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 }