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.ArrayList;
020import java.util.Collection;
021import java.util.Collections;
022import java.util.HashMap;
023import java.util.Map;
024
025/**
026 * <p>
027 * A simple data class used by node models to store parameters of an update
028 * operation.
029 * </p>
030 * <p>
031 * The {@code Configuration} interface provides a method for setting the value
032 * of a given key. The passed in value can be a single object or a collection of
033 * values. This makes an update operation rather complicated because a
034 * collection of query results selected by the passed in key has to be matched
035 * to another collection of values - and both collections can have different
036 * sizes. Therefore, an update operation may involve changing of existing nodes,
037 * adding new nodes (if there are more values than currently existing nodes),
038 * and removing nodes (if there are more existing nodes than provided values).
039 * This class collects all this information making it possible to actually
040 * perform the update based on a passed in instance.
041 * </p>
042 *
043 * @version $Id: NodeUpdateData.java 1790899 2017-04-10 21:56:46Z ggregory $
044 * @since 2.0
045 * @param <T> the type of nodes involved in this update operation
046 */
047public class NodeUpdateData<T>
048{
049    /** The map with the query results whose value has to be changed. */
050    private final Map<QueryResult<T>, Object> changedValues;
051
052    /** The collection with the new values to be added. */
053    private final Collection<Object> newValues;
054
055    /** The collection with query results about the nodes to be removed. */
056    private final Collection<QueryResult<T>> removedNodes;
057
058    /** The key of the current update operation. */
059    private final String key;
060
061    /**
062     * Creates a new instance of {@code NodeUpdateData} and initializes all its
063     * properties. All passed in collections are optional and can be
064     * <b>null</b>.
065     *
066     * @param changedValues the map defining the changed values
067     * @param newValues the collection with the new values
068     * @param removedNodes the collection with the nodes to be removed
069     * @param key the key of the update operation
070     */
071    public NodeUpdateData(Map<QueryResult<T>, Object> changedValues,
072            Collection<Object> newValues,
073            Collection<QueryResult<T>> removedNodes, String key)
074    {
075        this.changedValues = copyMap(changedValues);
076        this.newValues = copyCollection(newValues);
077        this.removedNodes = copyCollection(removedNodes);
078        this.key = key;
079    }
080
081    /**
082     * Returns an unmodifiable map with the values to be changed. The keys of
083     * the map are the query results for the nodes affected, the values are the
084     * new values to be assigned to these nodes.
085     *
086     * @return the map with values to be changed
087     */
088    public Map<QueryResult<T>, Object> getChangedValues()
089    {
090        return changedValues;
091    }
092
093    /**
094     * Returns a collection with the values to be newly added. For these values
095     * new nodes have to be created and added under the key stored in this
096     * object.
097     *
098     * @return the collection with new values
099     */
100    public Collection<Object> getNewValues()
101    {
102        return newValues;
103    }
104
105    /**
106     * Adds a collection with the nodes to be removed. These nodes are no longer
107     * needed and have to be removed from the node model processing this
108     * request.
109     *
110     * @return the collection with nodes to be removed
111     */
112    public Collection<QueryResult<T>> getRemovedNodes()
113    {
114        return removedNodes;
115    }
116
117    /**
118     * Returns the key for this update operation.
119     *
120     * @return the key for this operation
121     */
122    public String getKey()
123    {
124        return key;
125    }
126
127    /**
128     * Creates an unmodifiable defensive copy of the passed in map which may be
129     * null.
130     *
131     * @param map the map to be copied
132     * @param <K> the type of the keys involved
133     * @param <V> the type of the values involved
134     * @return the unmodifiable copy
135     */
136    private static <K, V> Map<K, V> copyMap(Map<? extends K, ? extends V> map)
137    {
138        if (map == null)
139        {
140            return Collections.emptyMap();
141        }
142        else
143        {
144            return Collections.unmodifiableMap(new HashMap<>(map));
145        }
146    }
147
148    /**
149     * Creates an unmodifiable defensive copy of the passed in collection with
150     * may be null.
151     *
152     * @param col the collection to be copied
153     * @param <T> the element type of the collection
154     * @return the unmodifiable copy
155     */
156    private static <T> Collection<T> copyCollection(Collection<? extends T> col)
157    {
158        if (col == null)
159        {
160            return Collections.emptySet();
161        }
162        else
163        {
164            return Collections.unmodifiableCollection(new ArrayList<>(col));
165        }
166    }
167}