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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  import java.io.InterruptedIOException;
27  
28  /**
29    *
30    * The <code>FallbackErrorHandler</code> implements the ErrorHandler
31    * interface such that a secondary appender may be specified.  This
32    * secondary appender takes over if the primary appender fails for
33    * whatever reason.
34    *
35    * <p>The error message is printed on <code>System.err</code>, and
36    * logged in the new secondary appender.
37    *
38    * @author Ceki G&uuml;c&uuml;
39    * */
40  public class FallbackErrorHandler implements ErrorHandler {
41  
42  
43    Appender backup;
44    Appender primary;
45    Vector loggers;
46  
47    public FallbackErrorHandler() {
48    }
49    
50  
51    /**
52       <em>Adds</em> the logger passed as parameter to the list of
53       loggers that we need to search for in case of appender failure.
54    */
55    public 
56    void setLogger(Logger logger) {
57      LogLog.debug("FB: Adding logger [" + logger.getName() + "].");
58      if(loggers == null) {
59        loggers = new Vector();
60      }
61      loggers.addElement(logger);
62    }
63  
64  
65    /**
66       No options to activate.
67    */
68    public 
69    void activateOptions() {
70    }
71  
72  
73    /**
74       Prints the message and the stack trace of the exception on
75       <code>System.err</code>.  */
76    public
77    void error(String message, Exception e, int errorCode) { 
78      error(message, e, errorCode, null);
79    }
80  
81    /**
82       Prints the message and the stack trace of the exception on
83       <code>System.err</code>.
84     */
85    public
86    void error(String message, Exception e, int errorCode, LoggingEvent event) {
87      if (e instanceof InterruptedIOException) {
88          Thread.currentThread().interrupt();
89      }
90      LogLog.debug("FB: The following error reported: " + message, e);
91      LogLog.debug("FB: INITIATING FALLBACK PROCEDURE.");
92      if (loggers != null) {
93      	for(int i = 0; i < loggers.size(); i++) {
94        		Logger l = (Logger) loggers.elementAt(i);
95        		LogLog.debug("FB: Searching for ["+primary.getName()+"] in logger ["
96  		   		+l.getName() + "].");
97        		LogLog.debug("FB: Replacing ["+primary.getName()+"] by ["
98  		   		+ backup.getName() + "] in logger ["+ l.getName() +"].");
99        		l.removeAppender(primary);
100       		LogLog.debug("FB: Adding appender ["+backup.getName()+"] to logger "
101 		   		+  l.getName());
102       		l.addAppender(backup);
103         }
104     }    
105   }
106 
107 
108   /**
109      Print a the error message passed as parameter on
110      <code>System.err</code>.  
111   */
112   public 
113   void error(String message) {
114     //if(firstTime) {
115     //LogLog.error(message);
116     //firstTime = false;
117     //}
118   }
119   
120   /**
121      The appender to which this error handler is attached.
122    */
123   public
124   void setAppender(Appender primary) {
125     LogLog.debug("FB: Setting primary appender to [" + primary.getName() + "].");
126     this.primary = primary;
127   }
128 
129   /**
130      Set the backup appender.
131    */
132   public
133   void setBackupAppender(Appender backup) {
134     LogLog.debug("FB: Setting backup appender to [" + backup.getName() + "].");
135     this.backup = backup;
136   }
137   
138 }