Lucene example source code file (BoostQueryNode.java)

This example Lucene source code file (BoostQueryNode.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

boostquerynode, boostquerynode, charsequence, charsequence, clonenotsupportedexception, float, override, override, querynode, querynode, querynodeerror, querynodeexception, querynodeimpl, string, util

The Lucene BoostQueryNode.java source code

package org.apache.lucene.queryParser.core.nodes;

/**
 * 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.
 */

import java.util.List;

import org.apache.lucene.messages.MessageImpl;
import org.apache.lucene.queryParser.core.QueryNodeError;
import org.apache.lucene.queryParser.core.QueryNodeException;
import org.apache.lucene.queryParser.core.messages.QueryParserMessages;
import org.apache.lucene.queryParser.core.parser.EscapeQuerySyntax;

/**
 * A {@link BoostQueryNode} boosts the QueryNode tree which is under this node.
 * So, it must only and always have one child.
 * 
 * The boost value may vary from 0.0 to 1.0.
 * 
 */
public class BoostQueryNode extends QueryNodeImpl {

  private static final long serialVersionUID = -3929082630855807593L;

  private float value = 0;

  /**
   * Constructs a boost node
   * 
   * @param query
   *          the query to be boosted
   * @param value
   *          the boost value, it may vary from 0.0 to 1.0
   * 
   * @throws QueryNodeException
   */
  public BoostQueryNode(QueryNode query, float value) throws QueryNodeException {
    if (query == null) {
      throw new QueryNodeError(new MessageImpl(
          QueryParserMessages.NODE_ACTION_NOT_SUPPORTED, "query", "null"));
    }

    this.value = value;
    setLeaf(false);
    allocate();
    add(query);
  }

  /**
   * Returns the single child which this node boosts.
   * 
   * @return the single child which this node boosts
   */
  public QueryNode getChild() {
    List<QueryNode> children = getChildren();

    if (children == null || children.size() == 0) {
      return null;
    }

    return children.get(0);

  }

  /**
   * Returns the boost value. It may vary from 0.0 to 1.0.
   * 
   * @return the boost value
   */
  public float getValue() {
    return this.value;
  }

  /**
   * Returns the boost value parsed to a string.
   * 
   * @return the parsed value
   */
  private CharSequence getValueString() {
    Float f = Float.valueOf(this.value);
    if (f == f.longValue())
      return "" + f.longValue();
    else
      return "" + f;

  }

  @Override
  public String toString() {
    return "<boost value='" + getValueString() + "'>" + "\n"
        + getChild().toString() + "\n</boost>";
  }

  public CharSequence toQueryString(EscapeQuerySyntax escapeSyntaxParser) {
    if (getChild() == null)
      return "";
    return getChild().toQueryString(escapeSyntaxParser) + "^"
        + getValueString();
  }

  @Override
  public QueryNode cloneTree() throws CloneNotSupportedException {
    BoostQueryNode clone = (BoostQueryNode) super.cloneTree();

    clone.value = this.value;

    return clone;
  }

}