    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.configuration2;
    019
    020import java.io.PrintStream;
    021import java.io.PrintWriter;
    022import java.io.StringWriter;
    023import java.lang.reflect.InvocationTargetException;
    024import java.lang.reflect.Method;
    025import java.lang.reflect.Proxy;
    026import java.util.Iterator;
    027
    028import org.apache.commons.configuration2.event.ConfigurationErrorEvent;
    029import org.apache.commons.configuration2.event.Event;
    030import org.apache.commons.configuration2.event.EventListener;
    031import org.apache.commons.configuration2.event.EventSource;
    032import org.apache.commons.configuration2.event.EventType;
    033import org.apache.commons.configuration2.ex.ConfigurationRuntimeException;
    034import org.apache.commons.configuration2.sync.NoOpSynchronizer;
    035import org.apache.commons.configuration2.sync.Synchronizer;
    036import org.apache.commons.configuration2.tree.ExpressionEngine;
    037import org.apache.commons.logging.Log;
    038import org.apache.commons.logging.LogFactory;
    039
    040/**
    041 * Miscellaneous utility methods for configurations.
    042 *
    043 * @see ConfigurationConverter Utility methods to convert configurations.
    044 */
    045public final class ConfigurationUtils {
    046    /** Constant for the name of the clone() method. */
    047    private static final String METHOD_CLONE = "clone";
    048
    049    /**
    050     * An array with interfaces to be implemented by a proxy for an immutable configuration.
    051     */
    052    private static final Class<?>[] IMMUTABLE_CONFIG_IFCS = {ImmutableConfiguration.class};
    053
    054    /**
    055     * An array with interfaces to be implemented by a proxy for an immutable hierarchical configuration.
    056     */
    057    private static final Class<?>[] IMMUTABLE_HIERARCHICAL_CONFIG_IFCS = {ImmutableHierarchicalConfiguration.class};
    058    /**
    059     * A dummy event source that is returned by {@code asEventSource()} if a mock object has to be returned. It provides
    060     * empty dummy implementations for all interface methods.
    061     */
    062    private static final EventSource DUMMY_EVENT_SOURCE = new EventSource() {
    063
    064        @Override
    065        public <T extends Event> void addEventListener(final EventType<T> eventType, final EventListener<? super T> listener) {
    066            // empty
    067        }
    068
    069        @Override
    070        public <T extends Event> boolean removeEventListener(final EventType<T> eventType, final EventListener<? super T> listener) {
    071            return false;
    072        }
    073    };
    074
    075    /** The logger. */
    076    private static final Log LOG = LogFactory.getLog(ConfigurationUtils.class);
    077
    078    /**
    079     * <p>
    080     * Append all properties from the source configuration to the target configuration. Properties in the source
    081     * configuration are appended to the properties with the same key in the target configuration.
    082     * </p>
    083     * <p>
    084     * <em>Note:</em> This method is not able to handle some specifics of configurations derived from
    085     * {@code AbstractConfiguration} (e.g. list delimiters). For a full support of all of these features the {@code copy()}
    086     * method of {@code AbstractConfiguration} should be used. In a future release this method might become deprecated.
    087     * </p>
    088     *
    089     * @param source the source configuration
    090     * @param target the target configuration
    091     * @since 1.1
    092     */
    093    public static void append(final Configuration source, final Configuration target) {
    094        append((ImmutableConfiguration) source, target);
    095    }
    096
    097    /**
    098     * <p>
    099     * Append all properties from the source configuration to the target configuration. Properties in the source
    100     * configuration are appended to the properties with the same key in the target configuration.
    101     * </p>
    102     * <p>
    103     * <em>Note:</em> This method is not able to handle some specifics of configurations derived from
    104     * {@code AbstractConfiguration} (e.g. list delimiters). For a full support of all of these features the {@code copy()}
    105     * method of {@code AbstractConfiguration} should be used. In a future release this method might become deprecated.
    106     * </p>
    107     *
    108     * @param source the source configuration
    109     * @param target the target configuration
    110     * @since 2.2
    111     */
    112    public static void append(final ImmutableConfiguration source, final Configuration target) {
    113        source.getKeys().forEachRemaining(key -> target.addProperty(key, source.getProperty(key)));
    114    }
    115
    116    /**
    117     * Casts the specified object to an {@code EventSource} if possible. The boolean argument determines the method's
    118     * behavior if the object does not implement the {@code EventSource} event: if set to <b>false</b>, a
    119     * {@code ConfigurationRuntimeException} is thrown; if set to <b>true</b>, a dummy {@code EventSource} is returned; on
    120     * this object all methods can be called, but they do not have any effect.
    121     *
    122     * @param obj the object to be cast as {@code EventSource}
    123     * @param mockIfUnsupported a flag whether a mock object should be returned if necessary
    124     * @return an {@code EventSource}
    125     * @throws ConfigurationRuntimeException if the object cannot be cast to {@code EventSource} and the mock flag is
    126     *         <b>false</b>
    127     * @since 2.0
    128     */
    129    public static EventSource asEventSource(final Object obj, final boolean mockIfUnsupported) {
    130        if (obj instanceof EventSource) {
    131            return (EventSource) obj;
    132        }
    133
    134        if (!mockIfUnsupported) {
    135            throw new ConfigurationRuntimeException("Cannot cast to EventSource: " + obj);
    136        }
    137        return DUMMY_EVENT_SOURCE;
    138    }
    139
    140    /**
    141     * An internally used helper method for cloning objects. This implementation is not very sophisticated nor efficient.
    142     * Maybe it can be replaced by an implementation from Commons Lang later. The method checks whether the passed in object
    143     * implements the {@code Cloneable} interface. If this is the case, the {@code clone()} method is invoked by reflection.
    144     * Errors that occur during the cloning process are re-thrown as runtime exceptions.
    145     *
    146     * @param obj the object to be cloned
    147     * @return the cloned object
    148     * @throws CloneNotSupportedException if the object cannot be cloned
    149     */
    150    static Object clone(final Object obj) throws CloneNotSupportedException {
    151        if (obj instanceof Cloneable) {
    152            try {
    153                final Method m = obj.getClass().getMethod(METHOD_CLONE);
    154                return m.invoke(obj);
    155            } catch (final NoSuchMethodException nmex) {
    156                throw new CloneNotSupportedException("No clone() method found for class" + obj.getClass().getName());
    157            } catch (final IllegalAccessException | InvocationTargetException itex) {
    158                throw new ConfigurationRuntimeException(itex);
    159            }
    160        }
    161        throw new CloneNotSupportedException(obj.getClass().getName() + " does not implement Cloneable");
    162    }
    163
    164    /**
    165     * Clones the given configuration object if this is possible. If the passed in configuration object implements the
    166     * {@code Cloneable} interface, its {@code clone()} method will be invoked. Otherwise an exception will be thrown.
    167     *
    168     * @param config the configuration object to be cloned (can be <b>null</b>)
    169     * @return the cloned configuration (<b>null</b> if the argument was <b>null</b>, too)
    170     * @throws ConfigurationRuntimeException if cloning is not supported for this object
    171     * @since 1.3
    172     */
    173    public static Configuration cloneConfiguration(final Configuration config) throws ConfigurationRuntimeException {
    174        if (config == null) {
    175            return null;
    176        }
    177        try {
    178            return (Configuration) clone(config);
    179        } catch (final CloneNotSupportedException cnex) {
    180            throw new ConfigurationRuntimeException(cnex);
    181        }
    182    }
    183
    184    /**
    185     * Returns a clone of the passed in object if cloning is supported or the object itself if not. This method checks
    186     * whether the passed in object implements the {@code Cloneable} interface. If this is the case, the {@code clone()}
    187     * method is invoked. Otherwise, the object is directly returned. Errors that might occur during reflection calls are
    188     * caught and also cause this method to return the original object.
    189     *
    190     * @param obj the object to be cloned
    191     * @return the result of the cloning attempt
    192     * @since 2.0
    193     */
    194    public static Object cloneIfPossible(final Object obj) {
    195        try {
    196            return clone(obj);
    197        } catch (final Exception ex) {
    198            return obj;
    199        }
    200    }
    201
    202    /**
    203     * Creates a clone of the specified {@code Synchronizer}. This method can be called by {@code clone()} implementations
    204     * in configuration classes that also need to copy the {@code Synchronizer} object. This method can handle some
    205     * well-known {@code Synchronizer} implementations directly. For other classes, it uses the following algorithm:
    206     * <ul>
    207     * <li>If the class of the {@code Synchronizer} has a standard constructor, a new instance is created using
    208     * reflection.</li>
    209     * <li>If this is not possible, it is tried whether the object can be cloned.</li>
    210     * </ul>
    211     * If all attempts fail, a {@code ConfigurationRuntimeException} is thrown.
    212     *
    213     * @param sync the {@code Synchronizer} object to be cloned
    214     * @return the clone of this {@code Synchronizer}
    215     * @throws ConfigurationRuntimeException if no clone can be created
    216     * @throws IllegalArgumentException if <b>null</b> is passed in
    217     */
    218    public static Synchronizer cloneSynchronizer(final Synchronizer sync) {
    219        if (sync == null) {
    220            throw new IllegalArgumentException("Synchronizer must not be null!");
    221        }
    222        if (NoOpSynchronizer.INSTANCE == sync) {
    223            return sync;
    224        }
    225
    226        try {
    227            return sync.getClass().getConstructor().newInstance();
    228        } catch (final Exception ex) {
    229            LOG.info("Cannot create new instance of " + sync.getClass());
    230        }
    231
    232        try {
    233            return (Synchronizer) clone(sync);
    234        } catch (final CloneNotSupportedException cnex) {
    235            throw new ConfigurationRuntimeException("Cannot clone Synchronizer " + sync);
    236        }
    237    }
    238
    239    /**
    240     * Converts the passed in configuration to a hierarchical one. If the configuration is already hierarchical, it is
    241     * directly returned. Otherwise all properties are copied into a new hierarchical configuration.
    242     *
    243     * @param conf the configuration to convert
    244     * @return the new hierarchical configuration (the result is <b>null</b> if and only if the passed in configuration is
    245     *         <b>null</b>)
    246     * @since 1.3
    247     */
    248    public static HierarchicalConfiguration<?> convertToHierarchical(final Configuration conf) {
    249        return convertToHierarchical(conf, null);
    250    }
    251
    252    /**
    253     * Converts the passed in {@code Configuration} object to a hierarchical one using the specified
    254     * {@code ExpressionEngine}. This conversion works by adding the keys found in the configuration to a newly created
    255     * hierarchical configuration. When adding new keys to a hierarchical configuration the keys are interpreted by its
    256     * {@code ExpressionEngine}. If they contain special characters (e.g. brackets) that are treated in a special way by the
    257     * default expression engine, it may be necessary using a specific engine that can deal with such characters. Otherwise
    258     * <b>null</b> can be passed in for the {@code ExpressionEngine}; then the default expression engine is used. If the
    259     * passed in configuration is already hierarchical, it is directly returned. (However, the {@code ExpressionEngine} is
    260     * set if it is not <b>null</b>.) Otherwise all properties are copied into a new hierarchical configuration.
    261     *
    262     * @param conf the configuration to convert
    263     * @param engine the {@code ExpressionEngine} for the hierarchical configuration or <b>null</b> for the default
    264     * @return the new hierarchical configuration (the result is <b>null</b> if and only if the passed in configuration is
    265     *         <b>null</b>)
    266     * @since 1.6
    267     */
    268    public static HierarchicalConfiguration<?> convertToHierarchical(final Configuration conf, final ExpressionEngine engine) {
    269        if (conf == null) {
    270            return null;
    271        }
    272
    273        if (conf instanceof HierarchicalConfiguration) {
    274            final HierarchicalConfiguration<?> hc = (HierarchicalConfiguration<?>) conf;
    275            if (engine != null) {
    276                hc.setExpressionEngine(engine);
    277            }
    278
    279            return hc;
    280        }
    281        final BaseHierarchicalConfiguration hc = new BaseHierarchicalConfiguration();
    282        if (engine != null) {
    283            hc.setExpressionEngine(engine);
    284        }
    285
    286        // Per default, a DisabledListDelimiterHandler is set.
    287        // So list delimiters in property values are not an issue.
    288        hc.copy(conf);
    289        return hc;
    290    }
    291
    292    /**
    293     * <p>
    294     * Copy all properties from the source configuration to the target configuration. Properties in the target configuration
    295     * are replaced with the properties with the same key in the source configuration.
    296     * </p>
    297     * <p>
    298     * <em>Note:</em> This method is not able to handle some specifics of configurations derived from
    299     * {@code AbstractConfiguration} (e.g. list delimiters). For a full support of all of these features the {@code copy()}
    300     * method of {@code AbstractConfiguration} should be used. In a future release this method might become deprecated.
    301     * </p>
    302     *
    303     * @param source the source configuration
    304     * @param target the target configuration
    305     * @since 1.1
    306     */
    307    public static void copy(final Configuration source, final Configuration target) {
    308        copy((ImmutableConfiguration) source, target);
    309    }
    310
    311    /**
    312     * <p>
    313     * Copy all properties from the source configuration to the target configuration. Properties in the target configuration
    314     * are replaced with the properties with the same key in the source configuration.
    315     * </p>
    316     * <p>
    317     * <em>Note:</em> This method is not able to handle some specifics of configurations derived from
    318     * {@code AbstractConfiguration} (e.g. list delimiters). For a full support of all of these features the {@code copy()}
    319     * method of {@code AbstractConfiguration} should be used. In a future release this method might become deprecated.
    320     * </p>
    321     *
    322     * @param source the source configuration
    323     * @param target the target configuration
    324     * @since 2.2
    325     */
    326    public static void copy(final ImmutableConfiguration source, final Configuration target) {
    327        source.getKeys().forEachRemaining(key -> target.setProperty(key, source.getProperty(key)));
    328    }
    329
    330    /**
    331     * Helper method for creating a proxy for an unmodifiable configuration. The interfaces the proxy should implement are
    332     * passed as argument.
    333     *
    334     * @param ifcs an array with the interface classes the proxy must implement
    335     * @param c the configuration object to be wrapped
    336     * @return a proxy object for an immutable configuration
    337     * @throws NullPointerException if the configuration is <b>null</b>
    338     */
    339    private static ImmutableConfiguration createUnmodifiableConfiguration(final Class<?>[] ifcs, final Configuration c) {
    340        return (ImmutableConfiguration) Proxy.newProxyInstance(ConfigurationUtils.class.getClassLoader(), ifcs, new ImmutableConfigurationInvocationHandler(c));
    341    }
    342
    343    /**
    344     * Dump the configuration key/value mappings to some ouput stream. This version of the method exists only for backwards
    345     * compatibility reason.
    346     *
    347     * @param configuration the configuration
    348     * @param out the output stream to dump the configuration to
    349     */
    350    public static void dump(final Configuration configuration, final PrintStream out) {
    351        dump((ImmutableConfiguration) configuration, out);
    352    }
    353
    354    /**
    355     * Dump the configuration key/value mappings to some writer. This version of the method exists only for backwards
    356     * compatibility reason.
    357     *
    358     * @param configuration the configuration
    359     * @param out the writer to dump the configuration to
    360     */
    361    public static void dump(final Configuration configuration, final PrintWriter out) {
    362        dump((ImmutableConfiguration) configuration, out);
    363    }
    364
    365    /**
    366     * Dump the configuration key/value mappings to some ouput stream.
    367     *
    368     * @param configuration the configuration
    369     * @param out the output stream to dump the configuration to
    370     * @since 2.2
    371     */
    372    public static void dump(final ImmutableConfiguration configuration, final PrintStream out) {
    373        dump(configuration, new PrintWriter(out));
    374    }
    375
    376    /**
    377     * Dump the configuration key/value mappings to some writer.
    378     *
    379     * @param configuration the configuration
    380     * @param out the writer to dump the configuration to
    381     * @since 2.2
    382     */
    383    public static void dump(final ImmutableConfiguration configuration, final PrintWriter out) {
    384        for (final Iterator<String> keys = configuration.getKeys(); keys.hasNext();) {
    385            final String key = keys.next();
    386            final Object value = configuration.getProperty(key);
    387            out.print(key);
    388            out.print("=");
    389            out.print(value);
    390
    391            if (keys.hasNext()) {
    392                out.println();
    393            }
    394        }
    395
    396        out.flush();
    397    }
    398
    399    /**
    400     * Enables runtime exceptions for the specified configuration object. This method can be used for configuration
    401     * implementations that may face errors on normal property access, e.g. {@code DatabaseConfiguration} or
    402     * {@code JNDIConfiguration}. Per default such errors are simply logged and then ignored. This implementation will
    403     * register a special {@link EventListener} that throws a runtime exception (namely a
    404     * {@code ConfigurationRuntimeException}) on each received error event.
    405     *
    406     * @param src the configuration, for which runtime exceptions are to be enabled; this configuration must implement
    407     *        {@link EventSource}
    408     */
    409    public static void enableRuntimeExceptions(final Configuration src) {
    410        if (!(src instanceof EventSource)) {
    411            throw new IllegalArgumentException("Configuration must implement EventSource!");
    412        }
    413        ((EventSource) src).addEventListener(ConfigurationErrorEvent.ANY, event -> {
    414            // Throw a runtime exception
    415            throw new ConfigurationRuntimeException(event.getCause());
    416        });
    417    }
    418
    419    /**
    420     * Loads the class with the given name. This method is used whenever a class has to be loaded dynamically. It first
    421     * tries the current thread's context class loader. If this fails, the class loader of this class is tried.
    422     *
    423     * @param clsName the name of the class to be loaded
    424     * @return the loaded class
    425     * @throws ClassNotFoundException if the class cannot be resolved
    426     * @since 2.0
    427     */
    428    public static Class<?> loadClass(final String clsName) throws ClassNotFoundException {
    429        if (LOG.isDebugEnabled()) {
    430            LOG.debug("Loading class " + clsName);
    431        }
    432
    433        final ClassLoader cl = Thread.currentThread().getContextClassLoader();
    434        try {
    435            if (cl != null) {
    436                return cl.loadClass(clsName);
    437            }
    438        } catch (final ClassNotFoundException cnfex) {
    439            LOG.info("Could not load class " + clsName + " using CCL. Falling back to default CL.", cnfex);
    440        }
    441
    442        return ConfigurationUtils.class.getClassLoader().loadClass(clsName);
    443    }
    444
    445    /**
    446     * Loads the class with the specified name re-throwing {@code ClassNotFoundException} exceptions as runtime exceptions.
    447     * This method works like {@link #loadClass(String)}. However, checked exceptions are caught and re-thrown as
    448     * {@code ConfigurationRuntimeException}.
    449     *
    450     * @param clsName the name of the class to be loaded
    451     * @return the loaded class
    452     * @throws ConfigurationRuntimeException if the class cannot be resolved
    453     * @since 2.0
    454     */
    455    public static Class<?> loadClassNoEx(final String clsName) {
    456        try {
    457            return loadClass(clsName);
    458        } catch (final ClassNotFoundException cnfex) {
    459            throw new ConfigurationRuntimeException("Cannot load class " + clsName, cnfex);
    460        }
    461    }
    462
    463    /**
    464     * Gets a string representation of the key/value mappings of a configuration. This version of the method exists only for
    465     * backwards compatibility reason.
    466     *
    467     * @param configuration the configuration
    468     * @return a string representation of the configuration
    469     */
    470    public static String toString(final Configuration configuration) {
    471        return toString((ImmutableConfiguration) configuration);
    472    }
    473
    474    /**
    475     * Gets a string representation of the key/value mappings of a configuration.
    476     *
    477     * @param configuration the configuration
    478     * @return a string representation of the configuration
    479     * @since 2.2
    480     */
    481    public static String toString(final ImmutableConfiguration configuration) {
    482        final StringWriter writer = new StringWriter();
    483        dump(configuration, new PrintWriter(writer));
    484        return writer.toString();
    485    }
    486
    487    /**
    488     * Creates an {@code ImmutableConfiguration} from the given {@code Configuration} object. This method creates a proxy
    489     * object wrapping the original configuration and making it available under the {@code ImmutableConfiguration}
    490     * interface. Through this interface the configuration cannot be manipulated. It is also not possible to cast the
    491     * returned object back to a {@code Configuration} instance to circumvent this protection.
    492     *
    493     * @param c the {@code Configuration} to be wrapped (must not be <b>null</b>)
    494     * @return an {@code ImmutableConfiguration} view on the specified {@code Configuration} object
    495     * @throws NullPointerException if the passed in {@code Configuration} is <b>null</b>
    496     * @since 2.0
    497     */
    498    public static ImmutableConfiguration unmodifiableConfiguration(final Configuration c) {
    499        return createUnmodifiableConfiguration(IMMUTABLE_CONFIG_IFCS, c);
    500    }
    501
    502    /**
    503     * Creates an {@code ImmutableHierarchicalConfiguration} from the given {@code HierarchicalConfiguration} object. This
    504     * method works exactly like the method with the same name, but it operates on hierarchical configurations.
    505     *
    506     * @param c the {@code HierarchicalConfiguration} to be wrapped (must not be <b>null</b>)
    507     * @return an {@code ImmutableHierarchicalConfiguration} view on the specified {@code HierarchicalConfiguration} object
    508     * @throws NullPointerException if the passed in {@code HierarchicalConfiguration} is <b>null</b>
    509     * @since 2.0
    510     */
    511    public static ImmutableHierarchicalConfiguration unmodifiableConfiguration(final HierarchicalConfiguration<?> c) {
    512        return (ImmutableHierarchicalConfiguration) createUnmodifiableConfiguration(IMMUTABLE_HIERARCHICAL_CONFIG_IFCS, c);
    513    }
    514
    515    /**
    516     * Private constructor. Prevents instances from being created.
    517     */
    518    private ConfigurationUtils() {
    519        // to prevent instantiation...
    520    }
    521}