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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   
18  package org.apache.log4j.varia;
19  
20  import  org.apache.log4j.spi.ErrorHandler;
21  import  org.apache.log4j.spi.LoggingEvent;
22  import  org.apache.log4j.Appender;
23  import  org.apache.log4j.Logger;
24  import  org.apache.log4j.helpers.LogLog;
25  import java.util.Vector;
26   
27  /***
28    *
29    * The <code>FallbackErrorHandler</code> implements the ErrorHandler
30    * interface such that a secondary appender may be specified.  This
31    * secondary appender takes over if the primary appender fails for
32    * whatever reason.
33    *
34    * <p>The error message is printed on <code>System.err</code>, and
35    * logged in the new secondary appender.
36    *
37    * @author Ceki G&uuml;c&uuml;
38    * */
39  public class FallbackErrorHandler implements ErrorHandler {
40  
41  
42    Appender backup;
43    Appender primary;
44    Vector loggers;
45  
46    public FallbackErrorHandler() {
47    }
48    
49  
50    /***
51       <em>Adds</em> the logger passed as parameter to the list of
52       loggers that we need to search for in case of appender failure.
53    */
54    public 
55    void setLogger(Logger logger) {
56      LogLog.debug("FB: Adding logger [" + logger.getName() + "].");
57      if(loggers == null) {
58        loggers = new Vector();
59      }
60      loggers.addElement(logger);
61    }
62  
63  
64    /***
65       No options to activate.
66    */
67    public 
68    void activateOptions() {
69    }
70  
71  
72    /***
73       Prints the message and the stack trace of the exception on
74       <code>System.err</code>.  */
75    public
76    void error(String message, Exception e, int errorCode) { 
77      error(message, e, errorCode, null);
78    }
79  
80    /***
81       Prints the message and the stack trace of the exception on
82       <code>System.err</code>.
83     */
84    public
85    void error(String message, Exception e, int errorCode, LoggingEvent event) {
86      LogLog.debug("FB: The following error reported: " + message, e);
87      LogLog.debug("FB: INITIATING FALLBACK PROCEDURE.");
88      if (loggers != null) {
89      	for(int i = 0; i < loggers.size(); i++) {
90        		Logger l = (Logger) loggers.elementAt(i);
91        		LogLog.debug("FB: Searching for ["+primary.getName()+"] in logger ["
92  		   		+l.getName() + "].");
93        		LogLog.debug("FB: Replacing ["+primary.getName()+"] by ["
94  		   		+ backup.getName() + "] in logger ["+ l.getName() +"].");
95        		l.removeAppender(primary);
96        		LogLog.debug("FB: Adding appender ["+backup.getName()+"] to logger "
97  		   		+  l.getName());
98        		l.addAppender(backup);
99          }
100     }    
101   }
102 
103 
104   /***
105      Print a the error message passed as parameter on
106      <code>System.err</code>.  
107   */
108   public 
109   void error(String message) {
110     //if(firstTime) {
111     //LogLog.error(message);
112     //firstTime = false;
113     //}
114   }
115   
116   /***
117      The appender to which this error handler is attached.
118    */
119   public
120   void setAppender(Appender primary) {
121     LogLog.debug("FB: Setting primary appender to [" + primary.getName() + "].");
122     this.primary = primary;
123   }
124 
125   /***
126      Set the backup appender.
127    */
128   public
129   void setBackupAppender(Appender backup) {
130     LogLog.debug("FB: Setting backup appender to [" + backup.getName() + "].");
131     this.backup = backup;
132   }
133   
134 }