    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.combined;
    018
    019import java.util.ArrayList;
    020import java.util.Collection;
    021import java.util.Collections;
    022import java.util.Map;
    023import java.util.Set;
    024
    025import org.apache.commons.configuration2.FileBasedConfiguration;
    026import org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder;
    027import org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder;
    028import org.apache.commons.configuration2.ex.ConfigurationException;
    029import org.apache.commons.configuration2.reloading.CombinedReloadingController;
    030import org.apache.commons.configuration2.reloading.ReloadingController;
    031import org.apache.commons.configuration2.reloading.ReloadingControllerSupport;
    032
    033/**
    034 * <p>
    035 * A specialized {@code MultiFileConfigurationBuilder} implementation which adds
    036 * support for reloading.
    037 * </p>
    038 * <p>
    039 * This class - as its super class - allows operating on multiple configuration
    040 * files whose file names are determined using a file name pattern and a
    041 * {@code ConfigurationInterpolator} object. It provides the following
    042 * additional features:
    043 * </p>
    044 * <ul>
    045 * <li>Configuration builder for managed configurations have reloading support.
    046 * So reloading is possible for all configuration sources loaded by this builder
    047 * instance.</li>
    048 * <li>A {@link ReloadingController} is provided which can be used to trigger
    049 * reload checks on all managed configurations.</li>
    050 * </ul>
    051 * <p>
    052 * Although this builder manages an arbitrary number of child configurations, to
    053 * clients only a single configuration is visible - the one selected by the
    054 * evaluation of the file name pattern. Builder reset notifications triggered by
    055 * the reloading mechanism do not really take this fact into account; they are
    056 * not limited to the currently selected child configuration, but occur for each
    057 * of the managed configuration.
    058 * </p>
    059 *
    060 * @since 2.0
    061 * @param <T> the concrete type of {@code Configuration} objects created by this
    062 *        builder
    063 */
    064public class ReloadingMultiFileConfigurationBuilder<T extends FileBasedConfiguration>
    065        extends MultiFileConfigurationBuilder<T> implements
    066        ReloadingControllerSupport
    067{
    068    /** The reloading controller used by this builder. */
    069    private final ReloadingController reloadingController =
    070            createReloadingController();
    071
    072    /**
    073     * Creates a new instance of {@code ReloadingMultiFileConfigurationBuilder}
    074     * and sets initialization parameters and a flag whether initialization
    075     * failures should be ignored.
    076     *
    077     * @param resCls the result configuration class
    078     * @param params a map with initialization parameters
    079     * @param allowFailOnInit a flag whether initialization errors should be
    080     *        ignored
    081     * @throws IllegalArgumentException if the result class is <b>null</b>
    082     */
    083    public ReloadingMultiFileConfigurationBuilder(final Class<T> resCls,
    084            final Map<String, Object> params, final boolean allowFailOnInit)
    085    {
    086        super(resCls, params, allowFailOnInit);
    087    }
    088
    089    /**
    090     * Creates a new instance of {@code ReloadingMultiFileConfigurationBuilder}
    091     * and sets initialization parameters.
    092     *
    093     * @param resCls the result configuration class
    094     * @param params a map with initialization parameters
    095     * @throws IllegalArgumentException if the result class is <b>null</b>
    096     */
    097    public ReloadingMultiFileConfigurationBuilder(final Class<T> resCls,
    098            final Map<String, Object> params)
    099    {
    100        super(resCls, params);
    101    }
    102
    103    /**
    104     * Creates a new instance of {@code ReloadingMultiFileConfigurationBuilder}
    105     * without setting initialization parameters.
    106     *
    107     * @param resCls the result configuration class
    108     * @throws IllegalArgumentException if the result class is <b>null</b>
    109     */
    110    public ReloadingMultiFileConfigurationBuilder(final Class<T> resCls)
    111    {
    112        super(resCls);
    113    }
    114
    115    /**
    116     * {@inheritDoc} This implementation returns a special
    117     * {@code ReloadingController} that delegates to the reloading controllers
    118     * of the managed builders created so far.
    119     */
    120    @Override
    121    public ReloadingController getReloadingController()
    122    {
    123        return reloadingController;
    124    }
    125
    126    /**
    127     * {@inheritDoc} This implementation returns a file-based configuration
    128     * builder with reloading support.
    129     */
    130    @Override
    131    protected FileBasedConfigurationBuilder<T> createManagedBuilder(
    132            final String fileName, final Map<String, Object> params)
    133            throws ConfigurationException
    134    {
    135        return new ReloadingFileBasedConfigurationBuilder<>(getResultClass(),
    136                params, isAllowFailOnInit());
    137    }
    138
    139    /**
    140     * Creates the reloading controller used by this builder. This method
    141     * creates a specialized {@link CombinedReloadingController} which operates
    142     * on the reloading controllers of the managed builders created so far.
    143     *
    144     * @return the newly created {@code ReloadingController}
    145     */
    146    private ReloadingController createReloadingController()
    147    {
    148        final Set<ReloadingController> empty = Collections.emptySet();
    149        return new CombinedReloadingController(empty)
    150        {
    151            @Override
    152            public Collection<ReloadingController> getSubControllers()
    153            {
    154                final Collection<FileBasedConfigurationBuilder<T>> builders =
    155                        getManagedBuilders().values();
    156                final Collection<ReloadingController> controllers =
    157                        new ArrayList<>(builders.size());
    158                for (final FileBasedConfigurationBuilder<T> b : builders)
    159                {
    160                    controllers.add(((ReloadingControllerSupport) b)
    161                            .getReloadingController());
    162                }
    163                return controllers;
    164            }
    165        };
    166    }
    167}