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
018package 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 * @see AbstractLifeCycle
031 */
032public interface LifeCycle {
033
034    /**
035     * Status of a life cycle like a {@link LoggerContext}.
036     */
037    enum State {
038        /** Object is in its initial state and not yet initialized. */
039        INITIALIZING,
040        /** Initialized but not yet started. */
041        INITIALIZED,
042        /** In the process of starting. */
043        STARTING,
044        /** Has started. */
045        STARTED,
046        /** Stopping is in progress. */
047        STOPPING,
048        /** Has stopped. */
049        STOPPED
050    }
051
052    /**
053     * Gets the life-cycle state.
054     *
055     * @return the life-cycle state
056     */
057    State getState();
058
059    void initialize();
060
061    void start();
062
063    void stop();
064
065    boolean isStarted();
066
067    boolean isStopped();
068
069}