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.camel.util;
018
019import java.lang.reflect.Array;
020import java.util.ArrayList;
021import java.util.Arrays;
022import java.util.Collection;
023import java.util.Collections;
024import java.util.HashMap;
025import java.util.HashSet;
026import java.util.Iterator;
027import java.util.LinkedHashMap;
028import java.util.List;
029import java.util.Map;
030import java.util.Set;
031import java.util.function.Supplier;
032
033import org.w3c.dom.NodeList;
034
035/**
036 * A number of helper methods for working with collections
037 */
038public final class CollectionHelper {
039
040    /**
041     * Utility classes should not have a public constructor.
042     */
043    private CollectionHelper() {
044    }
045
046    /**
047     * Returns the size of the collection if it can be determined to be a collection
048     *
049     * @param value the collection
050     * @return the size, or <tt>null</tt> if not a collection
051     */
052    public static Integer size(Object value) {
053        if (value != null) {
054            if (value instanceof Collection) {
055                Collection<?> collection = (Collection<?>) value;
056                return collection.size();
057            } else if (value instanceof Map) {
058                Map<?, ?> map = (Map<?, ?>) value;
059                return map.size();
060            } else if (value instanceof Object[]) {
061                Object[] array = (Object[]) value;
062                return array.length;
063            } else if (value.getClass().isArray()) {
064                return Array.getLength(value);
065            } else if (value instanceof NodeList) {
066                NodeList nodeList = (NodeList) value;
067                return nodeList.getLength();
068            }
069        }
070        return null;
071    }
072
073    /**
074     * Sets the value of the entry in the map for the given key, though if the
075     * map already contains a value for the given key then the value is appended
076     * to a list of values.
077     *
078     * @param map the map to add the entry to
079     * @param key the key in the map
080     * @param value the value to put in the map
081     */
082    @SuppressWarnings("unchecked")
083    public static void appendValue(Map<String, Object> map, String key, Object value) {
084        Object oldValue = map.get(key);
085        if (oldValue != null) {
086            List<Object> list;
087            if (oldValue instanceof List) {
088                list = (List<Object>) oldValue;
089            } else {
090                list = new ArrayList<>();
091                list.add(oldValue);
092                // replace old entry with list
093                map.remove(key);
094                map.put(key, list);
095            }
096            list.add(value);
097        } else {
098            map.put(key, value);
099        }
100    }
101
102    public static <T> Set<T> createSetContaining(T... contents) {
103        return new HashSet<>(Arrays.asList(contents));
104    }
105
106    public static String collectionAsCommaDelimitedString(Collection<?> col) {
107        if (col == null || col.isEmpty()) {
108            return "";
109        }
110
111        StringBuilder sb = new StringBuilder();
112        Iterator<?> it = col.iterator();
113        while (it.hasNext()) {
114            sb.append(it.next().toString());
115            if (it.hasNext()) {
116                sb.append(",");
117            }
118        }
119
120        return sb.toString();
121    }
122
123    /**
124     * Traverses the given map recursively and flattern the keys by combining them with the optional separator.
125     *
126     * @param map  the map
127     * @param separator optional separator to use in key name, for example a hyphen or dot.
128     * @return the map with flattern keys
129     */
130    public static Map<String, Object> flattenKeysInMap(Map<String, Object> map, String separator) {
131        Map<String, Object> answer = new LinkedHashMap<>();
132        doFlattenKeysInMap(map, "", ObjectHelper.isNotEmpty(separator) ? separator : "", answer);
133        return answer;
134    }
135
136    private static void doFlattenKeysInMap(Map<String, Object> source, String prefix, String separator, Map<String, Object> target) {
137        for (Map.Entry<String, Object> entry : source.entrySet()) {
138            String key = entry.getKey();
139            Object value = entry.getValue();
140            String newKey = prefix.isEmpty() ? key : prefix + separator + key;
141
142            if (value instanceof Map) {
143                Map map = (Map) value;
144                doFlattenKeysInMap(map, newKey, separator, target);
145            } else {
146                target.put(newKey, value);
147            }
148        }
149    }
150
151    /**
152     * Build an unmodifiable map on top of a given map. Note tha thew given map is
153     * copied if not null.
154     *
155     * @param map a map
156     * @return an unmodifiable map.
157     */
158    public static <K, V> Map<K, V> unmodifiableMap(Map<K, V> map) {
159        return map == null
160            ? Collections.emptyMap()
161            : Collections.unmodifiableMap(new HashMap<>(map));
162    }
163
164
165    /**
166     * Build a map from varargs.
167     */
168    public static <K, V> Map<K, V> mapOf(Supplier<Map<K, V>> creator, K key, V value, Object... keyVals) {
169        Map<K, V> map = creator.get();
170        map.put(key, value);
171
172        for (int i = 0; i < keyVals.length; i += 2) {
173            map.put(
174                (K) keyVals[i],
175                (V) keyVals[i + 1]
176            );
177        }
178
179        return map;
180    }
181
182
183    /**
184     * Build an immutable map from varargs.
185     */
186    public static <K, V> Map<K, V> immutableMapOf(Supplier<Map<K, V>> creator, K key, V value, Object... keyVals) {
187        return Collections.unmodifiableMap(
188            mapOf(creator, key, value, keyVals)
189        );
190    }
191
192    /**
193     * Build a map from varargs.
194     */
195    public static <K, V> Map<K, V> mapOf(K key, V value, Object... keyVals) {
196        return mapOf(HashMap::new, key, value, keyVals);
197    }
198
199    /**
200     * Build an immutable map from varargs.
201     */
202    public static <K, V> Map<K, V> immutableMapOf(K key, V value, Object... keyVals) {
203        return Collections.unmodifiableMap(
204            mapOf(HashMap::new, key, value, keyVals)
205        );
206    }
207}