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Lucene example source code file (QueryNodeProcessorImpl.java)

This example Lucene source code file (QueryNodeProcessorImpl.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

arraylist, arraylist, childrenlist, childrenlist, list, nullpointerexception, queryconfighandler, querynode, querynode, querynodeexception, querynodeexception, querynodeprocessor, querynodeprocessorimpl, util

The Lucene QueryNodeProcessorImpl.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.ArrayList;
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;

/**
 * <p>
 * This is a default implementation for the {@link QueryNodeProcessor}
 * interface, it's an abstract class, so it should be extended by classes that
 * want to process a {@link QueryNode} tree.
 * </p>
 * <p>
 * This class process {@link QueryNode}s from left to right in the tree. While
 * it's walking down the tree, for every node,
 * {@link #preProcessNode(QueryNode)} is invoked. After a node's children are
 * processed, {@link #postProcessNode(QueryNode)} is invoked for that node.
 * {@link #setChildrenOrder(List)} is invoked before
 * {@link #postProcessNode(QueryNode)} only if the node has at least one child,
 * in {@link #setChildrenOrder(List)} the implementor might redefine the
 * children order or remove any children from the children list.
 * </p>
 * <p>
 * Here is an example about how it process the nodes:
 * </p>
 * 
 * <pre>
 *      a
 *     / \
 *    b   e
 *   / \
 *  c   d
 * </pre>
 * 
 * Here is the order the methods would be invoked for the tree described above:
 * 
 * <pre>
 *      preProcessNode( a );
 *      preProcessNode( b );
 *      preProcessNode( c );
 *      postProcessNode( c );
 *      preProcessNode( d );
 *      postProcessNode( d );
 *      setChildrenOrder( bChildrenList );
 *      postProcessNode( b );
 *      preProcessNode( e );
 *      postProcessNode( e );
 *      setChildrenOrder( aChildrenList );
 *      postProcessNode( a )
 * </pre>
 * 
 * @see org.apache.lucene.queryParser.core.processors.QueryNodeProcessor
 */
public abstract class QueryNodeProcessorImpl implements QueryNodeProcessor {

  private ArrayList<ChildrenList> childrenListPool = new ArrayList();

  private QueryConfigHandler queryConfig;

  public QueryNodeProcessorImpl() {
    // empty constructor
  }

  public QueryNodeProcessorImpl(QueryConfigHandler queryConfigHandler) {
    this.queryConfig = queryConfigHandler;
  }

  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
    return processIteration(queryTree);
  }

  private QueryNode processIteration(QueryNode queryTree)
      throws QueryNodeException {
    queryTree = preProcessNode(queryTree);

    processChildren(queryTree);

    queryTree = postProcessNode(queryTree);

    return queryTree;

  }

  /**
   * This method is called every time a child is processed.
   * 
   * @param queryTree
   *          the query node child to be processed
   * @throws QueryNodeException
   *           if something goes wrong during the query node processing
   */
  protected void processChildren(QueryNode queryTree) throws QueryNodeException {

    List<QueryNode> children = queryTree.getChildren();
    ChildrenList newChildren;

    if (children != null && children.size() > 0) {

      newChildren = allocateChildrenList();

      try {

        for (QueryNode child : children) {
          child = processIteration(child);

          if (child == null) {
            throw new NullPointerException();

          }

          newChildren.add(child);

        }

        List<QueryNode> orderedChildrenList = setChildrenOrder(newChildren);

        queryTree.set(orderedChildrenList);

      } finally {
        newChildren.beingUsed = false;
      }

    }

  }

  private ChildrenList allocateChildrenList() {
    ChildrenList list = null;

    for (ChildrenList auxList : this.childrenListPool) {

      if (!auxList.beingUsed) {
        list = auxList;
        list.clear();

        break;

      }

    }

    if (list == null) {
      list = new ChildrenList();
      this.childrenListPool.add(list);

    }

    list.beingUsed = true;

    return list;

  }

  /**
   * For reference about this method check:
   * {@link QueryNodeProcessor#setQueryConfigHandler(QueryConfigHandler)}.
   * 
   * @param queryConfigHandler
   *          the query configuration handler to be set.
   * 
   * @see QueryNodeProcessor#getQueryConfigHandler()
   * @see QueryConfigHandler
   */
  public void setQueryConfigHandler(QueryConfigHandler queryConfigHandler) {
    this.queryConfig = queryConfigHandler;
  }

  /**
   * For reference about this method check:
   * {@link QueryNodeProcessor#getQueryConfigHandler()}.
   * 
   * @return QueryConfigHandler the query configuration handler to be set.
   * 
   * @see QueryNodeProcessor#setQueryConfigHandler(QueryConfigHandler)
   * @see QueryConfigHandler
   */
  public QueryConfigHandler getQueryConfigHandler() {
    return this.queryConfig;
  }

  /**
   * This method is invoked for every node when walking down the tree.
   * 
   * @param node
   *          the query node to be pre-processed
   * 
   * @return a query node
   * 
   * @throws QueryNodeException
   *           if something goes wrong during the query node processing
   */
  abstract protected QueryNode preProcessNode(QueryNode node)
      throws QueryNodeException;

  /**
   * This method is invoked for every node when walking up the tree.
   * 
   * @param node
   *          node the query node to be post-processed
   * 
   * @return a query node
   * 
   * @throws QueryNodeException
   *           if something goes wrong during the query node processing
   */
  abstract protected QueryNode postProcessNode(QueryNode node)
      throws QueryNodeException;

  /**
   * This method is invoked for every node that has at least on child. It's
   * invoked right before {@link #postProcessNode(QueryNode)} is invoked.
   * 
   * @param children
   *          the list containing all current node's children
   * 
   * @return a new list containing all children that should be set to the
   *         current node
   * 
   * @throws QueryNodeException
   *           if something goes wrong during the query node processing
   */
  abstract protected List<QueryNode> setChildrenOrder(List children)
      throws QueryNodeException;

  private static class ChildrenList extends ArrayList<QueryNode> {

    private static final long serialVersionUID = -2613518456949297135L;

    boolean beingUsed;

  }

}

Other Lucene examples (source code examples)

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