lucene/queryparser/src/java/org/apache/lucene/queryparser/flexible/core/processors/QueryNodeProcessor.java

/*
 * 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.
 */
package org.apache.lucene.queryparser.flexible.core.processors;

import org.apache.lucene.queryparser.flexible.core.QueryNodeException;
import org.apache.lucene.queryparser.flexible.core.config.QueryConfigHandler;
import org.apache.lucene.queryparser.flexible.core.nodes.QueryNode;

/**
 * A {@link QueryNodeProcessor} is an interface for classes that process a
 * {@link QueryNode} tree.
 * <p>
 * The implementor of this class should perform some operation on a query node
 * tree and return the same or another query node tree.
 * <p>
 * It also may carry a {@link QueryConfigHandler} object that contains
 * configuration about the query represented by the query tree or the
 * collection/index where it's intended to be executed.
 * <p>
 * In case there is any {@link QueryConfigHandler} associated to the query tree
 * to be processed, it should be set using
 * {@link QueryNodeProcessor#setQueryConfigHandler(QueryConfigHandler)} before
 * {@link QueryNodeProcessor#process(QueryNode)} is invoked.
 * 
 * @see QueryNode
 * @see QueryNodeProcessor
 * @see QueryConfigHandler
 */
public interface QueryNodeProcessor {

  /**
   * Processes a query node tree. It may return the same or another query tree.
   * I should never return <code>null</code>.
   * 
   * @param queryTree
   *          tree root node
   * 
   * @return the processed query tree
   */
  public QueryNode process(QueryNode queryTree) throws QueryNodeException;

  /**
   * Sets the {@link QueryConfigHandler} associated to the query tree.
   */
  public void setQueryConfigHandler(QueryConfigHandler queryConfigHandler);

  /**
   * Returns the {@link QueryConfigHandler} associated to the query tree if any,
   * otherwise it returns <code>null</code>
   * 
   * @return the {@link QueryConfigHandler} associated to the query tree if any,
   *         otherwise it returns <code>null</code>
   */
  public QueryConfigHandler getQueryConfigHandler();

}