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 org.apache.commons.configuration2.event.Event;
020import org.apache.commons.configuration2.event.EventType;
021
022/**
023 * <p>
024 * A base event class for events generated by a {@link ConfigurationBuilder}.
025 * </p>
026 * <p>
027 * Configuration builders can trigger a number of different events. All these events are derived from this class. This
028 * event base class does not define any additional properties. However, it defines that the event source must be a
029 * {@code ConfigurationBuilder}.
030 * </p>
031 *
032 * @since 2.0
033 */
034public class ConfigurationBuilderEvent extends Event {
035
036    private static final long serialVersionUID = -7488811456039315104L;
037
038    /** The common super type for all events related to configuration builders. */
039    public static final EventType<ConfigurationBuilderEvent> ANY = new EventType<>(Event.ANY, "BUILDER");
040
041    /**
042     * The specific event type for builder reset events. Events of this type are generated each time the builder's
043     * {@code resetResult()} method is called.
044     */
045    public static final EventType<ConfigurationBuilderEvent> RESET = new EventType<>(ANY, "RESET");
046
047    /**
048     * The specific event type for configuration request events. Events of this type are generated each time the builder's
049     * {@code getConfiguration()} method is called (before the managed configuration is actually accessed and the lock is
050     * acquired). This gives listeners the opportunity to perform some checks which may invalidate the configuration, e.g.
051     * trigger a reload check. <strong>Note:</strong> A listener must not call the builder's {@code getConfiguration()}
052     * method - this will cause an infinite loop!
053     *
054     * @see ConfigurationBuilder#getConfiguration()
055     */
056    public static final EventType<ConfigurationBuilderEvent> CONFIGURATION_REQUEST = new EventType<>(ANY, "CONFIGURATION_REQUEST");
057
058    /**
059     * Creates a new instance of {@code ConfigurationBuilderEvent} and sets basic properties.
060     *
061     * @param source the {@code ConfigurationBuilder} object which triggered this event (must not be <b>null</b>)
062     * @param evType the type of this event (must not be <b>null</b>)
063     * @throws IllegalArgumentException if a required parameter is null
064     */
065    public ConfigurationBuilderEvent(final ConfigurationBuilder<?> source, final EventType<? extends ConfigurationBuilderEvent> evType) {
066        super(source, evType);
067    }
068
069    /**
070     * Gets the source of this event as a {@code ConfigurationBuilder}.
071     *
072     * @return the {@code ConfigurationBuilder} which generated this event
073     */
074    @Override
075    public ConfigurationBuilder<?> getSource() {
076        return (ConfigurationBuilder<?>) super.getSource();
077    }
078}