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1   /**
2    * Copyright (c) 2004-2011 QOS.ch
3    * All rights reserved.
4    *
5    * Permission is hereby granted, free  of charge, to any person obtaining
6    * a  copy  of this  software  and  associated  documentation files  (the
7    * "Software"), to  deal in  the Software without  restriction, including
8    * without limitation  the rights to  use, copy, modify,  merge, publish,
9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
10   * permit persons to whom the Software  is furnished to do so, subject to
11   * the following conditions:
12   *
13   * The  above  copyright  notice  and  this permission  notice  shall  be
14   * included in all copies or substantial portions of the Software.
15   *
16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23   *
24   */
25  package org.slf4j.impl;
26  
27  import java.util.concurrent.ConcurrentHashMap;
28  import java.util.concurrent.ConcurrentMap;
29  
30  import org.apache.log4j.LogManager;
31  import org.slf4j.ILoggerFactory;
32  import org.slf4j.Logger;
33  import org.slf4j.helpers.Util;
34  
35  /**
36   * Log4jLoggerFactory is an implementation of {@link ILoggerFactory} returning
37   * the appropriate named {@link Log4jLoggerAdapter} instance.
38   * 
39   * @author Ceki Gülcü
40   */
41  public class Log4jLoggerFactory implements ILoggerFactory {
42  
43      private static final String LOG4J_DELEGATION_LOOP_URL = "http://www.slf4j.org/codes.html#log4jDelegationLoop";
44  
45      // check for delegation loops
46      static {
47          try {
48              Class.forName("org.apache.log4j.Log4jLoggerFactory");
49              String part1 = "Detected both log4j-over-slf4j.jar AND bound slf4j-log4j12.jar on the class path, preempting StackOverflowError. ";
50              String part2 = "See also " + LOG4J_DELEGATION_LOOP_URL + " for more details.";
51  
52              Util.report(part1);
53              Util.report(part2);
54              throw new IllegalStateException(part1 + part2);
55          } catch (ClassNotFoundException e) {
56              // this is the good case
57          }
58      }
59  
60      // key: name (String), value: a Log4jLoggerAdapter;
61      ConcurrentMap<String, Logger> loggerMap;
62  
63      public Log4jLoggerFactory() {
64          loggerMap = new ConcurrentHashMap<String, Logger>();
65          // force log4j to initialize
66          org.apache.log4j.LogManager.getRootLogger();
67      }
68  
69      /*
70       * (non-Javadoc)
71       * 
72       * @see org.slf4j.ILoggerFactory#getLogger(java.lang.String)
73       */
74      public Logger getLogger(String name) {
75          Logger slf4jLogger = loggerMap.get(name);
76          if (slf4jLogger != null) {
77              return slf4jLogger;
78          } else {
79              org.apache.log4j.Logger log4jLogger;
80              if (name.equalsIgnoreCase(Logger.ROOT_LOGGER_NAME))
81                  log4jLogger = LogManager.getRootLogger();
82              else
83                  log4jLogger = LogManager.getLogger(name);
84  
85              Logger newInstance = new Log4jLoggerAdapter(log4jLogger);
86              Logger oldInstance = loggerMap.putIfAbsent(name, newInstance);
87              return oldInstance == null ? newInstance : oldInstance;
88          }
89      }
90  }