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} dependant on synchronization and concurrency requirements.
029 */
030public 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    void start();
049
050    void stop();
051
052    boolean isStarted();
053
054    boolean isStopped();
055}