    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 */
    017
    018package org.apache.commons.configuration2;
    019
    020import java.util.ArrayList;
    021import java.util.Collection;
    022import java.util.Iterator;
    023import java.util.LinkedHashSet;
    024import java.util.LinkedList;
    025import java.util.List;
    026import java.util.ListIterator;
    027import java.util.Set;
    028
    029import org.apache.commons.configuration2.convert.ListDelimiterHandler;
    030import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    031
    032/**
    033 * <p>
    034 * {@code CompositeConfiguration} allows you to add multiple {@code Configuration} objects to an aggregated
    035 * configuration. If you add Configuration1, and then Configuration2, any properties shared will mean that the value
    036 * defined by Configuration1 will be returned. If Configuration1 doesn't have the property, then Configuration2 will be
    037 * checked. You can add multiple different types or the same type of properties file.
    038 * </p>
    039 * <p>
    040 * When querying properties the order in which child configurations have been added is relevant. To deal with property
    041 * updates, a so-called <em>in-memory configuration</em> is used. Per default, such a configuration is created
    042 * automatically. All property writes target this special configuration. There are constructors which allow you to
    043 * provide a specific in-memory configuration. If used that way, the in-memory configuration is always the last one in
    044 * the list of child configurations. This means that for query operations all other configurations take precedence.
    045 * </p>
    046 * <p>
    047 * Alternatively it is possible to mark a child configuration as in-memory configuration when it is added. In this case
    048 * the treatment of the in-memory configuration is slightly different: it remains in the list of child configurations at
    049 * the position it was added, i.e. its priority for property queries can be defined by adding the child configurations
    050 * in the correct order.
    051 * </p>
    052 * <p>
    053 * This configuration class uses a {@code Synchronizer} to control concurrent access. While all methods for reading and
    054 * writing configuration properties make use of this {@code Synchronizer} per default, the methods for managing the list
    055 * of child configurations and the in-memory configuration
    056 * ({@code addConfiguration(), getNumberOfConfigurations(), removeConfiguration(),
    057 * getConfiguration(), getInMemoryConfiguration()}) are guarded, too. Because most methods for accessing configuration
    058 * data delegate to the list of child configurations, the thread-safety of a {@code CompositeConfiguration} object also
    059 * depends on the {@code Synchronizer} objects used by these children.
    060 * </p>
    061 */
    062public class CompositeConfiguration extends AbstractConfiguration implements Cloneable {
    063
    064    /** List holding all the configuration */
    065    private List<Configuration> configList = new LinkedList<>();
    066
    067    /**
    068     * Configuration that holds in memory stuff. Inserted as first so any setProperty() override anything else added.
    069     */
    070    private Configuration inMemoryConfiguration;
    071
    072    /**
    073     * Stores a flag whether the current in-memory configuration is also a child configuration.
    074     */
    075    private boolean inMemoryConfigIsChild;
    076
    077    /**
    078     * Creates an empty CompositeConfiguration object which can then be added some other Configuration files
    079     */
    080    public CompositeConfiguration() {
    081        clear();
    082    }
    083
    084    /**
    085     * Create a CompositeConfiguration with an empty in memory configuration and adds the collection of configurations
    086     * specified.
    087     *
    088     * @param configurations the collection of configurations to add
    089     */
    090    public CompositeConfiguration(final Collection<? extends Configuration> configurations) {
    091        this(new BaseConfiguration(), configurations);
    092    }
    093
    094    /**
    095     * Creates a CompositeConfiguration object with a specified <em>in-memory configuration</em>. This configuration will
    096     * store any changes made to the {@code CompositeConfiguration}. Note: Use this constructor if you want to set a special
    097     * type of in-memory configuration. If you have a configuration which should act as both a child configuration and as
    098     * in-memory configuration, use {@link #addConfiguration(Configuration, boolean)} with a value of <strong>true</strong> instead.
    099     *
    100     * @param inMemoryConfiguration the in memory configuration to use
    101     */
    102    public CompositeConfiguration(final Configuration inMemoryConfiguration) {
    103        this.configList.clear();
    104        this.inMemoryConfiguration = inMemoryConfiguration;
    105        this.configList.add(inMemoryConfiguration);
    106    }
    107
    108    /**
    109     * Creates a CompositeConfiguration with a specified <em>in-memory configuration</em>, and then adds the given
    110     * collection of configurations.
    111     *
    112     * @param inMemoryConfiguration the in memory configuration to use
    113     * @param configurations the collection of configurations to add
    114     * @see #CompositeConfiguration(Configuration)
    115     */
    116    public CompositeConfiguration(final Configuration inMemoryConfiguration, final Collection<? extends Configuration> configurations) {
    117        this(inMemoryConfiguration);
    118        if (configurations != null) {
    119            configurations.forEach(this::addConfiguration);
    120        }
    121    }
    122
    123    /**
    124     * Add a configuration.
    125     *
    126     * @param config the configuration to add
    127     */
    128    public void addConfiguration(final Configuration config) {
    129        addConfiguration(config, false);
    130    }
    131
    132    /**
    133     * Adds a child configuration and optionally makes it the <em>in-memory configuration</em>. This means that all future
    134     * property write operations are executed on this configuration. Note that the current in-memory configuration is
    135     * replaced by the new one. If it was created automatically or passed to the constructor, it is removed from the list of
    136     * child configurations! Otherwise, it stays in the list of child configurations at its current position, but it passes
    137     * its role as in-memory configuration to the new one.
    138     *
    139     * @param config the configuration to be added
    140     * @param asInMemory <strong>true</strong> if this configuration becomes the new <em>in-memory</em> configuration, <strong>false</strong>
    141     *        otherwise
    142     * @since 1.8
    143     */
    144    public void addConfiguration(final Configuration config, final boolean asInMemory) {
    145        syncWrite(() -> {
    146            if (!configList.contains(config)) {
    147                if (asInMemory) {
    148                    replaceInMemoryConfiguration(config);
    149                    inMemoryConfigIsChild = true;
    150                }
    151                if (!inMemoryConfigIsChild) {
    152                    // As the inMemoryConfiguration contains all manually added
    153                    // keys, we must make sure that it is always last. "Normal", non
    154                    // composed configurations add their keys at the end of the
    155                    // configuration and we want to mimic this behavior.
    156                    configList.add(configList.indexOf(inMemoryConfiguration), config);
    157                } else {
    158                    // However, if the in-memory configuration is a regular child,
    159                    // only the order in which child configurations are added is relevant
    160                    configList.add(config);
    161                }
    162                if (config instanceof AbstractConfiguration) {
    163                    ((AbstractConfiguration) config).setThrowExceptionOnMissing(isThrowExceptionOnMissing());
    164                }
    165            }
    166        }, false);
    167    }
    168
    169    /**
    170     * Add a configuration to the start of the list of child configurations.
    171     *
    172     * @param config the configuration to add
    173     * @since 2.3
    174     */
    175    public void addConfigurationFirst(final Configuration config) {
    176        addConfigurationFirst(config, false);
    177    }
    178
    179    /**
    180     * Adds a child configuration to the start of the collection and optionally makes it the <em>in-memory
    181     * configuration</em>. This means that all future property write operations are executed on this configuration. Note
    182     * that the current in-memory configuration is replaced by the new one. If it was created automatically or passed to the
    183     * constructor, it is removed from the list of child configurations! Otherwise, it stays in the list of child
    184     * configurations at its current position, but it passes its role as in-memory configuration to the new one.
    185     *
    186     * @param config the configuration to be added
    187     * @param asInMemory <strong>true</strong> if this configuration becomes the new <em>in-memory</em> configuration, <strong>false</strong>
    188     *        otherwise
    189     * @since 2.3
    190     */
    191    public void addConfigurationFirst(final Configuration config, final boolean asInMemory) {
    192        syncWrite(() -> {
    193            if (!configList.contains(config)) {
    194                if (asInMemory) {
    195                    replaceInMemoryConfiguration(config);
    196                    inMemoryConfigIsChild = true;
    197                }
    198                configList.add(0, config);
    199                if (config instanceof AbstractConfiguration) {
    200                    ((AbstractConfiguration) config).setThrowExceptionOnMissing(isThrowExceptionOnMissing());
    201                }
    202            }
    203        }, false);
    204    }
    205
    206    /**
    207     * Add this property to the in-memory Configuration.
    208     *
    209     * @param key The Key to add the property to.
    210     * @param token The Value to add.
    211     */
    212    @Override
    213    protected void addPropertyDirect(final String key, final Object token) {
    214        inMemoryConfiguration.addProperty(key, token);
    215    }
    216
    217    /**
    218     * Adds the value of a property to the given list. This method is used by {@code getList()} for gathering property
    219     * values from the child configurations.
    220     *
    221     * @param dest the list for collecting the data
    222     * @param config the configuration to query
    223     * @param key the key of the property
    224     */
    225    private void appendListProperty(final List<Object> dest, final Configuration config, final String key) {
    226        final Object value = interpolate(config.getProperty(key));
    227        if (value != null) {
    228            if (value instanceof Collection) {
    229                final Collection<?> col = (Collection<?>) value;
    230                dest.addAll(col);
    231            } else {
    232                dest.add(value);
    233            }
    234        }
    235    }
    236
    237    /**
    238     * Removes all child configurations and reinitializes the <em>in-memory configuration</em>. <strong>Attention:</strong>
    239     * A new in-memory configuration is created; the old one is lost.
    240     */
    241    @Override
    242    protected void clearInternal() {
    243        configList.clear();
    244        // recreate the in memory configuration
    245        inMemoryConfiguration = new BaseConfiguration();
    246        ((BaseConfiguration) inMemoryConfiguration).setThrowExceptionOnMissing(isThrowExceptionOnMissing());
    247        ((BaseConfiguration) inMemoryConfiguration).setListDelimiterHandler(getListDelimiterHandler());
    248        configList.add(inMemoryConfiguration);
    249        inMemoryConfigIsChild = false;
    250    }
    251
    252    @Override
    253    protected void clearPropertyDirect(final String key) {
    254        configList.forEach(config -> config.clearProperty(key));
    255    }
    256
    257    /**
    258     * Returns a copy of this object. This implementation will create a deep clone, i.e. all configurations contained in
    259     * this composite will also be cloned. This only works if all contained configurations support cloning; otherwise a
    260     * runtime exception will be thrown. Registered event handlers won't get cloned.
    261     *
    262     * @return the copy
    263     * @since 1.3
    264     */
    265    @Override
    266    public Object clone() {
    267        try {
    268            final CompositeConfiguration copy = (CompositeConfiguration) super.clone();
    269            copy.configList = new LinkedList<>();
    270            copy.inMemoryConfiguration = ConfigurationUtils.cloneConfiguration(getInMemoryConfiguration());
    271            copy.configList.add(copy.inMemoryConfiguration);
    272
    273            configList.forEach(config -> {
    274                if (config != getInMemoryConfiguration()) {
    275                    copy.addConfiguration(ConfigurationUtils.cloneConfiguration(config));
    276                }
    277            });
    278
    279            copy.cloneInterpolator(this);
    280            return copy;
    281        } catch (final CloneNotSupportedException cnex) {
    282            // cannot happen
    283            throw new ConfigurationRuntimeException(cnex);
    284        }
    285    }
    286
    287    @Override
    288    protected boolean containsKeyInternal(final String key) {
    289        return configList.stream().anyMatch(config -> config.containsKey(key));
    290    }
    291
    292    /**
    293     * Tests whether this configuration contains one or more matches to this value. This operation stops at first
    294     * match but may be more expensive than the containsKey method.
    295     *
    296     * @since 2.11.0
    297     */
    298    @Override
    299    protected boolean containsValueInternal(final Object value) {
    300        return configList.stream().anyMatch(config -> config.containsValue(value));
    301    }
    302
    303    /**
    304     * Gets the configuration at the specified index.
    305     *
    306     * @param index The index of the configuration to retrieve
    307     * @return the configuration at this index
    308     */
    309    public Configuration getConfiguration(final int index) {
    310        return syncRead(() -> configList.get(index), false);
    311    }
    312
    313    /**
    314     * Gets the &quot;in memory configuration&quot;. In this configuration changes are stored.
    315     *
    316     * @return the in memory configuration
    317     */
    318    public Configuration getInMemoryConfiguration() {
    319        return syncReadValue(inMemoryConfiguration, false);
    320    }
    321
    322    @Override
    323    protected Iterator<String> getKeysInternal() {
    324        final Set<String> keys = new LinkedHashSet<>();
    325        configList.forEach(config -> config.getKeys().forEachRemaining(keys::add));
    326        return keys.iterator();
    327    }
    328
    329    @Override
    330    protected Iterator<String> getKeysInternal(final String key) {
    331        final Set<String> keys = new LinkedHashSet<>();
    332        configList.forEach(config -> config.getKeys(key).forEachRemaining(keys::add));
    333        return keys.iterator();
    334    }
    335
    336    @Override
    337    protected Iterator<String> getKeysInternal(final String key, final String delimiter) {
    338        final Set<String> keys = new LinkedHashSet<>();
    339        configList.forEach(config -> config.getKeys(key, delimiter).forEachRemaining(keys::add));
    340        return keys.iterator();
    341    }
    342
    343    @Override
    344    public List<Object> getList(final String key, final List<?> defaultValue) {
    345        final List<Object> list = new ArrayList<>();
    346
    347        // add all elements from the first configuration containing the requested key
    348        final Iterator<Configuration> it = configList.iterator();
    349        while (it.hasNext() && list.isEmpty()) {
    350            final Configuration config = it.next();
    351            if (config != inMemoryConfiguration && config.containsKey(key)) {
    352                appendListProperty(list, config, key);
    353            }
    354        }
    355
    356        // add all elements from the in memory configuration
    357        appendListProperty(list, inMemoryConfiguration, key);
    358
    359        if (list.isEmpty()) {
    360            // This is okay because we just return this list to the caller
    361            @SuppressWarnings("unchecked")
    362            final List<Object> resultList = (List<Object>) defaultValue;
    363            return resultList;
    364        }
    365
    366        final ListIterator<Object> lit = list.listIterator();
    367        while (lit.hasNext()) {
    368            lit.set(interpolate(lit.next()));
    369        }
    370
    371        return list;
    372    }
    373
    374    /**
    375     * Gets the number of configurations.
    376     *
    377     * @return the number of configuration
    378     */
    379    public int getNumberOfConfigurations() {
    380        return syncRead(configList::size, false);
    381    }
    382
    383    /**
    384     * Reads property from underlying composite
    385     *
    386     * @param key key to use for mapping
    387     * @return object associated with the given configuration key.
    388     */
    389    @Override
    390    protected Object getPropertyInternal(final String key) {
    391        return configList.stream().filter(config -> config.containsKey(key)).findFirst().map(config -> config.getProperty(key)).orElse(null);
    392    }
    393
    394    /**
    395     * Gets the configuration source, in which the specified key is defined. This method will iterate over all existing
    396     * child configurations and check whether they contain the specified key. The following constellations are possible:
    397     * <ul>
    398     * <li>If exactly one child configuration contains the key, this configuration is returned as the source configuration.
    399     * This may be the <em>in memory configuration</em> (this has to be explicitly checked by the calling application).</li>
    400     * <li>If none of the child configurations contain the key, <strong>null</strong> is returned.</li>
    401     * <li>If the key is contained in multiple child configurations or if the key is <strong>null</strong>, a
    402     * {@code IllegalArgumentException} is thrown. In this case the source configuration cannot be determined.</li>
    403     * </ul>
    404     *
    405     * @param key the key to be checked
    406     * @return the source configuration of this key
    407     * @throws IllegalArgumentException if the source configuration cannot be determined
    408     * @since 1.5
    409     */
    410    public Configuration getSource(final String key) {
    411        if (key == null) {
    412            throw new IllegalArgumentException("Key must not be null.");
    413        }
    414
    415        Configuration source = null;
    416        for (final Configuration conf : configList) {
    417            if (conf.containsKey(key)) {
    418                if (source != null) {
    419                    throw new IllegalArgumentException("The key " + key + " is defined by multiple sources.");
    420                }
    421                source = conf;
    422            }
    423        }
    424
    425        return source;
    426    }
    427
    428    @Override
    429    public String[] getStringArray(final String key) {
    430        final List<Object> list = getList(key);
    431
    432        // transform property values into strings
    433        final String[] tokens = new String[list.size()];
    434
    435        for (int i = 0; i < tokens.length; i++) {
    436            tokens[i] = String.valueOf(list.get(i));
    437        }
    438
    439        return tokens;
    440    }
    441
    442    @Override
    443    protected boolean isEmptyInternal() {
    444        return configList.stream().allMatch(Configuration::isEmpty);
    445    }
    446
    447    /**
    448     * Remove a configuration. The in memory configuration cannot be removed.
    449     *
    450     * @param config The configuration to remove
    451     */
    452    public void removeConfiguration(final Configuration config) {
    453        syncWrite(() -> {
    454            // Make sure that you can't remove the inMemoryConfiguration from
    455            // the CompositeConfiguration object
    456            if (!config.equals(inMemoryConfiguration)) {
    457                configList.remove(config);
    458            }
    459        }, false);
    460    }
    461
    462    /**
    463     * Replaces the current in-memory configuration by the given one.
    464     *
    465     * @param config the new in-memory configuration
    466     */
    467    private void replaceInMemoryConfiguration(final Configuration config) {
    468        if (!inMemoryConfigIsChild) {
    469            // remove current in-memory configuration
    470            configList.remove(inMemoryConfiguration);
    471        }
    472        inMemoryConfiguration = config;
    473    }
    474
    475    /**
    476     * {@inheritDoc} This implementation ensures that the in memory configuration is correctly initialized.
    477     */
    478    @Override
    479    public void setListDelimiterHandler(final ListDelimiterHandler listDelimiterHandler) {
    480        if (inMemoryConfiguration instanceof AbstractConfiguration) {
    481            ((AbstractConfiguration) inMemoryConfiguration).setListDelimiterHandler(listDelimiterHandler);
    482        }
    483        super.setListDelimiterHandler(listDelimiterHandler);
    484    }
    485}