    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.configuration2.builder.combined;
    018
    019import java.net.URL;
    020import java.util.ArrayList;
    021import java.util.Collection;
    022import java.util.Collections;
    023import java.util.HashMap;
    024import java.util.Iterator;
    025import java.util.LinkedList;
    026import java.util.List;
    027import java.util.Map;
    028import java.util.Set;
    029import java.util.stream.Collectors;
    030
    031import org.apache.commons.configuration2.CombinedConfiguration;
    032import org.apache.commons.configuration2.Configuration;
    033import org.apache.commons.configuration2.ConfigurationLookup;
    034import org.apache.commons.configuration2.HierarchicalConfiguration;
    035import org.apache.commons.configuration2.SystemConfiguration;
    036import org.apache.commons.configuration2.XMLConfiguration;
    037import org.apache.commons.configuration2.beanutils.BeanDeclaration;
    038import org.apache.commons.configuration2.beanutils.BeanHelper;
    039import org.apache.commons.configuration2.beanutils.CombinedBeanDeclaration;
    040import org.apache.commons.configuration2.beanutils.XMLBeanDeclaration;
    041import org.apache.commons.configuration2.builder.BasicBuilderParameters;
    042import org.apache.commons.configuration2.builder.BasicConfigurationBuilder;
    043import org.apache.commons.configuration2.builder.BuilderParameters;
    044import org.apache.commons.configuration2.builder.ConfigurationBuilder;
    045import org.apache.commons.configuration2.builder.ConfigurationBuilderEvent;
    046import org.apache.commons.configuration2.builder.FileBasedBuilderParametersImpl;
    047import org.apache.commons.configuration2.builder.FileBasedBuilderProperties;
    048import org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder;
    049import org.apache.commons.configuration2.builder.XMLBuilderParametersImpl;
    050import org.apache.commons.configuration2.builder.XMLBuilderProperties;
    051import org.apache.commons.configuration2.event.EventListener;
    052import org.apache.commons.configuration2.ex.ConfigurationException;
    053import org.apache.commons.configuration2.interpol.ConfigurationInterpolator;
    054import org.apache.commons.configuration2.interpol.Lookup;
    055import org.apache.commons.configuration2.io.FileSystem;
    056import org.apache.commons.configuration2.resolver.CatalogResolver;
    057import org.apache.commons.configuration2.tree.DefaultExpressionEngineSymbols;
    058import org.apache.commons.configuration2.tree.OverrideCombiner;
    059import org.apache.commons.configuration2.tree.UnionCombiner;
    060import org.xml.sax.EntityResolver;
    061
    062/**
    063 * <p>
    064 * A specialized {@code ConfigurationBuilder} implementation that creates a {@link CombinedConfiguration} from multiple
    065 * configuration sources defined by an XML-based <em>configuration definition file</em>.
    066 * </p>
    067 * <p>
    068 * This class provides an easy and flexible means for loading multiple configuration sources and combining the results
    069 * into a single configuration object. The sources to be loaded are defined in an XML document that can contain certain
    070 * tags representing the different supported configuration classes. If such a tag is found, a corresponding
    071 * {@code ConfigurationBuilder} class is instantiated and initialized using the classes of the {@code beanutils} package
    072 * (namely {@link org.apache.commons.configuration2.beanutils.XMLBeanDeclaration XMLBeanDeclaration} will be used to
    073 * extract the configuration's initialization parameters, which allows for complex initialization scenarios).
    074 * </p>
    075 * <p>
    076 * It is also possible to add custom tags to the configuration definition file. For this purpose an implementation of
    077 * {@link CombinedConfigurationBuilderProvider} has to be created which is responsible for the creation of a
    078 * {@code ConfigurationBuilder} associated with the custom tag. An instance of this class has to be registered at the
    079 * {@link CombinedBuilderParametersImpl} object which is used to initialize this {@code CombinedConfigurationBuilder}.
    080 * This provider will then be called when the corresponding custom tag is detected. For many default configuration
    081 * classes providers are already registered.
    082 * </p>
    083 * <p>
    084 * The configuration definition file has the following basic structure:
    085 * </p>
    086 *
    087 * <pre>
    088 * &lt;configuration systemProperties="properties file name"&gt;
    089 *   &lt;header&gt;
    090 *     &lt;!-- Optional meta information about the combined configuration --&gt;
    091 *   &lt;/header&gt;
    092 *   &lt;override&gt;
    093 *     &lt;!-- Declarations for override configurations --&gt;
    094 *   &lt;/override&gt;
    095 *   &lt;additional&gt;
    096 *     &lt;!-- Declarations for union configurations --&gt;
    097 *   &lt;/additional&gt;
    098 * &lt;/configuration&gt;
    099 * </pre>
    100 *
    101 * <p>
    102 * The name of the root element (here {@code configuration}) is arbitrary. The optional {@code systemProperties}
    103 * attribute identifies the path to a property file containing properties that should be added to the system properties.
    104 * If specified on the root element, the system properties are set before the rest of the configuration is processed.
    105 * </p>
    106 * <p>
    107 * There are two sections (both of them are optional) for declaring <em>override</em> and <em>additional</em>
    108 * configurations. Configurations in the former section are evaluated in the order of their declaration, and properties
    109 * of configurations declared earlier hide those of configurations declared later. Configurations in the latter section
    110 * are combined to a union configuration, i.e. all of their properties are added to a large hierarchical configuration.
    111 * Configuration declarations that occur as direct children of the root element are treated as override declarations.
    112 * </p>
    113 * <p>
    114 * Each configuration declaration consists of a tag whose name is associated with a
    115 * {@code CombinedConfigurationBuilderProvider}. This can be one of the predefined tags like {@code properties}, or
    116 * {@code xml}, or a custom tag, for which a configuration builder provider was registered (as described above).
    117 * Attributes and sub elements with specific initialization parameters can be added. There are some reserved attributes
    118 * with a special meaning that can be used in every configuration declaration:
    119 * </p>
    120 * <table border="1">
    121 * <caption>Standard attributes for configuration declarations</caption>
    122 * <tr>
    123 * <th>Attribute</th>
    124 * <th>Meaning</th>
    125 * </tr>
    126 * <tr>
    127 * <td>{@code config-name}</td>
    128 * <td>Allows specifying a name for this configuration. This name can be used to obtain a reference to the configuration
    129 * from the resulting combined configuration (see below). It can also be passed to the {@link #getNamedBuilder(String)}
    130 * method.</td>
    131 * </tr>
    132 * <tr>
    133 * <td>{@code config-at}</td>
    134 * <td>With this attribute an optional prefix can be specified for the properties of the corresponding
    135 * configuration.</td>
    136 * </tr>
    137 * <tr>
    138 * <td>{@code config-optional}</td>
    139 * <td>Declares a configuration source as optional. This means that errors that occur when creating the configuration
    140 * are ignored.</td>
    141 * </tr>
    142 * <tr>
    143 * <td>{@code config-reload}</td>
    144 * <td>Many configuration sources support a reloading mechanism. For those sources it is possible to enable reloading by
    145 * providing this attribute with a value of <strong>true</strong>.</td>
    146 * </tr>
    147 * </table>
    148 * <p>
    149 * The optional <em>header</em> section can contain some meta data about the created configuration itself. For instance,
    150 * it is possible to set further properties of the {@code NodeCombiner} objects used for constructing the resulting
    151 * configuration.
    152 * </p>
    153 * <p>
    154 * The default configuration object returned by this builder is an instance of the {@link CombinedConfiguration} class.
    155 * This allows for convenient access to the configuration objects maintained by the combined configuration (for example for
    156 * updates of single configuration objects). It has also the advantage that the properties stored in all declared
    157 * configuration objects are collected and transformed into a single hierarchical structure, which can be accessed using
    158 * different expression engines. The actual {@code CombinedConfiguration} implementation can be overridden by specifying
    159 * the class in the <em>config-class</em> attribute of the result element.
    160 * </p>
    161 * <p>
    162 * A custom EntityResolver can be used for all XMLConfigurations by adding
    163 * </p>
    164 *
    165 * <pre>
    166 * &lt;entity-resolver config-class="EntityResolver fully qualified class name"&gt;
    167 * </pre>
    168 *
    169 * <p>
    170 * A specific CatalogResolver can be specified for all XMLConfiguration sources by adding
    171 * </p>
    172 *
    173 * <pre>
    174 * &lt;entity-resolver catalogFiles="comma separated list of catalog files"&gt;
    175 * </pre>
    176 *
    177 * <p>
    178 * Additional ConfigurationProviders can be added by configuring them in the <em>header</em> section.
    179 * </p>
    180 *
    181 * <pre>
    182 * &lt;providers&gt;
    183 *   &lt;provider config-tag="tag name" config-class="provider fully qualified class name"/&gt;
    184 * &lt;/providers&gt;
    185 * </pre>
    186 *
    187 * <p>
    188 * Additional variable resolvers can be added by configuring them in the <em>header</em> section.
    189 * </p>
    190 *
    191 * <pre>
    192 * &lt;lookups&gt;
    193 *   &lt;lookup config-prefix="prefix" config-class="StrLookup fully qualified class name"/&gt;
    194 * &lt;/lookups&gt;
    195 * </pre>
    196 *
    197 * <p>
    198 * All declared override configurations are directly added to the resulting combined configuration. If they are given
    199 * names (using the {@code config-name} attribute), they can directly be accessed using the
    200 * {@code getConfiguration(String)} method of {@code CombinedConfiguration}. The additional configurations are
    201 * altogether added to another combined configuration, which uses a union combiner. Then this union configuration is
    202 * added to the resulting combined configuration under the name defined by the {@code ADDITIONAL_NAME} constant. The
    203 * {@link #getNamedBuilder(String)} method can be used to access the {@code ConfigurationBuilder} objects for all
    204 * configuration sources which have been assigned a name; care has to be taken that these names are unique.
    205 * </p>
    206 *
    207 * @since 1.3
    208 */
    209public class CombinedConfigurationBuilder extends BasicConfigurationBuilder<CombinedConfiguration> {
    210    /**
    211     * A data class for storing information about all configuration sources defined for a combined builder.
    212     */
    213    private final class ConfigurationSourceData {
    214        /** A list with data for all builders for override configurations. */
    215        private final List<ConfigurationDeclaration> overrideDeclarations;
    216
    217        /** A list with data for all builders for union configurations. */
    218        private final List<ConfigurationDeclaration> unionDeclarations;
    219
    220        /** A list with the builders for override configurations. */
    221        private final List<ConfigurationBuilder<? extends Configuration>> overrideBuilders;
    222
    223        /** A list with the builders for union configurations. */
    224        private final List<ConfigurationBuilder<? extends Configuration>> unionBuilders;
    225
    226        /** A map for direct access to a builder by its name. */
    227        private final Map<String, ConfigurationBuilder<? extends Configuration>> namedBuilders;
    228
    229        /** A collection with all child builders. */
    230        private final Collection<ConfigurationBuilder<? extends Configuration>> allBuilders;
    231
    232        /** A listener for reacting on changes of sub builders. */
    233        private final EventListener<ConfigurationBuilderEvent> changeListener;
    234
    235        /**
    236         * Creates a new instance of {@code ConfigurationSourceData}.
    237         */
    238        public ConfigurationSourceData() {
    239            overrideDeclarations = new ArrayList<>();
    240            unionDeclarations = new ArrayList<>();
    241            overrideBuilders = new ArrayList<>();
    242            unionBuilders = new ArrayList<>();
    243            namedBuilders = new HashMap<>();
    244            allBuilders = new LinkedList<>();
    245            changeListener = createBuilderChangeListener();
    246        }
    247
    248        /**
    249         * Creates a new configuration using the specified builder and adds it to the resulting combined configuration.
    250         *
    251         * @param ccResult the resulting combined configuration
    252         * @param decl the current {@code ConfigurationDeclaration}
    253         * @param builder the configuration builder
    254         * @throws ConfigurationException if an error occurs
    255         */
    256        private void addChildConfiguration(final CombinedConfiguration ccResult, final ConfigurationDeclaration decl,
    257            final ConfigurationBuilder<? extends Configuration> builder) throws ConfigurationException {
    258            try {
    259                ccResult.addConfiguration(builder.getConfiguration(), decl.getName(), decl.getAt());
    260            } catch (final ConfigurationException cex) {
    261                // ignore exceptions for optional configurations
    262                if (!decl.isOptional()) {
    263                    throw cex;
    264                }
    265            }
    266        }
    267
    268        /**
    269         * Returns a set with the names of all known named builders.
    270         *
    271         * @return the names of the available sub builders
    272         */
    273        public Set<String> builderNames() {
    274            return namedBuilders.keySet();
    275        }
    276
    277        /**
    278         * Frees resources used by this object and performs clean up. This method is called when the owning builder is reset.
    279         */
    280        public void cleanUp() {
    281            getChildBuilders().forEach(b -> b.removeEventListener(ConfigurationBuilderEvent.RESET, changeListener));
    282            namedBuilders.clear();
    283        }
    284
    285        /**
    286         * Processes the declaration of configuration builder providers, creates the corresponding builder if necessary, obtains
    287         * configurations, and adds them to the specified result configuration.
    288         *
    289         * @param ccResult the result configuration.
    290         * @param srcDecl the collection with the declarations of configuration sources to process.
    291         * @param builders List of configuration builders.
    292         * @return a list with configuration builders.
    293         * @throws ConfigurationException if an error occurs.
    294         */
    295        public List<ConfigurationBuilder<? extends Configuration>> createAndAddConfigurations(final CombinedConfiguration ccResult,
    296            final List<ConfigurationDeclaration> srcDecl, final List<ConfigurationBuilder<? extends Configuration>> builders) throws ConfigurationException {
    297            final boolean createBuilders = builders.isEmpty();
    298            final List<ConfigurationBuilder<? extends Configuration>> newBuilders;
    299            if (createBuilders) {
    300                newBuilders = new ArrayList<>(srcDecl.size());
    301            } else {
    302                newBuilders = builders;
    303            }
    304
    305            for (int i = 0; i < srcDecl.size(); i++) {
    306                final ConfigurationBuilder<? extends Configuration> b;
    307                if (createBuilders) {
    308                    b = createConfigurationBuilder(srcDecl.get(i));
    309                    newBuilders.add(b);
    310                } else {
    311                    b = builders.get(i);
    312                }
    313                addChildConfiguration(ccResult, srcDecl.get(i), b);
    314            }
    315
    316            return newBuilders;
    317        }
    318
    319        /**
    320         * Creates a listener for builder change events. This listener is registered at all builders for child configurations.
    321         */
    322        private EventListener<ConfigurationBuilderEvent> createBuilderChangeListener() {
    323            return event -> resetResult();
    324        }
    325
    326        /**
    327         * Creates a configuration builder based on a source declaration in the definition configuration.
    328         *
    329         * @param decl the current {@code ConfigurationDeclaration}
    330         * @return the newly created builder
    331         * @throws ConfigurationException if an error occurs
    332         */
    333        private ConfigurationBuilder<? extends Configuration> createConfigurationBuilder(final ConfigurationDeclaration decl) throws ConfigurationException {
    334            final ConfigurationBuilderProvider provider = providerForTag(decl.getConfiguration().getRootElementName());
    335            if (provider == null) {
    336                throw new ConfigurationException("Unsupported configuration source: " + decl.getConfiguration().getRootElementName());
    337            }
    338
    339            final ConfigurationBuilder<? extends Configuration> builder = provider.getConfigurationBuilder(decl);
    340            if (decl.getName() != null) {
    341                namedBuilders.put(decl.getName(), builder);
    342            }
    343            allBuilders.add(builder);
    344            builder.addEventListener(ConfigurationBuilderEvent.RESET, changeListener);
    345            return builder;
    346        }
    347
    348        /**
    349         * Finds the override configurations that are defined as top level elements in the configuration definition file. This
    350         * method fetches the child elements of the root node and removes the nodes that represent other configuration sections.
    351         * The remaining nodes are treated as definitions for override configurations.
    352         *
    353         * @param config the definition configuration
    354         * @return a list with sub configurations for the top level override configurations
    355         */
    356        private List<? extends HierarchicalConfiguration<?>> fetchTopLevelOverrideConfigs(final HierarchicalConfiguration<?> config) {
    357
    358            final List<? extends HierarchicalConfiguration<?>> configs = config.childConfigurationsAt(null);
    359            for (final Iterator<? extends HierarchicalConfiguration<?>> it = configs.iterator(); it.hasNext();) {
    360                final String nodeName = it.next().getRootElementName();
    361                for (final String element : CONFIG_SECTIONS) {
    362                    if (element.equals(nodeName)) {
    363                        it.remove();
    364                        break;
    365                    }
    366                }
    367            }
    368            return configs;
    369        }
    370
    371        /**
    372         * Gets a collection containing the builders for all child configuration sources.
    373         *
    374         * @return the child configuration builders
    375         */
    376        public Collection<ConfigurationBuilder<? extends Configuration>> getChildBuilders() {
    377            return allBuilders;
    378        }
    379
    380        /**
    381         * Gets the {@code ConfigurationBuilder} with the given name. If no such builder is defined in the definition
    382         * configuration, result is <strong>null</strong>.
    383         *
    384         * @param name the name of the builder in question
    385         * @return the builder with this name or <strong>null</strong>
    386         */
    387        public ConfigurationBuilder<? extends Configuration> getNamedBuilder(final String name) {
    388            return namedBuilders.get(name);
    389        }
    390
    391        /**
    392         * Gets a collection with all configuration source declarations defined in the override section.
    393         *
    394         * @return the override configuration builders
    395         */
    396        public List<ConfigurationDeclaration> getOverrideSources() {
    397            return overrideDeclarations;
    398        }
    399
    400        /**
    401         * Gets a collection with all configuration source declarations defined in the union section.
    402         *
    403         * @return the union configuration builders
    404         */
    405        public List<ConfigurationDeclaration> getUnionSources() {
    406            return unionDeclarations;
    407        }
    408
    409        /**
    410         * Initializes this object from the specified definition configuration.
    411         *
    412         * @param config the definition configuration
    413         * @throws ConfigurationException if an error occurs
    414         */
    415        public void initFromDefinitionConfiguration(final HierarchicalConfiguration<?> config) throws ConfigurationException {
    416            overrideDeclarations.addAll(createDeclarations(fetchTopLevelOverrideConfigs(config)));
    417            overrideDeclarations.addAll(createDeclarations(config.childConfigurationsAt(KEY_OVERRIDE)));
    418            unionDeclarations.addAll(createDeclarations(config.childConfigurationsAt(KEY_UNION)));
    419        }
    420    }
    421
    422    /**
    423     * Constant for the name of the additional configuration. If the configuration definition file contains an
    424     * {@code additional} section, a special union configuration is created and added under this name to the resulting
    425     * combined configuration.
    426     */
    427    public static final String ADDITIONAL_NAME = CombinedConfigurationBuilder.class.getName() + "/ADDITIONAL_CONFIG";
    428
    429    /** Constant for the name of the configuration bean factory. */
    430    static final String CONFIG_BEAN_FACTORY_NAME = CombinedConfigurationBuilder.class.getName() + ".CONFIG_BEAN_FACTORY_NAME";
    431
    432    /** Constant for the reserved name attribute. */
    433    static final String ATTR_NAME = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + XMLBeanDeclaration.RESERVED_PREFIX + "name"
    434        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    435
    436    /** Constant for the name of the at attribute. */
    437    static final String ATTR_ATNAME = "at";
    438
    439    /** Constant for the reserved at attribute. */
    440    static final String ATTR_AT_RES = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + XMLBeanDeclaration.RESERVED_PREFIX + ATTR_ATNAME
    441        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    442
    443    /** Constant for the at attribute without the reserved prefix. */
    444    static final String ATTR_AT = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + ATTR_ATNAME + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    445
    446    /** Constant for the name of the optional attribute. */
    447    static final String ATTR_OPTIONALNAME = "optional";
    448
    449    /** Constant for the reserved optional attribute. */
    450    static final String ATTR_OPTIONAL_RES = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + XMLBeanDeclaration.RESERVED_PREFIX + ATTR_OPTIONALNAME
    451        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    452
    453    /** Constant for the optional attribute without the reserved prefix. */
    454    static final String ATTR_OPTIONAL = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + ATTR_OPTIONALNAME
    455        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    456
    457    /** Constant for the forceCreate attribute. */
    458    static final String ATTR_FORCECREATE = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + XMLBeanDeclaration.RESERVED_PREFIX + "forceCreate"
    459        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    460
    461    /** Constant for the reload attribute. */
    462    static final String ATTR_RELOAD = DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_START + XMLBeanDeclaration.RESERVED_PREFIX + "reload"
    463        + DefaultExpressionEngineSymbols.DEFAULT_ATTRIBUTE_END;
    464
    465    /**
    466     * Constant for the tag attribute for providers.
    467     */
    468    static final String KEY_SYSTEM_PROPS = "[@systemProperties]";
    469
    470    /** Constant for the name of the header section. */
    471    static final String SEC_HEADER = "header";
    472
    473    /** Constant for an expression that selects the union configurations. */
    474    static final String KEY_UNION = "additional";
    475
    476    /** An array with the names of top level configuration sections. */
    477    static final String[] CONFIG_SECTIONS = {"additional", "override", SEC_HEADER};
    478
    479    /**
    480     * Constant for an expression that selects override configurations in the override section.
    481     */
    482    static final String KEY_OVERRIDE = "override";
    483
    484    /**
    485     * Constant for the key that points to the list nodes definition of the override combiner.
    486     */
    487    static final String KEY_OVERRIDE_LIST = SEC_HEADER + ".combiner.override.list-nodes.node";
    488
    489    /**
    490     * Constant for the key that points to the list nodes definition of the additional combiner.
    491     */
    492    static final String KEY_ADDITIONAL_LIST = SEC_HEADER + ".combiner.additional.list-nodes.node";
    493
    494    /**
    495     * Constant for the key for defining providers in the configuration file.
    496     */
    497    static final String KEY_CONFIGURATION_PROVIDERS = SEC_HEADER + ".providers.provider";
    498
    499    /**
    500     * Constant for the tag attribute for providers.
    501     */
    502    static final String KEY_PROVIDER_KEY = XMLBeanDeclaration.ATTR_PREFIX + "tag]";
    503
    504    /**
    505     * Constant for the key for defining variable resolvers
    506     */
    507    static final String KEY_CONFIGURATION_LOOKUPS = SEC_HEADER + ".lookups.lookup";
    508
    509    /**
    510     * Constant for the key for defining entity resolvers
    511     */
    512    static final String KEY_ENTITY_RESOLVER = SEC_HEADER + ".entity-resolver";
    513
    514    /**
    515     * Constant for the prefix attribute for lookups.
    516     */
    517    static final String KEY_LOOKUP_KEY = XMLBeanDeclaration.ATTR_PREFIX + "prefix]";
    518
    519    /**
    520     * Constant for the FileSystem.
    521     */
    522    static final String FILE_SYSTEM = SEC_HEADER + ".fileSystem";
    523
    524    /**
    525     * Constant for the key of the result declaration. This key can point to a bean declaration, which defines properties of
    526     * the resulting combined configuration.
    527     */
    528    static final String KEY_RESULT = SEC_HEADER + ".result";
    529
    530    /** Constant for the key of the combiner in the result declaration. */
    531    static final String KEY_COMBINER = KEY_RESULT + ".nodeCombiner";
    532
    533    /** Constant for the XML file extension. */
    534    static final String EXT_XML = "xml";
    535
    536    /** Constant for the basic configuration builder class. */
    537    private static final String BASIC_BUILDER = "org.apache.commons.configuration2.builder.BasicConfigurationBuilder";
    538
    539    /** Constant for the file-based configuration builder class. */
    540    private static final String FILE_BUILDER = "org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder";
    541
    542    /** Constant for the reloading file-based configuration builder class. */
    543    private static final String RELOADING_BUILDER = "org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder";
    544
    545    /** Constant for the name of the file-based builder parameters class. */
    546    private static final String FILE_PARAMS = "org.apache.commons.configuration2.builder.FileBasedBuilderParametersImpl";
    547
    548    /** Constant for the provider for properties files. */
    549    private static final ConfigurationBuilderProvider PROPERTIES_PROVIDER = new FileExtensionConfigurationBuilderProvider(FILE_BUILDER, RELOADING_BUILDER,
    550        "org.apache.commons.configuration2.XMLPropertiesConfiguration", "org.apache.commons.configuration2.PropertiesConfiguration", EXT_XML,
    551        Collections.singletonList(FILE_PARAMS));
    552
    553    /** Constant for the provider for XML files. */
    554    private static final ConfigurationBuilderProvider XML_PROVIDER = new BaseConfigurationBuilderProvider(FILE_BUILDER, RELOADING_BUILDER,
    555        "org.apache.commons.configuration2.XMLConfiguration", Collections.singletonList("org.apache.commons.configuration2.builder.XMLBuilderParametersImpl"));
    556
    557    /** Constant for the provider for JNDI sources. */
    558    private static final BaseConfigurationBuilderProvider JNDI_PROVIDER = new BaseConfigurationBuilderProvider(BASIC_BUILDER, null,
    559        "org.apache.commons.configuration2.JNDIConfiguration",
    560        Collections.singletonList("org.apache.commons.configuration2.builder.JndiBuilderParametersImpl"));
    561
    562    /** Constant for the provider for system properties. */
    563    private static final BaseConfigurationBuilderProvider SYSTEM_PROVIDER = new BaseConfigurationBuilderProvider(BASIC_BUILDER, null,
    564        "org.apache.commons.configuration2.SystemConfiguration", Collections.singletonList("org.apache.commons.configuration2.builder.BasicBuilderParameters"));
    565
    566    /** Constant for the provider for ini files. */
    567    private static final BaseConfigurationBuilderProvider INI_PROVIDER = new BaseConfigurationBuilderProvider(FILE_BUILDER, RELOADING_BUILDER,
    568        "org.apache.commons.configuration2.INIConfiguration", Collections.singletonList(FILE_PARAMS));
    569
    570    /** Constant for the provider for environment properties. */
    571    private static final BaseConfigurationBuilderProvider ENV_PROVIDER = new BaseConfigurationBuilderProvider(BASIC_BUILDER, null,
    572        "org.apache.commons.configuration2.EnvironmentConfiguration",
    573        Collections.singletonList("org.apache.commons.configuration2.builder.BasicBuilderParameters"));
    574
    575    /** Constant for the provider for plist files. */
    576    private static final BaseConfigurationBuilderProvider PLIST_PROVIDER = new FileExtensionConfigurationBuilderProvider(FILE_BUILDER, RELOADING_BUILDER,
    577        "org.apache.commons.configuration2.plist.XMLPropertyListConfiguration", "org.apache.commons.configuration2.plist.PropertyListConfiguration", EXT_XML,
    578        Collections.singletonList(FILE_PARAMS));
    579
    580    /** Constant for the provider for configuration definition files. */
    581    private static final BaseConfigurationBuilderProvider COMBINED_PROVIDER = new CombinedConfigurationBuilderProvider();
    582
    583    /** Constant for the provider for multiple XML configurations. */
    584    private static final MultiFileConfigurationBuilderProvider MULTI_XML_PROVIDER = new MultiFileConfigurationBuilderProvider(
    585        "org.apache.commons.configuration2.XMLConfiguration", "org.apache.commons.configuration2.builder.XMLBuilderParametersImpl");
    586
    587    /** An array with the names of the default tags. */
    588    private static final String[] DEFAULT_TAGS = {"properties", "xml", "hierarchicalXml", "plist", "ini", "system", "env", "jndi", "configuration",
    589        "multiFile"};
    590
    591    /** An array with the providers for the default tags. */
    592    private static final ConfigurationBuilderProvider[] DEFAULT_PROVIDERS = {PROPERTIES_PROVIDER, XML_PROVIDER, XML_PROVIDER, PLIST_PROVIDER, INI_PROVIDER,
    593        SYSTEM_PROVIDER, ENV_PROVIDER, JNDI_PROVIDER, COMBINED_PROVIDER, MULTI_XML_PROVIDER};
    594
    595    /** A map with the default configuration builder providers. */
    596    private static final Map<String, ConfigurationBuilderProvider> DEFAULT_PROVIDERS_MAP;
    597
    598    static {
    599        DEFAULT_PROVIDERS_MAP = createDefaultProviders();
    600    }
    601
    602    /**
    603     * Creates the map with the default configuration builder providers.
    604     *
    605     * @return the map with default providers
    606     */
    607    private static Map<String, ConfigurationBuilderProvider> createDefaultProviders() {
    608        final Map<String, ConfigurationBuilderProvider> providers = new HashMap<>();
    609        for (int i = 0; i < DEFAULT_TAGS.length; i++) {
    610            providers.put(DEFAULT_TAGS[i], DEFAULT_PROVIDERS[i]);
    611        }
    612        return providers;
    613    }
    614
    615    /**
    616     * Initializes the list nodes of the node combiner for the given combined configuration. This information can be set in
    617     * the header section of the configuration definition file for both the override and the union combiners.
    618     *
    619     * @param cc the combined configuration to initialize
    620     * @param defConfig the definition configuration
    621     * @param key the key for the list nodes
    622     */
    623    private static void initNodeCombinerListNodes(final CombinedConfiguration cc, final HierarchicalConfiguration<?> defConfig, final String key) {
    624        defConfig.getList(key).forEach(listNode -> cc.getNodeCombiner().addListNode((String) listNode));
    625    }
    626
    627    /** The builder for the definition configuration. */
    628    private ConfigurationBuilder<? extends HierarchicalConfiguration<?>> definitionBuilder;
    629
    630    /** Stores temporarily the configuration with the builder definitions. */
    631    private HierarchicalConfiguration<?> definitionConfiguration;
    632
    633    /** The object with data about configuration sources. */
    634    private ConfigurationSourceData sourceData;
    635
    636    /** Stores the current parameters object. */
    637    private CombinedBuilderParametersImpl currentParameters;
    638
    639    /** The current XML parameters object. */
    640    private XMLBuilderParametersImpl currentXMLParameters;
    641
    642    /** The configuration that is currently constructed. */
    643    private CombinedConfiguration currentConfiguration;
    644
    645    /**
    646     * A {@code ConfigurationInterpolator} to be used as parent for all child configurations to enable cross-source
    647     * interpolation.
    648     */
    649    private ConfigurationInterpolator parentInterpolator;
    650
    651    /**
    652     * Creates a new instance of {@code CombinedConfigurationBuilder}. No parameters are set.
    653     */
    654    public CombinedConfigurationBuilder() {
    655        super(CombinedConfiguration.class);
    656    }
    657
    658    /**
    659     *
    660     * Creates a new instance of {@code CombinedConfigurationBuilder} and sets the specified initialization parameters.
    661     *
    662     * @param params a map with initialization parameters
    663     */
    664    public CombinedConfigurationBuilder(final Map<String, Object> params) {
    665        super(CombinedConfiguration.class, params);
    666    }
    667
    668    /**
    669     *
    670     * Creates a new instance of {@code CombinedConfigurationBuilder} and sets the specified initialization parameters and
    671     * the <em>allowFailOnInit</em> flag.
    672     *
    673     * @param params a map with initialization parameters
    674     * @param allowFailOnInit the <em>allowFailOnInit</em> flag
    675     */
    676    public CombinedConfigurationBuilder(final Map<String, Object> params, final boolean allowFailOnInit) {
    677        super(CombinedConfiguration.class, params, allowFailOnInit);
    678    }
    679
    680    /**
    681     * Adds a listener at the given definition builder which resets this builder when a reset of the definition builder
    682     * happens. This way it is ensured that this builder produces a new combined configuration when its definition
    683     * configuration changes.
    684     *
    685     * @param defBuilder the definition builder
    686     */
    687    private void addDefinitionBuilderChangeListener(final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> defBuilder) {
    688        defBuilder.addEventListener(ConfigurationBuilderEvent.RESET, event -> {
    689            synchronized (this) {
    690                reset();
    691                definitionBuilder = defBuilder;
    692            }
    693        });
    694    }
    695
    696    /**
    697     * <p>
    698     * Returns a set with the names of all child configuration builders. A tag defining a configuration source in the
    699     * configuration definition file can have the {@code config-name} attribute. If this attribute is present, the
    700     * corresponding builder is assigned this name and can be directly accessed through the {@link #getNamedBuilder(String)}
    701     * method. This method returns a collection with all available builder names.
    702     * </p>
    703     * <p>
    704     * <strong>Important note:</strong> This method only returns a meaningful result after the result configuration has been
    705     * created by calling {@code getConfiguration()}. If called before, always an empty set is returned.
    706     * </p>
    707     *
    708     * @return a set with the names of all builders
    709     */
    710    public synchronized Set<String> builderNames() {
    711        if (sourceData == null) {
    712            return Collections.emptySet();
    713        }
    714        return Collections.unmodifiableSet(sourceData.builderNames());
    715    }
    716
    717    /**
    718     * {@inheritDoc} This method is overridden to adapt the return type.
    719     */
    720    @Override
    721    public CombinedConfigurationBuilder configure(final BuilderParameters... params) {
    722        super.configure(params);
    723        return this;
    724    }
    725
    726    /**
    727     * Creates and initializes a default {@code EntityResolver} if the definition configuration contains a corresponding
    728     * declaration.
    729     *
    730     * @param config the definition configuration
    731     * @param xmlParams the (already partly initialized) object with XML parameters; here the new resolver is to be stored
    732     * @throws ConfigurationException if an error occurs
    733     */
    734    protected void configureEntityResolver(final HierarchicalConfiguration<?> config, final XMLBuilderParametersImpl xmlParams) throws ConfigurationException {
    735        if (config.getMaxIndex(KEY_ENTITY_RESOLVER) == 0) {
    736            final XMLBeanDeclaration decl = new XMLBeanDeclaration(config, KEY_ENTITY_RESOLVER, true);
    737            final EntityResolver resolver = (EntityResolver) fetchBeanHelper().createBean(decl, CatalogResolver.class);
    738            final FileSystem fileSystem = xmlParams.getFileHandler().getFileSystem();
    739            if (fileSystem != null) {
    740                BeanHelper.setProperty(resolver, "fileSystem", fileSystem);
    741            }
    742            final String basePath = xmlParams.getFileHandler().getBasePath();
    743            if (basePath != null) {
    744                BeanHelper.setProperty(resolver, "baseDir", basePath);
    745            }
    746            final ConfigurationInterpolator ci = new ConfigurationInterpolator();
    747            ci.registerLookups(fetchPrefixLookups());
    748            BeanHelper.setProperty(resolver, "interpolator", ci);
    749
    750            xmlParams.setEntityResolver(resolver);
    751        }
    752    }
    753
    754    /**
    755     * Creates the {@code CombinedConfiguration} for the configuration sources in the {@code &lt;additional&gt;} section.
    756     * This method is called when the builder constructs the final configuration. It creates a new
    757     * {@code CombinedConfiguration} and initializes some properties from the result configuration.
    758     *
    759     * @param resultConfig the result configuration (this is the configuration that will be returned by the builder)
    760     * @return the {@code CombinedConfiguration} for the additional configuration sources
    761     * @since 1.7
    762     */
    763    protected CombinedConfiguration createAdditionalsConfiguration(final CombinedConfiguration resultConfig) {
    764        final CombinedConfiguration addConfig = new CombinedConfiguration(new UnionCombiner());
    765        addConfig.setListDelimiterHandler(resultConfig.getListDelimiterHandler());
    766        return addConfig;
    767    }
    768
    769    /**
    770     * Creates {@code ConfigurationDeclaration} objects for the specified configurations.
    771     *
    772     * @param configs the list with configurations
    773     * @return a collection with corresponding declarations
    774     */
    775    private Collection<ConfigurationDeclaration> createDeclarations(final Collection<? extends HierarchicalConfiguration<?>> configs) {
    776        return configs.stream().map(c -> new ConfigurationDeclaration(this, c)).collect(Collectors.toList());
    777    }
    778
    779    /**
    780     * {@inheritDoc} This implementation evaluates the {@code result} property of the definition configuration. It creates a
    781     * combined bean declaration with both the properties specified in the definition file and the properties defined as
    782     * initialization parameters.
    783     */
    784    @Override
    785    protected BeanDeclaration createResultDeclaration(final Map<String, Object> params) throws ConfigurationException {
    786        final BeanDeclaration paramsDecl = super.createResultDeclaration(params);
    787        final XMLBeanDeclaration resultDecl = new XMLBeanDeclaration(getDefinitionConfiguration(), KEY_RESULT, true, CombinedConfiguration.class.getName());
    788        return new CombinedBeanDeclaration(resultDecl, paramsDecl);
    789    }
    790
    791    /**
    792     * Creates the data object for configuration sources and the corresponding builders.
    793     *
    794     * @return the newly created data object
    795     * @throws ConfigurationException if an error occurs
    796     */
    797    private ConfigurationSourceData createSourceData() throws ConfigurationException {
    798        final ConfigurationSourceData result = new ConfigurationSourceData();
    799        result.initFromDefinitionConfiguration(getDefinitionConfiguration());
    800        return result;
    801    }
    802
    803    /**
    804     * Creates a default builder for the definition configuration and initializes it with a parameters object. This method
    805     * is called if no definition builder is defined in this builder's parameters. This implementation creates a default
    806     * file-based builder which produces an {@code XMLConfiguration}; it expects a corresponding file specification. Note:
    807     * This method is called in a synchronized block.
    808     *
    809     * @param builderParams the parameters object for the builder
    810     * @return the standard builder for the definition configuration
    811     */
    812    protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> createXMLDefinitionBuilder(final BuilderParameters builderParams) {
    813        return new FileBasedConfigurationBuilder<>(XMLConfiguration.class).configure(builderParams);
    814    }
    815
    816    /**
    817     * Returns a map with the current prefix lookup objects. This map is obtained from the {@code ConfigurationInterpolator}
    818     * of the configuration under construction.
    819     *
    820     * @return the map with current prefix lookups (may be <strong>null</strong>)
    821     */
    822    private Map<String, ? extends Lookup> fetchPrefixLookups() {
    823        final CombinedConfiguration cc = getConfigurationUnderConstruction();
    824        return cc != null ? cc.getInterpolator().getLookups() : null;
    825    }
    826
    827    /**
    828     * Gets the current base path of this configuration builder. This is used for instance by all file-based child
    829     * configurations.
    830     *
    831     * @return the base path
    832     */
    833    private String getBasePath() {
    834        return currentXMLParameters.getFileHandler().getBasePath();
    835    }
    836
    837    /**
    838     * Gets a collection with the builders for all child configuration sources. This method can be used by derived
    839     * classes providing additional functionality on top of the declared configuration sources. It only returns a defined
    840     * value during construction of the result configuration instance.
    841     *
    842     * @return a collection with the builders for child configuration sources
    843     */
    844    protected synchronized Collection<ConfigurationBuilder<? extends Configuration>> getChildBuilders() {
    845        return sourceData.getChildBuilders();
    846    }
    847
    848    /**
    849     * Gets the configuration object that is currently constructed. This method can be called during construction of the
    850     * result configuration. It is intended for internal usage, for example some specialized builder providers need access to this
    851     * configuration to perform advanced initialization.
    852     *
    853     * @return the configuration that us currently under construction
    854     */
    855    CombinedConfiguration getConfigurationUnderConstruction() {
    856        return currentConfiguration;
    857    }
    858
    859    /**
    860     * Gets the {@code ConfigurationBuilder} which creates the definition configuration.
    861     *
    862     * @return the builder for the definition configuration
    863     * @throws ConfigurationException if an error occurs
    864     */
    865    public synchronized ConfigurationBuilder<? extends HierarchicalConfiguration<?>> getDefinitionBuilder() throws ConfigurationException {
    866        if (definitionBuilder == null) {
    867            definitionBuilder = setupDefinitionBuilder(getParameters());
    868            addDefinitionBuilderChangeListener(definitionBuilder);
    869        }
    870        return definitionBuilder;
    871    }
    872
    873    /**
    874     * Gets the configuration containing the definition of the combined configuration to be created. This method only
    875     * returns a defined result during construction of the result configuration. The definition configuration is obtained
    876     * from the definition builder at first access and then stored temporarily to ensure that during result construction
    877     * always the same configuration instance is used. (Otherwise, it would be possible that the definition builder returns
    878     * a different instance when queried multiple times.)
    879     *
    880     * @return the definition configuration
    881     * @throws ConfigurationException if an error occurs
    882     */
    883    protected HierarchicalConfiguration<?> getDefinitionConfiguration() throws ConfigurationException {
    884        if (definitionConfiguration == null) {
    885            definitionConfiguration = getDefinitionBuilder().getConfiguration();
    886        }
    887        return definitionConfiguration;
    888    }
    889
    890    /**
    891     * <p>
    892     * Gets the configuration builder with the given name. With this method a builder of a child configuration which was
    893     * given a name in the configuration definition file can be accessed directly.
    894     * </p>
    895     * <p>
    896     * <strong>Important note:</strong> This method only returns a meaningful result after the result configuration has been
    897     * created by calling {@code getConfiguration()}. If called before, always an exception is thrown.
    898     * </p>
    899     *
    900     * @param name the name of the builder in question
    901     * @return the child configuration builder with this name
    902     * @throws ConfigurationException if information about named builders is not yet available or no builder with this name
    903     *         exists
    904     */
    905    public synchronized ConfigurationBuilder<? extends Configuration> getNamedBuilder(final String name) throws ConfigurationException {
    906        if (sourceData == null) {
    907            throw new ConfigurationException("Information about child builders has not been setup yet! Call getConfiguration() first.");
    908        }
    909        final ConfigurationBuilder<? extends Configuration> builder = sourceData.getNamedBuilder(name);
    910        if (builder == null) {
    911            throw new ConfigurationException("Builder cannot be resolved: " + name);
    912        }
    913        return builder;
    914    }
    915
    916    /**
    917     * Obtains the data object for the configuration sources and the corresponding builders. This object is created on first
    918     * access and reset when the definition builder sends a change event. This method is called in a synchronized block.
    919     *
    920     * @return the object with information about configuration sources
    921     * @throws ConfigurationException if an error occurs
    922     */
    923    private ConfigurationSourceData getSourceData() throws ConfigurationException {
    924        if (sourceData == null) {
    925            if (currentParameters == null) {
    926                setUpCurrentParameters();
    927                setUpCurrentXMLParameters();
    928            }
    929            sourceData = createSourceData();
    930        }
    931        return sourceData;
    932    }
    933
    934    /**
    935     * Initializes a bean using the current {@code BeanHelper}. This is needed by builder providers when the configuration
    936     * objects for sub builders are constructed.
    937     *
    938     * @param bean the bean to be initialized
    939     * @param decl the {@code BeanDeclaration}
    940     */
    941    void initBean(final Object bean, final BeanDeclaration decl) {
    942        fetchBeanHelper().initBean(bean, decl);
    943    }
    944
    945    /**
    946     * Initializes basic builder parameters for a child configuration with default settings set for this builder. This
    947     * implementation ensures that all {@code Lookup} objects are propagated to child configurations and interpolation is
    948     * setup correctly.
    949     *
    950     * @param params the parameters object
    951     */
    952    private void initChildBasicParameters(final BasicBuilderParameters params) {
    953        params.setPrefixLookups(fetchPrefixLookups());
    954        params.setParentInterpolator(parentInterpolator);
    955        if (currentParameters.isInheritSettings()) {
    956            params.inheritFrom(getParameters());
    957        }
    958    }
    959
    960    /**
    961     * Initializes a parameters object for a child builder. This combined configuration builder has a bunch of properties
    962     * which may be inherited by child configurations, for example the base path, the file system, etc. While processing the
    963     * builders for child configurations, this method is called for each parameters object for a child builder. It
    964     * initializes some properties of the passed in parameters objects which are derived from this parent builder.
    965     *
    966     * @param params the parameters object to be initialized
    967     */
    968    protected void initChildBuilderParameters(final BuilderParameters params) {
    969        initDefaultChildParameters(params);
    970
    971        if (params instanceof BasicBuilderParameters) {
    972            initChildBasicParameters((BasicBuilderParameters) params);
    973        }
    974        if (params instanceof XMLBuilderProperties<?>) {
    975            initChildXMLParameters((XMLBuilderProperties<?>) params);
    976        }
    977        if (params instanceof FileBasedBuilderProperties<?>) {
    978            initChildFileBasedParameters((FileBasedBuilderProperties<?>) params);
    979        }
    980        if (params instanceof CombinedBuilderParametersImpl) {
    981            initChildCombinedParameters((CombinedBuilderParametersImpl) params);
    982        }
    983    }
    984
    985    /**
    986     * Initializes a parameters object for a combined configuration builder with properties already set for this parent
    987     * builder. This implementation deals only with a subset of properties. Other properties are already handled by the
    988     * specialized builder provider.
    989     *
    990     * @param params the parameters object
    991     */
    992    private void initChildCombinedParameters(final CombinedBuilderParametersImpl params) {
    993        params.registerMissingProviders(currentParameters);
    994        params.setBasePath(getBasePath());
    995    }
    996
    997    /**
    998     * Initializes the event listeners of the specified builder from this object. This method is used to inherit all
    999     * listeners from a parent builder.
    1000     *
    1001     * @param dest the destination builder object which is to be initialized
    1002     */
    1003    void initChildEventListeners(final BasicConfigurationBuilder<? extends Configuration> dest) {
    1004        copyEventListeners(dest);
    1005    }
    1006
    1007    /**
    1008     * Initializes a parameters object for a file-based configuration with properties already set for this parent builder.
    1009     * This method handles properties like a default file system or a base path.
    1010     *
    1011     * @param params the parameters object
    1012     */
    1013    private void initChildFileBasedParameters(final FileBasedBuilderProperties<?> params) {
    1014        params.setBasePath(getBasePath());
    1015        params.setFileSystem(currentXMLParameters.getFileHandler().getFileSystem());
    1016    }
    1017
    1018    /**
    1019     * Initializes a parameters object for an XML configuration with properties already set for this parent builder.
    1020     *
    1021     * @param params the parameters object
    1022     */
    1023    private void initChildXMLParameters(final XMLBuilderProperties<?> params) {
    1024        params.setEntityResolver(currentXMLParameters.getEntityResolver());
    1025    }
    1026
    1027    /**
    1028     * Initializes the default base path for all file-based child configuration sources. The base path can be explicitly
    1029     * defined in the parameters of this builder. Otherwise, if the definition builder is a file-based builder, it is
    1030     * obtained from there.
    1031     *
    1032     * @throws ConfigurationException if an error occurs
    1033     */
    1034    private void initDefaultBasePath() throws ConfigurationException {
    1035        assert currentParameters != null : "Current parameters undefined!";
    1036        if (currentParameters.getBasePath() != null) {
    1037            currentXMLParameters.setBasePath(currentParameters.getBasePath());
    1038        } else {
    1039            final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> defBuilder = getDefinitionBuilder();
    1040            if (defBuilder instanceof FileBasedConfigurationBuilder) {
    1041                @SuppressWarnings("rawtypes")
    1042                final FileBasedConfigurationBuilder fileBuilder = (FileBasedConfigurationBuilder) defBuilder;
    1043                final URL url = fileBuilder.getFileHandler().getURL();
    1044                currentXMLParameters.setBasePath(url != null ? url.toExternalForm() : fileBuilder.getFileHandler().getBasePath());
    1045            }
    1046        }
    1047    }
    1048
    1049    /**
    1050     * Executes the {@link org.apache.commons.configuration2.builder.DefaultParametersManager DefaultParametersManager}
    1051     * stored in the current parameters on the passed in parameters object. If default handlers have been registered for
    1052     * this type of parameters, an initialization is now performed. This method is called before the parameters object is
    1053     * initialized from the configuration definition file. So default values can be overridden later with concrete property
    1054     * definitions.
    1055     *
    1056     * @param params the parameters to be initialized
    1057     * @throws org.apache.commons.configuration2.ex.ConfigurationRuntimeException if an error occurs when copying properties
    1058     */
    1059    private void initDefaultChildParameters(final BuilderParameters params) {
    1060        currentParameters.getChildDefaultParametersManager().initializeParameters(params);
    1061    }
    1062
    1063    /**
    1064     * Creates and initializes a default {@code FileSystem} if the definition configuration contains a corresponding
    1065     * declaration. The file system returned by this method is used as default for all file-based child configuration
    1066     * sources.
    1067     *
    1068     * @param config the definition configuration
    1069     * @return the default {@code FileSystem} (may be <strong>null</strong>)
    1070     * @throws ConfigurationException if an error occurs
    1071     */
    1072    protected FileSystem initFileSystem(final HierarchicalConfiguration<?> config) throws ConfigurationException {
    1073        if (config.getMaxIndex(FILE_SYSTEM) == 0) {
    1074            final XMLBeanDeclaration decl = new XMLBeanDeclaration(config, FILE_SYSTEM);
    1075            return (FileSystem) fetchBeanHelper().createBean(decl);
    1076        }
    1077        return null;
    1078    }
    1079
    1080    /**
    1081     * {@inheritDoc} This implementation processes the definition configuration in order to
    1082     * <ul>
    1083     * <li>initialize the resulting {@code CombinedConfiguration}</li>
    1084     * <li>determine the builders for all configuration sources</li>
    1085     * <li>populate the resulting {@code CombinedConfiguration}</li>
    1086     * </ul>
    1087     */
    1088    @Override
    1089    protected void initResultInstance(final CombinedConfiguration result) throws ConfigurationException {
    1090        super.initResultInstance(result);
    1091
    1092        currentConfiguration = result;
    1093        final HierarchicalConfiguration<?> config = getDefinitionConfiguration();
    1094        if (config.getMaxIndex(KEY_COMBINER) < 0) {
    1095            // No combiner defined => set default
    1096            result.setNodeCombiner(new OverrideCombiner());
    1097        }
    1098
    1099        setUpCurrentParameters();
    1100        initNodeCombinerListNodes(result, config, KEY_OVERRIDE_LIST);
    1101        registerConfiguredProviders(config);
    1102        setUpCurrentXMLParameters();
    1103        currentXMLParameters.setFileSystem(initFileSystem(config));
    1104        initSystemProperties(config, getBasePath());
    1105        registerConfiguredLookups(config, result);
    1106        configureEntityResolver(config, currentXMLParameters);
    1107        setUpParentInterpolator(currentConfiguration, config);
    1108
    1109        final ConfigurationSourceData data = getSourceData();
    1110        final boolean createBuilders = data.getChildBuilders().isEmpty();
    1111        final List<ConfigurationBuilder<? extends Configuration>> overrideBuilders = data.createAndAddConfigurations(result, data.getOverrideSources(),
    1112            data.overrideBuilders);
    1113        if (createBuilders) {
    1114            data.overrideBuilders.addAll(overrideBuilders);
    1115        }
    1116        if (!data.getUnionSources().isEmpty()) {
    1117            final CombinedConfiguration addConfig = createAdditionalsConfiguration(result);
    1118            result.addConfiguration(addConfig, ADDITIONAL_NAME);
    1119            initNodeCombinerListNodes(addConfig, config, KEY_ADDITIONAL_LIST);
    1120            final List<ConfigurationBuilder<? extends Configuration>> unionBuilders = data.createAndAddConfigurations(addConfig, data.unionDeclarations,
    1121                data.unionBuilders);
    1122            if (createBuilders) {
    1123                data.unionBuilders.addAll(unionBuilders);
    1124            }
    1125        }
    1126
    1127        result.isEmpty(); // this sets up the node structure
    1128        currentConfiguration = null;
    1129    }
    1130
    1131    /**
    1132     * Handles a file with system properties that may be defined in the definition configuration. If such property file is
    1133     * configured, all of its properties are added to the system properties.
    1134     *
    1135     * @param config the definition configuration
    1136     * @param basePath the base path defined for this builder (may be <strong>null</strong>)
    1137     * @throws ConfigurationException if an error occurs.
    1138     */
    1139    protected void initSystemProperties(final HierarchicalConfiguration<?> config, final String basePath) throws ConfigurationException {
    1140        final String fileName = config.getString(KEY_SYSTEM_PROPS);
    1141        if (fileName != null) {
    1142            try {
    1143                SystemConfiguration.setSystemProperties(basePath, fileName);
    1144            } catch (final Exception ex) {
    1145                throw new ConfigurationException("Error setting system properties from " + fileName, ex);
    1146            }
    1147        }
    1148    }
    1149
    1150    /**
    1151     * Returns the {@code ConfigurationBuilderProvider} for the given tag. This method is called during creation of the
    1152     * result configuration. (It is not allowed to call it at another point of time; result is then unpredictable!) It
    1153     * supports all default providers and custom providers added through the parameters object as well.
    1154     *
    1155     * @param tagName the name of the tag
    1156     * @return the provider that was registered for this tag or <strong>null</strong> if there is none
    1157     */
    1158    protected ConfigurationBuilderProvider providerForTag(final String tagName) {
    1159        return currentParameters.providerForTag(tagName);
    1160    }
    1161
    1162    /**
    1163     * Processes custom {@link Lookup} objects that might be declared in the definition configuration. Each {@code Lookup}
    1164     * object is registered at the definition configuration and at the result configuration. It is also added to all child
    1165     * configurations added to the resulting combined configuration.
    1166     *
    1167     * @param defConfig the definition configuration
    1168     * @param resultConfig the resulting configuration
    1169     * @throws ConfigurationException if an error occurs
    1170     */
    1171    protected void registerConfiguredLookups(final HierarchicalConfiguration<?> defConfig, final Configuration resultConfig) throws ConfigurationException {
    1172        final Map<String, Lookup> lookups = defConfig.configurationsAt(KEY_CONFIGURATION_LOOKUPS).stream().collect(
    1173                Collectors.toMap(config -> config.getString(KEY_LOOKUP_KEY), config -> (Lookup) fetchBeanHelper().createBean(new XMLBeanDeclaration(config))));
    1174
    1175        if (!lookups.isEmpty()) {
    1176            final ConfigurationInterpolator defCI = defConfig.getInterpolator();
    1177            if (defCI != null) {
    1178                defCI.registerLookups(lookups);
    1179            }
    1180            resultConfig.getInterpolator().registerLookups(lookups);
    1181        }
    1182    }
    1183
    1184    /**
    1185     * Registers providers defined in the configuration.
    1186     *
    1187     * @param defConfig the definition configuration
    1188     */
    1189    private void registerConfiguredProviders(final HierarchicalConfiguration<?> defConfig) {
    1190        defConfig.configurationsAt(KEY_CONFIGURATION_PROVIDERS).forEach(config -> {
    1191            final XMLBeanDeclaration decl = new XMLBeanDeclaration(config);
    1192            final String key = config.getString(KEY_PROVIDER_KEY);
    1193            currentParameters.registerProvider(key, (ConfigurationBuilderProvider) fetchBeanHelper().createBean(decl));
    1194        });
    1195    }
    1196
    1197    /**
    1198     * {@inheritDoc} This implementation resets some specific internal state of this builder.
    1199     */
    1200    @Override
    1201    public synchronized void resetParameters() {
    1202        super.resetParameters();
    1203        definitionBuilder = null;
    1204        definitionConfiguration = null;
    1205        currentParameters = null;
    1206        currentXMLParameters = null;
    1207
    1208        if (sourceData != null) {
    1209            sourceData.cleanUp();
    1210            sourceData = null;
    1211        }
    1212    }
    1213
    1214    /**
    1215     * Initializes the current parameters object. This object has either been passed at builder configuration time or it is
    1216     * newly created. In any case, it is manipulated during result creation.
    1217     */
    1218    private void setUpCurrentParameters() {
    1219        currentParameters = CombinedBuilderParametersImpl.fromParameters(getParameters(), true);
    1220        currentParameters.registerMissingProviders(DEFAULT_PROVIDERS_MAP);
    1221    }
    1222
    1223    /**
    1224     * Sets up an XML parameters object which is used to store properties related to XML and file-based configurations
    1225     * during creation of the result configuration. The properties stored in this object can be inherited to child
    1226     * configurations.
    1227     *
    1228     * @throws ConfigurationException if an error occurs
    1229     */
    1230    private void setUpCurrentXMLParameters() throws ConfigurationException {
    1231        currentXMLParameters = new XMLBuilderParametersImpl();
    1232        initDefaultBasePath();
    1233    }
    1234
    1235    /**
    1236     * Obtains the {@code ConfigurationBuilder} object which provides access to the configuration containing the definition
    1237     * of the combined configuration to create. If a definition builder is defined in the parameters, it is used. Otherwise,
    1238     * we check whether the combined builder parameters object contains a parameters object for the definition builder. If
    1239     * this is the case, a builder for an {@code XMLConfiguration} is created and configured with this object. As a last
    1240     * resort, it is looked for a {@link FileBasedBuilderParametersImpl} object in the properties. If found, also a XML
    1241     * configuration builder is created which loads this file. Note: This method is called from a synchronized block.
    1242     *
    1243     * @param params the current parameters for this builder
    1244     * @return the builder for the definition configuration
    1245     * @throws ConfigurationException if an error occurs
    1246     */
    1247    protected ConfigurationBuilder<? extends HierarchicalConfiguration<?>> setupDefinitionBuilder(final Map<String, Object> params)
    1248        throws ConfigurationException {
    1249        final CombinedBuilderParametersImpl cbParams = CombinedBuilderParametersImpl.fromParameters(params);
    1250        if (cbParams != null) {
    1251            final ConfigurationBuilder<? extends HierarchicalConfiguration<?>> defBuilder = cbParams.getDefinitionBuilder();
    1252            if (defBuilder != null) {
    1253                return defBuilder;
    1254            }
    1255
    1256            if (cbParams.getDefinitionBuilderParameters() != null) {
    1257                return createXMLDefinitionBuilder(cbParams.getDefinitionBuilderParameters());
    1258            }
    1259        }
    1260
    1261        final BuilderParameters fileParams = FileBasedBuilderParametersImpl.fromParameters(params);
    1262        if (fileParams != null) {
    1263            return createXMLDefinitionBuilder(fileParams);
    1264        }
    1265
    1266        throw new ConfigurationException("No builder for configuration definition specified!");
    1267    }
    1268
    1269    /**
    1270     * Sets up a parent {@code ConfigurationInterpolator} object. This object has a default {@link Lookup} querying the
    1271     * resulting combined configuration. Thus interpolation works globally across all configuration sources.
    1272     *
    1273     * @param resultConfig the result configuration
    1274     * @param defConfig the definition configuration
    1275     */
    1276    private void setUpParentInterpolator(final Configuration resultConfig, final Configuration defConfig) {
    1277        parentInterpolator = new ConfigurationInterpolator();
    1278        parentInterpolator.addDefaultLookup(new ConfigurationLookup(resultConfig));
    1279        final ConfigurationInterpolator defInterpolator = defConfig.getInterpolator();
    1280        if (defInterpolator != null) {
    1281            defInterpolator.setParentInterpolator(parentInterpolator);
    1282        }
    1283    }
    1284}