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Lucene example source code file (RemoveDeletedQueryNodesProcessor.java)

This example Lucene source code file (RemoveDeletedQueryNodesProcessor.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

deletedquerynode, deletedquerynode, iterator, list, matchnodocsquerynode, override, override, querynode, querynode, querynodeexception, querynodeexception, querynodeprocessorimpl, removedeletedquerynodesprocessor, util

The Lucene RemoveDeletedQueryNodesProcessor.java source code

package org.apache.lucene.queryParser.core.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.Iterator;
import java.util.List;

import org.apache.lucene.queryParser.core.QueryNodeException;
import org.apache.lucene.queryParser.core.nodes.DeletedQueryNode;
import org.apache.lucene.queryParser.core.nodes.MatchNoDocsQueryNode;
import org.apache.lucene.queryParser.core.nodes.QueryNode;

/**
 * A {@link QueryNodeProcessorPipeline} class removes every instance of
 * {@link DeletedQueryNode} from a query node tree. If the resulting root node
 * is a {@link DeletedQueryNode}, {@link MatchNoDocsQueryNode} is returned.
 * 
 */
public class RemoveDeletedQueryNodesProcessor extends QueryNodeProcessorImpl {

  public RemoveDeletedQueryNodesProcessor() {
    // empty constructor
  }

  @Override
  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
    queryTree = super.process(queryTree);

    if (queryTree instanceof DeletedQueryNode
        && !(queryTree instanceof MatchNoDocsQueryNode)) {

      return new MatchNoDocsQueryNode();

    }

    return queryTree;

  }

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

    if (!node.isLeaf()) {
      List<QueryNode> children = node.getChildren();
      boolean removeBoolean = false;

      if (children == null || children.size() == 0) {
        removeBoolean = true;

      } else {
        removeBoolean = true;

        for (Iterator<QueryNode> it = children.iterator(); it.hasNext();) {

          if (!(it.next() instanceof DeletedQueryNode)) {
            removeBoolean = false;
            break;

          }

        }

      }

      if (removeBoolean) {
        return new DeletedQueryNode();
      }

    }

    return node;

  }

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

    for (int i = 0; i < children.size(); i++) {

      if (children.get(i) instanceof DeletedQueryNode) {
        children.remove(i--);
      }

    }

    return children;

  }

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

    return node;

  }

}

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