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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  package org.apache.logging.log4j.core.appender;
18  
19  import java.util.HashMap;
20  import java.util.Map;
21  import java.util.concurrent.locks.Lock;
22  import java.util.concurrent.locks.ReentrantLock;
23  
24  import org.apache.logging.log4j.Logger;
25  import org.apache.logging.log4j.status.StatusLogger;
26  
27  /**
28   * Abstract base class used to register managers.
29   */
30  public abstract class AbstractManager {
31  
32      /**
33       * Allow subclasses access to the status logger without creating another instance.
34       */
35      protected static final Logger LOGGER = StatusLogger.getLogger();
36  
37      // Need to lock that map instead of using a ConcurrentMap due to stop removing the
38      // manager from the map and closing the stream, requiring the whole stop method to be locked.
39      private static final Map<String, AbstractManager> MAP = new HashMap<String, AbstractManager>();
40  
41      private static final Lock LOCK = new ReentrantLock();
42  
43      /**
44       * Number of Appenders using this manager.
45       */
46      protected int count;
47  
48      private final String name;
49  
50      protected AbstractManager(final String name) {
51          this.name = name;
52          LOGGER.debug("Starting {} {}", this.getClass().getSimpleName(), name);
53      }
54  
55      /**
56       * Retrieves a Manager if it has been previously created or creates a new Manager.
57       * @param name The name of the Manager to retrieve.
58       * @param factory The Factory to use to create the Manager.
59       * @param data An Object that should be passed to the factory when creating the Manager.
60       * @param <M> The Type of the Manager to be created.
61       * @param <T> The type of the Factory data.
62       * @return A Manager with the specified name and type.
63       */
64      public static <M extends AbstractManager, T> M getManager(final String name, final ManagerFactory<M, T> factory,
65                                                                final T data) {
66          LOCK.lock();
67          try {
68              @SuppressWarnings("unchecked")
69              M manager = (M) MAP.get(name);
70              if (manager == null) {
71                  manager = factory.createManager(name, data);
72                  if (manager == null) {
73                      throw new IllegalStateException("Unable to create a manager");
74                  }
75                  MAP.put(name, manager);
76              }
77              manager.count++;
78              return manager;
79          } finally {
80              LOCK.unlock();
81          }
82      }
83  
84      /**
85       * Determines if a Manager with the specified name exists.
86       * @param name The name of the Manager.
87       * @return True if the Manager exists, false otherwise.
88       */
89      public static boolean hasManager(final String name) {
90          LOCK.lock();
91          try {
92              return MAP.containsKey(name);
93          } finally {
94              LOCK.unlock();
95          }
96      }
97  
98      /**
99       * May be overridden by Managers to perform processing while the Manager is being released and the
100      * lock is held.
101      */
102     protected void releaseSub() {
103     }
104 
105     protected int getCount() {
106         return count;
107     }
108 
109     /**
110      * Called to signify that this Manager is no longer required by an Appender.
111      */
112     public void release() {
113         LOCK.lock();
114         try {
115             --count;
116             if (count <= 0) {
117                 MAP.remove(name);
118                 LOGGER.debug("Shutting down {} {}", this.getClass().getSimpleName(), getName());
119                 releaseSub();
120             }
121         } finally {
122             LOCK.unlock();
123         }
124     }
125 
126     /**
127      * Returns the name of the Manager.
128      * @return The name of the Manager.
129      */
130     public String getName() {
131         return name;
132     }
133 
134     /**
135      * Provide a description of the content format supported by this Manager.  Default implementation returns an empty
136      * (unspecified) Map.
137      *
138      * @return a Map of key/value pairs describing the Manager-specific content format, or an empty Map if no content
139      * format descriptors are specified.
140      */
141     public Map<String, String> getContentFormat() {
142         return new HashMap<String, String>();
143     }
144 }