Lucene example source code file (DefaultPhraseSlopQueryNodeProcessor.java)

This example Lucene source code file (DefaultPhraseSlopQueryNodeProcessor.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.

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The Lucene DefaultPhraseSlopQueryNodeProcessor.java source code

package org.apache.lucene.queryParser.standard.processors;

/**
 * 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.queryParser.core.QueryNodeException;
import org.apache.lucene.queryParser.core.config.QueryConfigHandler;
import org.apache.lucene.queryParser.core.nodes.QueryNode;
import org.apache.lucene.queryParser.core.nodes.SlopQueryNode;
import org.apache.lucene.queryParser.core.nodes.TokenizedPhraseQueryNode;
import org.apache.lucene.queryParser.core.processors.QueryNodeProcessorImpl;
import org.apache.lucene.queryParser.standard.config.DefaultPhraseSlopAttribute;
import org.apache.lucene.queryParser.standard.nodes.MultiPhraseQueryNode;

/**
 * This processor verifies if the attribute {@link DefaultPhraseSlopAttribute}
 * is defined in the {@link QueryConfigHandler}. If it is, it looks for every
 * {@link TokenizedPhraseQueryNode} and {@link MultiPhraseQueryNode} that does
 * not have any {@link SlopQueryNode} applied to it and creates an
 * {@link SlopQueryNode} and apply to it. The new {@link SlopQueryNode} has the
 * same slop value defined in the attribute. <br/>
 * 
 * @see SlopQueryNode
 * @see DefaultPhraseSlopAttribute
 */
public class DefaultPhraseSlopQueryNodeProcessor extends QueryNodeProcessorImpl {

  private boolean processChildren = true;

  private int defaultPhraseSlop;

  public DefaultPhraseSlopQueryNodeProcessor() {
    // empty constructor
  }

  @Override
  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
    QueryConfigHandler queryConfig = getQueryConfigHandler();

    if (queryConfig != null) {

      if (queryConfig.hasAttribute(DefaultPhraseSlopAttribute.class)) {
        this.defaultPhraseSlop = queryConfig.getAttribute(
            DefaultPhraseSlopAttribute.class).getDefaultPhraseSlop();

        return super.process(queryTree);

      }

    }

    return queryTree;

  }

  @Override
  protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {

    if (node instanceof TokenizedPhraseQueryNode
        || node instanceof MultiPhraseQueryNode) {

      return new SlopQueryNode(node, this.defaultPhraseSlop);

    }

    return node;

  }

  @Override
  protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {

    if (node instanceof SlopQueryNode) {
      this.processChildren = false;

    }

    return node;

  }

  @Override
  protected void processChildren(QueryNode queryTree) throws QueryNodeException {

    if (this.processChildren) {
      super.processChildren(queryTree);

    } else {
      this.processChildren = true;
    }

  }

  @Override
  protected List<QueryNode> setChildrenOrder(List children)
      throws QueryNodeException {

    return children;

  }

}