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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.helpers;
19  
20  import  org.apache.log4j.spi.ErrorHandler;
21  import  org.apache.log4j.spi.LoggingEvent;
22  import  org.apache.log4j.Logger;
23  import  org.apache.log4j.Appender;
24  
25  /***
26  
27     The <code>OnlyOnceErrorHandler</code> implements log4j's default
28     error handling policy which consists of emitting a message for the
29     first error in an appender and ignoring all following errors.
30  
31     <p>The error message is printed on <code>System.err</code>. 
32  
33     <p>This policy aims at protecting an otherwise working application
34     from being flooded with error messages when logging fails.
35  
36     @author Ceki G&uuml;lc&uuml;
37     @since 0.9.0 */
38  public class OnlyOnceErrorHandler implements ErrorHandler {
39  
40  
41    final String WARN_PREFIX = "log4j warning: ";
42    final String ERROR_PREFIX = "log4j error: ";
43  
44    boolean firstTime = true;
45  
46  
47    /***
48       Does not do anything.
49     */
50    public 
51    void setLogger(Logger logger) {
52    }
53  
54  
55    /***
56       No options to activate.
57    */
58    public 
59    void activateOptions() {
60    }
61  
62  
63    /***
64       Prints the message and the stack trace of the exception on
65       <code>System.err</code>.  */
66    public
67    void error(String message, Exception e, int errorCode) { 
68      error(message, e, errorCode, null);
69    }
70  
71    /***
72       Prints the message and the stack trace of the exception on
73       <code>System.err</code>.
74     */
75    public
76    void error(String message, Exception e, int errorCode, LoggingEvent event) {
77      if(firstTime) {
78        LogLog.error(message, e);
79        firstTime = false;
80      }
81    }
82  
83  
84    /***
85       Print a the error message passed as parameter on
86       <code>System.err</code>.  
87    */
88    public 
89    void error(String message) {
90      if(firstTime) {
91        LogLog.error(message);
92        firstTime = false;
93      }
94    }
95    
96    /***
97       Does not do anything.
98     */
99    public
100   void setAppender(Appender appender) {
101   }
102 
103   /***
104      Does not do anything.
105    */
106   public
107   void setBackupAppender(Appender appender) {
108   }
109 }