001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *     http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.configuration2.tree;
018
019import java.util.List;
020import java.util.Map;
021
022/**
023 * <p>
024 * Definition of an interface which allows resolving a (property) key for different manipulating operations.
025 * </p>
026 * <p>
027 * This interface is used when interacting with a node model. It is an abstraction over a concrete
028 * {@link ExpressionEngine} instance. It also implements some functionality for creating special helper objects for the
029 * processing of complex update operations.
030 * </p>
031 *
032 * @since 2.0
033 * @param <T> the type of the nodes supported by this resolver
034 */
035public interface NodeKeyResolver<T> {
036    /**
037     * Generates a unique key for the specified node. This method is used if keys have to be generated for nodes received as
038     * query results. An implementation must generate a canonical key which is compatible with the current expression
039     * engine. The passed in map can be used by an implementation as cache. It is created initially by the caller and then
040     * passed in subsequent calls. An implementation may use this to avoid that keys for nodes already encountered have to
041     * be generated again.
042     *
043     * @param node the node in question
044     * @param cache a map serving as cache
045     * @param handler the {@code NodeHandler}
046     * @return a key for the specified node
047     */
048    String nodeKey(T node, Map<T, String> cache, NodeHandler<T> handler);
049
050    /**
051     * Resolves a key of an add operation. Result is a {@code NodeAddData} object containing all information for actually
052     * performing the add operation at the specified key.
053     *
054     * @param root the root node
055     * @param key the key to be resolved
056     * @param handler the {@code NodeHandler}
057     * @return a {@code NodeAddData} object to be used for the add operation
058     */
059    NodeAddData<T> resolveAddKey(T root, String key, NodeHandler<T> handler);
060
061    /**
062     * Performs a query for the specified key on the given root node. This is a thin wrapper over the {@code query()} method
063     * of an {@link ExpressionEngine}.
064     *
065     * @param root the root node
066     * @param key the key to be resolved
067     * @param handler the {@code NodeHandler}
068     * @return a list with query results
069     */
070    List<QueryResult<T>> resolveKey(T root, String key, NodeHandler<T> handler);
071
072    /**
073     * Performs a query for the specified key on the given root node returning only node results. Some operations require
074     * results of type node and do not support attributes (e.g. for tracking nodes). This operation can be used in such
075     * cases. It works like {@code resolveKey()}, but filters only for results of type node.
076     *
077     * @param root the root node
078     * @param key the key to be resolved
079     * @param handler the {@code NodeHandler}
080     * @return a list with the resolved nodes
081     */
082    List<T> resolveNodeKey(T root, String key, NodeHandler<T> handler);
083
084    /**
085     * Resolves a key for an update operation. Result is a {@code NodeUpdateData} object containing all information for
086     * actually performing the update operation at the specified key using the provided new value object.
087     *
088     * @param root the root node
089     * @param key the key to be resolved
090     * @param newValue the new value for the key to be updated; this can be a single value or a container for multiple
091     *        values
092     * @param handler the {@code NodeHandler}
093     * @return a {@code NodeUpdateData} object to be used for this update operation
094     */
095    NodeUpdateData<T> resolveUpdateKey(T root, String key, Object newValue, NodeHandler<T> handler);
096}