    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 *      https://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.collections4.properties;
    018
    019import java.util.AbstractCollection;
    020import java.util.AbstractMap.SimpleEntry;
    021import java.util.AbstractSet;
    022import java.util.Collection;
    023import java.util.Collections;
    024import java.util.Enumeration;
    025import java.util.Iterator;
    026import java.util.LinkedHashSet;
    027import java.util.Map;
    028import java.util.Objects;
    029import java.util.Properties;
    030import java.util.Set;
    031import java.util.function.BiConsumer;
    032import java.util.function.BiFunction;
    033import java.util.function.Function;
    034import java.util.stream.Collectors;
    035
    036/**
    037 * A drop-in replacement for {@link Properties} for ordered keys.
    038 * <p>
    039 * Overrides methods to keep keys in insertion order. Allows other methods in the superclass to work with ordered keys.
    040 * </p>
    041 *
    042 * @see OrderedPropertiesFactory#INSTANCE
    043 * @since 4.5.0-M1
    044 */
    045public class OrderedProperties extends Properties {
    046
    047    /**
    048     * A key set view in insertion order.
    049     */
    050    private final class KeySet extends AbstractSet<Object> {
    051
    052        @Override
    053        public void clear() {
    054            OrderedProperties.this.clear();
    055        }
    056
    057        @Override
    058        public boolean contains(final Object key) {
    059            return containsKey(key);
    060        }
    061
    062        @Override
    063        public Iterator<Object> iterator() {
    064            return orderedKeysIterator();
    065        }
    066
    067        @Override
    068        public boolean remove(final Object key) {
    069            return OrderedProperties.this.remove(key) != null;
    070        }
    071
    072        @Override
    073        public int size() {
    074            return OrderedProperties.this.size();
    075        }
    076    }
    077
    078    /**
    079     * A values view in key insertion order.
    080     */
    081    private final class Values extends AbstractCollection<Object> {
    082
    083        @Override
    084        public void clear() {
    085            OrderedProperties.this.clear();
    086        }
    087
    088        @Override
    089        public boolean contains(final Object value) {
    090            return containsValue(value);
    091        }
    092
    093        @Override
    094        public Iterator<Object> iterator() {
    095            final Iterator<Object> keys = orderedKeysIterator();
    096            return new Iterator<Object>() {
    097
    098                @Override
    099                public boolean hasNext() {
    100                    return keys.hasNext();
    101                }
    102
    103                @Override
    104                public Object next() {
    105                    return get(keys.next());
    106                }
    107
    108                @Override
    109                public void remove() {
    110                    keys.remove();
    111                }
    112            };
    113        }
    114
    115        @Override
    116        public int size() {
    117            return OrderedProperties.this.size();
    118        }
    119    }
    120
    121    private static final long serialVersionUID = 1L;
    122
    123    /**
    124     * Preserves the insertion order.
    125     */
    126    private final LinkedHashSet<Object> orderedKeys = new LinkedHashSet<>();
    127
    128    /**
    129     * Constructs a new instance.
    130     */
    131    public OrderedProperties() {
    132        // empty
    133    }
    134
    135    @Override
    136    public synchronized void clear() {
    137        orderedKeys.clear();
    138        super.clear();
    139    }
    140
    141    @Override
    142    public synchronized Object compute(final Object key, final BiFunction<? super Object, ? super Object, ? extends Object> remappingFunction) {
    143        final Object compute = super.compute(key, remappingFunction);
    144        if (compute != null) {
    145            orderedKeys.add(key);
    146        } else {
    147            orderedKeys.remove(key);
    148        }
    149        return compute;
    150    }
    151
    152    @Override
    153    public synchronized Object computeIfAbsent(final Object key, final Function<? super Object, ? extends Object> mappingFunction) {
    154        final Object computeIfAbsent = super.computeIfAbsent(key, mappingFunction);
    155        if (computeIfAbsent != null) {
    156            orderedKeys.add(key);
    157        }
    158        return computeIfAbsent;
    159    }
    160
    161    @Override
    162    public Set<Map.Entry<Object, Object>> entrySet() {
    163        return orderedKeys.stream().map(k -> new SimpleEntry<>(k, get(k))).collect(Collectors.toCollection(LinkedHashSet::new));
    164    }
    165
    166    /**
    167     * Enumerates all key/value pairs in the specified LinkedHashSet and omits the property if the key or value is not a string.
    168     *
    169     * @param result The result set to populate.
    170     * @return The given set.
    171     */
    172    private synchronized LinkedHashSet<String> enumerateStringProperties(final LinkedHashSet<String> result) {
    173        if (defaults != null) {
    174            result.addAll(defaults.stringPropertyNames());
    175        }
    176        for (final Enumeration<?> e = keys(); e.hasMoreElements();) {
    177            final Object k = e.nextElement();
    178            final Object v = get(k);
    179            if (k instanceof String && v instanceof String) {
    180                result.add((String) k);
    181            }
    182        }
    183        return result;
    184    }
    185
    186    @Override
    187    public synchronized void forEach(final BiConsumer<? super Object, ? super Object> action) {
    188        Objects.requireNonNull(action, "action");
    189        orderedKeys.forEach(k -> action.accept(k, get(k)));
    190    }
    191
    192    @Override
    193    public synchronized Enumeration<Object> keys() {
    194        return Collections.enumeration(orderedKeys);
    195    }
    196
    197    @Override
    198    public Set<Object> keySet() {
    199        return new KeySet();
    200    }
    201
    202    @Override
    203    public synchronized Object merge(final Object key, final Object value,
    204            final BiFunction<? super Object, ? super Object, ? extends Object> remappingFunction) {
    205        final Object merge = super.merge(key, value, remappingFunction);
    206        if (merge != null) {
    207            orderedKeys.add(key);
    208        } else {
    209            orderedKeys.remove(key);
    210        }
    211        return merge;
    212    }
    213
    214    /**
    215     * Creates an iterator over the keys in insertion order whose {@link Iterator#remove()} also removes the mapping.
    216     *
    217     * @return A new iterator.
    218     */
    219    private Iterator<Object> orderedKeysIterator() {
    220        final Iterator<Object> iterator = orderedKeys.iterator();
    221        return new Iterator<Object>() {
    222
    223            private Object last;
    224
    225            @Override
    226            public boolean hasNext() {
    227                return iterator.hasNext();
    228            }
    229
    230            @Override
    231            public Object next() {
    232                last = iterator.next();
    233                return last;
    234            }
    235
    236            @Override
    237            public void remove() {
    238                // All orderedKeys writes happen under the OrderedProperties monitor.
    239                synchronized (OrderedProperties.this) {
    240                    // Not remove(Object), which would edit orderedKeys while this iterator walks it.
    241                    iterator.remove();
    242                    OrderedProperties.super.remove(last);
    243                }
    244            }
    245        };
    246    }
    247
    248    @Override
    249    public Enumeration<?> propertyNames() {
    250        return Collections.enumeration(stringPropertyNames());
    251    }
    252
    253    @Override
    254    public synchronized Object put(final Object key, final Object value) {
    255        final Object put = super.put(key, value);
    256        if (put == null) {
    257            orderedKeys.add(key);
    258        }
    259        return put;
    260    }
    261
    262    @Override
    263    public synchronized void putAll(final Map<? extends Object, ? extends Object> t) {
    264        orderedKeys.addAll(t.keySet());
    265        super.putAll(t);
    266    }
    267
    268    @Override
    269    public synchronized Object putIfAbsent(final Object key, final Object value) {
    270        final Object putIfAbsent = super.putIfAbsent(key, value);
    271        if (putIfAbsent == null) {
    272            orderedKeys.add(key);
    273        }
    274        return putIfAbsent;
    275    }
    276
    277    @Override
    278    public synchronized Object remove(final Object key) {
    279        final Object remove = super.remove(key);
    280        if (remove != null) {
    281            orderedKeys.remove(key);
    282        }
    283        return remove;
    284    }
    285
    286    @Override
    287    public synchronized boolean remove(final Object key, final Object value) {
    288        final boolean remove = super.remove(key, value);
    289        if (remove) {
    290            orderedKeys.remove(key);
    291        }
    292        return remove;
    293    }
    294
    295    @Override
    296    public Set<String> stringPropertyNames() {
    297        return enumerateStringProperties(new LinkedHashSet<>());
    298    }
    299
    300    @Override
    301    public synchronized String toString() {
    302        // Must override for Java 17 to maintain order since the implementation is based on a map
    303        final int max = size() - 1;
    304        if (max == -1) {
    305            return "{}";
    306        }
    307        final StringBuilder sb = new StringBuilder();
    308        final Iterator<Map.Entry<Object, Object>> it = entrySet().iterator();
    309        sb.append('{');
    310        for (int i = 0;; i++) {
    311            final Map.Entry<Object, Object> e = it.next();
    312            final Object key = e.getKey();
    313            final Object value = e.getValue();
    314            sb.append(key == this ? "(this Map)" : key.toString());
    315            sb.append('=');
    316            sb.append(value == this ? "(this Map)" : value.toString());
    317            if (i == max) {
    318                return sb.append('}').toString();
    319            }
    320            sb.append(", ");
    321        }
    322    }
    323
    324    @Override
    325    public Collection<Object> values() {
    326        return new Values();
    327    }
    328}