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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  
18  package org.apache.logging.log4j.core;
19  
20  /**
21   * All proper Java frameworks implement some sort of object life cycle. In Log4j, the main interface for handling
22   * the life cycle context of an object is this one. An object first starts in the {@link State#INITIALIZED} state
23   * by default to indicate the class has been loaded. From here, calling the {@link #start()} method will change this
24   * state to {@link State#STARTING}. After successfully being started, this state is changed to {@link State#STARTED}.
25   * When the {@link #stop()} is called, this goes into the {@link State#STOPPING} state. After successfully being
26   * stopped, this goes into the {@link State#STOPPED} state. In most circumstances, implementation classes should
27   * store their {@link State} in a {@code volatile} field or inside an
28   * {@link java.util.concurrent.atomic.AtomicReference} dependent on synchronization and concurrency requirements.
29   */
30  public interface LifeCycle {
31      
32      /**
33       * Status of a life cycle like a {@link LoggerContext}.
34       */
35      public enum State {
36          /** Initialized but not yet started. */
37          INITIALIZED,
38          /** In the process of starting. */
39          STARTING,
40          /** Has started. */
41          STARTED,
42          /** Stopping is in progress. */
43          STOPPING,
44          /** Has stopped. */
45          STOPPED
46      }
47      
48      /**
49       * Gets the life-cycle state
50       * 
51       * @return the life-cycle state
52       */
53      State getState();
54      
55      void start();
56  
57      void stop();
58  
59      boolean isStarted();
60  
61      boolean isStopped();
62  }