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
025 * different manipulating operations.
026 * </p>
027 * <p>
028 * This interface is used when interacting with a node model. It is an
029 * abstraction over a concrete {@link ExpressionEngine} instance. It also
030 * implements some functionality for creating special helper objects for the
031 * processing of complex update operations.
032 * </p>
033 *
034 * @since 2.0
035 * @param <T> the type of the nodes supported by this resolver
036 */
037public interface NodeKeyResolver<T>
038{
039    /**
040     * Performs a query for the specified key on the given root node. This is a
041     * thin wrapper over the {@code query()} method of an
042     * {@link ExpressionEngine}.
043     *
044     * @param root the root node
045     * @param key the key to be resolved
046     * @param handler the {@code NodeHandler}
047     * @return a list with query results
048     */
049    List<QueryResult<T>> resolveKey(T root, String key, NodeHandler<T> handler);
050
051    /**
052     * Performs a query for the specified key on the given root node returning
053     * only node results. Some operations require results of type node and do
054     * not support attributes (e.g. for tracking nodes). This operation can be
055     * used in such cases. It works like {@code resolveKey()}, but filters only
056     * for results of type node.
057     *
058     * @param root the root node
059     * @param key the key to be resolved
060     * @param handler the {@code NodeHandler}
061     * @return a list with the resolved nodes
062     */
063    List<T> resolveNodeKey(T root, String key, NodeHandler<T> handler);
064
065    /**
066     * Resolves a key of an add operation. Result is a {@code NodeAddData}
067     * object containing all information for actually performing the add
068     * operation at the specified key.
069     *
070     * @param root the root node
071     * @param key the key to be resolved
072     * @param handler the {@code NodeHandler}
073     * @return a {@code NodeAddData} object to be used for the add operation
074     */
075    NodeAddData<T> resolveAddKey(T root, String key, NodeHandler<T> handler);
076
077    /**
078     * Resolves a key for an update operation. Result is a
079     * {@code NodeUpdateData} object containing all information for actually
080     * performing the update operation at the specified key using the provided
081     * new value object.
082     *
083     * @param root the root node
084     * @param key the key to be resolved
085     * @param newValue the new value for the key to be updated; this can be a
086     *        single value or a container for multiple values
087     * @param handler the {@code NodeHandler}
088     * @return a {@code NodeUpdateData} object to be used for this update
089     *         operation
090     */
091    NodeUpdateData<T> resolveUpdateKey(T root, String key, Object newValue,
092            NodeHandler<T> handler);
093
094    /**
095     * Generates a unique key for the specified node. This method is used if
096     * keys have to be generated for nodes received as query results. An
097     * implementation must generate a canonical key which is compatible with the
098     * current expression engine. The passed in map can be used by an
099     * implementation as cache. It is created initially by the caller and then
100     * passed in subsequent calls. An implementation may use this to avoid that
101     * keys for nodes already encountered have to be generated again.
102     *
103     * @param node the node in question
104     * @param cache a map serving as cache
105     * @param handler the {@code NodeHandler}
106     * @return a key for the specified node
107     */
108    String nodeKey(T node, Map<T, String> cache, NodeHandler<T> handler);
109}