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1   /*
2    * Copyright 2001-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.apache.log4j;
18  
19  import java.util.Hashtable;
20  
21  import org.apache.log4j.spi.LoggerFactory;
22  import org.slf4j.helpers.Util;
23  
24  /**
25   * This class is a factory that creates and maintains org.apache.log4j.Loggers
26   * wrapping org.slf4j.Loggers.
27   * 
28   * It keeps a hashtable of all created org.apache.log4j.Logger instances so that
29   * all newly created instances are not dulpicates of existing loggers.
30   * 
31   * @author Sébastien Pennec
32   */
33  class Log4jLoggerFactory {
34  
35    // String, Logger
36    private static Hashtable log4jLoggers = new Hashtable();
37  
38    private static final String LOG4J_DELEGATION_LOOP_URL = "http://www.slf4j.org/codes.html#log4jDelegationLoop";
39    
40    // check for delegation loops
41    static {
42      try {
43        Class.forName("org.slf4j.impl.Log4jLoggerFactory");
44        String part1 = "Detected both log4j-over-slf4j.jar AND slf4j-log4j12.jar on the class path, preempting StackOverflowError. ";
45        String part2 = "See also " + LOG4J_DELEGATION_LOOP_URL
46            + " for more details.";
47  
48        Util.report(part1);
49        Util.report(part2);
50              throw new IllegalStateException(part1 + part2);
51      } catch (ClassNotFoundException e) {
52        // this is the good case
53      }
54    }
55  
56    public static synchronized Logger getLogger(String name) {
57      if (log4jLoggers.containsKey(name)) {
58        return (org.apache.log4j.Logger) log4jLoggers.get(name);
59      } else {
60        Logger log4jLogger = new Logger(name);
61  
62        log4jLoggers.put(name, log4jLogger);
63        return log4jLogger;
64      }
65    }
66    
67    public static synchronized Logger getLogger(String name, LoggerFactory loggerFactory) {
68  	  if (log4jLoggers.containsKey(name)) {
69  		  return (org.apache.log4j.Logger) log4jLoggers.get(name);
70  	  } else {
71  		  Logger log4jLogger = loggerFactory.makeNewLoggerInstance(name);
72  
73  		  log4jLoggers.put(name, log4jLogger);
74  		  return log4jLogger;
75  	  }
76    }
77  
78  }