    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
    018    package org.apache.logging.log4j.core;
    019
    020    /**
    021     * All proper Java frameworks implement some sort of object life cycle. In Log4j, the main interface for handling
    022     * the life cycle context of an object is this one. An object first starts in the {@link State#INITIALIZED} state
    023     * by default to indicate the class has been loaded. From here, calling the {@link #start()} method will change this
    024     * state to {@link State#STARTING}. After successfully being started, this state is changed to {@link State#STARTED}.
    025     * When the {@link #stop()} is called, this goes into the {@link State#STOPPING} state. After successfully being
    026     * stopped, this goes into the {@link State#STOPPED} state. In most circumstances, implementation classes should
    027     * store their {@link State} in a {@code volatile} field or inside an
    028     * {@link java.util.concurrent.atomic.AtomicReference} dependent on synchronization and concurrency requirements.
    029     */
    030    public interface LifeCycle {
    031
    032        /**
    033         * Status of a life cycle like a {@link LoggerContext}.
    034         */
    035        public enum State {
    036            /** Initialized but not yet started. */
    037            INITIALIZED,
    038            /** In the process of starting. */
    039            STARTING,
    040            /** Has started. */
    041            STARTED,
    042            /** Stopping is in progress. */
    043            STOPPING,
    044            /** Has stopped. */
    045            STOPPED
    046        }
    047
    048        /**
    049         * Gets the life-cycle state
    050         *
    051         * @return the life-cycle state
    052         */
    053        State getState();
    054
    055        void start();
    056
    057        void stop();
    058
    059        boolean isStarted();
    060
    061        boolean isStopped();
    062    }