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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<>();
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("ManagerFactory [" + factory + "] unable to create manager for ["
74                              + name + "] with data [" + data + "]");
75                  }
76                  MAP.put(name, manager);
77              }
78              manager.count++;
79              return manager;
80          } finally {
81              LOCK.unlock();
82          }
83      }
84  
85      /**
86       * Determines if a Manager with the specified name exists.
87       * @param name The name of the Manager.
88       * @return True if the Manager exists, false otherwise.
89       */
90      public static boolean hasManager(final String name) {
91          LOCK.lock();
92          try {
93              return MAP.containsKey(name);
94          } finally {
95              LOCK.unlock();
96          }
97      }
98  
99      /**
100      * May be overridden by Managers to perform processing while the Manager is being released and the
101      * lock is held.
102      */
103     protected void releaseSub() {
104     }
105 
106     protected int getCount() {
107         return count;
108     }
109 
110     /**
111      * Called to signify that this Manager is no longer required by an Appender.
112      */
113     public void release() {
114         LOCK.lock();
115         try {
116             --count;
117             if (count <= 0) {
118                 MAP.remove(name);
119                 LOGGER.debug("Shutting down {} {}", this.getClass().getSimpleName(), getName());
120                 releaseSub();
121             }
122         } finally {
123             LOCK.unlock();
124         }
125     }
126 
127     /**
128      * Returns the name of the Manager.
129      * @return The name of the Manager.
130      */
131     public String getName() {
132         return name;
133     }
134 
135     /**
136      * Provide a description of the content format supported by this Manager.  Default implementation returns an empty
137      * (unspecified) Map.
138      *
139      * @return a Map of key/value pairs describing the Manager-specific content format, or an empty Map if no content
140      * format descriptors are specified.
141      */
142     public Map<String, String> getContentFormat() {
143         return new HashMap<>();
144     }
145 }