost value
 * defined in the {@link BoostQueryNode}.
 */
public class BoostQueryNodeBuilder implements KeywordQueryBuilder {

  public BoostQueryNodeBuilder() {
    // empty constructor
  }

  public Query build(final QueryNode queryNode) throws QueryNodeException {
    final BoostQueryNode boostNode = (BoostQueryNode) queryNode;
    final QueryNode child = boostNode.getChild();

    if (child == null) {
      return null;
    }

    final Query query = (Query) child
        .getTag(QueryTreeBuilder.QUERY_TREE_BUILDER_TAGID);
    query.setBoost(boostNode.getValue());

    return query;
  }

}