    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *     http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017package org.apache.commons.configuration2.builder;
    018
    019import java.util.Map;
    020import java.util.concurrent.ConcurrentHashMap;
    021
    022import org.apache.commons.configuration2.FileBasedConfiguration;
    023import org.apache.commons.configuration2.PropertiesConfiguration;
    024import org.apache.commons.configuration2.XMLPropertiesConfiguration;
    025import org.apache.commons.configuration2.event.ConfigurationEvent;
    026import org.apache.commons.configuration2.ex.ConfigurationException;
    027import org.apache.commons.configuration2.io.FileHandler;
    028import org.apache.commons.lang3.ClassUtils;
    029import org.apache.commons.lang3.StringUtils;
    030
    031/**
    032 * <p>
    033 * A specialized {@code ConfigurationBuilder} implementation which can handle configurations read from a
    034 * {@link FileHandler}.
    035 * </p>
    036 * <p>
    037 * This class extends its base class by the support of a {@link FileBasedBuilderParametersImpl} object, and especially
    038 * of the {@link FileHandler} contained in this object. When the builder creates a new object the resulting
    039 * {@code Configuration} instance is associated with the {@code FileHandler}. If the {@code FileHandler} has a location
    040 * set, the {@code Configuration} is directly loaded from this location.
    041 * </p>
    042 * <p>
    043 * The {@code FileHandler} is kept by this builder and can be queried later on. It can be used for instance to save the
    044 * current {@code Configuration} after it was modified. Some care has to be taken when changing the location of the
    045 * {@code FileHandler}: The new location is recorded and also survives an invocation of the {@code resetResult()}
    046 * method. However, when the builder's initialization parameters are reset by calling {@code resetParameters()} the
    047 * location is reset, too.
    048 * </p>
    049 *
    050 * @since 2.0
    051 * @param <T> the concrete type of {@code Configuration} objects created by this builder
    052 */
    053public class FileBasedConfigurationBuilder<T extends FileBasedConfiguration> extends BasicConfigurationBuilder<T> {
    054    /** A map for storing default encodings for specific configuration classes. */
    055    private static final Map<Class<?>, String> DEFAULT_ENCODINGS = initializeDefaultEncodings();
    056
    057    /** Stores the FileHandler associated with the current configuration. */
    058    private FileHandler currentFileHandler;
    059
    060    /** A specialized listener for the auto save mechanism. */
    061    private AutoSaveListener autoSaveListener;
    062
    063    /** A flag whether the builder's parameters were reset. */
    064    private boolean resetParameters;
    065
    066    /**
    067     * Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class.
    068     *
    069     * @param resCls the result class (must not be <b>null</b>
    070     * @throws IllegalArgumentException if the result class is <b>null</b>
    071     */
    072    public FileBasedConfigurationBuilder(final Class<? extends T> resCls) {
    073        super(resCls);
    074    }
    075
    076    /**
    077     * Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class
    078     * and sets initialization parameters.
    079     *
    080     * @param resCls the result class (must not be <b>null</b>
    081     * @param params a map with initialization parameters
    082     * @throws IllegalArgumentException if the result class is <b>null</b>
    083     */
    084    public FileBasedConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params) {
    085        super(resCls, params);
    086    }
    087
    088    /**
    089     * Creates a new instance of {@code FileBasedConfigurationBuilder} which produces result objects of the specified class
    090     * and sets initialization parameters and the <em>allowFailOnInit</em> flag.
    091     *
    092     * @param resCls the result class (must not be <b>null</b>
    093     * @param params a map with initialization parameters
    094     * @param allowFailOnInit the <em>allowFailOnInit</em> flag
    095     * @throws IllegalArgumentException if the result class is <b>null</b>
    096     */
    097    public FileBasedConfigurationBuilder(final Class<? extends T> resCls, final Map<String, Object> params, final boolean allowFailOnInit) {
    098        super(resCls, params, allowFailOnInit);
    099    }
    100
    101    /**
    102     * Gets the default encoding for the specified configuration class. If an encoding has been set for the specified
    103     * class (or one of its super classes), it is returned. Otherwise, result is <b>null</b>.
    104     *
    105     * @param configClass the configuration class in question
    106     * @return the default encoding for this class (may be <b>null</b>)
    107     */
    108    public static String getDefaultEncoding(final Class<?> configClass) {
    109        String enc = DEFAULT_ENCODINGS.get(configClass);
    110        if (enc != null || configClass == null) {
    111            return enc;
    112        }
    113
    114        for (final Class<?> cls : ClassUtils.getAllSuperclasses(configClass)) {
    115            enc = DEFAULT_ENCODINGS.get(cls);
    116            if (enc != null) {
    117                return enc;
    118            }
    119        }
    120
    121        for (final Class<?> cls : ClassUtils.getAllInterfaces(configClass)) {
    122            enc = DEFAULT_ENCODINGS.get(cls);
    123            if (enc != null) {
    124                return enc;
    125            }
    126        }
    127
    128        return null;
    129    }
    130
    131    /**
    132     * Sets a default encoding for a specific configuration class. This encoding is used if an instance of this
    133     * configuration class is to be created and no encoding has been set in the parameters object for this builder. The
    134     * encoding passed here not only applies to the specified class but also to its sub classes. If the encoding is
    135     * <b>null</b>, it is removed.
    136     *
    137     * @param configClass the name of the configuration class (must not be <b>null</b>)
    138     * @param encoding the default encoding for this class
    139     * @throws IllegalArgumentException if the class is <b>null</b>
    140     */
    141    public static void setDefaultEncoding(final Class<?> configClass, final String encoding) {
    142        if (configClass == null) {
    143            throw new IllegalArgumentException("Configuration class must not be null!");
    144        }
    145
    146        if (encoding == null) {
    147            DEFAULT_ENCODINGS.remove(configClass);
    148        } else {
    149            DEFAULT_ENCODINGS.put(configClass, encoding);
    150        }
    151    }
    152
    153    /**
    154     * {@inheritDoc} This method is overridden here to change the result type.
    155     */
    156    @Override
    157    public FileBasedConfigurationBuilder<T> configure(final BuilderParameters... params) {
    158        super.configure(params);
    159        return this;
    160    }
    161
    162    /**
    163     * Gets the {@code FileHandler} associated with this builder. If already a result object has been created, this
    164     * {@code FileHandler} can be used to save it. Otherwise, the {@code FileHandler} from the initialization parameters is
    165     * returned (which is not associated with a {@code FileBased} object). Result is never <b>null</b>.
    166     *
    167     * @return the {@code FileHandler} associated with this builder
    168     */
    169    public synchronized FileHandler getFileHandler() {
    170        return currentFileHandler != null ? currentFileHandler : fetchFileHandlerFromParameters();
    171    }
    172
    173    /**
    174     * {@inheritDoc} This implementation just records the fact that new parameters have been set. This means that the next
    175     * time a result object is created, the {@code FileHandler} has to be initialized from initialization parameters rather
    176     * than reusing the existing one.
    177     */
    178    @Override
    179    public synchronized BasicConfigurationBuilder<T> setParameters(final Map<String, Object> params) {
    180        super.setParameters(params);
    181        resetParameters = true;
    182        return this;
    183    }
    184
    185    /**
    186     * Convenience method which saves the associated configuration. This method expects that the managed configuration has
    187     * already been created and that a valid file location is available in the current {@code FileHandler}. The file handler
    188     * is then used to store the configuration.
    189     *
    190     * @throws ConfigurationException if an error occurs
    191     */
    192    public void save() throws ConfigurationException {
    193        getFileHandler().save();
    194    }
    195
    196    /**
    197     * Gets a flag whether auto save mode is currently active.
    198     *
    199     * @return <b>true</b> if auto save is enabled, <b>false</b> otherwise
    200     */
    201    public synchronized boolean isAutoSave() {
    202        return autoSaveListener != null;
    203    }
    204
    205    /**
    206     * Enables or disables auto save mode. If auto save mode is enabled, every update of the managed configuration causes it
    207     * to be saved automatically; so changes are directly written to disk.
    208     *
    209     * @param enabled <b>true</b> if auto save mode is to be enabled, <b>false</b> otherwise
    210     */
    211    public synchronized void setAutoSave(final boolean enabled) {
    212        if (enabled) {
    213            installAutoSaveListener();
    214        } else {
    215            removeAutoSaveListener();
    216        }
    217    }
    218
    219    /**
    220     * {@inheritDoc} This implementation deals with the creation and initialization of a {@code FileHandler} associated with
    221     * the new result object.
    222     */
    223    @Override
    224    protected void initResultInstance(final T obj) throws ConfigurationException {
    225        super.initResultInstance(obj);
    226        final FileHandler srcHandler = currentFileHandler != null && !resetParameters ? currentFileHandler : fetchFileHandlerFromParameters();
    227        currentFileHandler = new FileHandler(obj, srcHandler);
    228
    229        if (autoSaveListener != null) {
    230            autoSaveListener.updateFileHandler(currentFileHandler);
    231        }
    232        initFileHandler(currentFileHandler);
    233        resetParameters = false;
    234    }
    235
    236    /**
    237     * Initializes the new current {@code FileHandler}. When a new result object is created, a new {@code FileHandler} is
    238     * created, too, and associated with the result object. This new handler is passed to this method. If a location is
    239     * defined, the result object is loaded from this location. Note: This method is called from a synchronized block.
    240     *
    241     * @param handler the new current {@code FileHandler}
    242     * @throws ConfigurationException if an error occurs
    243     */
    244    protected void initFileHandler(final FileHandler handler) throws ConfigurationException {
    245        initEncoding(handler);
    246        if (handler.isLocationDefined()) {
    247            handler.locate();
    248            handler.load();
    249        }
    250    }
    251
    252    /**
    253     * Obtains the {@code FileHandler} from this builder's parameters. If no {@code FileBasedBuilderParametersImpl} object
    254     * is found in this builder's parameters, a new one is created now and stored. This makes it possible to change the
    255     * location of the associated file even if no parameters object was provided.
    256     *
    257     * @return the {@code FileHandler} from initialization parameters
    258     */
    259    private FileHandler fetchFileHandlerFromParameters() {
    260        FileBasedBuilderParametersImpl fileParams = FileBasedBuilderParametersImpl.fromParameters(getParameters(), false);
    261        if (fileParams == null) {
    262            fileParams = new FileBasedBuilderParametersImpl();
    263            addParameters(fileParams.getParameters());
    264        }
    265        return fileParams.getFileHandler();
    266    }
    267
    268    /**
    269     * Installs the listener for the auto save mechanism if it is not yet active.
    270     */
    271    private void installAutoSaveListener() {
    272        if (autoSaveListener == null) {
    273            autoSaveListener = new AutoSaveListener(this);
    274            addEventListener(ConfigurationEvent.ANY, autoSaveListener);
    275            autoSaveListener.updateFileHandler(getFileHandler());
    276        }
    277    }
    278
    279    /**
    280     * Removes the listener for the auto save mechanism if it is currently active.
    281     */
    282    private void removeAutoSaveListener() {
    283        if (autoSaveListener != null) {
    284            removeEventListener(ConfigurationEvent.ANY, autoSaveListener);
    285            autoSaveListener.updateFileHandler(null);
    286            autoSaveListener = null;
    287        }
    288    }
    289
    290    /**
    291     * Initializes the encoding of the specified file handler. If already an encoding is set, it is used. Otherwise, the
    292     * default encoding for the result configuration class is obtained and set.
    293     *
    294     * @param handler the handler to be initialized
    295     */
    296    private void initEncoding(final FileHandler handler) {
    297        if (StringUtils.isEmpty(handler.getEncoding())) {
    298            final String encoding = getDefaultEncoding(getResultClass());
    299            if (encoding != null) {
    300                handler.setEncoding(encoding);
    301            }
    302        }
    303    }
    304
    305    /**
    306     * Creates a map with default encodings for configuration classes and populates it with default entries.
    307     *
    308     * @return the map with default encodings
    309     */
    310    private static Map<Class<?>, String> initializeDefaultEncodings() {
    311        final Map<Class<?>, String> enc = new ConcurrentHashMap<>();
    312        enc.put(PropertiesConfiguration.class, PropertiesConfiguration.DEFAULT_ENCODING);
    313        enc.put(XMLPropertiesConfiguration.class, XMLPropertiesConfiguration.DEFAULT_ENCODING);
    314        return enc;
    315    }
    316}