    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.reloading;
    018
    019/**
    020 * <p>
    021 * An interface to be implemented by objects which can detect whether a reload
    022 * operation is required.
    023 * </p>
    024 * <p>
    025 * This interface is used by a {@link ReloadingController} object. When a
    026 * reloading check is to be performed, it is delegated to a concrete
    027 * implementation. The implementation decides whether (specific) criteria for a
    028 * reload are fulfilled, so that the controller can react accordingly.
    029 * </p>
    030 * <p>
    031 * This interface does not define how a check for a reload is performed. This is
    032 * completely up to a concrete implementation. There is just one method for
    033 * executing the check and one method to notify the {@code ReloadingDetector}
    034 * that the reload actually happened; this method can be used to reset the
    035 * internal state so that the conditions for the next reload can be detected.
    036 * </p>
    037 * <p>
    038 * When used together with {@code ReloadingController} an implementation does
    039 * not have to be thread-safe. The controller takes care for synchronization so
    040 * that an instance is accessed by a single thread only.
    041 * </p>
    042 *
    043 * @since 2.0
    044 */
    045public interface ReloadingDetector
    046{
    047    /**
    048     * Checks whether all criteria for a reload operation are fulfilled. This
    049     * method is called by external components to find out when reloading should
    050     * take place.
    051     *
    052     * @return <b>true</b> if a reload operation should be performed,
    053     *         <b>false</b> otherwise
    054     */
    055    boolean isReloadingRequired();
    056
    057    /**
    058     * Notifies this object that a reload operation has been performed. This
    059     * method is called after {@code reloadingRequired()} has returned
    060     * <b>true</b>. It can be used to reset internal state in order to detect
    061     * the next reload operation.
    062     */
    063    void reloadingPerformed();
    064}